A study linking trans fats to higher risk of miscarriage suggests that substituting more healthful fats into the diet is one positive step toward ensuring healthier pregnancies.

Trans fats have been around for over a century, since scientists first discovered how to make them through a process called hydrogenation. Their shelf-stability and lower cost initially made trans fats a popular addition to the food supply, but in the past few decades they have come under scrutiny because of their negative effects on health.

A new link: trans fats and fetal loss

To arrive at their conclusions, researchers assessed the amount of trans fats eaten by 104 women who had been involved in a long-term cardiovascular risk-factor study and who had had at least one pregnancy during the 25- to 30-year follow-up. Even after controlling for other factors that can affect pregnancy, such as diabetes, age, race, height, weight, physical activity levels, and education, a connection between trans fats and miscarriage was evident.

Only 30% of women in the group eating the fewest amount of trans fats had one or more miscarriages, while 52% of women consuming the most trans fats experienced more miscarriages. In other words, the more trans fat a woman ate, the more likely she was to suffer a miscarriage.

While this method of examining the evidence does not allow for a direct comparison between grams of trans fat and risk of miscarriage, it demonstrates that even small increases in dietary trans fats were associated with greater risk.

The researchers acknowledged that more studies are needed, but it appears they have the full weight of the medical establishment to support their findings already. The American Medical Association has already issued a strong statement supporting a nationwide ban on the use of trans fats in restaurants and bakeries.

Giving trans fats the boot

Beyond concern over miscarriage, trans fats have been linked to heart disease, insulin resistance, type 2 diabetes, cancer, and stroke. Use the following simple tips to give trans fats the boot and ensure a healthier pregnancy.

• Emphasize whole foods: The closer a food is to its natural form—what it looks like when it comes out of the ground or off the tree or vine—the less likely it contains harmful fats.

• Avoid traditional trans fat sources: Trans fats are commonly found in chips, crackers, cookies, donuts, pastries, and other convenience foods.

• Look at the label: Avoid foods that contain the words “partially hydrogenated” in the ingredient list, a clue to the presence of trans fats.

• Pay attention to amounts: Trans fat intake should not exceed 1% of total calories each day. For a 2,000-calorie diet, this means eating no more than 2.2 grams of trans fat per day.

• Choose good oils: Avoid trans fats by cooking with olive oil and choosing foods such as nuts, avocados, and fatty fish rather than chips, crackers, instant and microwave meals, and commercially produced baked goods.

• Eat whole: Base your diet around unprocessed foods such as vegetables, fruit, nuts and seeds, whole grains, and legumes (beans).

(Fertil Steril 2008;90:385–90)

Suzanne Dixon, MPH, MS, RD