Effects of maternal use of hormonal contraception during breastfeeding: Results from a British birth cohort

Objective: The impact of early hormonal contraception (HC) exposure during breastfeeding on child growth and pubertal and behavioural development was assessed using data from the Avon Longitudinal Study of Parents and Children (Avon study).

Study design: The Avon study is a prospective cohort study designed to identify environmental factors affecting child health and development (n = 14,541; delivery dates: 1 April 1991-31 December 1992). This secondary analysis was restricted to breastfed singleton infants. The main independent predictor variable was HC exposure during the first 8 weeks postpartum. Growth variables were changes from baseline in weight and height at ages 2 and 4 years. Behavioural variables were assessed at age 47 months. Pubertal development was evaluated between ages 8- and 16-years using Tanner scales.

Results: 9508 children were breastfed during the first 4 weeks postpartum; 8927 had complete data for breastfeeding and HC exposure. Multivariate analyses demonstrated no difference in growth outcome variables between breastfed infants exposed to HC and those who were not. Similarly, no differences in behavioural problems or pubertal development were observed between the two groups.

Conclusions: Early HC exposure during breastfeeding did not appear to influence negatively child growth and development. Limitations include short-term exposure to HC, the discrepancy between the timepoints when HC intake and breastfeeding were measured and the missing data, particularly regarding growth measurements Further clinical studies are required to confirm this lack of negative impact.

Implications statement: Guidance on the use of HC during breastfeeding remains controversial; however, the Avon study did not detect any signal to suggest that early exposure to HC via breastfeeding has a negative impact on child growth, development or behaviour.