Parity and the Association Between Maternal Sociodemographic Characteristics and Breastfeeding

Abstract

Objective:

Although clinicians recognize the importance of breastfeeding for child health, breastfeeding initiation can be limited by maternal characteristics such as race/ethnicity, age at first birth, and educational attainment. We hypothesized that the strong influence of prior infant feeding experiences on multiparous women's decision to initiate and continue breastfeeding may mean that these maternal characteristics influence breastfeeding more strongly for primiparas than multiparas.

Materials and Methods:

Using Pregnancy Risk Assessment and Monitoring System (PRAMS) (Phase 8) survey data from 2016 to 2017, we analyzed mothers' responses to the supplemental question about parity, “Before you got pregnant with your new baby, did you ever have any other babies who were born alive?” Study variables were summarized by using weighted means and proportions and compared according to parity by using Wald tests. In the overall cohort, we evaluated the interaction between parity and each covariate by using logistic regression.

Results:

In our sample (N = 20,694), 40% of respondents were first-time mothers, and 88% had initiated breastfeeding. Primiparas were more likely to breastfeed than multiparas (92% versus 86%; p < 0.001), but they had shorter mean breastfeeding duration. On unadjusted analysis, four covariates were more strongly associated with breastfeeding initiation among primiparas than multiparas (maternal age, educational attainment, receiving breastfeeding information from a nurse or other medical professional, and receiving breastfeeding information from family or friends).

Conclusions:

Breastfeeding initiation is impacted more strongly by maternal characteristics for primiparas than multiparas.

Introduction

The American Academy of Pediatrics (AAP) recommends exclusive breastfeeding for about 6 months, with continuation of breastfeeding to 12 months of age.¹ Meeting these recommendations remains a challenge in the United States: For example, among U.S. children born in 2015, 83% were ever breastfed, but only 25% were breastfed exclusively for 6 months.² Hospitals and community organizations have trialed a wide range of interventions to help mothers overcome barriers to breastfeeding, including early breastfeeding initiation in the hospital, education and consultation on breastfeeding, and creation of breastfeeding support groups.³ Success with breastfeeding after a previous birth increases mothers' likelihood of initiating and sustaining breastfeeding for subsequent children.^4,5 Conversely, multiparous women may experience a unique set of challenges to breastfeeding, including caring for older children and recalling barriers to breastfeeding their first child.^6,7 Evidence for the association between parity and breastfeeding outcomes is mixed, with some studies confirming that multiparous women are less likely to initiate breastfeeding than primiparous women,⁸ and other studies finding no difference between the two groups.⁹ Still other studies demonstrate that multiparous women are more likely than primiparous women to be exclusively breastfeeding at 12 weeks of life, and to continue breastfeeding until at least 24–28 weeks.^10,11

Conflicting findings on the association between parity and breastfeeding outcomes suggest that parity may not act to increase or decrease the likelihood of breastfeeding in the same way for all mothers. Multiparous women's decisions about breastfeeding initiation and duration are strongly influenced by their experience with prior births.^7,12 Parity also impacts reasons to stop breastfeeding,¹³ and it may moderate the effectiveness of hospital-based interventions promoting breastfeeding.¹⁴ Therefore, predictors of breastfeeding outcomes in multiparous women may be different from the factors that predict breastfeeding initiation or duration among primiparous women, and models which assume that parity impacts breastfeeding independently of other characteristics may have led to inaccurate conclusions about the association between parity and breastfeeding. In this study, we hypothesized that the strong influence of prior infant feeding experiences on multiparous women's decision to initiate and continue breastfeeding limits the influence of maternal characteristics that remain constant between pregnancies (e.g., race/ethnicity, age at first birth, and educational attainment). We tested this hypothesis by using multi-state data from the Pregnancy Risk Assessment and Monitoring System (PRAMS), which includes a sufficiently large sample of new mothers to test for moderating effects on the association between maternal characteristics and breastfeeding outcomes.⁹ Our secondary aim was to assess whether parity moderates the association between infants' characteristics (e.g., gestational age, birth weight, and neonatal intensive care unit [NICU] stay) and breastfeeding outcomes.

Materials and Methods

PRAMS is a national survey of mothers who have had a live birth within the past 2–6 months, addressing prenatal care, health, and behaviors during pregnancy, and their postpartum experiences.¹⁵ This mixed-mode (mail or telephone) survey is sponsored by the Centers for Disease Control and Prevention (CDC) and administered by state health departments. We limited our analysis to survey data from 14 states participating in the 2016–2017 PRAMS (Phase 8) that included a supplemental question about parity, “Before you got pregnant with your new baby, did you ever have any other babies who were born alive?” The included states were Connecticut, Delaware, Georgia, Massachusetts, Maryland, Missouri, Montana, North Carolina, Nebraska, New Jersey, Pennsylvania, South Dakota, Utah, and Wisconsin. We excluded respondents with unknown parity status, respondents whose most recent pregnancy resulted in multiple live births, respondents whose infant was not living with them at the time of the survey, infants born with a birth defect, and cases with missing data on the primary outcome or the study covariates. All data analyzed for this study were de-identified, and the study received Institutional Review Board exemption by East Carolina University.

