Twins healthier at birth if they shared womb with a sister

Twins who have shared the womb with a sister are healthier at birth than those who shared with a brother. Newborn twins with a sister are less likely to be pre-term, have a low birth weight, and have fewer respiratory problems, a new study suggests. However, the researchers are warning women expecting male or mixed-sex twins not to panic, since they see these higher risks of birth problems as demonstrative of a male 'disadvantage' rather than a female 'protective factor'. Previous research has already shown that boys are more likely than girls to be born prematurely, need a caesarean or have health problems at delivery. Experts have suggested that in addition to the negative effect of certain hormones, there is a possibility that males compete better for nutrients because females grow more slowly in the womb. BioNews