Giving mothers more omega-3s may help ensure full-term pregnancies, especially when their diets are low in these essential gestational nutrients
by Craig Weatherby
Nutrition-savvy medical doctors like Christiane Northrup, M.D. have long urged pregnant and nursing mothers to ensure adequate intake of omega-3s, which play a key role in the development of babies’ brains and eyes. (For general information, visit our Healthy Mom page.) After years of lobbying, nutrition experts succeeded in getting DHA—the key marine omega-3 for child development—added to infant formulas a few years back.
And, while we lack conclusive proof, the results of some recent studies and evidence reviews indicate that omega-3s may also help prevent premature births like the ones described in our July 10, 2006 story titled “Fish Oil Saves “Premie” Babies’ Livers and Lives”, which prompted one reader to send us an incredibly gratifying letter.
Expert panel calls prevention key
A report released earlier this month by the Institute of Medicine (IOM) of the National Academies of Science addresses the growing problem of premature (preterm) births.
First, we need to define some terms. A “full-term” pregnancy is one that lasts 38 to 42 weeks, and the IOM report uses the word "preterm" in reference to births that occur at less than 37 weeks.
Babies born before 32 weeks have the greatest risk of disease and death. But compared with full-term newborns, "near-term" or "late-preterm" infants born between 32 and 36 weeks, which make up the greatest number of preterm births, also have high rates of health and developmental problems.
These three findings were among the IOM’s dismaying discoveries:
- In 2005, 12.5 percent of births in the United States were preterm: a whopping 30 percent increase over 1981 rates.
- Premature births in the United States cost society an estimated $26 billion or more a year, or $51,600-plus per infant. Most of the expense was for medical care in infancy, while maternal care, early intervention services, special education for infants with learning difficulties, and lost household and labor productivity contribute to the cost.
- Multiple births resulting from infertility treatments present a significant risk factor for preterm birth.
- There are large disparities in preterm birth rates among different racial and ethnic groups.
The IOM recommended more research aimed at improving the prediction and prevention of preterm labor. According to Richard E. Behrman, chair of the IOM panel that wrote the report, "Despite great strides in improving the survival of infants born preterm, little is known about how preterm births can be prevented. Any significant gains to be made in the study of preterm birth will be in the area of prevention."
Research on omega-3s offers some hope
If prevention is the key to mitigating the serious suffering and soaring costs of premature births, nutrition appears may be the best bet.
In 2001, researchers from Colorado State University (Allen KG, Harris MA) made these observations (scientific terms replaced with equivalent lay language):
- “Women who deliver prematurely have increased pools of [omega-6 fatty acids] and decreased [omega-3 fatty acids] …Several human pregnancy supplementation trials with [omega-3 fatty acids] have shown a significant reduction in the incidence of premature deliver and increased birth weight associated with increased gestational duration.”
- “Supplementation with long chain [omega-3 fatty acids] such as docosahexaenoic acid [DHA] may be useful in prolonging the duration of gestation in some high-risk pregnancies. Evidence presented in this review is discussed in terms of the roles of dietary [omega-3 and omega-6 fatty acids] …and the human trials suggesting that increased dietary long-chain [omega-3 fatty acids] decrease the incidence of premature delivery.”
Three years later, Dr. Sjúrdur Olsen—a leading maternal nutrition researcher based at the Danish Epidemiology Sciences Centre in Copenhagen—published the results of his review of the evidence that omega-3s might help prevent preterm birth (Olsen SF 2004).
As Dr. Olsen said in his introduction, women in countries with high fish consumption levels enjoy longer pregnancies:
- “The hypothesis that omega-3 fatty acids could prevent preterm birth was inspired from studies in the Faeroe Islands, which are located in the North Atlantic Ocean between Iceland, Norway, and Scotland. Birth weights in this island population of approximately 50,000, where fishery [fishing] is the predominant way of living, were increased by approximately 200 grams [7 ounces] on average, compared to birth weights in Denmark.”
- “Gestations [durations of pregnancies] were also longer, by approximately 3 to 4 days on average, which could account for half of the observed difference in birth weight between the 2 populations.”
And he proposed three plausible mechanisms by which omega-3s might help prevent premature births and low-weight babies.
- Omega-3s could reduce the mother’s production of prostaglandins (hormone-like messenger chemicals) called PGE2 and PGF2a, which are involved in initiating the childbirth process through impacts on labor and the uterine cervix.
- Omega-3s could increase production for certain prostacyclins (PGI2 and PGI3) that may have a relaxant effect on the myometrium (muscular wall of the uterus).
- Omega-3s may have an anti-arrhythmic effect on the myometrium—similar to their anti-arrhythmic effect on the electrical activity of the heart—which could explain their delaying effect on initiation of labor.
