Association Between Gestational Weight Gain and Delayed Onset of Lactation: The Moderating Effects of Race/Ethnicity

Abstract

Background:

In the United States, a high percentage of pregnant women gain weight outside of the current Institute of Medicine's (IOM) gestational weight gain (GWG) recommendations. There is limited research examining the relationship between GWG and onset of lactation. Delayed onset of lactation (DOL) can negatively affect breastfeeding outcomes.

Methods:

Secondary data analysis was conducted using data from 2,053 women who participated in the population-based Infant Feeding Practices Study II between 2005 and 2007. The main outcome of interest was maternal perception of DOL, defined as milk coming in >3 days postpartum. Three categories of GWG were created based on the IOM's revised cutoff: inadequate, adequate, and excessive. Descriptive statistics and multivariable logistic regression modeling were performed. Interactions between GWG and race/ethnicity on DOL were examined to test whether the relationship between GWG and DOL differs by race/ethnicity.

Results:

Overall, 23.7% of the study sample reported DOL. Of these, 49.5% and 19.5% of women had excessive GWG and inadequate GWG, respectively. After adjusting for potential confounders, there was a significant interaction between GWG and race/ethnicity on DOL. Among non-Hispanic white women, the odds of DOL were higher in women with excessive GWG compared to those who had the recommended GWG (OR 1.47, 95% CI 1.14–1.90, p = 0.003). For other race/ethnicity groups, no significant relationships between GWG and DOL were detected.

Conclusions:

With the increasing rates of excessive GWG, it is critical to identify populations at increased risk of DOL and provide targeted breastfeeding support, especially in the early postpartum period.

Background

Breast milk is the ideal nutrition for nearly all infants and is recommended to be the exclusive nutrition provided to infants in the first 6 months of life.^1–4 Breastfeeding and provision of expressed breast milk (included from herein as breastfeeding) promote infant development, growth, and health, as well as afford maternal health benefits.⁵ While breastfeeding rates in the United States have been steadily increasing over the past couple of decades,⁶ exclusive breastfeeding rates are lagging behind recommendations. In addition, there are maternal subpopulations who have characteristically had lower breastfeeding rates than the general population.

Previous studies have found that maternal obesity, prepregnancy, and/or postpartum are associated with lower rates of exclusive breastfeeding⁷ and shorter duration of breastfeeding.^8,9 A population-based study conducted in Florida found that women who were underweight or obese before pregnancy had lower breastfeeding initiation rates than normal weight women.¹⁰ Similarly, a hospital-based cohort study also found lower breastfeeding initiation rates among women who were overweight or obese before pregnancy compared to women who were normal weight or underweight.¹¹ Maternal obesity has also been associated with delayed onset of lactation (DOL),^12–14 defined as maternal report of onset of lactation beyond 72 hours postpartum.¹⁵ Researchers also found that overweight/obese women had a lower prolactin response to infant suckling at 48 hours compared to normal weight women,¹⁶ which suggests a possible biological mechanism of action. DOL negatively affects breastfeeding outcomes, especially exclusive breastfeeding.¹²

Prepregnancy overweight and obesity rates among women of childbearing age in the United States are increasing.¹⁷ Excessive or inadequate prepregnancy body mass index (BMI) is associated with excessive or insufficient gestational weight gain (GWG).¹⁸ Over half of pregnant women in the United States fail to achieve the recommended amount of GWG during pregnancy with a majority of those pregnant women gaining excessive weight and a smaller proportion gaining insufficient weight.^19,20

Few studies have been published examining the association between GWG and breastfeeding outcomes. Among white women in New York and women in Brazil who had abnormal prepregnancy BMI levels and experienced excessive GWG, exclusive breastfeeding duration was shorter compared to women with a normal BMI and adequate GWG.^18,19 Among women in a cohort study in Pennsylvania who were overweight or obese and/or had excessive GWG, breastfeeding duration was not significantly different from women who had a normal BMI and adequate GWG, although obese women with excessive GWG experienced DOL.²¹ However, there is limited research examining the relationship between GWG and onset of lactation. This study utilizes population-based approaches to examine the association between GWG in women and their perceived onset of lactation after adjusting for potential confounders.

