Study finds more chance of stillbirth after caesareans

Women who have their first baby by caesarean section increase the risk of losing their next baby to an unexplained stillbirth before labour, a new study says.

One expert who was not associated with the study, published in the Lancet medical journal, said hospitals which tended to do a lot of caesareans might need to consider strategies for reducing them.

A New Zealand health report published in April found 22 per cent of hospital births in 2001 were caesareans, compared with 20.8 per cent in 2000 and 20.4 per cent in 1999.

The Cambridge University study looked at 120,633 second births of single babies in Scotland. It found that among 17,754 women who had delivered their first child by caesarean section, there were 68 stillbirths before labour - or 239 per 10,000 women per week.

Among 102,879 who had delivered their first child vaginally, there were 244 stillbirths before labour, the equivalent of 144 per 10,000 women per week.

The researchers found that the risk of unexplained stillbirth associated with previous caesarean delivery differed markedly with the age of the foetus: the most dangerous time was at 34 weeks.

The risk was not reduced by factors like the mother's age or the outcome of her first pregnancy, the researchers found.

"The absolute risk of unexplained stillbirth at or after 39 weeks' gestation was 1.1 per 1000 women who had had a previous caesarean section and 0.5 per 1000 in those who had not," the study said.

The researchers concluded that "delivery by caesarean section in the first pregnancy could increase the risk of unexplained stillbirth in the second".

Previous studies have indicated that women who have had a caesarean and who later attempt to deliver by labour are more likely to suffer a uterine rupture - a splitting open of the womb that is life-threatening for both mother and infant - than women who go on to have a repeat caesarean delivery.

The researchers said that in women with one previous caesarean delivery, the risk of unexplained stillbirth before labour at or after 39 weeks' gestation "is about double the risk" of stillbirth or neonatal death from uterine rupture during labour.

The risk of uterine rupture during childbirth is estimated at around 0.45 per 1000 births; the risk of unexplained stillbirth at around 39 weeks among women with one previous caesarean is 1.06 per 1000, they said.

Judith M. Lumley, of the Centre for the Study of Mothers' and Children's Health in Victoria, said the study "could redefine the nature of the debate caesarean delivery in maternity care".

Writing separately in the Lancet, Lumley said it was already known that previous caesarean delivery was associated with an increase in problems such as placenta praevia, where the mother's placenta becomes detached too early, and ectopic pregnancy, where a foetus implants outside the womb.

But "an association of previous caesarean section with an increase in foetal death at and after 34 weeks' gestation" was not known.

She said one implication of the study "might be that maternity hospitals where caesarean first births are more common than in other local settings need to think more seriously about strategies for reducing the number of caesarean sections".

- NZPA, STAFF REPORTER