Genetic conflict with the fetus influences when women give birth

When it comes to gestational age, the interests of the fetus and the pregnant person may differ slightly. Currently, the largest study of how genes influence the timing of births suggests that the two have reached an evolutionary compromise.

A genetic variant that shortens a woman’s gestation period, if present in the fetus, causes the fetus to grow faster. “They have kind of come to an agreement. The mother says, ‘I will allow you to grow a little bit, but I will give birth a little earlier,'” says Pol Sole Nave. University of Gothenburg, Sweden.

Premature birth, defined as delivery before 37 weeks of gestation, is one of the leading causes of neonatal mortality worldwide, but its causes are poorly understood.

To investigate the genetic effects of gestational age, Solé Navais’ team pooled the results of previous studies that compiled approximately 200,000 women who initiated labor at various stages of pregnancy without being medically induced. Did. Transgender people were not included.

In these studies, the DNA of both women and babies was sequenced and aspects such as gestational age and baby’s birth weight were recorded.

Solé Navais’ team found 22 sites in the genome that each have a small influence on the timing of birth. Five of them had opposite effects when present in the mother or fetus. In other words, when a particular variant was present in the mother, it was associated with shorter gestational age, but when present in the fetus, it was associated with longer gestational age.

This supports the notion that the fetus and the person carrying it have conflicting interests, as the longer the gestation period the larger the fetus and the higher the risk of delivery for the mother. , he says, is concerned with the fetus growing larger than the mother.

However, the situation became more complicated when the birth weight of the fetus was considered. Aggregating the effects of all gene variants, those associated with shortened gestational age were also associated with increased birth weight, if inherited to the fetus.

If some genetic mutations in the fetus are associated with increased birth weight, the mother’s genome counteracts it by using the same mutations to reduce gestational age, says John Perry of the University of Cambridge. “The fetus moves in one direction and the mother in the opposite direction.”

The team also found that some of the variants that affect the duration of pregnancy can interfere with the onset of labor. It has been suggested that it may be involved in regulation.

Sole Nave says further understanding of how this contractility-regulating effect may lead to new drugs that induce or prevent labor.