Methods

Secondary data analysis was conducted using data from 2,053 women who participated in the population-based Infant Feeding Practices Study II (IFPS-II) between 2005 and 2007. Conducted by the U.S. Food and Drug Administration (FDA) and the Centers of Disease Control and Prevention (CDC), IFPS-II is a longitudinal study of women and their children, following women from their late pregnancy until first 12 months postpartum to better understand the changes in the infant feeding practices among women in the United States.²² Detailed IFPS study methods are reported elsewhere.²² In brief, women eligible for IFPS were 18 years of age or older, delivered a singleton weighing at least 5 pounds, born after at least 35 weeks of gestation, not have stayed in intensive care for more than 3 days, and both mother and the baby are free from medical condition impeding breastfeeding. Data were collected longitudinally by a prenatal questionnaire, a short telephone interview near infant's birth, and a neonatal questionnaire that was sent to the mother when her infant was ∼3 weeks old followed by nine questionnaires sent monthly from 2 to 7 months and every 7 weeks until 12 months postpartum. However, our analysis utilized data only from the prenatal and neonatal questionnaires. The study sample included women who reported the time of onset of lactation (n = 2,555). Women with missing data on any of the study variables were excluded from the analysis (n = 502). Thus the final analysis included 2,053 women.

Outcome of interest: DOL

The main outcome of interest for our study was DOL. Onset of lactation is the period of transition from colostrum (early milk) to copious breast milk production, which usually occurs between 2 and 3 days postpartum.²³ The neonatal questionnaire included a question wherein women were asked, “How long did it take for your milk to come in?” (1 day or less, 2 days, 3 days, 4 days, more than 4 days). For the purpose of analysis, we dichotomized it into “≤3 days” and “>3 days.” Thus our outcome variable was classified as DOL if women reported their milk coming in “>3 days” after delivery and not having DOL if women reported their milk coming in “≤3” after delivery.

Exposure measurement

Prepregnancy BMI and weight gain during pregnancy were used to determine GWG. We used the Institute of Medicine (IOM) guidelines for GWG namely “underweight” (BMI <18.5; recommended weight gain 12.5–18 kg), “normal weight” (BMI 18.5–24.9; recommended weight gain 11.5–16 kg), “overweight” (BMI 25.0–29.9; recommended weight gain 7–11.5 kg), and “obese” (BMI ≥30; recommended weight gain 5–9 kg). Based on this guideline GWG was classified as “inadequate,” “adequate,” and “excessive.”

Covariates

The following covariates were included in our analysis: maternal age (18–24, 25–34, ≥35), race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic, other), maternal education (high school or less, some college, college graduate), marital status (never married, married, other), prepregnancy BMI (<18.5, 18.5–25, 25–30, ≥30), poverty-to-income ratio (PIR) (<185%, 185–349%, ≥350%), gestational diabetes mellitus (yes, no), prenatal breastfeeding intention (yes, no), prenatal smoking (yes, no), method of delivery (vaginal, caesarean), labor pain medications or anesthesia (yes, no), and the number of Baby Friendly Hospital Initiative (BFHI) hospital practices experienced (0–2, 3–4, 5–6). Based on the evidence, the BFHI program identifies 10 baby friendly hospital practices that support early breastfeeding.²⁴ Six of these practices (breastfeeding within 1 hour of birth, giving only breast milk, rooming in, breastfeeding on demand, not giving pacifiers, and providing information on postdischarge support) were measured in IFPS-II and were used to determine number of practices the mother experienced during her hospital stay.

