Cardiovascular Health of Mothers in the United States: National Health and Nutrition Examination Survey 2007

Abstract

Background:

Pregnancy and childrearing can impact women's health and alter chronic disease trajectories in later life, including cardiovascular disease. The purpose of this study was to assess measures of women's cardiovascular health by time since last live birth.

Materials and Methods:

Data were from 4,021 nonpregnant U.S. women, 20–44 years of age, participating in the 2007–2014 National Health and Nutrition Examination Survey (NHANES). Cardiovascular health was assessed using physical measures, laboratory measures, self-reported behaviors, medical conditions, and selected psychosocial factors by time since last live birth.

Results:

Women reported their last live birth within the past 12 months (“mothers of infants”; 7.4%), >12 months, but <3 years ago (“mothers of toddlers”; 10.0%), or ≥3 years ago (“mothers of older children”; 45.2%); 37.3% were nulliparous. Compared with nulliparous women, mothers of older children had a higher prevalence of selected cardiovascular risk factors, including unhealthy diet (75.6% vs. 68.8%) and smoking (28.1% vs. 21.9%), after adjustment for sociodemographics (including age). Mothers of toddlers had a higher prevalence of unhealthy diet (78.0% vs. 68.8%). Mothers also had poorer metabolic health as indicated by a higher prevalence of low HDL cholesterol among mothers of toddlers and older children (44.2% and 40.4%, respectively, vs. 33.6%), and a higher prevalence of high waist circumference among mothers of infants (65.6% vs. 53.8%). Some mothers also had a higher prevalence of other cardiovascular risk factors, including low physical activity and poor sleep.

Conclusion:

Prior pregnancy and childrearing may be associated with selected cardiovascular risk factors among nonpregnant reproductive-aged U.S. women.

Introduction

Cardiovascular disease (CVD) is a leading cause of death and disability among women in the United States. In 2016, an estimated 296,000 U.S. women died from heart disease and an additional 83,000 died from cerebrovascular disease.¹ Several risk factors have been identified for CVD in women, including smoking, overweight and obesity, physical inactivity, hypertension, dyslipidemia, and diabetes.² Growing evidence suggests that pregnancy and childrearing may be additional risk factors, and these life events may accelerate the development of CVD in women and influence lifelong health.^2,3

Researchers have suggested that pregnancy is a “stress test” that can reveal increased risk for chronic diseases later in life.^4,5 While physiological changes occurring during pregnancy often revert to the nonpregnant state following delivery, some changes may persist, including higher cholesterol, glucose intolerance, and vascular dysfunction.⁶ These changes, as well as complications during pregnancy, are associated with a higher risk of adverse cardiovascular health outcomes in later life, including coronary heart disease, stroke, and heart failure.^7,8 In addition, behavioral and emotional changes associated with childrearing (e.g., breastfeeding, stress, sleep deprivation, and anxiety) may shape a woman's cardiovascular health.^9,10 Therefore, the period following pregnancy may be an ideal time to initiate preventive efforts to improve a woman's health and alter her chronic disease trajectory. Assessing the cardiovascular health status of mothers can help to inform these efforts.

More than 80% of women in high-income countries have ≥1 child in their lifetime.⁶ Thus, millions of women in these countries are impacted by the physiological and behavioral changes that occur during childbearing and childrearing. While several studies have looked at longitudinal changes in women's cardiovascular health associated with pregnancy,^11

–14 there is a lack of information on the cardiovascular health profile of mothers in the United States. To date, only one study has examined chronic conditions and behavioral risk factors among a nationally representative sample of reproductive-aged women in the United State.¹⁵ However, this study did not focus on cardiovascular health factors or include physical or biological measures. It also did not assess differences by parity or time since delivery, yet consideration of the time since delivery would allow for a better understanding of which cardiovascular changes may persist after delivery and for how long. The objective of our study was to provide a national snapshot of the cardiovascular health status of nonpregnant U.S. women, 20–44 years of age, by time since last live birth using physical, biological, and behavioral measures of cardiovascular health from the National Health and Nutrition Examination Survey (NHANES).

Materials and Methods

Study population

NHANES is a cross-sectional survey conducted by the CDC's National Center for Health Statistics (NCHS) designed to assess the health and nutritional status of noninstitutionalized civilians living in the United States. NHANES employs a multistage probability sampling survey design and includes interviews and standardized physical examinations. Data are released for 2-year periods and are nationally representative.

From 2007 to 2014, 8,011 women, 20–49 years of age, were eligible for the survey; 6,152 (77%) were interviewed, and 5,990 (75%) participated in the examination component. For this analysis, we excluded pregnant women (n = 247) and those missing information on pregnancy history (n = 718). We also excluded women ≥45 years of age (n = 1,004) to reduce confounding by age and the potential for violating positivity assumptions due to the small probability of women >44 years of age having a live birth ≤12 months ago. In addition, these women are not asked about pregnancy status in NHANES, which was an exclusion criterion for our analysis. The final sample included 4,021 nonpregnant reproductive-aged women. The CDC's NCHS Ethics Review Board approved the NHANES data collection; data for this analysis were obtained from public-use files.

