Overweight Pregnancies Have Higher Risk of Complications Than Underweight Pregnancies: Lancet Study Highlights - Video

The risk of complications during pregnancy is particularly high in women born in certain parts of the world. It is not clear why, but many different factors that affect health can contribute to this inequality. One possible factor is body weight. It is more common among migrant women from certain regions to have underweight, overweight or when they become pregnant.

What is new about this study is that the researchers have been able to estimate to what extent the complications, such as gestational diabetes, could be avoided if all women were of normal weight when they became pregnant.

“For example, we concluded that about half of all cases of gestational diabetes could potentially be prevented. This applies to both women born in Sweden and foreign-born women,” says Maryam Shirvanifar, PhD student at Linköping University and first author of the study.

The researchers believe that efforts to promote a healthy weight could help all women, no matter where in the world they were born.

The study paints a complex picture. The importance of body weight differs between different complications. For example, high body weight contributes more to gestational diabetes than other complications.

But what about being underweight in early pregnancy, how does this affect the risks? To the surprise of the researchers, underweight does not seem to contribute significantly to the complications investigated.

In their study, the researchers followed almost two million pregnancies – basically all births in Sweden from 2000 to 2020. The researchers studied eight complications that can affect the mother or baby during pregnancy, or during and after childbirth. Using data from several national registers, they were able to investigate the relationship between a woman’s BMI at the first antenatal visit and complications depending on which region of the world the mother was born in.

In their analyses, the researchers took into account several factors, including socio-economic data. However, some factors that could affect a woman’s health during pregnancy and childbirth, such as quality of treatment in healthcare, communication barriers, stress linked to migration and differences in health-promoting behaviour, could not be investigated in the current study as it uses register data.

In their study, the researchers examined eight different complications in the mother and baby:

- severe complication in the mother that could be fatal

- preeclampsia

- gestational diabetes

- infant mortality in the first year of life

- preterm birth (before 37 weeks of pregnancy) and extremely preterm birth (before 28 weeks of pregnancy)

- low Apgar score (assessment of newborn baby's vitality)

- large baby (in relation to length of pregnancy)

- small baby (in relation to length of pregnancy)

Reference: Adverse pregnancy outcomes attributable to overweight and obesity across maternal birth regions: a Swedish population-based cohort study Shirvanifar, Maryam et al. the Lancet Public Health, Volume 9, Issue 10, e776 - e786