Our primary outcome of breastfeeding initiation was defined by a mother's answer to the question, “Did you ever breastfeed or pump breast milk to feed your new baby, even for a short period of time?” Our secondary outcome, defined for mothers who had initiated breastfeeding, was breastfeeding duration, in weeks. This duration was set to the infant's age at the time the questionnaire was completed, if the mother was still breastfeeding, and we used survival analysis techniques in our regression analysis to account for the resulting data truncation. Independent variables evaluated from the survey questionnaire included prepregnancy insurance coverage (any private insurance, only public insurance, other coverage, or no insurance before pregnancy); number of prenatal care visits (≤8, 9–11, or ≥12); mother's report of diabetes, hypertension, or depression in the 3 months before pregnancy; and receiving any postpartum care.

We included data from the core question, “Before or after your new baby was born, did you receive information about breastfeeding from any of the following sources?” Mothers could then endorse any of the following options: my doctor; a nurse, midwife, or doula; a breastfeeding or lactation specialist; my baby's doctor or health care provider; a breastfeeding support group; a breastfeeding hotline or toll-free number; family or friends; or other. We also included several maternal and infant characteristics extracted from birth certificate data. Maternal demographic characteristics obtained from birth certificates included: race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic, and other), educational attainment (<12, 12, or 13+ years), maternal age, prepregnancy body mass index category (underweight, normal weight, overweight, or obese), and marital status (married or other). Infant characteristics examined in our analysis were delivery by Cesarean section, gestational age in weeks, birth weight in grams, and infants' hospital length of stay in days.

Study variables were summarized by using weighted means and proportions and compared according to parity by using Wald tests. Due to the large sample size, we planned to include all covariates in the multivariable regression models. A selection strategy based on statistical significance was used to identify relevant interaction terms to add to the model. First, we evaluated the interaction between parity and each covariate of interest by using unadjusted logistic regression, to determine whether the strength of each covariate's association with breastfeeding initiation varied between primiparous and multiparous mothers. Any statistically significant interaction from the unadjusted analysis (p < 0.05) was then included in a full logistic regression model, adjusted for all study covariates.

We applied the same approach to evaluating interactions between parity and other covariates when analyzing the secondary outcome of breastfeeding duration, using Cox proportional hazards regression to model the hazard of discontinuing breastfeeding, while accounting for truncation of breastfeeding duration among mothers still breastfeeding at the time of the PRAMS survey. All analyses were weighted to account for unequal probability of participation in the survey, and the standard errors were adjusted for the complex survey design, as recommended by the PRAMS technical documentation.¹⁵ All multivariable analyses included controls for state of residence (not shown in the tables for brevity). Data analysis was performed in Stata/SE 16.0 (StataCorp, LP, College Station, TX), and p < 0.05 was considered statistically significant.

Results

The 2016–2017 PRAMS included data on 27,349 cases in 14 states that asked a question about parity during this round of the survey. We excluded data on 49 cases with unknown parity, 491 children born as part of a multiple birth, 1,342 cases where the child was no longer living with the mother at the time of the survey, and 109 infants with a birth defect. After excluding 4,664 cases with missing data on breastfeeding initiation or study covariates, we retained 20,694 cases for the primary analysis. Based on the analytic sample, the weighted age distribution was 21% age ≤24 years, 29% age 25–29, 32% age 30–34, and 18% age 35 or older. Forty percent were first-time mothers, and 88% had initiated breastfeeding. The average duration of breastfeeding, among mothers who initiated breastfeeding, was 13 weeks (95% confidence interval [CI]: 12–13). Study variables are compared according to parity in Table 1. Primiparas were more likely to breastfeed than multiparas (92% versus 86%; p < 0.001). Among mothers who initiated breastfeeding, mean breastfeeding duration was longer for multiparous women (12.9 weeks) as compared with primiparous women (12.2 weeks; p < 0.001).

Table 1.

