Smart moms make smart babies

In a big longitudal study Kramer and colleagues in the PROBIT research group studied the effects of an increase in exclusive breastfeeding on academic performance in 6.5 year olds. 17,000 children born in 31 hospitals were included The hospitals were randomly assigned to work according to BFHI guidelines in order to increase breastfeeding initiation, exclusivity and duration, or traditional operating hospitals. The BFHI designated hospitals did show an increase in breastfeeding statistics at age 3 months. IQ testing at age 6,5 showed an increase of 8 IQ points for boys and 7 for girls as compared to children born in the traditional working hospitals. Research regarding breastfeeding and subsequent intelligence scores are often thought to be flawed because it is thought that IQ is inherited (smarter parents make smarter kids) and that smarter moms are more prone to choose to breastfeed. Iacovou & Sevilla-Sanz escaped this trap by using the twinning technique in very large (12,000 children) study. Twinning means that children who are the same in all kinds of aspects (parent characteristics, demography, health etc) but the fact one is breastfed and the other not are compared. They found a small but very significant positive difference for breastfed children (as short as 4 weeks) in the score on in IQ test at age 14 and a tendency that the effects grow as time goes on.
Kramer MS, Aboud F, Mironova E, Vanilovich I, Platt RW, Matush L, Igumnov S, Fombonne E, Bogdanovich N, Ducruet T, Collet JP, Chalmers B, Hodnett E, Davidovsky S, Skugarevsky O, Trofimovich O, Kozlova L, Shapiro S; Promotion of Breastfeeding Intervention Trial (PROBIT) Study Group: Breastfeeding and child cognitive development: new evidence from a large randomized trial. Arch Gen Psychiatry. 2008 May;65(5):578-84.
Iacovou M, Sevilla-Sanz A: The Effect of Breastfeeding on Children’s Cognitive Development. ISER Working Paper Series, 2010-40