Measures

Participant characteristics

Age, Hispanic origin, race, marital status, education, family income as a percentage of poverty level, employment, and health insurance were assessed during the interview.

Time since last live birth

Female participants completed a reproductive health questionnaire in the mobile examination center (MEC) that assessed pregnancy history, including the number of prior pregnancies (gravidity), prior births (parity), and age at first and last live birth; date of last live birth was not collected. Women whose last live birth occurred at their current age or 1 year before their current age were asked additional questions to assess the number of months since their last live birth and their current breastfeeding status.

Since we lacked information on the date and months since last live birth for women whose last live birth was more than 1 year prior to the interview, we compared women's current age with her age at the time of her last live birth to estimate time (in approximate years) since last live birth. Together with the information above, we used this information to categorize women into four mutually exclusive groups: (1) nulliparous (no prior live births); (2) mothers of infants (last live birth ≤12 months ago); (3) mothers of toddlers (last live birth >12 months ago, but less than current age minus 3 years ago); and (4) mothers of older children (last live birth more than current age minus 3 years ago).

Cardiovascular health—definitions

Cardiovascular health factors were identified using the American Heart Association's set of seven cardiovascular health metrics for adults.¹⁶ These factors included blood pressure, total cholesterol, glucose, body mass index (BMI), physical activity, diet, and current smoking. All measures were categorized as “nonideal” or “ideal” cardiovascular health with most using the criteria outlined in the American Heart Association's 2020 Strategic Impact Goals for poor/intermediate (“nonideal”) and ideal cardiovascular health.¹⁶ Nonideal cardiovascular health factors included high systolic and diastolic blood pressure, high total cholesterol, unhealthy weight, not meeting the 2008 U.S. Department of Health and Human Services physical activity guidelines,¹⁷ unhealthy diet, and current or former (quit within the past year) cigarette smoking. Definitions for these measures are provided in Table 1.

Table 1.

Definitions of Cardiovascular Health Factors and Related Health Behaviors, Conditions, and Psychosocial Factors for Nonpregnant Reproductive-Aged U.S. Women

	Definitions
	Nonideal	Ideal
Cardiovascular health factors^a
Systolic blood pressure	≥120 mmHg or taking medication for high blood pressure	<120 mmHg and not taking medication for high blood pressure
Diastolic blood pressure	≥80 mmHg or taking medication for high blood pressure	<80 mmHg and not taking medication for high blood pressure
Total cholesterol	≥200 mg/dL or taking medication for high cholesterol	<200 mg/dL and not taking medication for high cholesterol
Blood glucose (fasting)	≥100 mg/dL or taking medication for blood sugar/diabetes	<100 mg/dL and not taking medication for blood sugar/diabetes
Body mass index	≥25 kg/m²	<25 kg/m²
Physical activity	<150 min/week of moderate intensity and <75 min/week of vigorous intensity (not met the 2008 physical activity guidelines¹⁷)	≥150 min/week of moderate intensity, ≥75 min/week of vigorous intensity, or ≥150 min/week of moderate + vigorous (met the 2008 physical activity guidelines¹⁷)
Healthy diet score components^b	0–2	3–9
Current smoking	Currently smokes cigarettes or quit <12 months previously	Never smoked cigarettes or quit ≥12 months previously
	High risk	Lower risk
Other cardiovascular health factors, and related health behaviors and conditions
Waist circumference^c	≥88 cm	<88 cm
HDL cholesterol^d	<50 mg/dL or taking medication for cholesterol	≥50 mg/dL and not taking medication for cholesterol
Hemoglobin a_1C (HbA_1C)^e	>5.7% or taking medication for high blood sugar/diabetes	≤5.7% and not taking medication for high blood sugar/diabetes
Currently breastfeeding	No	Yes
Sleep duration^f	<7 hours per night	≥7 hours per night
Chronic hypertension or diabetes	Yes	No
Related psychosocial factors
Depressive symptoms^g	≥10 score on Patient Health Questionnaire	<10 score on Patient Health Questionnaire
Anxious days in past 30	≥7 days	<7 days

See Lloyd-Jones et al.,¹⁶ for additional details regarding the criteria used to define “nonideal” cardiovascular health.