Sample Characteristics and Breastfeeding Outcomes, by Parity

Variable	Primiparas (N = 8,156)	Multiparas (N = 12,538)	p^a
Variable	Weighted proportion or mean (95% CI)	Weighted proportion or mean (95% CI)	p^a
Maternal characteristics
Age
≤24 years	0.32 (0.30–0.33)	0.13 (0.13–0.14)	<0.001
24–29 years	0.30 (0.29–0.32)	0.29 (0.28–0.30)	0.096
30–34 years	0.27 (0.25–0.28)	0.35 (0.34–0.36)	<0.001
≥35 years	0.11 (0.10–0.12)	0.23 (0.22–0.24)	<0.001
Race/ethnicity
Non-Hispanic White	0.64 (0.63–0.66)	0.62 (0.60–0.63)	0.005
Non-Hispanic Black	0.13 (0.12–0.14)	0.15 (0.14–0.16)	0.004
Hispanic	0.13 (0.12–0.14)	0.16 (0.15–0.17)	<0.001
Other	0.10 (0.09–0.11)	0.08 (0.07–0.08)	<0.001
Years of education
<12	0.07 (0.06–0.08)	0.11 (0.10–0.11)	<0.001
12	0.20 (0.19–0.21)	0.23 (0.22–0.24)	<0.001
>12	0.73 (0.72–0.75)	0.66 (0.65–0.67)	<0.001
Married	0.63 (0.61–0.64)	0.68 (0.66–0.69)	<0.001
Prepregnancy insurance coverage
Any private insurance	0.69 (0.67–0.70)	0.57 (0.56–0.58)	<0.001
Public insurance only	0.27 (0.26–0.28)	0.38 (0.37–0.39)	<0.001
Other insurance	0.02 (0.02–0.03)	0.02 (0.02–0.02)	0.239
No insurance	0.02 (0.02–0.03)	0.03 (0.02–0.03)	0.041
Prenatal care visits
≤8	0.13 (0.12–0.14)	0.16 (0.15–0.17)	<0.001
9–11	0.27 (0.26–0.29)	0.32 (0.31–0.33)	<0.001
≥12	0.59 (0.58–0.61)	0.52 (0.51–0.54)	<0.001
Postpartum checkup	0.94 (0.94–0.95)	0.91 (0.90–0.91)	<0.001
Received breastfeeding information^b
Doctor	0.88 (0.87–0.89)	0.84 (0.83–0.85)	<0.001
Nurse, midwife, lactation consultant	0.92 (0.91–0.92)	0.87 (0.86–0.88)	<0.001
Support group or hotline	0.28 (0.27–0.29)	0.24 (0.23–0.25)	<0.001
Friends or family	0.79 (0.78–0.80)	0.56 (0.54–0.57)	<0.001
Prepregnancy health problems^b
Diabetes	0.03 (0.02–0.03)	0.03 (0.02–0.03)	0.785
Hypertension	0.04 (0.04–0.05)	0.05 (0.04–0.05)	0.114
Depression	0.12 (0.11–0.13)	0.13 (0.12–0.14)	0.125
BMI category
Underweight	0.04 (0.03–0.04)	0.03 (0.02–0.03)	0.018
Normal weight	0.50 (0.49–0.52)	0.43 (0.41–0.44)	<0.001
Overweight	0.24 (0.23–0.25)	0.27 (0.26–0.28)	<0.001
Obese	0.22 (0.21–0.24)	0.28 (0.26–0.29)	<0.001
Infant characteristics
Delivered by C-section	0.30 (0.29–0.32)	0.30 (0.28–0.31)	0.480
Born preterm (<37 weeks of gestation)	0.08 (0.07–0.09)	0.08 (0.07–0.08)	0.590
Birth weight (kg)	3.27 (3.25–3.29)	3.36 (3.35–3.37)	<0.001
Hospital length of stay
≤2 days	0.53 (0.51–0.55)	0.63 (0.62–0.64)	<0.001
3–5 days	0.39 (0.37–0.40)	0.31 (0.30–0.32)	<0.001
≥6 days	0.08 (0.07–0.09)	0.06 (0.06–0.07)	<0.001
Breastfeeding outcomes
Initiated breastfeeding	0.92 (0.91–0.92)	0.86 (0.85–0.87)	<0.001
Breastfeeding duration (weeks)^c	12.2 (12.0–12.4)	12.9 (12.7–13.0)	<0.001

p-Values from Wald tests of weighted estimates, with variance adjusted for complex survey sampling design.

Categories not mutually exclusive.

Reported for 18,187 mothers who had initiated breastfeeding.

BMI, body mass index; CI, confidence interval.

On unadjusted logistic regression analysis of breastfeeding initiation, we identified four covariates that had statistically significant interactions with parity (Table 2; age, educational attainment, receiving breastfeeding information from a nurse or other medical professional, and receiving breastfeeding information from family or friends). For each of these covariates, the variable had a stronger association with breastfeeding initiation among first-time mothers, than among multiparous mothers. For example, receiving breastfeeding information from friends or family was associated with 236% greater likelihood of breastfeeding initiation among primiparas (odds ratio [OR] = 3.36; 95% CI: 2.63–4.29; p < 0.001), as compared with 117% among multiparas (OR = 2.17; 95% CI: 1.85–2.55; p < 0.001). The magnitude of this association was significantly reduced by parity, as indicated by the direction and statistical significance of the interaction term (p = 0.003). The same was true for the other variables shown.

Table 2.

