Expecting moms with low blood levels of long chain omega-3 fatty acids in their first and second trimesters may be at a significantly higher risk of early preterm birth compared to moms with higher levels of these fatty acids, according to a new study published in the journal EBioMedicine.

“At a time when many pregnant women are hearing messages encouraging them to avoid intake of fish altogether due to mercury content, our results support the importance of ensuring adequate intake of long chain omega-3 fatty acids in pregnancy,” said lead author Dr. Sjurdur F. Olsen, adjunct professor of nutrition at Harvard Chan School and head of the Centre for Fetal Programming at Statens Serum Institut in Copenhagen, Denmark.

The team discovered that low concentrations of certain long chain fatty acids — eicosapentaenoic acid and docosahexaenoic acid (EPA+DHA) — appear to be a strong risk factor for preterm birth.

Preterm birth is a leading cause of neonatal death and is associated with cognitive deficiencies and cardiometabolic problems later in life among survivors. For decades, many researchers have suggested that a high intake of EPA+DHA, which is found in cold-water fish such as Atlantic mackerel, anchovies, salmon, and tuna and also in leaner species such as cod and haddock, can lower the odds of preterm birth. But the research findings have been inconsistent.

For the current study, researchers looked at data from the Danish National Birth Cohort, a nationwide study that follows 96,000 children in Denmark through questionnaires and registry linkages.

They analyzed blood samples from 376 women who gave birth very prematurely (prior to 34 weeks of gestation) between 1996 and 2003 and 348 women who had a full-term birth. All of the women had given blood samples during their first and second trimesters of pregnancy.

The findings reveal that women who were in the lowest quintile of EPA+DHA serum levels — with EPA+DHA levels of 1.6 percent or less of total plasma fatty acids — had a 10 times greater risk of early preterm birth when compared with women in the three highest quintiles, whose EPA+DHA levels were 1.8 percent or higher. Women in the second lowest quintile had a 2.7 times greater risk compared with those in the three highest quintiles.

The results suggest that, among pregnant women with low levels of EPA+DHA, eating more fish or taking a fish oil supplement could potentially lower the risk of preterm birth.

The researchers warn, however, that broad generalizations about the study’s findings may be limited due to the fact that it was conducted in Demark where preterm birth rates are low, and that the study should be repeated in other populations.

They also note that the findings may not solely reflect a variation in diet; differences in underlying genetic factors may also play a role.

“An effect of this magnitude is rare, but the precision of the estimate is tight, which supports the reliability of these findings,” said co-author Dr. Jeremy Furtado, senior research scientist at Harvard Chan School.

“It will be important to replicate these findings in other populations, but the results of this study certainly suggest that assessment of plasma EPA+DHA status in women has the potential to be used in the future to help predict women’s risk.”

Source: Harvard T.H. Chan School of Public Health