Consanguinity and fetal growth in Pakistani Moslems.

There is conflicting evidence about the effect of parental consanguinity on fetal growth. Previous studies have not always allowed for other factors that are known to affect birth weight, in particular, gestational age, parity, and maternal height. We have therefore studied this question in the Pakistani Moslem population in Birmingham. Babies born to parents who were first cousins were on average 80 g lighter than those born to unrelated parents, but this difference was not significant for the size of the sample studied. Nor were there any differences in the other measurements of the babies. After expressing birth weight in terms of centiles for gestational age, sex, parity, and maternal height, however, while there was no difference in the overall distribution of centiles, there were more poorly grown babies--that is, weight below the 10th centile--in the first cousin group. We conclude that parental consanguinity is associated with an increase in the number of poorly grown babies but that the overall effect on mean birth weight is small.