Breastfeeding Medicine

Combined hormonal contraception (CHC) is habitually not prescribed to breastfeeding women due to concerns of decreased milk production. This habit is based on inconclusive studies that examined lactation suppression of CHC with high-dose Ethinylestradiol (EE ≥ 30 µg/day). Notably, the effect of oral CHC with current low-dose EE (20 µg/day EE), and of vaginal rings (15 µg/day EE), has not yet been studied. Here, we examine their effect on breastmilk production.

This study included 172 breastfeeding women, and evaluated self-reported breastmilk production, with and without hormonal contraception. Breastfeeding women using CHC with low-dose EE, either orally (N = 20), or vaginally (N = 32), were asked to complete a questionnaire, at two time-points: (1) Before starting CHC, and (2) some 7–10 days after. The questionnaire recorded 12 variables linked with breastfeeding. As a control group, breastfeeding women using progestin-only pills (POP, N = 54) with Desogestrel 75 µg/day, were used. As another control group, breastfeeding women using no hormonal contraception (N = 66) were also asked to complete the same questionnaire.

Vaginal rings, but not oral CHC pills, containing low-dose EE, are associated with a reduction of self-reported expressed breastmilk volume by 20%. Likewise, vaginal rings, but not oral pills, are correlated with impairment of 5 out of 12 breastfeeding variables, namely: (1) breastfeeding interval, (2) self-expressed milk volume, (3) use of milk substitutes, (4) number of night-feedings, and (5) full diapers.

Vaginal rings with low-dose EE (15 µg/day) are associated with a modest, yet significant, decrease in self-expressed breastmilk volume. In contrast, oral CHC pills with low-dose EE (20 µg/day) are not associated with a significant impact on breastmilk production. These findings may have clinical implications for prescribers and patients.

Breastfeeding shows persistent disparities shaped by complex maternal, infant, and household factors, making prediction challenging. As traditional models struggle to capture such complexity, this study aims to identify predictors of ever breastfeeding and longer breastfeeding duration using multiple machine learning models and to assess the potential of these methods in breastfeeding prediction.

Using nationally representative data from the U.K. Household Longitudinal Study, we apply Lasso (Least Absolute Shrinkage and Selection Operator) logistic regression, decision tree, random forest, XGBoost, support vector machine, and neural network models to examine factors associated with whether infants were ever breastfed and whether breastfeeding stopped at or after 3 months.

Maternal, household, and birth-related factors all relate to breastfeeding, but maternal socioeconomic factors, especially education and ethnicity, emerge as the strongest predictors. Across the two breastfeeding outcomes, model performance is better for whether infants were ever breastfed than for breastfeeding duration, which is more difficult to predict. Within each outcome, the models show similar performance without substantial differences.

Breastfeeding outcomes can be reasonably predicted, and the predictive signal is driven primarily by maternal socioeconomic characteristics, enabling targeted support at relatively low informational cost. However, prediction remains limited, especially for breastfeeding duration, suggesting that while key influences are captured, more nuanced or situational mechanisms remain difficult to anticipate. Lasso logistic regression, with its low complexity and transparent structure, performs comparably to more complex models and may therefore be a more appropriate methodological choice for breastfeeding prediction.

To examine hospital breastfeeding initiation trends and their association with COVID-19 pandemic and the infant formula shortage.

Using a multivariable logistic regression model, we examined associations between breastfeeding initiation and exposure to the COVID-19 pandemic and infant formula shortage, and the modifying roles of race/ethnicity, residence, and WIC participation in 1,060,057 individuals aged 15–49 years with institutional childbirths in Florida between January 1, 2018, and December 31, 2022.

Overall, 922,922 (87.06%) initiated breastfeeding before hospital discharge. Initiation declined as COVID-19 progressed, but started increasing as the formula shortage hit and continued. The rates show a declining trend once the shortage was addressed. Compared with non-Hispanic White, the odds of breastfeeding initiation were higher for all groups except for non-Hispanic Black, and for urban than rural mothers. The odds increased with formula shortage onset for WIC beneficiaries across race/ethnicities and among urban WIC beneficiaries compared with nonbeneficiaries.

The combined pressures of COVID-19 pandemic and formula scarcity increased breastfeeding initiation rates, especially in WIC beneficiaries. However, breastfeeding initiation rates returned to prepandemic levels as the formula shortage resolved.