A single long-term partner seems to ensure healthier babies for women, says a new study.
In other words, prolonged exposure to the father's semen protects new mothers against pre-eclampsia (pregnancy induced hypertension) and having an undersized baby.
In this study conducted by the University of Auckland (U-A), 2,507 first-time pregnant women were interviewed about the length of their relationship with the baby's biological father.
When the pregnancies came to term (37 weeks), pre-eclampsia was found to be less prevalent among women who had long-term sexual relations exclusively with the biological father, than in those who had been with their partner only for a short time (less than six months).
The study also revealed that women who had undersized babies were also more likely to have been in shorter relationships, but only when an ultrasound during the 20th week showed reduced blood flow to the foetus.
"Whether prolonged semen exposure does protect against developing pre-eclampsia is not yet resolved," says researcher Larry Chamley, "this paper seems to tip the weight of evidence back in favour of suggesting that prolonged semen exposure is protective."