Unadjusted Logistic Regression Models of Breastfeeding Initiation, Interacting Select Independent Variables with Parity

Variable	Main effect^a		Interaction with parity^b
Variable	OR (95% CI)	p	OR (95% CI)	p
Age
≤24 years	Ref.		Ref.
24–29 years	1.99 (1.48–2.67)	<0.001	0.62 (0.42–0.90)	0.013
30–34 years	1.77 (1.31–2.40)	<0.001	1.02 (0.69–1.50)	0.931
≥35 years	1.90 (1.22–2.95)	0.004	0.97 (0.59–1.61)	0.912
Years of education
<12	Ref.		Ref.
12	1.75 (1.18–2.59)	0.005	0.57 (0.36–0.90)	0.015
>12	4.27 (2.98–6.11)	<0.001	0.58 (0.38–0.88)	0.011
Received breastfeeding information from a nurse, midwife, or lactation consultant	8.04 (6.11–10.59)	<0.001	0.50 (0.36–0.69)	<0.001
Received breastfeeding information from friends or family	3.36 (2.63–4.29)	<0.001	0.65 (0.48–0.86)	0.003

Association between independent variable and odds of breastfeeding initiation for primiparous mothers. (Main effects for parity are included in each model, ORs not shown.)

Modification of the association for multiparous mothers. The association between each independent variable and breastfeeding initiation for multiparous women equals the product of the main effect OR and the interaction OR. A statistically significant interaction indicates that the strength of the association is different between primiparous and multiparous mothers.

CI, confidence interval; OR, odds ratio.

Table 3 demonstrates the fully adjusted model of breastfeeding initiation, including all interaction terms that reached statistical significance on unadjusted analysis. Of the four covariates with statistically significant interactions on unadjusted analysis, the only one to retain statistical significance in the multivariable model was receiving breastfeeding information from a nurse, midwife, lactation consultant, or other medical professional (other than a doctor). For primiparas, receiving breastfeeding information from a professional in one of these roles was associated with sixfold greater odds of breastfeeding initiation for primiparas (OR = 6.16; 95% CI: 4.59–8.25; p < 0.001), but only fourfold greater odds of breastfeeding initiation for multiparas (OR = 3.84; 95% CI: 3.13–4.72; p < 0.001). Other covariates associated with greater odds of breastfeeding initiation in the multivariable model included Hispanic ethnicity, higher maternal educational attainment, being married, prepregnancy coverage by private insurance (versus public), and receiving information on breastfeeding from family, friends, support groups, or help lines.

Table 3.

Multivariable Logistic Regression Model of Breastfeeding Initiation, Including Interaction Terms Selected from the Unadjusted Analysis

Variable	Main effect^a		Interaction with parity^b
Variable	OR (95% CI)	p	OR (95% CI)	p
Maternal characteristics
Parity^c	1.52 (0.87–2.64)	0.143
Age
≤24 years	Ref.
24–29 years	1.09 (0.76–1.58)	0.632	0.88 (0.56–1.38)	0.586
30–34 years	0.87 (0.59–1.29)	0.490	1.31 (0.82–2.08)	0.258
≥35 years	0.83 (0.50–1.38)	0.472	1.33 (0.75–2.36)	0.330
Race/ethnicity
Non-Hispanic White	Ref.
Non-Hispanic Black	1.02 (0.83–1.27)	0.824
Hispanic	2.42 (1.90–3.08)	<0.001
Other	1.52 (1.14–2.01)	0.004
Years of education
<12	Ref.
12	1.87 (1.19–2.96)	0.007	0.61 (0.36–1.05)	0.072
>12	2.77 (1.71–4.47)	<0.001	0.70 (0.41–1.21)	0.204
Married	1.86 (1.56–2.21)	<0.001
Prepregnancy insurance coverage
Any private insurance	Ref.
Public insurance only	0.72 (0.60–0.86)	<0.001
Other insurance	0.73 (0.48–1.10)	0.132
No insurance	1.03 (0.56–1.89)	0.923
Prenatal care visits
≤8	Ref.
9–11	1.14 (0.92–1.42)	0.227
≥12	1.04 (0.85–1.28)	0.705
Postpartum checkup	1.28 (1.02–1.62)	0.035
Received breastfeeding information^b
Doctor	0.66 (0.54–0.80)	<0.001
Nurse, midwife, lactation consultant	6.16 (4.59–8.25)	<0.001	0.62 (0.44–0.89)	0.008
Support group or hotline	1.74 (1.43–2.11)	<0.001
Friends or family	2.17 (1.66–2.82)	<0.001	0.78 (0.57–1.07)	0.129
Prepregnancy health problems^b
Diabetes	0.84 (0.55–1.28)	0.410
Hypertension	0.90 (0.65–1.24)	0.512
Depression	0.93 (0.76–1.14)	0.478
BMI category
Underweight	0.91 (0.62–1.36)	0.655
Normal weight	Ref.
Overweight	0.94 (0.78–1.13)	0.508
Obese	0.69 (0.58–0.82)	<0.001
Infant characteristics
Delivered by C-section	0.94 (0.78–1.12)	0.465
Born preterm (<37 weeks gestation)	0.86 (0.64–1.16)	0.316
Birth weight (kg)	1.01 (0.88–1.16)	0.900
Hospital length of stay
≤2 days	Ref.
3–5 days	0.96 (0.81–1.15)	0.685
≥6 days	1.17 (0.85–1.59)	0.337

Association between independent variable and odds of breastfeeding initiation for primiparous mothers. Model also controls for state of residence (ORs not shown).

