Factors associated with small head circumference at birth among infants born before the 28th week

Abstract

Objective: We sought to identify risk factors for congenital microcephaly in extremely low gestational age newborns.

Study design: Demographic, clinical, and placental characteristics of 1445 infants born before the 28th week were gathered and evaluated for their relationship with congenital microcephaly.

Results: Almost 10% of newborns (n = 138), rather than the expected 2.2%, had microcephaly defined as a head circumference >2 SD below the median. In multivariable models, microcephaly was associated with nonwhite race, severe intrauterine growth restriction, delivery for preeclampsia, placental infarction, and being female. The risk factors for a head circumference between <1 and >2 SD below the median were similar to those of microcephaly.

Conclusion: Characteristics associated with fetal growth restriction and preeclampsia are among the strongest correlates of microcephaly among children born at extremely low gestational ages. The elevated risk of a small head among nonwhites and females might reflect the lack of appropriate head circumference standards.

Figure. Observed and expected distributions of birth head circumference Z-scores

Vertical bars represent narrow groupings of head circumference Z-scores in extremely low gestational age newborns study sample. Expected normal distribution of Z-scores (red line; mean = 0, SD = 1) is overlaid. McElrath. Factors associated with small head circumference at birth among ELGAN. Am J Obstet Gynecol 2010.