Paternal influences on birthweight.

OBJECTIVE: To assess the influence of paternal size on birthweight after suitable control for maternal and fetal factors.

DESIGN: Prospective observational study.

SETTING: Delivery suite, City Hospital, Nottingham.

SUBJECTS: 571 husbands/partners of unselected women delivering August 1992 to February 1993.

MAIN OUTCOME METHODS: Individualised birthweight ratio and thereby an adjusted birthweight for a typical mother. The results of a multiple regression analysis with the individualised birthweight ratio as the dependent variable.

RESULTS: When considered in isolation both paternal height and weight are significantly positively associated with crude and adjusted birthweight (p < 0.01, analysis of variance). Due to correlations of paternal size with maternal size and smoking habit, only paternal height is significant in the multiple regression analysis (p = 0.01).

CONCLUSION: If the partner of an average woman is short (mean-2s.d.) then the baby will be 183 g lighter than if he is tall (mean + 2s.d.). This effect of paternal height on birthweight must be genetic and therefore should be taken into account when defining intra-uterine growth retardation and macrosomia.