Statistical analysis

Descriptive statistics were used to summarize and describe the distribution of different variables. Using chi-square (χ²) test statistic, bivariate analyses were performed to compare women with and without DOL by GWG, race, and all the potential covariates. Variables significant at 0.2 level in χ² test were retained in the multivariable modeling analysis. Logistic regression analysis was used to determine association between GWG and DOL. Pairwise interactions between GWG and race/ethnicity were examined to test whether the relationship between GWG and DOL differs by race/ethnicity. All other interaction terms between GWG and each covariate adjusted in the multivariable model were not significant, and the model with interaction term between GWG and race/ethnicity was fitted. Odds ratio (OR), 95% confidence interval (95% CI), and p-value were determined for each of the independent variables and interaction terms. We assessed potential multicollinearity using variance inflation factor. Results revealed that our regression analysis is not prone to multicollinearity. We evaluated model fit through inspection of Hosmer and Lemeshow Goodness-of-Fit Test (p = 0.415), implying that the model's estimates fit the data at an acceptable level. All analyses were conducted using SAS 9.4 (SAS Institute, Inc., Cary, NC). All p-values were two sided, and statistical significance was set as p < 0.05.

Results

Among the sample of 2,053 women, 24.0% (n = 487) reported DOL and 49.5% (n = 1,016) had GWG above the recommended guidelines. Table 1 contains the descriptive analysis results. Having DOL significantly differed by prepregnancy BMI, breastfeeding intention, method of delivery, use of pain medication/anesthesia during delivery, number of baby friendly hospital practices, and GWG. Significantly higher proportion of obese women had DOL followed by women who were overweight, normal, and underweight prepregnancy BMI. GWG significantly differed by age, marital status, race/ethnicity, education, PIR, prepregnancy BMI, gestational diabetes, prenatal smoking method of delivery, number of BFHI practices, and DOL (Table 2).

Table 1.

Characteristics of the Study Sample by Onset of Lactation

		Delayed onset of lactation
	Overall, n (%)	No, n (%)	Yes, n (%)	p
Age, years				0.217
18–24	397 (19.3)	308 (77.6)	89 (22.4)
25–34	1,318 (64.2)	990 (75.1)	328 (24.9)
≥35	338 (16.5)	268 (79.3)	70 (20.7)
Marital				0.837
Never married	300 (14.6)	228 (76.0)	72 (24.0)
Married	1,672 (81.4)	1,274 (76.2)	398 (23.8)
Other	81 (4.0)	64 (79.0)	17 (21.0)
Race/ethnicity				0.070
Non-Hispanic white	1,731 (84.3)	1,321 (76.3)	410 (23.7)
Non-Hispanic black	89 (4.3)	76 (85.4)	13 (14.6)
Hispanic	133 (6.5)	93 (69.9)	40 (30.1)
Other	100 (4.9)	76 (76.0)	24 (24.0)
Education				0.967
High school or less	363 (17.7)	275 (75.8)	88 (24.2)
Some college	838 (40.8)	640 (76.4)	198 (23.6)
College graduate	852 (41.5)	651 (76.4)	201 (23.6)
Poverty-to-income ratio, %				0.061
<185	806 (39.3)	631 (78.3)	175 (21.7)
185–349	751 (36.6)	575 (76.6)	176 (23.4)
≥350	496 (24.2)	360 (72.6)	136 (27.4)
Prepregnancy body mass index				0.019
Underweight	111 (5.4)	93 (83.8)	18 (16.2)
Normal	957 (46.6)	749 (78.3)	208 (21.7)
Overweight	524 (25.5)	388 (74.0)	136 (26.0)
Obese	461 (22.5)	336 (72.9)	125 (27.1)
Gestational diabetes mellitus				0.404
No	1,926 (93.8)	1,473 (76.5)	453 (23.5)
Yes	127 (6.2)	93 (73.2)	34 (26.8)
Breastfeeding intention				0.048
No	573 (27.9)	420 (73.3)	153 (26.7)
Yes	1,480 (72.1)	1,146 (77.4)	334 (22.6)
Prenatal smoking				0.861
No	1,906 (92.8)	1,453 (76.2)	453 (23.8)
Yes	147 (7.2)	113 (76.9)	34 (23.1)
Delivery				<0.001
Vaginal	1,498 (73.0)	1,179 (78.7)	319 (21.3)
Caesarean	555 (27.0)	387 (69.7)	168 (30.3)
Pain medication/anesthesia				<0.001
No	336 (16.4)	295 (87.8)	41 (12.2)
Yes	1,717 (83.6)	1,271 (74.0)	446 (26.0)
Baby Friendly Hospital Initiative Practices				0.008
Meet 0–2 criteria	836 (40.7)	612 (73.2)	224 (26.8)
Meet 3–4 criteria	1,130 (55.0)	880 (77.9)	250 (22.1)
Meet 5–6 criteria	87 (4.2)	74 (85.1)	13 (14.9)
Gestational weight gain				0.004
Inadequate	401 (19.5)	311 (77.6)	90 (22.4)
Adequate	636 (31.0)	510 (80.2)	126 (19.8)
Excessive	1,016 (49.5)	745 (73.3)	271 (26.7)
Onset of lactation
Delayed	487 (24.0)
Not delayed	1,566 (76.0)

