PREGNANT women often anxiously wait weeks for the moment their waters break.
But a new blood test could one day pinpoint when a woman will go into labour up to a month before she is due.
Pregnant women could soon be able to prepare for their labour weeks in advance with a more precise “due date” based on a blood sample[/caption]
The test would give an estimation with a two-week window, but may become even more precise as technology develops.
A normal time to go into labour is anywhere from 37 to 42 weeks into pregnancy, with 40 weeks the average.
Some women go into labour early and their baby is born premature – which the test would also be able to signal.
Doctors usually predict a mum-to-be’s due date by calculating 40 weeks from her last period, as well as looking at the baby’s size.
But the date is rarely accurate, with only around five per cent of babies born when doctors expect.
The baby comes when it feels ready, sometimes as a complete shock to the mum if it’s early.
Researchers at Stanford University School of Medicine say they have found a way to predict when the baby is coming in the mum’s blood.
They expect their findings to yield a test in the next two to three years.
Dr Ina Stelzer, the study’s lead author, said: “We found a transition from ‘progressing pregnancy’ to a ‘pre-labor’ phase that happens two to four weeks before the mom goes into labor.
“We’ve identified a novel way to use the maternal blood to predict when a mother will go into labor.”
Dr Stelzer and team looked at 63 women who gave two or three blood samples in the last 100 days of their pregnancies.
All of them went into labour spontaneously and docs were able to compare their labour date with signals in their blood.
Each blood sample was screened for more than 7,000 markers, including immune cells, proteins and hormones.
Using mathematical modeling, the researchers plotted which features in the blood best predicted labour was coming.
As they went into the last couple of weeks before labour, women’s blood showed surges in steroid hormones such as progesterone and cortisol.
The blood had lower levels of chemicals that form blood vessels – a sign the placenta and uterus are breaking apart.
And there were higher levels of blood clotting markers, as the body prepared to prevent any severe loss of blood during birth.
One protein was the most predictive that a woman was set to go into labour – IL-1R4, that prevents inflammation.
How do doctors currently predict due date?
- By calculating 40 weeks (280 days) from the first day of the woman’s last period
- By measuring how pregnancy symptoms are changing over time
- By measuring the size of the feotus using an ultrasound
The body needs to carefully tailor the amount of inflammation in the body during labour, Dr Stelzer said.
Five of the women gave birth prematurely but the changes in their blood were still detectable weeks earlier.
If doctors can predict if a woman will give birth earlier they can put control measures in place, such as giving drugs that mature the baby’s lungs quicker.
It’s the first time the biological process that happens to a woman’s body just before labour has been described, previously being a mystery.
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Dr Virginia Winn, associate professor of obstetrics and gynecology at Stanford, said: “The mum’s body and physiology start to change about three weeks before the actual onset of labour.
“It’s not a single switch; there’s this preparation that the body has to go through.”
The findings, published today in Science Translational Medicine, need to be backed up with more trials of pregnant women.