Pregnant women are less likely to suffer pre eclampsia very high blood pressure if the father of the child is also a regular lover.
Frequent exposure to the same semen may alter a woman's immune system, and so protect her against high blood pressure or hypertension, a common problem usually occurring during the sixth month of pregnancy and with first time mothers.
This extraordinary discovery, made by researchers in Guadeloupe, West Indies, suggests that hypertension during pregnancy may be a result of first time fatherhood with a particular woman, and not first time motherhood per se.
Women who had the same partner for longer than one year all reported the lowest incidents of hypertension, whether it was their first child or not.
They averaged 5 per cent of cases, against an average of 40 per cent of cases of hypertension among women with a partner of less than four months.
Those with a partner of between five and eight months averaged 23 per cent of cases, and those whose relationships were between nine months to a year averaged 15 per cent.
However, these advantages are lost if the man wears a condom, even if he has been a long term lover, apparently ruling out the possibility that protection from hypertension has to do with any psychological factors, such as the woman feeling more secure.
The findings of the study, led by Dr Pierre-Yves Robillard of the Point a Petre University Hospital, were based on conversations with 1011 women who gave birth consecutively.