Table 2.

Characteristics of Study Sample by Categories of Gestational Weight Gain

	Gestational weight gain
	Inadequate, n (%)	Adequate, n (%)	Excessive, n (%)	p
Age, years				0.038
18–24	70 (17.6)	110 (27.7)	217 (54.7)
25–34	263 (20.0)	403 (30.6)	652 (49.4)
≥35	68 (20.1)	123 (36.4)	147 (43.5)
Marital status				<0.001
Never married	48 (16.0)	74 (24.7)	178 (59.3)
Married	331 (19.8)	545 (32.6)	796 (47.6)
Other	22 (27.2)	17 (21.0)	42 (51.8)
Race/ethnicity				0.007
Non-Hispanic white	319 (18.4)	534 (30.9)	878 (50.7)
Non-Hispanic black	26 (29.2)	20 (22.5)	43 (48.3)
Hispanic	30 (22.6)	43 (32.3)	60 (45.1)
Other	26 (26.0)	39 (39.0)	35 (35.0)
Education				0.004
High school or less	74 (20.4)	99 (27.3)	190 (52.3)
Some college	182 (21.7)	236 (28.2)	420 (50.1)
College graduate	145 (17.0)	301 (35.3)	406 (47.7)
Poverty-to-income ratio, %				0.002
<185	188 (23.3)	220 (27.3)	398 (49.4)
185–349	136 (18.1)	246 (32.8)	369 (49.1)
≥350	77 (15.5)	170 (34.3)	249 (50.2)
Prepregnancy body mass index				<0.001
Underweight	28 (25.3)	48 (43.2)	35 (31.5)
Normal	207 (21.6)	381 (39.8)	369 (38.6)
Overweight	59 (11.3)	126 (24.0)	339 (64.7)
Obese	107 (23.2)	81 (17.6)	273 (59.2)
Gestational diabetes mellitus				<0.001
No	354 (18.4)	596 (30.9)	976 (50.7)
Yes	47 (37.0)	40 (31.5)	40 (31.5)
Breastfeeding intention				0.123
No	127 (22.2)	179 (31.2)	267 (46.6)
Yes	274 (18.5)	457 (30.9)	749 (50.6)
Prenatal smoking				0.037
No	364 (19.1)	603 (31.6)	939 (49.3)
Yes	37 (25.2)	33 (22.4)	77 (52.4)
Delivery				<0.001
Vaginal	308 (20.6)	493 (32.9)	697 (46.5)
Caesarean	93 (16.8)	143 (25.8)	319 (57.4)
Pain medication/anesthesia				0.278
No	75 (22.3)	106 (31.6)	155 (46.1)
Yes	326 (19.0)	530 (30.9)	861 (50.1)
Baby Friendly Hospital Initiative Practices				0.047
Meet 0–2 criteria	174 (20.8)	252 (30.2)	410 (49.0)
Meet 3–4 criteria	218 (19.3)	346 (30.6)	566 (50.1)
Meet 5–6 criteria	9 (10.3)	38 (43.7)	40 (46.0)
Onset of lactation				0.004
Delayed	90 (18.5)	126 (25.9)	271 (55.6)
Not delayed	311 (19.9)	510 (32.6)	745 (47.5)

