A simple blood test may detect risk of preterm delivery in expectant mothers

Researchers from Mount Sinai Hospital and the University of Toronto showed that low levels of placental growth factor (PlGF) -- a protein that signals placental development -- are associated with preterm birth. Preterm birth is defined as a birth before 34 weeks' gestation.

Their findings, published in JAMA Network Open, also suggests that a simple blood test to detect the level in expectant mothers could alert physicians to a need for enhanced monitoring and delivery planning. PIGF is a protein released by the placenta into maternal blood.

It acts to promote relaxation of the maternal blood vessels and helps normalise the blood pressure of pregnant women despite the large increase in blood volume and cardiac output needed to support the growth of the baby. It also protects the mother from blood loss at delivery.

The team showed that low levels of PlGF contribute to the development of a potentially dangerous type of hypertension called preeclampsia. The condition ultimately necessitates physician-initiated early delivery in two-thirds of patients with low PlGF levels.

A second complication, foetal growth restriction -- accounts for the majority of other medically indicated preterm births.

“If you know in advance that you're high risk, there are ways to improve pregnancy outcomes. "It starts with self-monitoring for elevated blood pressure and perhaps taking anti-hypertensive medications to keep it under control," said Rachel Gladstone, from Sinai Health.

"And if you originally had plans to deliver at a community hospital or remote location, you could decide to receive care at a tertiary centre, which may be safer for both mother and baby than emergency transport to such centres for unanticipated complications," she added.

PlGF levels rise as the healthy placenta develops, reaching a peak by 28 weeks as the third trimester commences.

The study found that if the level of PlGF is below 100 picograms per millilitre between 24 and 28 weeks' gestation, the risk of birth before 34 weeks' gestation is almost 50-fold higher. Since only about 1.5 per cent of the population falls in this range, a PlGF screening test is highly specific and few people would have false-positive results, the researchers said.

The study was conducted from 2020 to 2023 and involved over 9,000 pregnant women. The observational study also showed that other factors, including weight, and previous pregnancy outcomes did not affect the association of low PlGF with preterm birth.