Dear Editor, it is with great interest that we read the paper by Whitehouse et colleagues (1) on positive associations between small head circumference at birth and specific language impairment (SLI). They point out that their findings are consistent with the notion that atypical brain development in SLI may commence prenatally. This is a case-control study. Matching criteria for SLI cases were maternal race, sex, gestational age, maternal age at conception and maternal smoking and alcohol intake during pregnancy, and non-verbal ability. We regret that a feature that might have been influential, i.e. breastfeeding, was not included among matching criteria. Previous studies have concluded that breastfeeding may be protective against language development delay (2) and recent studies show that the biological pathway between hormone levels in pregnancy, head circumference at birth, and breastfeeding success is evident (3,4). In 2010, Whitehouse described that elevated levels of androgens restrict foetal cranial growth and Carlsen described that breastfeeding success is negatively associated with maternal androgen levels in pregnancy. Other researchers have identified that in utero exposure to glucocorticoids reduces both head circumference at birth (5) and the volume of milk production on days 1 to 10 postpartum. The mechanisms explaining the relationship between head circumference at birth and language development are not completely understood and further research ought to take into account breastfeeding to distinguish postnatal from prenatal biological influences on it.

REFERENCES

1. Whitehouse AJ, Zubrick SR, Blair E, Newnham JP, Hickey M. Fetal head circumference growth in children with specific language impairment. Arch Dis Child 2012;97:49-51.

2. Dee DL, Li R, Lee LC, Grummer-Strawn LM. Associations between breastfeeding practices and young children's language and motor skill development. Pediatrics 2007;119 Suppl 1:S92-8.

3. Whitehouse AJ, Maybery MT, Hart R, Sloboda DM, Stanley FJ, Newnham JP, Hickey M. Free testosterone levels in umbilical-cord blood predict infant head circumference in females. Dev Med Child Neurol 2010;52:e73-7.

4. Carlsen SM, Jacobsen G, Vanky E. 2010. Mid-pregnancy androgen levels are negatively associated with breastfeeding. Acta Obstet Gynecol Scand 2010; 89:87-94.

5. Ali Khan A, Rodriguez A, Kaakinen M, Pouta A, Hartikainen A-L, Jarvelin M-R. Does in utero exposure to synthetic glucocorticoids influence birthweight, head circumference and birth length? A systematic review of current evidence in humans. Paed Perinat Epidemiol 2011;25: 20- 36.

Conflict of Interest:

None declared