Main effect for parity represents the difference between multiparous and primiparous women when all categorical covariates are set to their reference value.

CI, confidence interval; OR, odds ratio.

In further analysis, we used Cox proportional hazards regression to evaluate the hazard of breastfeeding discontinuation among the 18,545 women who had initiated breastfeeding. Table 4 summarized unadjusted Cox models for 10 variables that had statistically significant interactions with parity. Five of these variables (older age, race/ethnicity other than Hispanic, White, or Black, greater educational attainment, receiving breastfeeding information from a support group or hotline, receiving breastfeeding information from friends or family) were associated with prolonged breastfeeding for primiparas (hazard ratio [HR] <1), whereas these associations were weakened or reversed for multiparas.

Table 4.

Unadjusted Cox Proportional Hazards Regression Models of Breastfeeding Discontinuation, Interacting Select Independent Variables with Parity

Variable	Main effect^a		Interaction with parity^b
Variable	HR (95% CI)	p	HR (95% CI)	p
Maternal characteristics
Age
≤24 years	Ref.
24–29 years	0.48 (0.42–0.55)	<0.001	1.44 (1.18–1.75)	<0.001
30–34 years	0.39 (0.34–0.45)	<0.001	1.26 (1.03–1.55)	0.026
≥35 years	0.41 (0.33–0.50)	<0.001	1.17 (0.91–1.50)	0.235
Race/ethnicity
Non-Hispanic White	Ref.
Non-Hispanic Black	1.68 (1.42–1.97)	<0.001	1.02 (0.82–1.26)	0.862
Hispanic	1.70 (1.48–1.97)	<0.001	0.89 (0.74–1.07)	0.229
Other	0.81 (0.67–0.97)	0.025	1.33 (1.04–1.71)	0.024
Years of education
<12	Ref.
12	0.96 (0.78–1.17)	0.683	1.18 (0.92–1.53)	0.195
>12	0.39 (0.32–0.46)	<0.001	1.46 (1.15–1.84)	0.002
Prepregnancy insurance coverage
Any private insurance	Ref.
Public insurance only	1.96 (1.74–2.21)	<0.001	1.00 (0.86–1.16)	0.978
Other insurance	1.63 (1.18–2.26)	0.003	0.58 (0.36–0.94)	0.028
No insurance	2.05 (1.32–3.19)	0.001	0.63 (0.37–1.08)	0.095
Received breastfeeding information^b
Doctor	1.21 (1.00–1.46)	0.050	1.39 (1.10–1.76)	0.006
Nurse, midwife, lactation consultant	0.84 (0.67–1.05)	0.116	1.47 (1.12–1.96)	0.006
Support group or hotline	0.77 (0.68–0.88)	<0.001	1.30 (1.10–1.54)	0.002
Friends or family	0.65 (0.57–0.74)	<0.001	1.57 (1.34–1.85)	<0.001
Infant characteristics
Delivered by C-section	1.06 (0.94–1.19)	0.373	1.37 (1.17–1.60)	<0.001
Hospital length of stay
≤2 days	Ref.
3–5 days	1.09 (0.97–1.23)	0.144	1.22 (1.04–1.44)	0.013
≥6 days	1.35 (1.13–1.61)	0.001	1.55 (1.23–1.95)	<0.001

Association between independent variable and hazard of breastfeeding discontinuation for primiparous mothers. (Main effects for parity are included in each model, HRs not shown.)

Modification of the association for multiparous mothers. The association between each independent variable and breastfeeding initiation for multiparous women equals the product of the main effect HR and the interaction HR. A statistically significant interaction indicates that the strength of the association is different between primiparous and multiparous mothers.

CI, confidence interval; HR, hazard ratio.

After adding interactions for all 10 variables to a multivariable Cox model (Table 5), only two of the interaction terms remained statistically significant (receiving information from friends or family; infant length of stay). For primiparas, receiving breastfeeding information from friends or family was associated with 27% lower hazard of stopping breastfeeding (HR = 0.73; 95% CI: 0.64–0.83; p < 0.001); whereas for multiparas, the same factor was not associated with breastfeeding duration as evaluated by the Cox model (HR = 1.02; 95% CI: 0.92–1.13; p = 0.713). Factors associated with prolonged breastfeeding included higher educational attainment, attending a postpartum check-up, and higher infant birth weight. Factors associated with earlier breastfeeding discontinuation (HR >1) included prepregnancy depression, maternal overweight or obesity, delivery by C-section, and preterm birth. Although parity was not associated with the likelihood of breastfeeding initiation (Table 3), the multivariable Cox model suggested that among mothers who initiated breastfeeding, the hazard of breastfeeding discontinuation was significantly lower for multiparas (HR = 0.39; 95% CI: 0.25–0.60; p < 0.001).

Table 5.

