Preterm Birth, Duration of Pregnancy and Genetic Associations

Preterm Birth

A genome wide study published recently in The New England Journal of Medicine has identified variations in a half a dozen genes associated either with gestational duration (length of a pregnancy), spontaneous preterm birth (premature birth that is not induced intentionally), or both. The researchers used spit samples that 43,568 women of European descent had sent to 23andMe, a private ancestry tracking company. Testing of DNA from the samples focused on roughly 16 million single nucleotide polymorphisms (SNPs, single letters of the DNA language that vary between humans).

Such sequences represent just a small fraction of the human genome, a fraction that’s most useful for elucidating ancestry. However, some of those SNPs also may have some relevance to human health. Normally, in fact, along with the ancestry information, 23andMe provides information connected with a handful of diseases. Whether doing so is a good idea is a subject of intense controversy, since having an SNP with an association with a health condition does not mean that a person will ever be afflicted with that condition, nor even that their risk is especially high.

But you can think of this particular study as more a survey of the human genome whose goal was to identify genetic sequences with some connection to how early labor occurs. Once identified, such sequences, or the products that they create in human cells, could be investigated more closely to help scientists, obstetricians, and neonatologists understand prematurity much better. With such a long-term goal in mind, the researchers not only compared genetic sequence information from volunteers with the length of their pregnancies, and with whether or not they gave birth prior to 37 weeks gestation (a gestational age that was used to distinguish between premature and term birth), but also with information from thousands of infants and mothers in three previously published Nordic birth studies. That comparison supported the finding of associations between the six genes and pregnancy length or prematurity.

The news is exciting, because any revelation of a genetic factor associated with a condition opens the possibility for a treatment that modifies the relevant gene, or its products in a patient’s cells, or that modulates a biochemical pathway in which that gene is a player. On the other hand, it’s always important not to jump to conclusions about new treatments based on a single study, particularly when the study merely suggests that something needs to be investigated in more detail. It’s also important not to read too deeply into genome wide studies, the point of which is to identify genetic sequence differences among people that have an interesting connection with a health condition, but not to define the precise cause of the condition.

Funded by the Bill and Melinda Gates Foundation, the March of Dimes, and a handful of other groups, including 23andMe (a company offers genetic testing to track your ancestry but also gives you a few health data as a bonus), the new study is enjoying a fair amount of publicity. The story has appeared on NBC, Medline Plus, Science Daily, and Parents.com to name a few, though each one of these media outlets has basically circulated the same core story with a few things modified here and there. This a common phenomenon in science stories related to health. A press release is issued around the time that a study is to be published in a scientific journal. Then various news outlets take the press release, format it, and put their own twists onto it.

In such cases, often a comment from a quoted expert in the press release or in an article built from that release (or a paraphrasing of such a comment) survives through the various incarnations of the story. In the case of this prematurity study, this happened with a comment saying that the study had “identified a simple, low-cost solution – selenium supplements for expectant mothers – that, if confirmed, could save thousands of lives.”

Whether as an exact quote, or paraphrased, this idea about selenium was reproduced in the various articles that went out for the public to read. But it is not consistent with what was actually written in the New England Journal article, whose authors merely cited a previous study showing an association between a reduced selenium concentration and preterm birth, plus they wrote that there’s a “potential benefit for further evaluation of the role of maternal selenium micronutrient status on prematurity risk, as suggested by one.”

So you don’t need to start supplementing selenium just yet, but keep the study mind, because you may be hearing more in the years to come.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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