Ethnicity factor in length of pregnancy

A FINDING that says the length of a healthy pregnancy differs for different ethnicities could overhaul the definition of a “term birth”, providing safer, race-based obstetric care.

Results from the study of almost 700,000 Australian births over 11 years show that mothers born in South Asia, the Middle East, Africa and Europe have a greater stillbirth risk than Australian or New Zealand-born women but Southeast Asian-born women have less risk.

It also showed the risk starts to increase earlier, rising at 37 weeks rather than the recognised standard of 41 weeks, suggesting the placenta “ages” differently for different races.

A South Asian-born woman had 1.5 times the risk of an Australian-born mum, putting her in the same high-risk category as women who smoke, have pre-eclampsia or are obese.

Now researchers from the Hudson Institute of Medical Research and Monash University are looking to uncover why women born in Southeast Asia generally have both a shorter pregnancy and are 40 per cent less likely to have a stillbirth compared to Australian-born mothers.

Lead author, Ritchie Centre research fellow Dr Miranda Davies-Tuck, said previous studies linked stillbirth risk to migration or social disadvantage.

“We’ve found it looks like there might be differences in the gestation length and how the placenta functions, particularly towards the end of pregnancy,” she said.

“Normal clinical guidelines say that, at 41 weeks’ gestation, all women should be scanned to check their baby and the placenta, and if they are struggling be offered an induction.

“We know that as the pregnancy progresses the placenta is less able to provide for the baby. The risk of stillbirth in Australian-born women at 41 weeks actually commences at 39 weeks for South Asian women. By the time we’re monitoring them at 41 weeks, it might be too late.”