Multivariable Cox Proportional Hazards Regression Model of Breastfeeding Discontinuation, Including Interaction Terms Selected from the Unadjusted Analysis

Variable	Main effect^a		Interaction with parity^b
Variable	HR (95% CI)	p	HR (95% CI)	p
Maternal characteristics
Parity^c	0.39 (0.25–0.60)	<0.001
Age
≤24 years	Ref.
24–29 years	0.74 (0.63–0.86)	<0.001	1.10 (0.89–1.36)	0.378
30–34 years	0.68 (0.58–0.81)	<0.001	1.01 (0.80–1.26)	0.949
≥35 years	0.67 (0.53–0.84)	0.001	1.01 (0.76–1.34)	0.955
Race/ethnicity
Non-Hispanic White	Ref.
Non-Hispanic Black	1.06 (0.89–1.26)	0.501	1.01 (0.81–1.26)	0.916
Hispanic	1.13 (0.96–1.33)	0.157	0.96 (0.78–1.19)	0.714
Other	0.81 (0.68–0.98)	0.029	1.20 (0.94–1.54)	0.151
Years of education
<12	Ref.
12	1.02 (0.84–1.26)	0.815	1.03 (0.79–1.34)	0.819
>12	0.68 (0.55–0.84)	<0.001	1.20 (0.91–1.57)	0.195
Married	0.64 (0.59–0.71)	<0.001
Prepregnancy insurance coverage
Any private insurance	Ref.
Public insurance only	1.10 (0.95–1.27)	0.189	1.07 (0.89–1.28)	0.477
Other insurance	0.94 (0.66–1.33)	0.721	0.70 (0.42–1.17)	0.173
No insurance	1.13 (0.72–1.78)	0.592	0.71 (0.41–1.23)	0.223
Prenatal care visits
≤8	Ref.
9–11	1.05 (0.94–1.17)	0.395
≥12	0.97 (0.87–1.09)	0.638
Postpartum checkup	0.79 (0.70–0.89)	<0.001
Received breastfeeding information^b
Doctor	1.27 (1.05–1.54)	0.013	1.15 (0.91–1.47)	0.247
Nurse, midwife, lactation consultant	0.94 (0.75–1.17)	0.567	1.19 (0.90–1.57)	0.226
Support group or hotline	0.70 (0.62–0.80)	<0.001	1.15 (0.97–1.37)	0.107
Friends or family	0.73 (0.64–0.83)	<0.001	1.41 (1.19–1.66)	<0.001
Prepregnancy health problems^b
Diabetes	1.16 (0.93–1.46)	0.192
Hypertension	1.02 (0.85–1.23)	0.802
Depression	1.22 (1.10–1.35)	<0.001
BMI category
Underweight	0.87 (0.69–1.09)	0.231
Normal weight	Ref.
Overweight	1.21 (1.10–1.33)	<0.001
Obese	1.52 (1.39–1.67)	<0.001
Infant characteristics
Delivered by C-section	1.20 (1.04–1.39)	0.011	1.06 (0.88–1.28)	0.529
Born preterm (<37 weeks gestation)	1.21 (1.04–1.41)	0.014
Birth weight (kg)	0.90 (0.84–0.98)	0.011
Hospital length of stay
≤2 days	Ref.
3–5 days	0.92 (0.80–1.07)	0.283	1.12 (0.93–1.36)	0.245
≥6 days	0.83 (0.67–1.03)	0.087	1.46 (1.12–1.90)	0.005

Association between independent variable and hazard of breastfeeding discontinuation for primiparous mothers. Model also controls for state of residence (HRs not shown).

Modification of the association for multiparous mothers. The association between each independent variable and breastfeeding initiation for multiparous women equals the product of the main effect HR and the interaction HR. A statistically significant interaction indicates that the strength of the association is different between primiparous and multiparous mothers.

Main effect for parity represents the difference between multiparous and primiparous women when all categorical covariates are set to their reference value.

CI, confidence interval, HR, hazard ratio.

Discussion

Multiparous women who struggle with breastfeeding their first child are less likely to attempt or continue breastfeeding in subsequent pregnancies.^5,8 Further, parity influences women's reasons to stop breastfeeding, and their perception of when the infant is self-weaning, which influences breastfeeding duration.^13,16 Research on parity as an independent predictor of breastfeeding outcomes has returned mixed results.^7,8,17,18 Therefore, we considered whether parity was moderating the impact of other factors on breastfeeding initiation and duration. For several maternal characteristics, such as age and educational attainment, we found that unadjusted associations with breastfeeding initiation were indeed weaker among multiparas than among primiparas. However, we found that the association between receiving breastfeeding information from nurses, midwives, or lactation consultants remained the strongest predictor of breastfeeding initiation among multiparas, even though this association was weaker than among primiparas. This indicates an opportunity to optimize communication from health care providers to support breastfeeding initiation and continuation among multiparous women, although further research is needed to determine the most effective messaging or interventions for this population.

