Objective: To evaluate the association between breastfeeding duration and educational outcomes at the end of secondary education among children from the Millennium Cohort Study.
Design: Cohort study comparing school results at age 16 according to breastfeeding duration.
Setting: England.
Participants: Children born in 2000–2002 (nationally representative sample).
Exposure: Self-reported breastfeeding duration (categorised).
Main outcome measures: Standardised school assessments taken at the end of secondary education (General Certificate of Secondary Education (GCSEs), marked 9–1) in English and Mathematics, categorised as: ‘fail, marks <4’, ‘low pass, marks 4–6’ and ‘high pass, marks ≥7 (equivalent to A–A*)’. Additionally, overall achievement was measured using the ‘attainment 8’ score (adding the marks of eight GCSEs, English and Mathematics double weighted; 0–90).
Results: Approximately 5000 children were included. Longer breastfeeding was associated with better educational outcomes. For example, after full adjustment for socioeconomic markers and maternal cognitive ability, in comparison with children who were never breastfed, those who were breastfed for longer were more likely to have a high pass in their English and Mathematics GCSEs, and less likely to fail the English GCSE (but not the Mathematics GCSE). Additionally, compared with those never breastfed, those breastfed for at least 4 months had, on average, a 2–3 point higher attainment 8 score (coefficients: 2.10, 95% CI 0.06 to 4.14 at 4–6 months; 2.56, 95% CI 0.65 to 4.47 at 6–12 months and 3.09, 95% CI 0.84 to 5.35 at ≥12 months).
Conclusions: A longer breastfeeding duration was associated with modest improvements in educational outcomes at age 16, after controlling for important confounders
