Babies born before 37 weeks of pregnancy are considered premature, or preterm. Because they were not carried for the full 40 weeks of pregnancy, preterm babies tend to weigh less and are at increased risk of health problems, some of which can be fatal. Some studies have indicated that consumption of omega-3 fatty acids in fish oil may help increase birth weight and prevent preterm delivery. But findings from other studies have yielded contradictory results.

Research recently published in the British Medical Journal suggests that women who eat seafood during the first 16 weeks of pregnancy are less likely to give birth prematurely than those who eat no seafood.

About the study

Between 1992 and 1996, researchers in Denmark enrolled 8729 pregnant women receiving prenatal care in Aarhus, Denmark into this study. Women were excluded from the study if they were carrying multiple or malformed fetuses or had taken fish oil supplements since they became pregnant.

At week 16 of pregnancy, each woman completed a questionnaire rating how often she had eaten seafood in the last 16 weeks. Seafood consumption included fish filets and steaks, as well as shellfish and roe (fish eggs). The women were grouped into the following categories based on their frequency of eating seafood:

  • Never
  • Less than once per month
  • 1 to 3 times per month
  • 1 to 2 times per week
  • 3 to 6 times per week
  • Every day

The questionnaire also included questions about other factors that could affect time of delivery and birth weight:

  • Mother's age, height, pre-pregnancy weight, smoking, alcohol consumption, education, and previous pregnancies
  • Sex of the baby
  • Father's involvement

After the women gave birth, the researchers looked at how many women in each of the seafood consumption categories delivered preterm. In addition, they compared the birth weights of the babies born to women in each of these categories.

The findings

Women who ate no seafood were about 3 times more likely to have a preterm delivery or a baby with low birth weight (less than 2500 g, or about 5.5 lb) than women who ate the most seafood. This association was present after accounting for other risk factors for preterm delivery and low birth weight.

Although eating some seafood was shown to be beneficial compared with eating no seafood, the results do not show a clear relationship between the amount of seafood eaten and the risks of preterm delivery and low birth weight. The data do suggest, however, that even eating small amounts of seafood (in the range of 15 g, or about 1/2 oz) may be beneficial.

There are limitations to this study, however. There may be other factors, as yet unknown, that influence preterm delivery and birth weight. In addition, consumption of seafood was based on estimates provided by the women, which may have compromised the accuracy of the information. Finally, because the study subjects were Danish women, it is not clear whether these results apply to women of other ethnic and racial groups.

How does this affect you?

Will eating seafood while you're pregnant help prevent preterm birth and low birth weight?

Possibly. The findings of this study support evidence from previous studies that consumption of fish oil may help reduce the risk of preterm delivery and low birth weight. However, more research is needed to understand how much seafood is beneficial and if there is a limit to the amount of seafood pregnant women should eat.

Although eating fish is an essential part of a heart healthy diet, it presents some risks for pregnant women. The U.S. Food and Drug Administration advises pregnant women to avoid eating shark, swordfish, king mackerel, and tilefish. These fish may contain high levels of mercury, which may potentially harm a growing fetus. In addition, it is best to eat only cooked seafood, because cooking will kill any bacteria that may be present.

In order to safely consume fish and other seafood during pregnancy, contact your local health department for information about the safety of fish caught in your area. And work with your health care provider to ensure that your overall diet and lifestyle habits, including your seafood consumption, are geared toward the healthy development of your growing baby.

In addition to possibly preventing premature births, seafood is an excellent source of protein and a tasty meat replacement. So even if you're not likely to eat fish as a main course, you might consider the following:

  • Fish chowders
  • Tuna fish salad
  • Crab cakes
  • Grilled fish sandwich
  • Seafood pasta salad