Breastfeeding and timing of pubertal onset in girls: a multiethnic population-based prospective cohort study

Abstract

Background Early puberty is associated with higher risk of adverse health and behavioral outcomes throughout adolescence and adulthood. US girls are experiencing earlier puberty with substantial racial/ethnic differences. We examined the association between breastfeeding and pubertal timing to identify modifiable risk factors of early puberty and potential sources of racial/ethnic differences in the timing of pubertal development. Methods A prospective cohort study of 3331 racially/ethnically diverse girls born at Kaiser Permanente Northern California (KPNC) between 2004 and 06. All data were obtained from KPNC electronic clinical and administrative datasets. Mother-reported duration of breastfeeding was obtained from questionnaires administered at each ‘well-baby’ check-up exam throughout the baby’s first year and categorized as ‘Not breastfed’, ‘Breastfed < 6 months’, and ‘Breastfed ≥ 6 months’. Pubertal development data used Tanner stages assessed by pediatricians during routine pediatric checkups starting at age 6. Pubertal onset was defined as transition from Tanner Stage 1 to Tanner Stage 2+ for breast (thelarche) and pubic hair (pubarche). Weibull regression models accommodating for left, right, and interval censoring were used in all analyses. Models were adjusted for maternal age, education, race/ethnicity, parity and prepubertal body mass index (BMI). We also examined race/ethnicity as a potential effect modifier of these associations. Results Not breastfeeding was associated with earlier onset of breast and pubic hair development compared to breastfeeding ≥6 months (adjusted hazard ratio [HR]: 1.25; 95% confidence interval [CI]: 1.07–1.46; HR: 1.24; 95% CI: 1.05–1.46, respectively). Breastfeeding for < 6 months was also associated with the risk of earlier pubic hair development (HR: 1.14; 95% CI: 1.00–1.30, compared to breastfeeding ≥6 months). Inclusion of girls’ prepubertal BMI slightly attenuated the association between breastfeeding and timing of breast onset but remained significant. The association between not breastfeeding and early breast development may be stronger among African American girls (HR: 1.92; 95% CI: 1.01–3.66, no breastfeeding vs. ≥6 months) than other racial/ethnic groups. Conclusions Breastfeeding is an independent predictor of pubertal onset in girls, and the strength of the association may vary by race/ethnicity. Providing breastfeeding support and lactation education for high risk mothers may help prevent earlier pubertal onset and promote positive health outcomes later in life.

Association of Soy and Exclusive Breastfeeding With Central Precocious Puberty: A Case-Control Study

“…Our study also found breastfeeding as a possible protective factor for the onset of precocious puberty, agreeing with many others (10,11,36). This may occur due to breastfeeding also being a protective factor for obesity, and obesity itself could interfere with the onset and development of precocious puberty (37,38), which was also reaffirmed by our study.…”

“…Moreover, Kale et al (11) found that mixed-fed or predominantly breastfed girls showed later onset of breast development compared to formula fed girls, also, the duration of breastfeeding was directly associated with age at onset of breast development. Aghaee et al (36) in a study with 3,331 girls, found that those not breastfed were more likely to experience earlier thelarche and pubarche compared with girls who were breastfed ≥6 months. Similarly, a prospective observational study with boys and girls found an independent preventive association of breastfeeding for ≥6 months and early pubertal development, reinforcing our findings (10).…”

Prenatal anxiety, breastfeeding and child growth and puberty: linking evolutionary models with human cohort studies

“…Finally, we examined the link between breastfeeding outcome and age at puberty onset in girls and boys. We found that, when considering breastfeeding alone, girls who were breastfed for at least six months experienced menarche at a slightly later age, as has been shown in other cohorts (Aghaee et al 2019). This effect attenuated, however, when body mass index at 10 years was included in the model.…”

The Role of Fetal, Infant, and Childhood Nutrition in the Timing of Sexual Maturation

“…Despite these findings, breastfeeding has recently been referred to as a critical independent factor in postponing sexual maturation in girls at higher risk of early puberty onset [ 89 ]. Authors observed an association between breastfeeding and thelarche at later age in 3331 mother–daughter pairs, after adjusting for maternal age at delivery, education level, and ethnicity, revealing that girls who were not breastfed were more likely to experience earlier thelarche than girls who were breastfed for six months [ 89 ]. In another study on 219 Korean children [ 10 ], authors found that subjects who were breastfed for over six months had lower odds of Tanner stage attainment ≥2 at nine years, compared with those who stopped breastfeeding before six months.…”