The unadjusted multivariable analysis showed a significant interaction between GWG and race/ethnicity on DOL. Even after adjusting for potential confounders, there was a significant interaction between GWG and race/ethnicity on DOL. Among non-Hispanic white women, those who had GWG above the recommended guidelines had higher odds of DOL compared to women with GWG within the recommended guidelines (OR 1.47, 95% CI 1.14–1.90, p = 0.003). For other race/ethnicity groups, there was no significant association between GWG and DOL. In addition, in the multivariable model, women with the highest poverty ratio of PIR ≥350% had higher odds of DOL compared to women with PIR <185% (OR 1.39, 95% CI 1.07–1.80, p < 0.013). Women who delivered by caesarean section had higher odds of DOL compared to women who delivered vaginally (OR 1.27, 95% CI 1.02–1.58, p < 0.035), and women who received pain medication or anesthesia at the time of delivery had higher odds of DOL compared to women who did not receive any pain medication or anesthesia (OR 2.37, 95% CI 1.68–3.35, p < 0.001) (Table 3).

Table 3.

Crude and Multivariable Adjusted Association Between Gestational Weight Gain and Delayed Onset of Lactation

	Crude OR (95% CI)	p	Adjusted OR (95% CI)	p
Age, years
18–24	Ref.		Ref.
25–34	1.19 (0.93–1.51)	0.118	1.16 (0.90–1.51)	0.245
≥35	1.03 (0.75–1.42)	0.703	0.94 (0.67–1.34)	0.754
Prepregnancy body mass index
Underweight	Ref.		Ref.
Normal	0.71 (0.44–1.15)	0.033	1.38 (0.84–2.25)	0.195
Overweight	1.30 (1.03–1.64)	0.022	1.67 (1.01–2.78)	0.046
Obese	1.29 (1.02–1.64)	0.031	1.57 (0.94–2.62)	0.082
Poverty income ratio, %
<185	Ref.		Ref.
185–349	1.09 (0.87–1.36)	0.353	1.07 (0.84–1.35)	0.569
≥350	1.43 (1.13–1.82)	0.003	1.38 (1.07–1.80)	0.012
Breastfeeding intention
No	Ref.		Ref.
Yes	0.81 (0.66–1.00)	0.051	0.83 (0.66–1.03)	0.091
Delivery
Vaginal	Ref.		Ref.
Caesarean	1.59 (1.30–1.95)	<0.001	1.26 (1.01–1.58)	0.034
Pain medication/anesthesia
No	Ref.		Ref.
Yes	2.72 (1.95–3.79)	<0.001	2.37 (1.68–3.35)	<0.000
Baby Friendly Hospital Initiative Practices
Meet 0–2 criteria	Ref.		Ref.
Meet 3–4 criteria	0.82 (0.67–0.99)	0.868	0.86 (0.70–1.06)	0.166
Meet 5–6 criteria	0.63 (0.37–1.08)	0.188	0.73 (0.42–1.25)	0.258
Race/ethnicity
Non-Hispanic white
Adequate	Ref.		Ref.
Inadequate	1.17 (0.83–1.64)	0.367	1.16 (0.83–1.61)	0.377
Excessive	1.64 (1.26–2.13)	<0.001	1.47 (1.13–1.90)	0.003
Non-Hispanic black
Adequate	Ref.		Ref.
Inadequate	1.14 (0.80–1.63)	0.446	0.24 (0.02–2.57)	0.243
Excessive	1.17 (0.86–1.60)	0.303	1.55 (0.39–6.15)	0.527
Hispanic
Adequate	Ref.		Ref.
Inadequate	1.12 (0.62–2.01)	0.695	0.97 (0.36–2.58)	0.954
Excessive	0.84 (0.48–1.45)	0.542	0.71 (0.31–1.61)	0.414
Other
Adequate	Ref.		Ref.
Inadequate	1.10 (0.45–2.64)	0.828	1.54 (0.54–4.39)	0.412
Excessive	0.60 (0.26–1.37)	0.229	0.55 (0.19–1.58)	0.274

CI, confidence interval; OR, odds ratio.