Healthy dietary pattern that is consistent with a Dietary Approach to Stop Hypertension [DASH]-type eating pattern consisting of nine components based on the following recommended intake amounts, to consume daily: fruit (≥ 1.2 cup equivalents per 1,000 kcal), vegetables (≥ 1.2 cup equivalents per 1,000 kcal), whole grains (≥ 2.0 oz equivalents per 1,000 kcal), dairy (≥ 1.6 cup equivalents per 1,000 kcal), plant protein (≥ 0.7 oz equivalent per 1,000 kcal), animal protein (≤ 2.4 oz equivalents per 1,000 kcal), added sugars (≤ 2.3 tsp equivalents per 1,000 kcal), sodium (≤ 1095 mg per 1,000 kcal), and saturated fat (≤ 6% of total energy). See Matsunaga et al.,²⁵ for additional details.

See Alberti et al.,¹⁸ for additional details regarding the criteria used to define high waist circumference.

See the “Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report,” 2002, for additional details regarding the criteria used to define low HDL cholesterol.

See American Diabetes Association, 2011, “Standards of Medical Care in Diabetes–2011²⁰” for additional details regarding the criteria used to define high hemoglobin A_1C.

See Yin et al.,²¹ for additional details regarding criteria most frequently used to define short sleep duration.

See Brody et al.,²⁷ for additional details regarding the criteria used to identify participants at higher risk of depression.

HDL, high-density lipoprotein.

Other relevant cardiovascular health factors were identified from the literature and defined as “high risk” using previously established cut points, including high waist circumference (≥ 88 cm),¹⁸ low high-density lipoprotein (HDL) cholesterol (< 50 mg/dL) or taking medication for cholesterol,¹⁹ and high hemoglobin A_1C (> 5.7%) or taking medication for high blood sugar/diabetes (Table 1).²⁰ Related health behaviors and conditions included current breastfeeding, short sleep duration (< 7 hours of sleep per night),²¹ and lifetime diagnosis of hypertension or diabetes. Related psychosocial factors (depressive symptoms and anxious days) were also assessed. Current breastfeeding was only asked of women with a last live birth at current age or within 1 year before their current age.

Cardiovascular health—assessment

A trained examiner measured the height, weight, and waist circumference of each participant during the physical examination in the MEC. Height and weight were used to calculate BMI (kg/m²). Biological measures, including total cholesterol, HDL cholesterol, and hemoglobin A_1C, were measured in blood specimens. Glucose was measured in plasma specimens from a fasting subsample of participants (n = 1,918). Laboratory procedures and methods for biospecimen analyses have been previously described.^22,23

For the assessment of diet, we used data from the NHANES dietary interview component, What We Eat in America, which captures information on all food, beverages, and supplements consumed during the 24 hours prior to the interview, as well as information from follow-up questions on salt use and whether the participant's overall intake on the previous day was much more than usual, usual, or much less than usual. Each food and beverage reported was categorized in terms of energy, nutrients, and contribution to food group types.²⁴ Using this information, adherence to the Dietary Approaches to Stop Hypertension (DASH) dietary pattern was assessed by whether or not ideal amounts of nine dietary components were met (fruits, vegetables, whole grains, dairy products, plant proteins, animal proteins, added sugars, sodium, and saturated fat).²⁵

Health behaviors, conditions, and psychosocial factors were self-reported using interviewer-administered questionnaires at the participant's home or during their physical examination in the MEC. The Global Physical Activity Questionnaire assessed weekly minutes of moderate and vigorous aerobic physical activity at work, for transportation, and/or for recreation. Depressive symptoms were assessed using the 9-item Patient Health Questionnaire.²⁶ Scores for each item range from “0” (not at all) to “3” (nearly every day); a cut point of ≥10 identified participants at higher risk of depression.²⁷ The number of days in the past month that the participant felt “worried, tense, or anxious,” was assessed and dichotomized into at least 7 days versus less than 7 days. Information on anxious days was only collected for 2007–2012.

Statistical analysis

Descriptive analyses were conducted to examine participant sociodemographics by time since last live birth. We estimated the prevalence of each cardiovascular health factor and related health behaviors, conditions, and psychosocial measures using predicted margins from logistic regression models. We also estimated the mean number of nonideal cardiovascular factors using predicted margins from linear regression models. Models were adjusted for maternal demographics (age, race/ethnicity, marital status, education, poverty level, health insurance, and employment status) to assess the impact of time since last live birth on indicators of women's cardiovascular health, independent of sociodemographic profile. Secondary analyses further controlled for parity by restricting the analysis to nulliparous and primiparous (one prior live birth) women.

For each cardiovascular health factor and related health behaviors, conditions, and psychosocial measures, we included Wald P-values for the comparison of each category of time since last live birth with nulliparous women as the referent group, with the exception of current breastfeeding, which was primarily restricted to parous women. We did not adjust p-values for multiple comparisons.²⁸ All analyses accounted for the multistage, complex sampling design and used the MEC weights, subsample fasting weights, or day 1 dietary recall weights. We multiply imputed missing poverty level data using the Markov Chain Monte Carlo method (n = 10 imputations). Variables in the imputation models included age, race/ethnicity, marital status, education, employment, health insurance, and survey cycle. Analyses were conducted using SAS 9.4 (SAS Institute, Cary, North Carolina) and SAS-callable SUDAAN 11.0 (RTI International, Research Triangle Park, North Carolina).

