Junk food ahead of pregnancy may harm baby-to-be

For a healthy baby, a woman’s diet before pregnancy seems to matter. Consuming a lot of sugars, fats and take-out foods might increase the likelihood of delivering a baby preterm, Australian researchers report in the July Journal of Nutrition.

Preterm birth, defined as birth before 37 weeks of gestation, increases the risk of infant mortality or health problems later in life. While healthful eating during pregnancy has been associated with a lower risk of preterm birth, the study authors say that their findings now extend this link to the period before conception.

Poor nutrition, says study coauthor Jessica Grieger, a nutrition researcher at the University of Adelaide, may promote inflammation in women and activate hormones such as oxytocin and cortisol that have been linked to preterm birth. 

Grieger and her colleagues identified 309 women who had recently become pregnant and obtained from them dietary intake data for the year preceding conception. The researchers then scored each woman based on how much of her diet drew from three categories: a high-protein diet including fish, whole grains, chicken and fruits; a diet with plenty of vegetables, legumes and whole grains; and one with lots of take-out foods, refined grains, sugars and junk food such as potato chips.

After the women gave birth, the researchers calculated that those who had scored high on the high-protein diet before conception were the least likely to give birth preterm and women with a high junk food score were the most likely. The preterm birth rate was middling among women consuming a predominantly veggie-legumes diet. The researchers took into account differences between the women in body mass, smoking status, asthma, age, socioeconomic factors and ethnicity.

Physician Bo Jacobsson of Sahlgrenska University Hospital in Gothenburg, Sweden, says the possibility that diet before pregnancy affects delivery “seems rational but is not scientifically proven with this study.”To establish a clear effect, scientists will also need to control for diet differences throughout pregnancy itself, he says. Nevertheless, Jacobsson endorses this line of research, arguing that maintaining a good pattern of diet and exercise when planning to get pregnant could help to ensure a healthy start to gestation.

To some extent, the new findings resemble results from a study of thousands of pregnant Norwegian women that Jacobsson and his colleagues published earlier this year. That study divided women’s intake into one of three groups: a diet high in protein and veggies, a traditional diet heavy on fish and potatoes or one featuring processed and fast foods. Writing in BMJ in March, the researchers found low preterm birth rates among the first two groups.

Eating patterns before and during pregnancy typically overlap since most women don’t know exactly when they become pregnant and many pregnancies are unplanned. What’s more, women don’t necessarily change their diet upon learning they are pregnant. Researchers at England’s University of Southampton reported in 2009 that newly pregnant women reduced their smoking, drinking and caffeine intake but didn’t alter their eating habits markedly.

“We feel there is often a lack of understanding about the important role of nutrition in pregnancy by mums-to-be and even partners,” Grieger says. She says the new findings should provide doctors with additional information as they counsel women.