"March of Dimes leads the fight for the health of all moms and babies. We believe that every baby deserves the best possible start. Unfortunately, not all babies get one. We are changing that."
Preterm birth is defined as birth before 37 weeks of gestation. Babies need to complete at least 40 weeks of gestation to prevent complications including cerebral palsy, lung disease, blindness, hearing loss, and even death. One out of every 10 babies in the US are born before 40 weeks. There are multiple syndromes that may lead to preterm birth including preeclampsia and high blood pressure. Additionally, we know that women whose relatives have had a preterm birth are at a higher risk of delivering preterm -- this means there is likely a genetic component to predisposition to preterm birth.
From the CDC: https://www.cdc.gov/nchs/products/databriefs/db24.htm
In collaboration with the March of Dimes Ohio Collaborative we are working to understand how genetic variants that have been associated with preterm birth through genome-wide association studies may be functionally involved in pregnancy. Specifically, by examining these genetic variants through the lens of human evolution we gain insight into how this disease persists in the human population.
Evolution of Human Pregnancy
Evolutionary biologists have begun to think of pregnancy as an epic battle between mother and fetus. In this vision, the fetus's goal is to remain within the womb as long as possible, drawing nutrients from the mother, and emerging just before growing too large to pass through the birth canal. The mother's goal, however, is to stay alive in order to reproduce again in the future. Therefore, she cannot afford to allow the fetus to sap all of her nutrients. We see this battle playout in the hormones that the fetus releases and the barriers (ie the placenta) that the mother puts in place during pregnancy. Evolution has created a delicate balance between these forces in humans resulting in a gestation period of 40 days.
From the Abbot & Rokas 2017
GWAS and Evolution
Genome Wide Association Studies (GWAS) have begun to highlight regions within the human genome that are associated with complex traits such as human birth timing. We have developed a pipeline that examines the signature of natural selection on these regions to understand how different evolutionary forces have shaped human pregnancy. Our work suggests that no single evolutionary force has dominated regions associated with preterm birth. Furthermore we find evidence for multiple evolutionary processes including positive selection, purifying selection, balancing selection, and population differentiation.
This evolutionary analysis helps us understand and interpret the findings of GWAS--which are by definition and design a product of our evolution.