Results

Study population

A total of 4,021 women met the eligibility criteria for this study; 7.4% were mothers of infants, 10.0% were mothers of toddlers, and 45.2% were mothers of older children (median time since last live birth was 9 years [interquartile range, 5–13]); 37.3% were nulliparous. Higher proportions of all mothers, regardless of time since last live birth, were 30–39 years old, married, had less than college education, income <200% of poverty level, were less likely to have private health insurance, and were less likely to be employed in a job or business compared with nulliparous women (Table 2).

Table 2.

Characteristics of Nonpregnant Reproductive-Aged U.S. Women by Time Since Last Live Birth (N = 4021), NHANES 2007–2014

		Nulliparous women		Mothers of infants			Mothers of toddlers			Mothers of older children
		n = 1,309		n = 316			n = 428			n = 1,968
	N	%	95% CI	%	95% CI	p^a	%	95% CI	p^a	%	95% CI	p^a
All	4,021	37.3		7.4			10.0			45.2
Age, years						<0.01			<0.01			<0.01
20–24	823	40.0	34.6–45.5	33.9	27.9–40.3		19.0	14.2–24.5		3.7	2.9–4.6
25–29	728	26.7	23.3–30.4	24.7	18.6–31.7		25.5	20.9–30.5		11.3	9.7–13.1
30–34	777	13.7	11.6–16.0	24.8	19.1–31.4		28.1	23.9–32.7		18.5	16.7–20.4
35–39	805	10.2	8.2–12.4	12.6	8.4–18.0		20.4	15.9–25.4		28.7	26.0–31.5
40–44	888	9.5	7.2–12.1	3.9	1.7–7.7		7.0	4.5–10.4		37.8	35.0–40.7
Hispanic origin and race						<0.01			<0.01			<0.01
Mexican American	686	6.4	4.7–8.5	14.3	10.5–18.9		12.9	9.7–16.7		13.1	10.3–16.3
Non-Hispanic white	1,631	67.1	63.1–70.9	58.1	49.4–66.4		60.5	53.7–67.0		57.6	52.2–63.0
Non-Hispanic black	820	11.2	9.0–13.7	12.0	8.6–16.1		10.4	7.3–14.3		15.6	12.8–18.7
Other^b	884	15.3	13.1–17.7	15.5	11.1–20.9		16.2	12.8–20.0		13.7	11.5–16.1
Marital status^c						<0.01			<0.01			<0.01
Married	1,750	23.0	19.4–26.9	63.3	56.7–69.6		70.4	65.5–75.1		58.7	55.2–62.1
Living with partner	493	12.4	10.2–14.9	17.3	13.2–22.0		12.8	9.6–16.6		10.4	8.9–12.0
Separated, divorced, or widowed	487	5.9	4.1–8.2	4.3	2.1–7.7		5.0	2.9–8.1		18.0	15.8–20.3
Never married	1,290	58.7	54.4–62.9	15.1	11.3–19.6		11.7	8.4–15.8		12.9	11.1–15.0
Gravidity
0 prior pregnancies	1,090	84.3	81.4–86.9	0		NA	0		NA	0		NA
1 prior pregnancy	582	10.3	8.2–12.6	29.1	23.0–35.8		25.5	20.1–31.5		15.4	13.2–17.8
2 prior pregnancies	812	3.3	2.3–4.7	29.8	23.4–36.7		28.8	23.8–34.3		31.4	29.3–33.6
3 prior pregnancies	642	1.7	1.0–2.7	15.4	11.4–20.3		19.9	15.0–25.4		24.4	22.3–26.6
4+ prior pregnancies	895	0.5	0.2–1.0	25.7	20.0–32.0		25.8	20.6–31.6		28.8	26.7–31.0
Parity						NA			NA			NA
0 prior live births	1,309	100.0		0			0			0
1 prior live birth	747	0		37.8	31.8–44.1		33.1	27.2–39.4		27.0	24.6–29.6
2 prior live births	987	0		34.2	28.2–40.5		40.0	33.6–46.7		40.2	37.7–42.7
3+ prior live births	978	0		28.0	22.8–33.8		26.9	22.2–31.9		32.8	30.1–35.5
Age at interview–age at last livebirth						NA			NA			NA
0 (same age)^d	177	0		52.1	44.7–59.4		2.0	0.8–4.0		0
1	308	0		47.9	40.6–55.3		37.9	32.1–44.0		0
2	259	0		0			60.1	54.1–66.0		0
3	206	0		0			0			10.8	9.2–12.5
4	194	0		0			0			10.3	8.9–11.8
5 or more	1,568	0		0			0			78.9	77.0–80.8
No live birth	1,309	100.0		0			0			0
Education^c						<0.01			<0.01			<0.01
No HS diploma or GED	782	6.7	5.3–8.3	19.2	13.9–25.5		17.2	13.4–21.5		19.3	16.9–22.0
HS diploma or GED	786	13.9	11.2–17.0	23.8	17.9–30.6		19.3	15.3–23.8		21.3	19.0–23.7
Some college, no degree	1,442	40.6	36.0–45.5	30.8	25.0–37.1		34.2	27.7–41.1		36.3	33.8–38.8
Bachelor's degree or higher	1,009	38.8	33.9–43.8	26.2	19.2–34.1		29.4	23.6–35.7		23.1	20.3–26.2
Percentage of poverty level^c						<0.01			<0.01			<0.01
Less than 100%	1,058	16.1	12.6–20.2	27.5	22.2–33.4		24.0	19.9–28.5		21.1	18.6–23.8
100%–199%	972	15.9	13.1–18.9	23.1	18.4–28.2		21.2	16.4–26.6		24.1	21.9–26.4
200%–399%	930	27.9	24.8–31.2	28.2	21.6–35.7		25.9	21.5–30.6		26.4	23.7–29.3
400% or more	794	35.7	30.9–40.6	14.4	10.2–19.4		22.0	17.5–27.0		22.6	19.5–26.0
Health insurance^c						<0.01			<0.01			<0.01
Private insurance	2,039	66.9	63.3–70.4	50.4	43.1–57.7		55.9	50.4–61.3		56.8	53.2–60.2
Other insurance	778	8.6	6.5–11.0	26.8	21.2–33.1		18.0	14.0–22.7		18.5	16.1–21.1
Uninsured	1,201	24.2	21.6–27.0	22.8	17.5–28.8		26.1	21.4–31.1		24.7	21.8–27.8
Employment status^e						<0.01			<0.01			<0.01
Employed	2,767	81.0	77.9–83.8	48.2	40.1–56.2		58.8	52.4–64.9		71.7	69.2–74.1
Not employed	1,252	19.0	16.2–22.1	51.8	43.8–59.9		41.2	35.1–47.6		28.3	25.9–30.8