Prior studies, using both PRAMS and other US data sets, have demonstrated varied effects of parity on breastfeeding outcomes. Several studies have found that parity did not affect breastfeeding initiation or cessation.^6,9,19 Conversely, Tanda et al. found that multiparous women were more likely to continue exclusive breastfeeding for at least 12 weeks,¹¹ whereas Li et al. found that first-time mothers discontinued breastfeeding earlier.¹³ Still other studies reported that multiparous women had a shorter duration of breastfeeding, particularly if they had trouble breastfeeding with their first child.^5,8 Our study found that although primiparas were more likely to breastfeed than multiparous women on unadjusted analysis, the latter ended up breastfeeding longer (as expressed by a lower hazard of discontinuing breastfeeding). Further, a growing number of studies have examined breastfeeding outcomes among mothers of premature infants.^20–22 Although breastfeeding initiation and duration of breastfeeding are reduced in infants who are born prematurely, our results suggest that prematurity was not differentially associated with breastfeeding initiation between primiparas and multiparas.

We hypothesized that these mixed results were due to treating parity as affecting breastfeeding independently of other maternal and infant characteristics. By contrast, qualitative and survey-based research suggests that multiparous women may be basing their decisions to start and stop breastfeeding on different factors.²³ Focusing on breastfeeding initiation, our analysis revealed four factors (age, educational attainment, receiving breastfeeding information from a nurse or other medical professional, and receiving breastfeeding information from family or friends) that predicted this outcome more strongly among first-time mothers. One of these factors, receiving breastfeeding information from nurses, midwives, or lactation consultants, was associated with an eightfold increase in the odds of breastfeeding initiation for first-time mothers, and a fourfold increase in the odds of breastfeeding initiation for multiparous mothers. Although the difference between these associations was consistent with our hypothesis, the strength of the association among multiparous women highlights the importance of communication from the clinical team in supporting breastfeeding initiation even among women who may have had prior experience with breastfeeding (or prior difficulties with breastfeeding their older children).

Breastfeeding among multiparous mothers has not been well characterized, as qualitative research on the breastfeeding experience has largely focused on primiparous mothers. The breastfeeding experience can be described as an “engrossing,” individualized, uncertain, insecure, and constantly changing journey for both multiparous and primiparous women.^24–27 However, studies focusing on primiparous mothers revealed that their breastfeeding experiences are unique in various ways, including experiencing more early breastfeeding problems, uncertainty, frustration, pain, anxiety regarding balancing breastfeeding with other life responsibilities and daily activities, and questions of maternal self-worth and identity, which may be why primiparous mothers stop breastfeeding before multiparous women.^25,26,28 One study also suggests that milk production in primiparous mothers may be influenced by different factors compared with multiparous mothers.²⁹ Although decisions to breastfeed are affected by professional support,²⁷ there is limited evidence on how this support is provided to multiparous mothers, or whether messaging can be successfully tailored to account for mothers' experience breastfeeding or considering breastfeeding after prior births.³⁰ In this study, breastfeeding duration was positively affected by receiving advice from friends or family, but only among primiparous mothers, and not among mothers with multiple children.

Communication from the clinical team can impact mothers' decisions in initiating and continuing breastfeeding. Previously, mothers reported that they received inconsistent messaging from clinical teams on the importance of breastfeeding or even felt that there was not a significant nutritional difference between bottle feeding and breastfeeding.³¹ Even when physicians delivered educational material on breastfeeding, mothers did not feel they had discussed their breastfeeding choices with their pediatricians or obstetricians.³¹ In response, hospitals have established the role of lactation specialists to coach mothers on the nutritional importance of breastfeeding. Our study adds to the evidence that suggests that communication from nurses, midwives, and lactation specialists is more strongly related to breastfeeding initiation than communication from physicians.^31,32 We found an eightfold greater odds of breastfeeding initiation for primiparas and fourfold greater odds of breastfeeding initiation for multiparas when receiving breastfeeding information from a professional in one of these roles, emphasizing the efficacy of these roles in delivering breastfeeding interventions. One hypothesis for this association is that clinical providers in these roles may have more time available to discuss material with patients and can tailor breastfeeding literature to mothers' specific life circumstances and barriers, whereas physicians have less time to devote specifically to breastfeeding since they have to address all other aspects of the pregnancy and health of the mother and fetus during visits.^33,34 However, the PRAMS survey did not assess the amount of time that providers in different roles spent counseling mothers on breastfeeding.

Several interventions have been shown to improve breastfeeding outcomes for both primiparous and multiparous mothers. To promote early initiation of breastfeeding, defined as breastfeeding within 1 hour of birth, interventions delivered at home and in the community (e.g., group counseling, education by health care providers) had the most effect.³ For promoting exclusive breastfeeding, education in health care settings (both inpatient and outpatient) and in the community resulted in the greatest improvement, especially when undertaken together.³ Perhaps the most widely studied intervention is the Baby Friendly Hospital Initiative (BFHI) launched by the World Health Organization (WHO) and the United Nations Children's Fund (UNICEF).³ Though many studies have documented the positive impact of the BFHI,³ a majority do not analyze its impact based on parity. One study enrolling Iranian women showed that the BFHI impacts primiparous and multiparous women differently.¹⁴ Completing at least 5 (of 10) BFHI steps had an impact on breastfeeding continuation through 6 months that was twice as strong among first-time mothers. Although our study could not analyze the impact of specific interventions, we noted that for many known predictors of breastfeeding, such as maternal age and educational attainment, associations with breastfeeding outcomes were weaker for multiparous mothers compared with primiparous mothers. Additional analysis of breastfeeding interventions stratified by parity may reveal which interventions are equally effective for both groups, or whether existing interventions can be tailored for greater effectiveness among multiparous mothers.

