News · Nutrition & Diet
Eating lots of eggs and peanuts in pregnancy did not prevent infant allergy, in a 2,137-woman trial
Exposing a baby to allergens before birth and through breast milk was a promising idea. An Australian trial of families prone to allergy found it made no difference by age one.
- A randomized trial of 2,137 pregnant women whose babies had a family history of allergy.
- One group ate at least 6 eggs and 60 peanuts a week; the other no more than 3 eggs and 30 peanuts.
- The diets ran from mid-pregnancy until the baby was 4 months old, through breastfeeding.
- By age one, 7.8% of babies in the high group had egg or peanut allergy, against 8.4%: no real difference.
- Eating these foods in pregnancy was safe, and it is still the baby's own early eating that matters.
Advice on allergies and pregnancy has turned almost completely around in a generation. Pregnant women were once told to steer clear of peanuts in case exposure sensitized the baby. Then trials in infants showed the opposite was true after birth: introducing peanut early protects against allergy. The natural next question was whether starting even earlier, in the womb and through breast milk, would protect more.
An Australian trial published in the New England Journal of Medicine put that to 2,137 pregnant women. Eating a lot of eggs and peanuts made no difference to their babies’ allergies at one year.
What a food allergy is
MedlinePlus describes a food allergy as an abnormal immune system reaction to certain foods. Eggs and peanuts are two of the commonest culprits in young children, and peanut allergy in particular tends to last and can be severe.
The page lists family history among the risk factors: you are more likely to have food allergies if someone in your family has allergies. That is why this trial recruited the families it did.
Why eggs and peanuts before birth seemed worth testing
The idea had a reasonable basis. The authors note that immune responses leading to food allergy may develop early in life, potentially before the introduction of solid foods. Fragments of what a mother eats reach the baby in the womb and later in breast milk, so a diet rich in allergens could, in theory, teach the developing immune system that these foods are harmless.
Until now it was a hypothesis. As the authors put it, evidence from randomized trials is lacking, which left the idea circulating without anything to test it against.
How the allergy trial was run
Every baby was at high risk. Pregnant women whose unborn child had at least two biologic family members with medically diagnosed allergic disease were eligible to participate.
The high group followed a diet that included at least 6 eggs and 60 peanuts per week, starting before 23 weeks of pregnancy and continuing until the baby was 4 months old. The comparison group kept to no more than 3 eggs and 30 peanuts a week. At one year, babies were tested for the fast, antibody-driven type of egg or peanut allergy that causes hives or swelling within minutes.
What happened to infant allergy rates
The two groups ended up almost identical. There was no significant difference in the percentage of infants with IgE-mediated egg or peanut allergy between the maternal high egg-peanut group and the standard-diet group: 83 of 1,066 babies against 89 of 1,064, or 7.8% against 8.4%.
A gap of that size could easily be chance, and the trial was large enough that a meaningful protective effect would very likely have shown up. It did not. The authors’ conclusion is direct: high intake during pregnancy and breastfeeding did not lower the risk of egg or peanut allergy by the age of one.
Why a clear no on peanut exposure is useful
A negative result is easy to skim past, and this one deserves better. It closes off a piece of advice that was spreading without evidence, and it reassures in the other direction too: safety measures were similar in the two groups, so heavy egg and peanut eating in pregnancy did not cause harm either.
It also sharpens where the effort belongs. The strategy with strong trial evidence behind it is the baby’s own early eating, not the mother’s diet, and this study points attention back there.
What one year of infant follow-up cannot tell us
The primary outcome was allergy at age one, and some allergies appear or resolve later. The trial also tested two specific foods at specific amounts; it does not speak to other allergens or to a different timing of exposure.
Everyone was in Australia, and every baby came from an allergy-prone family. Whether the answer would differ in lower-risk families is not known, though it is hard to see why the approach would help them more.
What this changes for eating in pregnancy
For pregnant women, very little changes in practice, which is itself the useful news. There is no need to load up on eggs and peanuts to protect the baby, and no need to avoid them either, unless you have an allergy yourself.
The step that does have evidence comes later: introducing allergenic foods such as peanut into the baby’s own diet during the first year, in a form safe for their age and with advice for babies at highest risk. That is where prevention works, and this trial suggests it cannot be shortcut from the other side of the placenta.
People also ask
What did the study find?
There was no significant difference, meaning no gap larger than chance would explain, in the percentage of infants with IgE-mediated egg or peanut allergy between the maternal high egg-peanut group (83 of 1066, 7.8%) and the standard-diet group (89 of 1064, 8.4%) (relative risk 0.93; 95% CI 0.69 to 1.26). Safety measures were similar in the two groups.
Why did anyone think this might work?
Food allergies can start forming very early, possibly before a baby eats solid food. Small amounts of what a mother eats reach the baby in the womb and in breast milk, so it seemed plausible that more exposure early on would teach the immune system to tolerate those foods.
What does IgE-mediated mean?
It is the classic, fast type of food allergy, driven by an antibody called IgE, that causes hives, swelling or worse within minutes of eating the food. It is the type that can be dangerous.
Should pregnant women avoid eggs and peanuts?
No. Safety was similar in both groups, and nothing here suggests eating them causes harm. Unless you have an allergy yourself, there is no reason to cut them out. This is general information rather than medical advice.
What does help prevent peanut allergy?
Earlier trials showed that introducing peanut foods into a baby's own diet in the first year, in a form safe for their age, lowers the risk. That advice is unchanged by this study.
Were these high-risk babies?
Yes. Every baby had at least two close relatives with a diagnosed allergic condition, which is the group most likely to benefit if the approach had worked.