high birthweight in an ethnic group of low socioeconomic status analysis of 14 219 births in west jerusalem showed that infants of north african origin had a higher birthweight than infants of other ethnic groups the group of mothers of north african origin included a relatively high proportion from the lowest social classes the observed excess birthweight was apparent after allowing for the effects of gestation maternal body size babys sex parity and smoking maternal age and season of birth also had a significant effect on birthweight birthweight was higher if the mother had immigrated to israel after the age of 10 years than if she had immigrated at a younger age or had been born in israel