Design: multisite randomised controlled trial (PrEggNut)
Population: 2,137 pregnant women whose unborn child had at least two biological family members with medically diagnosed allergic disease
Primary outcome: IgE-mediated egg or peanut allergy in the infant at 1 year
Effect: 7.8% (83/1066) with high egg-peanut diet vs 8.4% (89/1064) with standard diet; RR 0.93 (95% CI 0.69-1.26; P = 0.65)

PrEggNut enrolled 2,137 pregnant women whose unborn child had at least two biological family members with medically diagnosed allergic disease — a deliberately high-risk group. From before 23 weeks' gestation until four months postnatally, they followed either a high egg and peanut diet (at least six eggs and sixty peanuts a week) or a standard one (no more than three eggs and thirty peanuts).

IgE-mediated egg or peanut allergy at one year occurred in 7.8% of infants in the high-intake group and 8.4% in the standard group. Safety measures were similar.

The hypothesis was reasonable and worth testing: early introduction of peanut in infancy does reduce peanut allergy, so pushing exposure earlier still — in utero and through breast milk — looked like a plausible extension. It did not work. Sensitisation appears to depend on the infant's own exposure rather than the mother's.

What this settles for clinic is a question mothers ask directly. The answer is now evidence-based in both directions: there is no reason to increase egg and peanut intake in pregnancy to protect the baby, and equally no reason to avoid them. Eat normally. The intervention that does have evidence behind it is timely introduction of these foods to the infant.

Tell pregnant women with a family history of allergy to eat normally — neither loading nor avoiding egg and peanut
Keep the advice that matters: introduce egg and peanut to the infant in a timely way, not late
Do not read this as licence to delay infant introduction; that is a different question with different evidence
Record the family allergy history so the infant introduction conversation actually happens at the right visit

Don't overread it

A null result for increasing maternal intake is not an argument for avoiding these foods in pregnancy — avoidance was not tested and has no evidence behind it.

The statistics, in plain English

The relative risk was 0.93 with a 95% confidence interval from 0.69 to 1.26 — an interval that comfortably includes 1.0 and is narrow enough, in a trial of over 2,000 women, to exclude any large protective effect. This is a well-powered null result rather than an underpowered one. It cannot exclude a small effect: the lower bound of 0.69 leaves room for a benefit of up to about 31% in relative terms, which on an absolute risk of 8% would be a difference of roughly 2.5 percentage points.