Chi square p-value for comparison with nulliparous group. All tests accounted for multistage probability sampling and used weighted data.

Includes Hispanic or Latina women other than Mexican American and non-Hispanic women of races other than black or white, including multiracial women.

Missing information for the following characteristics: marital status (n = 1), education (n = 2), poverty level (n = 267), health insurance (n = 3), and employment status (n = 2).

Twelve women reported that their last birth occurred at their current age, but when asked the months since last live birth occurred, they reported it occurred 13–24 months ago. We report their last live birth was at their current age, but categorized them as having a last live birth more than 12 months ago and less than 3 years ago.

Employed in a job or business, or looking for employment.

CI, confidence interval; HS, high school; GED, general educational development; NA, not applicable.

Prevalence of nonideal cardiovascular health factors

Nonideal cardiovascular health factors were inconsistently associated with time since last live birth. Mothers of toddlers and mothers of older children had a higher prevalence of unhealthy diet (78.0% and 75.6%, respectively, vs. 68.8%), compared with nulliparous women, after adjustment for sociodemographics (which included age) (Table 3). They also had a lower prevalence of high systolic blood pressure (19.0% and 21.0%, respectively, vs. 27.9%) and high total cholesterol (23.6% and 31.3%, respectively, vs. 37.1%). In addition, mothers of older children had a higher prevalence of current smoking (28.1% vs. 21.9%) and mothers of infants had a higher prevalence of not meeting the 2008 physical activity guidelines (24.4% vs. 17.4%). Results were statistically significant at p < 0.05. No statistically significant differences were observed for the prevalence of high diastolic blood pressure, high fasting glucose, or unhealthy weight, by time since last live birth.

Table 3.

