Premature Birth Statistics: Shorter Women At Higher Risk Of Having A Preemie, Study Finds

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Premature birth can be caused by a large variety of factors. Shutterstock

Shorter mother, shorter pregnancy, according to new research by the March of Dimes Prematurity Research Center Ohio Collaborative. The data suggests that mothers who are smaller in stature also have smaller babies and a higher risk for a preterm birth.

Researchers looked at 3,485 Nordic women and their babies, and found that maternal height helped shape the fetal environment, affecting the length of pregnancy and incidence of prematurity.

Over 450,000 babies are born prematurely in the U.S., and preterm birth is the number one killer of newborns in the U.S. The national preterm birth rate is worse than that of many other highly developed countries, and there are also significant gaps between racial and ethnic groups. Babies who survive early birth often face health problems later in life — breathing problems, vision loss, cerebral palsy, and intellectual delays are all possible.

"A major goal of the nationwide network of March of Dimes prematurity research centers is identifying genes that govern fetal growth and length of pregnancy,” said Dr. Joe Leigh Simpson, March of Dimes senior vice president for Research and Global Programs. “That a woman's height influences gestational length, independent of the genes she passes on that determine fetal size, is a major finding by our research networks, and the first of what we expect to be many genetic contributions.”

The March of Dimes’ prematurity research centers bring together researchers of many diverse disciplines, including molecular biologists, geneticists, epidemiologists, engineers, and computer scientists. These teams have been working to find answers that could prevent premature birth.

"Our finding shows that a mother's height has a direct impact on how long her pregnancy lasts," said Dr. Louis Muglia, the primary investigator of the Ohio Collaborative, and co-director of the Perinatal Institute at Cincinnati Children's Hospital Medical Center. "The explanation for why this happens is unclear but could depend not only on unknown genes but also on woman's lifetime of nutrition and her environment."

Risk Factors Of Premature Birth — Not Always Controllable

It’s pretty well-known that certain behaviors during pregnancy put a fetus at risk for premature birth and other problems. Heavy drinking and drug use have long been identified as problematic for fetuses, but deliberate choices by the mother are far from the only things that can cause premature birth. Some risk factors, though they can be changed to reduce the risk, are not often in the mother’s control. A lack of health care during pregnancy and lack of social support can contribute to premature birth, as can exposure to pollutants or abuse.

Some risk factors are even further out of control and cannot be changed even with attentive medical care. Like a woman’s height, things like diabetes and high blood pressure are not able to be altered during pregnancy to reduce risk of preterm birth. A woman’s age is an important factor as well — being under 18 or above 35 significantly increases the risk of premature birth — and pregnancy resulting from in vitro fertilization is also considered a risk factor.

Experts say that as far as modifiable risk factors (like the consumption of alcohol) complete avoidance is the best way to reduce the risk of preterm birth. Factors that aren’t so easily evaded can at least be monitored — regular health care and prenatal checkups are the best way to keep tabs on risk factors and take early action against potential problems.  

Source: Muglia L, et al. Assesing The Casual Relationship Of Maternal Height On Birth Size And Gestational Age At Birth: A Mendelian Randomization Analysis. PLOS Medicine. 2015.

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