After he examined the outcomes of all seven of the relevant randomized intervention studies published before his 2004 review, Dr. Olsen's findings were encouraging but shy of conclusive. Of the seven relevant trials, the results of four indicated that higher intakes of fish oil increased the length of gestation, while the results of the other three did not.
As with some studies of the effects of omega-3s on heart health and cancer, one Danish study—the so-called Århus trial (Olsen SF et al 1992)—suggested that fish oil supplementation might not have a positive impact on pregnancy duration in women whose consumption of fish was already relatively high: probably because high tissue levels of omega-3s can persist for several weeks, and may have even longer-lasting physiological effects.
In contrast, a trial from Kansas City (Smuts CM et al 2003) suggested that women who start a study with a low omega-3 intake would see a positive effect even from very low doses of omega-3 fatty acids (100 mg of DHA per day). An old but unusually well-designed World War II-era from London (People's League of Health 1942) suggested that a similarly low dose of omega-3 fatty acids yielded a lower occurrence of premature delivery.
Yet another study (Olsen SF et al 2003) suggested that preterm birth and early preterm birth could be prevented in women with a history of preterm birth.
Dr. Olsen believes that the disappointing findings of two of the three negative trials (Onwude JL et al 1995 and Bulstra-Ramakers MT et al 1995) could stem from the fact that high proportions of the deliveries in these trials were induced or Caesarean, which reduces those studies’ statistical power considerably.
As Dr .Olsen concluded, “Further trials are needed to examine to what extent long-chain omega-3 fatty acids may reduce recurrence risk of preterm birth, as the current evidence in favor of a preventive effect is not very robust from a statistical point of view … A recent study has shown a preventive effect of progesterone treatment, and theoretically there could be a beneficial synergy between fish oil and progesterone in relation to preventing recurrent preterm birth.”
And he made one last comment that should cause the ears of obstetricians to prick up: “The indications that long-chain omega-3 fatty acids may have rapid effects suggest that they may have the potential to be used as an adjuvant to the treatment of preterm labor.” In other words, there are indications that administration of omega-3s during premature labor might help put off birth to a healthier point in pregnancy.
Much remains to be learned, and the problem of preterm births is serious and growing, so the invitation to researchers is clear: please get to work!
- Allen KG, Harris MA. The role of n-3 fatty acids in gestation and parturition. Exp Biol Med (Maywood). 2001 Jun;226(6):498-506. Review.
- Olsen SF. Is supplementation with marine omega-3 fatty acids during pregnancy a useful tool in the prevention of preterm birth? Clin Obstet Gynecol. 2004 Dec;47(4):768-74; discussion 881-2. Review.
- Szajewska H, Horvath A, Koletzko B. Effect of n-3 long-chain polyunsaturated fatty acid supplementation of women with low-risk pregnancies on pregnancy outcomes and growth measures at birth: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2006 Jun;83(6):1337-44. Review.
- Oken E, Kleinman KP, Olsen SF, Rich-Edwards JW, Gillman MW. Associations of seafood and elongated n-3 fatty acid intake with fetal growth and length of gestation: results from a US pregnancy cohort. Am J Epidemiol. 2004 Oct 15;160(8):774-83.
- People's League of Health. Nutrition of expectant and nursing mothers. Br Med J. 1942;ii:77-78.
- Olsen SF, Secher NJ. A possible preventive effect of low-dose fish oil on early delivery and pre-eclampsia: indications from a 50-year-old controlled trial. Br J Nutr. 1990;64:599-609.
- Olsen SF, Sorensen JD, Secher NJ, et al. Randomised controlled trial of effect of fish-oil supplementation on pregnancy duration. Lancet. 1992;339:1003-1007.
- Olsen SF, Secher NJ, Tabor A, et al. Randomised clinical trials of fish oil supplementation in high risk pregnancies. Fish Oil Trials In Pregnancy (FOTIP) Team. BJOG. 2000;107:382-395.
- Bulstra-Ramakers MT, Huisjes HJ, Visser GH. The effects of 3g eicosapentaenoic acid daily on recurrence of intrauterine growth retardation and pregnancy induced hypertension. Br J Obstet Gynaecol. 1995;102:123-126.
- Onwude JL, Lilford RJ, Hjartardottir H, et al. A randomised double blind placebo controlled trial of fish oil in high risk pregnancy. Br J Obstet Gynaecol. 1995;102:95-100.
- Helland IB, Saugstad OD, Smith L, et al. Similar effects on infants of n-3 and n-6 fatty acids supplementation to pregnant and lactating women. Pediatrics. 2001;108:E82.
- Begg C, Cho M, Eastwood S, et al. Improving the quality of reporting of randomized controlled trials. The CONSORT statement. JAMA. 1996;276:637-639.
- Smuts CM, Huang M, Mundy D, et al. A randomized trial of docosahexaenoic acid supplementation during the third trimester of pregnancy. Obstet Gynecol. 2003;101:469-479.