Cardiovascular Health Factors Among Nonpregnant Reproductive-Aged U.S. Women by Time Since Last Live Birth, NHANES 2007–2014

		Nulliparous women n = 1,305		Mothers of infants n = 316			Mothers of toddlers n = 428			Mothers of older children n = 1,964
	N	%	95% CI	%	95% CI	p^a	%	95% CI	p^a	%	95% CI	p^a
All	4,013	37.3		7.4			10.0			45.3
Nonideal cardiovascular health^b
High systolic blood pressure	3,925	27.9	23.8–32.0	24.6	18.1–31.1	0.39	19.0	14.7–23.2	<0.01	21.0	19.1–22.9	0.01
High diastolic blood pressure	3,925	19.1	15.9–22.4	16.7	10.5–23.0	0.51	13.7	9.7–17.6	0.05	16.3	14.1–18.4	0.15
High total cholesterol	3,853	37.1	33.9–40.4	33.6	26.0–41.3	0.37	23.6	19.5–27.6	<0.01	31.3	28.8–33.7	0.01
High blood glucose (fasting)	1,918	22.0	17.3–26.6	24.2	17.0–31.5	0.61	23.2	15.7–30.7	0.80	21.8	17.9–25.8	0.97
Unhealthy weight	3,992	58.4	54.7–62.0	65.2	58.3–72.1	0.10	63.4	57.9–68.9	0.14	61.4	57.8–64.9	0.25
Not met 2008 PA guidelines	3,113	17.4	14.5–20.4	24.4	18.3–30.4	0.03	18.1	12.8–23.3	0.84	20.1	17.5–22.6	0.23
Unhealthy diet	3,904	68.8	64.7–72.8	71.8	65.5–78.2	0.44	78.0	72.6–83.5	0.01	75.6	72.3–78.9	0.02
Current smoking	4,013	21.9	18.6–25.2	22.6	18.6–26.7	0.79	28.2	22.8–33.7	0.05	28.1	25.1–31.2	0.01
Other high-risk cardiovascular health factors, and related health behaviors and conditions
High waist circumference^c	3,928	53.8	50.3–57.4	65.6	59.8–71.3	<0.01	58.1	52.5–63.7	0.22	54.7	51.0–58.4	0.73
Low HDL cholesterol^c	3,853	33.6	30.0–37.1	38.8	31.4–46.2	0.18	44.2	38.6–49.9	<0.01	40.4	36.2–44.5	0.02
High hemoglobin a_1C (HbA_1C)^c	3,879	16.8	13.7–19.9	16.8	11.8–21.9	0.99	11.1	7.3–14.9	0.03	12.6	10.7–14.5	0.05
Currently breastfeeding^d	485	NA		41.9	35.7–48.2	NA	21.1	15.0–27.1	NA	NA		NA
Sleep <7 hours per night	4,012	30.2	26.8–33.7	58.8	51.8–65.9	<0.01	35.9	30.1–41.6	0.09	37.2	34.4–40.1	0.01
Chronic hypertension or diabetes^e	3,984	15.8	12.7–18.8	18.2	13.5–22.9	0.39	13.2	8.8–17.6	0.40	14.9	13.3–16.5	0.64
Related psychosocial factors
Depressive symptoms^f	4,006	8.5	6.2–10.9	6.4	3.5–9.4	0.31	9.2	6.3–12.2	0.74	13.4	11.3–15.4	0.01
≥7 anxious days in past 30^g	2,968	31.2	27.9–34.5	29.7	22.3–37.1	0.71	28.3	24.0–32.7	0.24	35.3	31.5–39.2	0.10

Significant values (p < 0.05) are bolded.

p-value for comparison with nulliparous group using logistic regression models adjusted for age, Hispanic origin and race, marital status, educational attainment, percentage of poverty level (includes multiply imputed data), health insurance, and employment status. Women missing marital status, education, or health insurance information were excluded from the analysis (n = 8). All tests accounted for multistage probability-based sampling and used weighted data.

Based on the American Health Association's seven metrics for cardiovascular health, see Table 1.

See Table 1 for cut points used.

Currently breastfeeding only asked of women with last live birth at current age or within 1 year before their current age.

Includes doctor ever telling participant she had hypertension or diabetes.

See Table 1 for cut points.

Not collected for 2013–2014.

%, percentage (from adjusted model); SE, standard error; PA, physical activity.

The total number of nonideal cardiovascular health factors was summed for each woman (range 0–7). The mean number of nonideal factors among women in each group was 2.40 ± standard error, 0.05 (nulliparous women), 2.56 ± 0.11 (mothers of infants), 2.45 ± 0.08 (mothers of toddlers), and 2.45 ± 0.05 (mothers of older children). No statistically significant differences were observed by time since last live birth after adjustment for age, race/ethnicity, marital status, education, poverty level, health insurance, and employment status. We further stratified the models by age to assess variations in the association between time since last live birth and the mean number of nonideal factors for younger and older women (<30 and ≥30 years). Among women <30 years of age, on average, mothers of infants and mothers of toddlers had a higher number of nonideal cardiovascular risk factors than nulliparous women (p < 0.05). No statistically significant differences were observed among women ≥30 years of age.

