preterm births

Preterm births are the most common cause of infant death worldwide. A new study is the first to identify relevant genes and a simple, potentially low-cost solution.

What are Preterm Births?

A human pregnancy normally lasts about 40 weeks. Preterm births, also known as premature births, are when a baby is at born 37 weeks or earlier. It is estimated that 10% of babies are born preterm. This is problematic since, in terms of development, every week counts.  Even the last month is critical since major organs such as the brain, lungs, and liver are still developing until week 39.  As such, a preterm baby is at higher risk of being admitted to hospital for a range of health problems such as:

  • Problems breathing
  • Trouble sucking and swallowing
  • Difficulty staying warm
  • Newborn jaundice

In addition, babies that survive an early birth can face serious, lifelong problems such as chronic lung disease, cerebral palsy, vision or hearing impairment, and cognitive or neurodevelopmental disabilities.

What Causes Preterm Births?

There are many factors that may lead to preterm births.  Women who have had a previous preterm baby, women with uterine or cervical abnormalities, or women carrying twins are all at higher risk for preterm births.  Other factors that can increase the risk for preterm birth include maternal:

  • Diabetes
  • Obesity
  • Smoking, drinking, or illicit drug use
  • Problems with the placenta or bleeding
  • Lack of prenatal care, or
  • Closely spaced pregnancies

Possible Genetic Links

However, previous research has suggested that preterm births may not be strictly due to environmental factors such as those mentioned above.  It is thought that approximately 30-40% of the risk for preterm births may be due to genetic factors.

A new study is the first to provide robust information on these genetic factors. A team of doctors and researchers from the U.S., Denmark, Finland, Norway, and Sweden recently conducted a large-scale study of the role of genetics in preterm births. Their results, published in the New England Journal of Medicine, were based upon extensive genomic data from nearly 44,000 women, primarily of Northern European descent. Each pregnant woman was asked to submit a saliva sample and was asked to answer a questionnaire providing information regarding the length of their pregnancy and other relevant data.

Genome examination determined that there were six gene areas that may be relevant to gestational length.  One gene area relates to cells that were found in the uterine lining.  Lastly, the role of the dietary mineral, selenium, was implicated in playing a role in determining risk for preterm births. Recommendations for prenatal diets rich in foods containing selenium (certain fish, turkey, eggs, beef liver, or spinach) or selenium supplementation could be a simple, low-cost intervention to reduce rates of preterm births, newborn hospitalizations, and infant mortality.

This study was limited by two factors. First, the data pool was very homogeneous since they were all of European descent. Future research should investigate if these findings are replicable in other populations.  Second, the gestational duration was self-reported.  However, it is estimated that 90% of reported gestations aligned with age estimates done by medical personnel after birth.

This important study was the first to successfully identify and categorize the genes associated with preterm birth.  Previous studies have already established the role of these genes in uterine development and vascular control.  This study indicates that these genes are one of the causes of preterm birth.

Written by Debra A. Kellen, PhD

Reference: Zhang, G., Feenstra, B., Bacelis, J., et al. (2017). Genetic Associations with Gestational Duration and Spontaneous Preterm Birth. New England Journal of Medicine. doi:10.1056/nejmoa1612665

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