Discussion

The main finding of the current study is that non-Hispanic white women with excessive GWG had DOL compared to non-Hispanic white women with adequate GWG. This association remained significant after adjusting for potential confounders. The study did not detect significant associations between race/ethnicity and GWG on DOL for other racial/ethnic groups. The clinical implication of DOL is that women may feel that their milk production is inadequate in the early postpartum period, which is associated with poor breastfeeding outcomes.²⁵ Women who perceive insufficient milk production are at risk for using formula, decreasing milk production, and terminating breastfeeding, especially among those from lower socioeconomic backgrounds.^25–27

In the current study, excessive GWG was highest among non-Hispanic white women compared to women from other racial/ethnic groups. This finding may explain the association between excessive weight gain and DOL among non-Hispanic white women observed in the current study. The biological mechanism for the negative association between excessive GWG and DOL could be similar to the biological mechanisms of the negative influence of obesity on delayed lactogenesis II.^28,29 Animal studies have found an association between obesity and impaired lactation failure.^30–32 Researchers found that overweight and obese women do not produce as much prolactin in response to suckling in the first week postpartum as normal weight women.¹⁶ Progesterone withdrawal that prepares mammary glands in the immediate postpartum period coupled with prolactin and cortisol secretion results in copious milk secretion thus marking the onset of lactation. Prolactin secretion is lower among obese women compared to women with normal weight. Furthermore, increased levels of progesterone concentration stored in adipose tissue as observed among obese women along with decreased prolactin secretion are associated with DOL.^16,33 Increased adipose tissue between ducts as commonly observed in obese women may also prevent proper milk flow resulting in a perceived delay in lactogenesis. Another possible reason would be mechanical difficulty impeding proper positioning of the baby among women with excessive GWG, thus affecting suckling.^10,34 In addition, women with excessive GWG may have lower perceived self-efficacy with regard to lactation compared to women with normal GWG, thus negatively affecting breastfeeding.¹³

The study findings are supported by a previous study conducted among non-Hispanic white women in the United States that showed excessive GWG to be associated with DOL and early termination of breastfeeding.^13,33 In a small longitudinal study in Connecticut, white and Hispanic women had higher odds of DOL compared to black women after adjusting for potential confounders.²³ However, due to small sample size, this study combined white and Hispanic women into one group. Another population-based study found that women who were obese before pregnancy or who had excessive GWG were less likely to initiate and maintain breastfeeding compared to women who had normal prepregnancy BMI or GWG.³⁵

The current findings of the association between PIR, mode of delivery, receipt of pain medication or anesthesia, and DOL are consistent with previous findings. Previous studies in the United States reported DOL among women who delivered by caesarean section and those who received pain medication and anesthesia during delivery.^12,25 Similarly, studies in urban Guatemala and Australia reported DOL among women who underwent caesarean section.^36,37

The major limitation of the study is that the study participants were not randomly selected, and the study sample is not representative of the U.S. population. To ensure a high response rate for the series of mailed questionnaires, the study participants were selected from a consumer panel. Thus, non-Hispanic white women, households with higher socioeconomic status, women who could read English, and households with stable mailing address were overrepresented in the study population, and hence, the results cannot be generalized to the overall U.S. population.²² In addition, the data were based on self-report, which are susceptible to recall bias. Furthermore, the cross-sectional study design precludes the determination of a causal link. Despite these limitations, the study has numerous strengths. The study had a large sample size with a high response rate. The survey questions were extensively tested thus increasing their validity. Finally, the availability of several covariates for adjustment was another strength of the study.

To conclude, the present study findings support findings from previous studies and effectively adds to the scant literature on the combined influence of GWG and race/ethnicity on DOL. Both race and GWG are associated with DOL and understanding these factors is essential for informing public health policy and actions. It is critical to identify populations at increased risk of DOL and to provide targeted breastfeeding support, especially in early postpartum period. Further research should be conducted in a more diverse and representative population.

Footnotes

Acknowledgment

The authors thank the Centers for Disease Control and Prevention for providing access to data from the Infant Feeding Practices Study II.

Disclosure Statement

No competing financial interests exist.

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