ICF: Maternal diet, body composition and metabolic adaptation to pregnancy

Each year, 20 million pregnant women develop gestational diabetes (high blood sugar that begins during pregnancy). This can carry health risks for the mother and baby during pregnancy and later in life.

In pregnancy, the mother's body must adapt to supply fuel and nutrients to the baby. Placenta hormones cause glucose (sugar) to be available for the baby by reducing how well the mother's insulin works. In most women, this change is balanced by making more insulin to keep blood glucose levels stable. However, some women can't increase how much insulin they make so blood glucose levels increase, causing gestational diabetes.

We don't fully understand why some bodies can make more insulin in pregnancy, while others cannot. There are some genetic causes of this, which cannot be changed. However, there must also be non-genetic causes because only about half of women who have gestational diabetes have it again in their next pregnancy. Understanding non-genetic causes may help to find new ways of preventing or managing gestational diabetes.

What we will do

We hope to find out if changing diet and body composition in early pregnancy can change the body's ability to control glucose levels in pregnancy. We will do this through an experimental study using diets designed to reduce body fat (reduced-calorie diet) or change where the body stores fat (reduced-carbohydrate diet).

How we will do it

We will recruit 75 women from diverse backgrounds, who are 12-16 weeks' pregnant with high risk of gestational diabetes. At baseline, we will measure their body composition, usual diet, and physical activity.

We will then randomly divide the women into three diet groups: 1) control, 2) reduced-calorie and 3) reduced-carbohydrate. The diets will be supplied weekly to participants' homes from 12-16 to 24-28 weeks of pregnancy. The diets are carefully developed to support healthy fetal development. We have successfully used the control and reduced-calorie diets in another study. We will use the same approach to develop the reduced-carbohydrate diet at the start of this project.

The women will return for follow-up data collection at 20, 24-28, and 36 weeks of pregnancy and after the baby is born. What we will measure

The primary outcome will be the mother's fasting glucose at 24-28 weeks on a standard test for gestational diabetes. Other outcomes will include the mother's glucose levels measured in the blood or using continuous glucose monitoring skin sensors, insulin and indices of insulin resistance or secretion; lipid (fat) types in maternal blood; body composition assessed using measurement (anthropometry) and imaging techniques that are safe in pregnancy (MRI, air displacement plethysmography and 3D scanning).

Compliance with the diet will be measured using food questionnaires and ordering information. Safety will be assessed using regular review of women's weight and wellbeing, glucose levels, blood measurements, fetal growth (via ultrasound scans in pregnancy) and pregnancy outcomes, such as birthweight.

Impact

New understanding of how our bodies adapt to pregnancy, especially in women with gestational diabetes, may provide new opportunities to improve human health in mothers and their babies. We expect that this impact will come from applying the findings into the NHS following a further study. We also expect that the samples that we collect will be helpful for discovery studies because there are very few experimental studies of diet interventions in pregnant women.