Scientists explain why it's bad for pregnant women to sit for long periods of time

The main conclusion is not that pregnant women need to exercise vigorously. On the contrary, the study shows the benefit of simpler behaviours: sitting less non-stop, getting up more often, walking more and adding light movement to a normal day.

Important: the work shows a correlation, not a direct cause-and-effect relationship. It cannot say that sitting by itself causes complications or that a certain number of steps is guaranteed to protect a pregnancy. For any restrictions, complications or doubts, the level of activity should be discussed with your doctor.

Details

Adverse pregnancy outcomes are complications that can occur during pregnancy, labour or immediately afterwards. They include, for example, gestational diabetes, premature labour, hypertensive disorders of pregnancy and a baby born small for its due date.

The new study involved 470 pregnant women from three US states: Iowa, Pennsylvania and West Virginia. In each trimester, the participants wore an activity sensor on their hip around the clock for a week. This sensor allowed them to more accurately distinguish between sitting, standing, walking and light activity. After delivery, the researchers checked medical records to determine if there were complications.

The results were notable. In pregnant women who spent about 7 hours a day sitting, complications occurred in about 20 per cent. And among those who sat for about 10-12 hours a day, the complication rate was already around 42-43%.

Not only the total amount of sitting time, but also long continuous periods of sitting were found to be particularly important. That is, the risk was higher when a person sat for long periods of time without breaks, rather than just resting during the day.

Light activity, on the other hand, was associated with a lower risk. In women who had light movement for about 3 hours a day, complications occurred in about 40%. Those who racked up about 7 hours of light activity a day had a rate of about 21%.

By light activity, you don't necessarily mean exercise. It can be standing, slow walking, household chores, short movements, normal daily activity. That is, the body is not in an immobile sitting position, even if the load remains light.

The number of steps also made a difference. Participants who walked about 3,900 steps a day had a higher risk of complications than those who walked about 6,000 to 8,500 steps. In the group around 3,900 steps, nearly 48% had complications, while in the groups around 6,000 and 8,500 steps, about 36% and 32% had complications, respectively.

Why it's important

During pregnancy, the body is already under a lot of strain: metabolism, blood vessel function, blood pressure, sugar levels, body weight, and circulation all change. Sitting for long periods of time may be associated with worse metabolic and vascular health, while light movement may be associated with more favourable cardiovascular and metabolic health.

The study is important because it shifts the focus from 'sport' to everyday behaviour. Not all pregnant women are suited to intense exercise, and not everyone can exercise regularly. But for many, it may be easier to start small: getting up more often, taking short walks, breaking up long periods of sitting, and walking more during the day.

Background

Physical activity during pregnancy has long been considered beneficial for most healthy pregnancies, unless there are medical contraindications. The American College of Obstetricians and Gynecologists indicates that pregnant women are generally recommended at least 150 minutes of moderate aerobic activity per week, spread out over the course of a day.

But most such recommendations tend to focus on exercise: brisk walking, swimming, moderate-intensity workouts. The new work adds to this picture: it shows that lighter activity - what happens between exercise and sleep - can also matter.

This is especially important for modern living conditions, where many people spend a significant part of the day sitting: at the computer, in transport, at home. For pregnant women, it's not just a question of whether to exercise, but how the whole day is structured.

Source

Research: Bethany Barone Gibbs et al, "Adverse Pregnancy Outcomes and Sedentary Behaviour, Light-Intensity Physical Activity, and Daily Steps," JAMA, 2026.