Prevalence of other high-risk cardiovascular health factors, behaviors, and conditions

Compared with nulliparous women, mothers of toddlers and mothers of older children had a higher prevalence of low HDL cholesterol (44.2% and 40.4%, respectively, vs. 33.6%), after adjustment for sociodemographics (Table 3). Mothers of infants and mothers of older children had a higher prevalence of short sleep duration (58.8% and 37.2%, respectively, vs. 30.2%). Mothers of infants also had a higher prevalence of high waist circumference (65.6% vs. 53.8%), while mothers of toddlers had a lower prevalence of high hemoglobin A_1C, compared with nulliparous women (11.1% vs. 16.8%). Results were statistically significant at p < 0.05. No statistically significant differences were observed for the prevalence of chronic hypertension or diabetes by time since last live birth.

Prevalence of related psychosocial factors

Compared with nulliparous women, mothers of older children had a higher prevalence of depressive symptoms than nulliparous women (13.4% vs. 8.5%, p = 0.01), after adjustment for sociodemographics (Table 3). No statistically significant differences were observed for the prevalence of anxious days by time since last live birth.

In secondary analyses restricted to nulliparous and primiparous women, many of the associations for cardiovascular health indicators by time since last live birth remained statistically significant (Supplementary Table S1; Supplementary Data are available online at www.liebertpub.com/jwh). While no statistically significant differences were observed in the primary analysis for the prevalence of high diastolic blood pressure or anxious days by time since last live birth, mothers of toddlers had a lower prevalence of high diastolic blood pressure (5.3% vs. 14.6%, p = 0.02) and mothers of older children had a higher prevalence of ≥7 anxious days (37.1% vs. 30.3%, p = 0.04), compared with nulliparous women after restriction to nulliparous and primiparous women.

In supplemental analyses, we compared the prevalence of cardiovascular health factors across the three groups of mothers. Mothers of infants and/or mothers of older children fared worse than mothers of toddlers with respect to several cardiovascular risk factors, including high total cholesterol, short sleep duration, depressive symptoms, and anxious days (all p < 0.05; Supplementary Table S2). Mothers of infants also had a higher prevalence of high waist circumference and short sleep duration, and a lower prevalence of smoking and depressive symptoms, compared with mothers of older children.

Discussion

To our knowledge, this is the first study to examine the cardiovascular health status of mothers by time since last live birth in a nationally representative sample of U.S. women. The cross-sectional nature of the study and assessment of a broad set of cardiometabolic, behavioral, and psychosocial measures allow for the generation of hypotheses for further research, exploring how pregnancy and childrearing may impact maternal cardiovascular health. Some mothers, categorized by time since last live birth, had poorer metabolic health than nulliparous women, as indicated by a higher prevalence of high waist circumference and low HDL cholesterol, after adjustment for sociodemographics. They also had a higher prevalence of other unfavorable cardiovascular health behaviors (low physical activity, unhealthy diet, and smoking). Some mothers had a lower prevalence of selected cardiovascular risk factors, including high systolic blood pressure, total cholesterol, and hemoglobin A_1C. Mothers did not differ from nulliparous women with respect to diastolic blood pressure, fasting glucose, BMI, chronic hypertension, or diabetes.

Previous longitudinal studies of reproductive-aged women suggest that cardiometabolic adaptations in pregnancy may not resolve during or after the postpartum period. These studies found that childbearing was associated with persistent increases in weight,^13,14 fat distribution,¹⁴ and waist girth,¹³ and persistent decreases in blood pressure¹² and HDL cholesterol¹¹ ≤10 years following a first birth, compared with preconception measures. Although our study was not longitudinal, we observed a higher prevalence of high waist circumference among mothers who were within the 12-month postpartum period at the time of study participation, and a higher prevalence of low HDL cholesterol among those whose last child was born >1 year before study participation. Similar to these prior studies, we also observed a lower prevalence of high systolic blood pressure among mothers whose last child was born >1 year before study participation, compared with a cross-sectional sample of nulliparous women.

Childbearing was associated with a higher prevalence of behavioral risk factors for CVD, with variations observed by time since last live birth. The low participation in physical activity observed among mothers of infants is similar to findings from another U.S. study.²⁹ Prior studies also report short sleep duration among postpartum women,^30,31 with frequent sleep disruptions for infant care and feeding.³⁰ Our finding that both mothers of infants and older children had a higher prevalence of short sleep duration suggests that sleeping problems may persist beyond the postpartum period. The higher prevalence of unhealthy diet among mothers of toddlers and older children suggests that mothers may be sharing the dietary patterns of their young children, who consume high amounts of processed foods.³² Despite declines in the overall prevalence of smoking among reproductive-aged U.S. women,¹⁵ our results suggest that mothers whose last child was born >3 years before study participation have a higher prevalence of smoking than nulliparous women. This finding is of particular importance for public health, given the adverse effects of smoking on both mothers and children.

