Preterm birth linked to increased risk of premature death in mothers

By Nicole MacKee
Pregnancy is often the ‘canary in the coalmine’ for a woman’s health, says a leading Australian expert after researchers reported in The BMJ that preterm birth was linked to an increased risk of premature death in mothers more than 40 years after delivery.

The cohort study included more than two million women with singleton deliveries in Sweden. The researchers found that, compared with women who had a full­term delivery (39 to 41 weeks), those with a preterm delivery (of less than 37 weeks) had an adjusted hazard ratio (aHR) of 1.73 for all­-cause mortality in the 10 years after birth. After an extremely preterm delivery (22 to 27 weeks), the risk was even greater (aHR, 2.20).

The researchers reported that the risk declined over time but remained significantly raised over more than 40 years of follow up (20 to 44 years after preterm delivery, aHR, 1.37).

Shared genetic or environmental factors were ruled out as contributing to the increased risk.

Professor John Newnham, Head of the University of Western Australia’s Division of Obstetrics and Gynaecology, Perth, and Chair of the Australian Preterm Births Prevention Alliance, said the findings confirmed the long­suspected link between preterm birth and increased maternal mortality.

‘The fascinating thing is that the association is present up to 39 weeks’ gestation,’ he said. ‘If a woman delivers before 39 weeks, she is at 20% increased risk of death in the 10 years thereafter [delivery at 37 to 28 weeks, aHR, 1.19].’

Professor Newnham said pregnancy was the ‘canary in the coalmine’ for a woman’s health.

‘The fetus often [gives us information about] the woman’s health that we can’t see by looking at the woman,’ he said.

‘The most obvious one is an overgrown baby; that tells us the woman is most likely to have diabetes. The next big one is a baby that has fetal growth restriction that can often be a sign of vascular disorder in the mother. That fits entirely here with the fact that growth­-restricted babies were associated with increased mortality from cardiovascular disease subsequently in the mother.’

Professor Newnham said the study highlighted the importance of inquiring about a woman’s pregnancies when taking a history.

‘Obstetric history is an important part of a woman’s history, particularly in relation to the cardiovascular system and risk of diabetes,’ he said.

Professor Newnham said the findings were also further reason to act to reduce Australia’s premature birth rate, which was currently around 8 to 9%.

‘We don’t have any evidence that preventing preterm birth will save the woman’s life as well, but it’s a possibility.’

Professor Newnham said the Western Australian­-developed ‘The Whole Nine Months Program’ had helped to reduce preterm births across the state by 8% and in the state’s major perinatal hospital by 20%. The program was now being adapted nationally.
BMJ 2020; 370: m2533; http://dx.doi.org/10.1136/bmj.m2533.