Higher prepregnancy BMI may be associated with shorter duration of breastfeeding

By Dr. Liji Thomas, MDReviewed by Lily Ramsey, LLMMay 19 2023

Earlier research suggests that women with a higher body mass index (BMI) feed their infants for shorter durations. The underlying reasons for this observation remain unclear.

A recent study published in The American Journal of Clinical Nutrition attempted to explore this relationship and elicit some mediating factors.

​​​​​​​Study: Mediators of the association between maternal body mass index and breastfeeding duration in 3 international cohorts. Image Credit: Pixel-Shot/Shutterstock.com

Introduction

Breastfeeding is an optimal nutritional and emotional interaction between the mother and infant, promoting overall health, bonding, growth, immunity, and neurodevelopment, among other gains. Current recommendations to practice exclusive breastfeeding for six months or more, and to continue breastfeeding for up to two years, are based on this recognition.

Nonetheless, breastfeeding is becoming less common in many developed countries. Studies indicate that lactation is less likely to continue for the optimal duration among women who are overweight or obese.

Unfortunately, almost two-thirds of women in their reproductive years fall into these categories and are at higher risk for suboptimal breastfeeding.

Animal studies have shown a reduced development of the lactational apparatus, including the mammary gland, with obesity and shortening of lactation. Obese animals also showed evidence of inflammation in the mammary glands, with increased shrinkage and autophagy within this tissue.

The current study included over 5,000 singleton pregnancies from multiple cohorts in Spain, Greece, and the USA.

The researchers wanted to observe specific associations between factors such as birth weight (BW), the C-reactive protein (CRP) level in pregnancy, mode of delivery (especially Caesarean delivery, C-section), intake of inflammatory foods via the dietary inflammatory index (DII), gestational age at delivery, and gestational diabetes mellitus (GDM).

Inflammation is potentially associated with shorter breastfeeding. Similarly, a higher DII is a predictor of this outcome. Since obese women are more likely to develop GDM, and since the latter itself predicts shorter breastfeeding duration, these were also included in the study parameters.

A higher maternal BMI also predicts an increased risk for a higher fetal BW and C-section risk and affects the gestational age at which delivery occurs.

The researchers also included three cohorts from different countries in this pooled study to help overcome culture- and society-specific risk factors that could confound the associations between obesity, diet, and breastfeeding practices.

What did the study show?

In this pooled study, over a tenth of the mothers were obese, while a fifth were overweight. Overall, almost a third had high BMIs.

Increased BMI was associated with higher CRP levels and a higher incidence of GDM and C-sections. DII was also found to be linked to overweight and obesity, but also with underweight.

The findings confirmed shorter periods of breastfeeding associated with both overweight and obesity, compared to mothers with normal prenatal BMI. The trend remained the same for both exclusive and breastfeeding.

There was a dose-dependent reduction in breastfeeding duration in both cases. With exclusive breastfeeding, the time is reduced by 1.5 days (0.05 months) for each unit of increase in the BMI and by 3.6 days (0.12 months) per unit increase in BMI for any breastfeeding.

For any breastfeeding, the duration was reduced by four weeks among overweight and almost eight weeks among obese mothers. With exclusive breastfeeding, the reduction was nine days (0.30 months) and three weeks (0.7 months), respectively.

This decrease in breastfeeding duration in mothers with a higher BMI appeared to be partly due to higher levels of inflammation. For instance, 5% of the effect of BMI on exclusive breastfeeding was mediated by the higher mean CRP levels, an indicator of systemic inflammation.

Again, among overweight/obese women, 7-8% of the reduction in any breastfeeding was due to the increase in DII. Similarly, 6-8% of the decrease in duration of any and exclusive breastfeeding among women with high BMI was mediated by delivery via C-section.

However, the presence of gestational diabetes mellitus (GDM), GDM, BW, and gestational age did not appear to be related causally to the observed reduction in breastfeeding duration with increased BMI. 

What are the implications?

While obesity is often multifactorial, and pregnancy is often a difficult time for dietary alterations aimed at weight reduction, it can also be a turning point for women who desire to promote the health of their babies.

These data support the need for obstetricians, nutritionists, and lactation support to provide integrated prenatal counseling for women who enter pregnancy with overweight or obesity.”

Again, these studies may provide additional evidence to support recommendations that reduce the proportion of C-sections.

Identifying modifiable factors mediating a decrease in the total duration of any and exclusive breastfeeding among mothers with increased BMI is a key gain from this study.

Alterations in the diet to reduce dietary inflammation, attention to measures to reduce systemic inflammation, and recognizing the role of the mode of delivery in the observed association with reduced lactation duration are potentially valuable interventions to avoid such adverse outcomes.

Because increasing numbers of women entering pregnancy have overweight/obesity, this finding has significant health implications for future generations.”