At present, pregnant women are told their due date will be 40 weeks after the first day of their final period – but this is a rough estimate, with some going into labour weeks earlier while others have to undergo induced labour. Giving birth at any point from 37 to 42 weeks’ gestational age is considered normal.
Now, scientists at Stanford University School of Medicine in California are pioneering an approach that could offer expectant women a more accurate indication of when they will give birth.
In a study published in Science Translational Medicine, lead author Ina Stelzer, PhD, and her colleagues used clinical blood tests to monitor biomarkers – biological features – in order to track how the body is preparing for labour.
The team took blood samples on two or three occasions from 63 pregnant women within their expected last 100 days of pregnancy, analysing them for 7,142 metabolic, protein and single-cell immune features.
All went into labour spontaneously, meaning none of the births were artificially induced.
Analysis of the samples revealed a surge in steroid hormones in the weeks before delivery alongside a fall in inflammatory immune responses.
“We found a transition from ‘progressing pregnancy’ to a ‘pre-labour’ phase that happens two to four weeks before the [woman] goes into labour,” said Ms Stelzer, PhD, a postdoctoral scholar in anesthesiology, perioperative and pain medicine.
“We’ve identified a novel way to use the maternal blood to predict when a mother will go into labor. This prediction is independent from the duration of pregnancy.”
The researchers then constructed a prediction model based on 45 of the biomarkers identified and tested this on 10 women, saying that the results “may be helpful for development of more accurate methods to predict labour”.
The model offered a probable delivery date within 17 days of the actual date the women gave birth, and Ms Stelzer believes that the model will become more accurate as results from more women are added to its database.
As well as narrowing down a woman’s due date, the research could also be used to improve the induction of labour.
Study co-author Virginia Winn, MD, PhD, associate professor of obstetrics and gynecology, said: “If we understand what’s regulating labour, we might be able to do a better job of inducing labour.”
Every year, one in five labours are induced in the UK, according to the NHS.