Poor metabolic health coupled with unhealthy behaviors may have cumulative effects on the likelihood of developing chronic diseases such as CVD. Evidence from a growing body of literature suggests that the combination of persistent physiological adaptations and changes in lifestyle risk factors associated with pregnancy and childrearing may increase the risk of adverse cardiovascular health outcomes in later life.⁶ Our results show that while mothers have similar or more favorable physical and biological measures of cardiovascular health compared with nulliparous women (e.g., glucose, diastolic blood pressure, BMI, systolic blood pressure, total cholesterol, and hemoglobin A_1C), they display an overall pattern of less-than-ideal cardiovascular health with respect to adherence to key health behaviors (e.g., low physical activity, unhealthy diet, and smoking). These findings underscore the importance of initiating preventive efforts to improve women's cardiovascular health by enabling healthy behaviors and providing material support for families following pregnancy and throughout parenthood.

Strengths and limitations

This study expands on prior studies and fills an important gap in the literature by examining the cardiovascular health of mothers in the United States, while also assessing differences by time since last live birth. The strengths of this study include the nationally representative sample of U.S. noninstitutionalized civilians, the use of standardized questionnaires, and consistent content over the 8-year time period for this analysis. NHANES also measured anthropometrics and collected detailed information on physical, biological, and behavioral measures.

This study has limitations. The cross-sectional design prevents assessment of changes in biological and lifestyle risk factors over time. Multiple factors are associated with childbearing, and these factors may confound observed associations. Although we accounted for the potential confounding effects of selected sociodemographic characteristics, there may be residual or unmeasured confounding that may explain the observed associations, and thus our findings cannot be attributed solely to prior pregnancy and childrearing. In addition, women may be nulliparous by choice, or they may be infertile due to conditions such as polycystic ovarian syndrome, which is associated with cardiometabolic disease risk³³; thus, comparisons with nulliparous women may underestimate the adverse impact of childbearing and childrearing on cardiovascular health. NHANES lacks information on several pregnancy-related complications and prior pregnancy outcomes, including preeclampsia and prior preterm birth, which have been found to be associated with adverse cardiovascular health outcomes in later life⁶ and may modify the associations that were observed. Several measures were self-reported and may be misclassified due to errors in recall. We were also unable to determine whether hypertension and diabetes developed before or after pregnancy, because they were assessed as lifetime diagnoses. Data were missing for a large proportion of responses for physical activity (19.5%); thus, the prevalence of not meeting the 2008 physical activity guidelines may not be representative of the entire study population. In addition, women who provided information on their pregnancy history may not be representative of all women in NHANES, potentially introducing selection bias.

We relied on current age and age at last live birth to categorize women into mutually exclusive groups based on time since last live birth. A more precise measure of time since last live birth (in months and years) is available in the 2015–2016 NHANES. In addition, although we considered mothers of older children as one group, these women represent a heterogeneous population with respect to time since last live birth. The wide range of ages of last live birth could have differentially impacted the associations with several health factors that were assessed. We were also unable to determine whether women were caring for nonbiological children, whether biological children from the most recent live birth were living with the mother at the time of the interview, and whether women had other caregiving roles. These additional responsibilities may impact health behaviors (e.g., physical activity and sleep) and other psychosocial factors (e.g., anxious days).

Conclusions

This study highlights important differences in selected measures of cardiovascular health between nonpregnant parous and nulliparous women. These findings suggest that pregnancy and childrearing may be associated with less favorable cardiovascular risk factors among reproductive-aged mothers in the United States, including low HDL cholesterol, high waist circumference, low physical activity, unhealthy diet, smoking, and poor sleep. This broad assessment of health indicators may suggest avenues for further research and interventions to improve maternal cardiovascular health. A better understanding of the long-term impact of pregnancy and childrearing on CVD is needed to develop effective strategies for improving the health trajectories of mothers.

Footnotes

Disclaimer

The views expressed in this publication are solely the opinions of the authors and do not necessarily reflect the official policies of the U.S. Department of Health and Human Services, Office of the Assistant Secretary for Health, and the Health Resources and Services Administration, nor does mention of the department or agency names imply endorsement by the U.S. Government.

Author Disclosure Statement

The authors declare that no competing financial interests exist.

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Supplementary Material

Please find the following supplemental material available below.

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Cardiovascular Health of Mothers in the United States: National Health and Nutrition Examination Survey 2007–2014

Abstract

Background:

Materials and Methods:

Results:

Conclusion:

Introduction

Materials and Methods

Study population

Measures

Participant characteristics

Time since last live birth

Cardiovascular health—definitions

Cardiovascular health—assessment

Statistical analysis

Results

Study population

Prevalence of nonideal cardiovascular health factors

Prevalence of other high-risk cardiovascular health factors, behaviors, and conditions

Prevalence of related psychosocial factors

Discussion

Strengths and limitations

Conclusions

Footnotes

Disclaimer

Author Disclosure Statement

References

Supplementary Material