Mother and Unborn Child’s Genes Struggle Against Each Other Before Birth

In a meta-analysis of parturition timing, researchers identified genes more strongly linked to preterm delivery than to gestational duration. The results of the analysis published in the journal Nature Genetics support large similarities in the maternal genetic effects on gestational duration and preterm delivery. Preterm birth refers to delivery before the 37th week of pregnancy. Globally, preterm (or premature) birth is the most frequent immediate cause of death among newborns and children aged up to five years. The earlier the parturition, the higher the risk.

Genetic Effects on the Timing of Parturition and Links to Fetal Birth Weight

The minimal margins in a human birth set us apart from other mammals. A woman’s pelvis barely allows a fully grown fetus to pass through; in contrast, a female chimpanzee’s pelvic passage, for example, has twice the diameter as that of her young.

The process preceding a human birth is thus extremely critical, and to enhance understanding of the processes governing when the onset of labor takes place, it is human beings specifically who need to be studied — in this case, the genetics of the woman and her unborn child.

The present study surpasses its predecessors in size and breadth. This time, some 90 researchers from the Early Growth Genetics Consortium (EGG), an international network, took part. Just over 20 international birth cohorts comprising a total of 279,043 individuals studied, were included.

Maternal–Fetal Genetic Deal Before Parturition

To understand whether the gestational duration is determined by the genes of the woman or the fetus, we examined 136,833 cases. These involve either the combination of both parents and their offspring or the woman and her offspring, enabling the effects of the woman’s and the child’s genome respectively to be distinguished with greater precision.

There might be a conflict between the genomes of the woman and unborn child respectively when it comes to the duration of pregnancy. Genetically, the woman’s genes favor the earlier onset of labor to expel the child, for her survival, while those of the unborn child favor extension of the pregnancy to gain weight.

The results have given us more routes to understanding how labor is initiated, both at full term and in premature labor. In samples too, researchers were able to identify numerous previously undiscovered genetic variants associated with the timing of parturition, and these provide unmatched insights into the underlying biological mechanisms.

In the long run, the research has the potential to develop drugs that can prevent preterm birth, and mitigate or boost contractions during delivery. These findings show that studies on human genetics are a good way to find conceivable targets for these drug therapies.

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Source-Eurekalert