Good for mum, but allergy incidences in her children increased fivefold

New research on PCOS, an endocrine disorder that affects about one in ten Norwegian women, has documented these divergent effects.

PCOS (polycystic ovary syndrome) is characterized by:

• infrequent or missing ovulation/menstruation
• elevated levels of male sex hormones
• small blisters/cysts on the ovaries
• insulin resistance
• mental health problems such as depression

"Most of the women with PCOS are overweight, but the condition also affects women of normal weight," says Eszter Ilona Vanky, senior consultant at St. Olav's Hospital and professor at the Norwegian University of Science and Technology (NTNU).

She has dedicated her entire award-winning research career to finding out as much as possible about PCOS. Now she is concerned about the increase in the syndrome.

"There are many more people who have troublesome symptoms with PCOS today than 25 years ago. The reason is increased obesity in the population, but also more awareness of the condition. Obesity provokes PCOS in women who are predisposed to it. Severe obesity can in itself lead to PCOS without being predisposed to it before," says Vanky.

Medicine crosses the placenta

It is estimated that 70 per cent of women with PCOS have insulin resistance. This means that the cells in the body respond less well to insulin, which is the body's blood-sugar-lowering hormone.

Insulin resistance leads to overproduction of insulin, which in turn interferes with ovulation and stimulates the ovaries to produce more testosterone.

Therefore, the diabetes drug metformin is often recommended as a basic treatment for PCOS in women who are not pregnant. In addition to increasing sensitivity to insulin and thereby lowering insulin levels, metformin contributes to weight loss along with lifestyle measures, regulation of menstruation and reduced male sex hormones.

It may almost sound as if metformin is a miracle drug for women with PCOS, but one challenge during pregnancy is that the medication crosses the placenta and can thus affect the fetus directly.

No teratogenic effects have been reported, but children who have been exposed to metformin in the womb appear to have:

• larger head circumference at birth
• increased vulnerability to developing obesity

Changes the immune system itself

The need for more knowledge about the long-term effects of metformin during pregnancy on the child has been highlighted in the international research community.

PhD candidate Mariell Ryssdal at NTNU has now delved into this.

She has just published an article that shows how metformin in pregnancy affects immunological outcomes in mother and child.  The study involved 634 women with PCOS who received either metformin or placebo throughout pregnancy. Of these, 292 mothers with children were invited to a follow-up study, eight years after pregnancy.

145 of the children joined.

"The study shows that metformin can affect the immune system of the fetus, so that the children more often develop eczema and allergies," says Ryssdal.

Her research shows that when children were around eight years old, they had twice the incidence of eczema, and almost fivefold the incidence of allergies.

So, if you only think about the child's health with allergies and eczema, it may not be such a good idea to take metformin during pregnancy, but unfortunately it is not that simple.

Fewer people give birth prematurely

Women with PCOS also have a somewhat elevated risk of most types of pregnancy complications such as miscarriages, excessive weight gain during pregnancy, gestational diabetes, preeclampsia, premature birth and stillbirth.  The risk is reduced if the woman has as much normal weight as possible.

Here, metformin comes in again as a good helper because the medicine leads to less weight gain in pregnancy and that fewer people give birth prematurely.

Vanky emphasizes that the most important thing is to avoid premature birth.

"Being born far too early is a threat to the child's health in the short and long term," says Vanky.

Children who are born very prematurely can, among other things, suffer lifelong brain damage, and an increased risk of a number of chronic diseases.

Metformin is by no means directly harmful to the fetus in pregnancy. We recommend women who are taking metformin and become pregnant to stop taking it within the first three months. In some cases where the woman has an increased risk of very premature birth, treatment with metformin may be considered throughout the pregnancy.

"Sometimes metformin is the right thing to give, even for pregnant women, but it should be done individually. We do not recommend women with PCOS use metformin routinely throughout pregnancy," says Vanky.

As with several women's diseases, knowledge in the health service about PCOS has been variable. Vanky is now working on an e-course for GPs under the auspices of the Norwegian Medical Association so that women with PCOS will receive equal treatment, and be met with knowledge.

"Midwives and GPs should know more about PCOS. One of my fads is that it should be on the health card if you have this syndrome," says Vanky.

Source:Mariell Ryssdal, Johanne E. Skage, Anders H. Jarmund, Liv Guro E. Hanem, Tone S. Løvvik, Guro F. Giskeødegård, Ann-Charlotte Iversen, Eszter Vanky. Metformin treatment in PCOS pregnancies reduces maternal infections and increases the risk of allergies and eczema in the offspring: post hoc analyses of two randomised controlled trials and one follow-up study. BJOG, August 2025, https://doi.org/10.1111/1471-0528.18320