Regularly consuming seafood and fish during pregnancy may be the key to preventing colic and eczema in infants, according to a recent study published in JAMA Network Open.

Infants whose mothers ate a Mediterranean-style diet during pregnancy had lower odds of developing colic and eczema by 6 months of age. For each weekly serving of fish and seafood a pregnant person consumed, infants had a 25% lower risk of developing the conditions.

“Diet affects your microbiome and your gut, and it affects what proteins you’re exposed to that can influence the immune system,” said Emily Oken, MD, professor in the Department of Nutrition at the Harvard T.H. Chan School of Public Health in Boston, who helped lead the study.

Up to one quarter of newborns have colic, and atopic dermatitis affects up to one fifth of infants. The two conditions often co-occur, and colic is associated with an increased risk for various allergies later in life.

To find out if fetal food exposure was associated with immunity issues later on, Oken and her team analyzed data from 1324 mother-child pairs (mean maternal age, 32.6 years; 75.2% White) between 1999 and 2003 in eastern Massachusetts. Approximately 40% of the mothers had a history of atopy, including 12.4% who had eczema. Outcomes were adjusted for age, race, education, parity, smoking history, and atopy.

The researchers surveyed patients on their diet during the first trimester of pregnancy and again around 28 weeks of gestation. Patients were asked to report on their diet in a typical week over the preceding 3 months.

These reports were used to create two scores measuring nutrition quality, one for a Mediterranean diet and one for an inflammatory diet. For each healthful food group in the Mediterranean diet — such as fruits, vegetables, legumes, and whole grains — patients scored a point if they exceeded a threshold of recommended servings, such as two servings of fish per week.

Patients also met with the study team when their infants (50% male) were approximately 6 months old. About 20% of infants had colic, 11.5% had eczema, and 4.6% had both conditions.

Each 1-point increase in Mediterranean diet intake was associated with 15% lower odds of infants having colic and eczema (odds ratio [OR], 0.85; 95% CI, 0.74-0.98) than in infants who did not have these conditions. For every serving of seafood per week, infants had lower odds of having both eczema and colic (OR, 0.71; 95% CI, 0.54-0.93). The association with eczema remained even in mothers with a history of atopy (OR, 0.81; 95% CI, 0.67-0.97).

Meanwhile, every 1-point increase in intake of an inflammatory food was associated with 34% higher odds of infants having both conditions. For every serving of nuts consumed in a week, pregnant women had slightly higher odds of having an infant with colic alone.

Because seafood contains many important nutrients, including vitamin D, iodine, and selenium, “it’s possible that some combination of these factors could influence fetal immune development or the developing gut microbiome,” said Peter Lio, MD, clinical assistant professor of dermatology and pediatrics at Northwestern University Feinberg School of Medicine in Chicago.

But genetics, immune regulation, microbial exposures, and environmental factors can contribute to the development of atopic dermatitis, independently of maternal diet, he said.

“I’ve seen some of the most health-conscious and diet-conscious families have children with very severe eczema. That reminds us that diet cannot be the entire story,” Lio said.

Adherence to guidelines recommending a healthy diet during pregnancy is often low. Only about one third of pregnant women eat the recommended two to three servings of fish per week.

“If you say, ‘Well, you should eat healthy because it will long term prevent your risk of heart disease and diabetes,’ that seems not so salient, but if you can add in, ‘This also may lower your risk of having a colicky baby who’s going to make everyone miserable,’ that might just resonate a little bit better,” Oken said.

Oken and Lio reported no financial conflicts of interest. The study was funded by a grant from the National Institutes of Health and an anonymous donor to the Harvard T.H. Chan School of Public Health.

Kelsey Mesmer, PhD, is a freelance journalist and journalism professor at Saint Louis University in St. Louis, Missouri.