A Cochrane review [Abstract] 1 included 5 studies with a total of 925 subjects. Two studies, involving 334 pregnant women, were included in the review of dietary antigen avoidance during pregnancy. The combined evidence from the trials does not suggest a strong protective effect of maternal antigen avoidance on the incidence of atopic eczema (RR 1.01, 95% CI 0.57 to 1.79) or asthma (RR 2.22, 95% CI 0.39 to 12.67) during the first 18 months of life. Data on allergic rhinitis or conjunctivitis, or both, and urticaria are limited to a single trial each and are insufficient to draw meaningful inferences. Longer-term atopic outcomes have not been reported. The restricted diet during pregnancy was associated with a slightly but statistically significantly lower mean gestational weight gain, a nonsignificantly higher risk of preterm birth, and a nonsignificant reduction in mean birthweight.
A systematic review 2 included 42 studies (over 40 000 children): 11 intervention studies (including 7 RCTs), 26 prospective cohort studies, 4 retrospective cohort studies, and 1 case-control study. In the randomized control trials, no significant difference was noted overall in the prevalence of eczema and asthma in the offspring of women on diets free from common food allergens during pregnancy. The prospective cohorts investigated a large number of potential associations, but reported few significant associations between maternal dietary intake and development of allergy. Maternal diets rich in fruits and vegetables, fish, and foods containing vitamin D and Mediterranean dietary patterns were among the few consistent associations with lower risk for allergic disease in their children. Foods associated with higher risk included vegetable oils and margarine, nuts, and fast food.
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals) and indirectness (only short-term results reported).
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