Before or after the term, childbirth does not always occur at the expected time. So how do you know when labor is going to start? Researchers at Stanford University have developed a blood test to find out the exact date of delivery. They published their research on May 5 in the journal Science Translational Medicine. Its principle: predict when a pregnant woman will give birth by analyzing the immune and biological signals in her blood.

More than 7,000 signals analyzed

The researchers followed 63 women during the last 100 days of their pregnancy. They gave blood samples for analysis two to three times before delivery. All of them had a spontaneous delivery, that is, none was artificially induced. 58 gave birth at term and five prematurely.

In each of the samples, the scientists analyzed 7,142 metabolic, protein and immune signals. They then compared these results to the dates of the sample and the date of delivery.

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The body prepares itself three weeks before

The researchers observed in the blood a clear transition between “pregnancy progression“and a phase of”pre-work“which occurs two to four weeks before a woman begins labor. This applies to women who have carried their pregnancy to term as well as to those who have given birth prematurely.

The physiology of the pregnant woman begins to change “approximately three weeks before the actual start of work “ comments Dr. Virginia Winn, co-author of the study, in a university press release. “It is not a single switch, there is this preparation that the body has to go through“she continues.

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Hormones, coagulation factors, proteins …

Concretely, the closer the date of delivery, the more the blood contained steroid hormones such as progesterone and cortisol. It also contained fewer molecules that promote blood vessel formation, a first step towards weakening the bond between the placenta and the uterus.

The blood also had more factors necessary for the blood to clot, which helps prevent blood loss after childbirth. But the main indicator is an immune protein, which is said to inhibit the inflammatory reaction that takes place during childbirth, when the placental material and fetal cells reach the mother’s blood.

A two week window

From this data, the researchers built a method that calculates a due date within a two week window. This is better than current estimates, which consider anything within a five-week window – from three weeks before to two weeks after the expected date of 37 to 42 weeks of pregnancy – is a date of pregnancy. normal childbirth.

And researchers expect the method to become even more precise as the technique is refined.

According to them, the final predictive test resulting from this work could be available within two to three years. Next step, until then: validate their results in a larger number of pregnant women and reduce the number of biological markers required for the prediction.

Better understand the work

In practice, what will it be used for? An accurate prediction is useful for planning reasons of course, but also for medical reasons. For example, being able to check whether a woman with premature contractions is in pre-labor could help doctors decide which protocol to adopt.

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But that’s not all : “if we understand what regulates labor, we might be able to trigger it better “, says Dr. Virginia Winn.