Our conclusions are limited by several other aspects of the data and analysis. First, we acknowledge that negative experiences in an initial pregnancy likely influence a woman's choice to pursue future pregnancies,³⁵ introducing potential bias in the multipara sample. Similarly, initial breastfeeding experience (positive or negative) is known to influence subsequent breastfeeding.⁴ Since PRAMS only collected data on the most recent pregnancy, we were unable to track maternal breastfeeding experience across multiple births to the same mother. Further, the core PRAMS questions lack data on the psychosocial components of breastfeeding, including the roles of maternal identity, self-efficacy, and confidence in breastfeeding success.^{17,24,27,36–38} Although we described predictors of breastfeeding according to parity, we did not examine moderating effects of other characteristics, such as ethnicity or socioeconomic status. In one study of breastfeeding among low-income Latina mothers, several cultural phenomena were described as swaying these mothers away from exclusive breastfeeding that may not be adequately captured on a standardized, closed-ended survey.³⁹ Given that we were unable to separate lactation specialists from nurses and midwives, it is uncertain whether this specific role was responsible for the large difference between clinical support staff and physician communication with mothers. Lastly, studies using PRAMS may be subject to recall bias, since responses from mothers are collected over a wide range of time since birth. Our analysis of breastfeeding duration treated the time until the interview as the breastfeeding duration for mothers who were still breastfeeding, but this may have understated breastfeeding duration among mothers who continued breastfeeding well after completing the survey. To mitigate this limitation, we used Cox proportional hazards regression in our secondary analysis.

In conclusion, we found that primiparas were more likely to initiate breastfeeding than multiparas. Several maternal characteristics, such as age and educational attainment, had a stronger association with breastfeeding among first-time mothers than among multiparous mothers. Similarly, age, race/ethnicity, educational attainment, and completing a postpartum checkup had a weaker association with breastfeeding duration among multiparas, compared with primiparas.

Footnotes

Acknowledgments

The authors would like to thank the PRAMS Working Group and the Centers for Disease Control and Prevention for collecting and preparing the data for this publication: Alabama—Tammie Yelldell, MPH; Alaska—Kathy Perham-Hester, MS, MPH; Arizona—Enid Quintana-Torres, MPH; Arkansas—Letitia de Graft-Johnson, DrPH, MHSA; Colorado—Ashley Juhl, MSPH; Connecticut—Jennifer Morin, MPH; Delaware—George Yocher, MS; Florida—Tara Hylton, MPH; Georgia—Florence A. Kanu, PhD, MPH; Hawaii—Matt Shim, PhD, MPH; Illinois—Julie Doetsch, MA; Indiana – Brittany Reynolds, MPH; Iowa—Jennifer Pham; Kentucky—Tracey D. Jewell, MPH; Louisiana—Rosaria Trichilo, MPH; Maine—Tom Patenaude, MPH; Maryland—Laurie Kettinger, MS; Massachusetts—Hafsatou Diop, MD, MPH; Michigan—Peterson Haak; Minnesota—Mira Grice Sheff, PhD, MS; Mississippi—Brenda Hughes, MPPA; Missouri—Venkata Garikapaty, PhD; Montana—Emily Healy, MS; Nebraska—Jessica Seberger; New Hampshire—David J. Laflamme, PhD, MPH; New Jersey—Sharon Smith Cooley, MPH; New Mexico—Sarah Schrock, MPH; New York State—Anne Radigan; New York City—Lauren Birnie, MPH; North Carolina—Kathleen Jones-Vessey, MS; North Dakota—Grace Njau, MPH; Oklahoma—Ayesha Lampkins, MPH, CHES; Oregon—Cate Wilcox, MPH; Pennsylvania—Sara Thuma, MPH; Puerto Rico—Wanda Hernandez, MPH; Rhode Island—Karine Tolentino Monteiro, MPH; South Carolina—Harley T. Davis, PhD, MSPH; South Dakota – Maggie Minett; Texas—Tanya Guthrie, PhD; Tennessee—Ransom Wyse, MPH, CPH; Utah—Nicole Stone, MPH; Vermont—Peggy Brozicevic; Virginia—Kenesha Smith, PhD, MSPH; Washington—Linda Lohdefinck; West Virginia—Melissa Baker, MA; Wisconsin—Fiona Weeks, MSPH; Wyoming—Lorie Chesnut, PhD.

Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.

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