Significant paternal contribution to the risk of small for gestational age.

The aim of this study is to investigate both maternal and paternal contributions in the familial aggregation of small for gestational age. Nested case-control study. Metropolitan area of Haguenau, France. Data were drawn from a French population-based maternity registry. After selection, 256 cases born either small for gestational age or average for gestational age were included. Controlling for known pregnancy-related risk factors, logistic regression models were used to determine the risk of the child being small for gestational age, given that the mother, father or both were small for gestational age, and to examine interactions between maternal small for gestational age and pregnancy risk factors. Specifically, we investigate to what extent having either or both parents born small for gestational age increases the risk of small for gestational age in their offspring, after controlling for the established risk factors of small for gestational age and maternal and paternal characteristics. We also explore the extent to which the intergenerational predictors of small for gestational age may modify the effect of current pregnancy-related risk factors. The risk of a small for gestational age offspring was 4.7 times greater for mothers and 3.5 times greater for fathers who were small for gestational age, compared with average for gestational age counterparts. Furthermore, the risk of a small for gestational age offspring was 16.3 times greater when both parents were small for gestational age. No significant interactions between maternal small for gestational age and maternal smoking, hypertension or parity were observed. These results indicate that small for gestational age in both mother and father significantly influences the risk of their offspring being small for gestational age. While previous research has indicated that the birth outcome of the mother is an important determinant of the birth outcome of her offspring, these data indicate that the birth outcome of the father plays an equally critical role in determining fetal growth, strongly suggesting a genetic component in the familial aggregation of small for gestational age.