Pregnancy 'less risky' in relationship

KEEPING WELL: Pre-eclampsia affects about 3000 New Zealand women and their babies every year - varying between 3 percent and 7 percent of pregnancies.

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Women in longterm relationships apparently have healthier pregnancies - possibly because of longterm exposure to the sperm of the baby's father, an Auckland survey has found.

Being in a long-term relationship before becoming pregnant gave the woman's body time to build up immunity to "foreign" proteins in her partner's sperm, according to Auckland University researchers.

If she became pregnant early in the relationship, she lacked this protection.

The survey also found women having single, long-term partners were less prone to developing pre-eclampsia - raised blood pressure that can be life threatening and cause serious harm to both mother and baby.

Pre-eclampsia affects about 3000 New Zealand women and their babies every year - varying between 3 percent and 7 percent of pregnancies.

It can also involve water retention that causes swelling in the feet, legs, and hands, and protein in the urine, a sign of possible kidney damage.

The only successful treatment for pre-eclampsia is delivery of the baby - often prematurely.

The researchers, led by Associate Professor Lesley McCowan, asked 2507 first-time pregnant women how long they had been with the baby's father.

The results of the study, published in the Journal of Reproductive Immunology, were adjusted for the lifestyle and background of the women including their weight, whether they smoked and their general health.

When the pregnancies came to term, pre-eclampsia was found to be less common in women who had long-term sexual relations only with the biological father, than in those who had been with their partner for a short time.

The quicker they became pregnant, the higher the odds of the condition, and its dangers of high blood pressure and organ damage.

Worst off were children conceived the first time a couple slept together.

They were eight times more likely to suffer problems in the womb leaving them underweight at birth, the study found.

Women who had undersized babies were also more likely to have been in shorter relationships.

Mothers who did not know the identity of the father were excluded from the analysis.

The results are thought to mesh with data showing that pre-eclampsia is more common in young mothers, first-time mothers and those who are having their first baby with a new partner.

An earlier study of the role of sperm in the development of pre-eclampsia, published in the American Journal of Obstetrics and Gynaecology, found a higher risk for women who had been living with the baby's father for less the four months and using barrier methods for contraception.

Several other studies have found a lower incidence of pre-eclampsia in women who had received blood transfusions from their partner, those with long, preceding histories of sex without barrier contraceptives, and in women who had been regularly performing oral sex.

The female immune system was boosted by exposure to "paternal antigens", beneficial antibodies in the male sperm, said Larry Chamley, an Associate Professor of Obstetrics and Gynaecology at Auckland University, who was not involved in the study.

"The issue of whether prolonged semen exposure does protect against developing pre-eclampsia is not yet resolved, this paper seems to tip the weight of evidence back in favour of suggesting that prolonged semen exposure is protective," he said.

Prof Chamley - who made his comment on the Faculty of 1000 experts website - is a member of another study which two years ago was given taxpayer funding of $779,000 over three years to probe whether dead cells from the placenta of a pregnant woman can trigger pre-eclampsia.