But new research challenges this long-held belief. In a study of 8,352 pregnant women published in the Journal of Diabetes Investigation, results indicate that excessive weight gain during pregnancy is not a significant risk factor for developing gestational diabetes, regardless of your pre-pregnancy body mass index (BMI).
This study took a unique perspective in that it looked at weight gain up until pregnant women took the oral glucose test used to screen for gestational diabetes. In previous studies examining the relationship between gestational diabetes and pregnancy weight gain, researchers typically looked at overall weight gain over the entire pregnancy—which may have contributed to a skewed picture of the cause-and-effect relationship.
What is diabetes?
Diabetes is a condition in which your body can’t make enough insulin or use it effectively. Insulin is a hormone that helps sugar (glucose) in your blood enter your body’s cells so that it can be used as energy. When glucose cannot enter your cells, it builds up in your blood, leading to high blood sugar.
While type 1 diabetes is an autoimmune disorder where you don’t make enough insulin, type 2 diabetes may occur when your cells stop responding to insulin, which results in insulin resistance and chronically elevated blood sugar levels.
What is gestational diabetes?
Gestational diabetes can develop in pregnancy in women who did not already have diabetes before becoming pregnant. It’s a condition in which your body can’t make enough insulin to meet your needs.
When you’re pregnant, glucose becomes the baby’s primary source of food, which alters how your body handles both glucose and insulin. As the placenta grows, it creates more hormones to support the pregnancy—but these hormones also have a simultaneous anti-insulin effect. All pregnant women have some level of insulin resistance in late pregnancy, and some women may already have diabetes or be mildly insulin resistant before getting pregnant.
Diabetes of any type can damage your blood vessels, nerves, eyes, kidneys, and heart. When you are pregnant, gestational diabetes can also cause high blood pressure, preeclampsia, birth defects, babies with large birth weight and complications that can result in preterm birth, or the likelihood of needing a C-section.
The relationship between gestational diabetes and pregnancy weight gain
For decades, experts pointed to a correlation between excessive weight gain in pregnancy and the onset of gestational diabetes, but this retrospective study may suggest otherwise.
For the purposes of the study, excessive weight gain is defined as weight gain above the 90th percentile of women in the same BMI category before and during pregnancy, or exceeding the upper range of the pregnancy weight gain guidelines from the Institute of Medicine.
The study’s authors found that the 1,129 women in the study who did develop gestational diabetes gained less weight than women who did not develop diabetes, even when they started out with a higher prepregnancy BMI. Additionally, there were no differences in weight gain during their first trimester and before their gestational diabetes screening.
“The amount of gestational weight gain in the first trimester and before gestational diabetes screening did not change the risk of developing gestational diabetes,” wrote Tai-Ho Hung, MD, PhD, director of maternal fetal medicine in the department of obstetrics and gynecology at Taipei Chang Gung Memorial Hospital and colleagues in the study. However, the researchers state that excessive gestational weight gain may still be correlated with other pregnancy complications, such as pre-eclampsia.
The researchers also stated that further studies of gestational diabetes are needed to confirm their findings.
Gaining weight during pregnancy is healthy and normal
Gaining weight during pregnancy—even a significant amount of weight—is a normal and healthy part of the process.
Factors that may contribute to pregnancy weight gain include:
- The development of the baby and the placenta
- An increase in maternal blood volume and extracellular fluid
- Growth of the pregnant uterus
- Enlargement of the mother’s breasts
- An increase in maternal fat stores
As always, it is best to follow through with your healthcare provider’s recommendations and to get regular physicals, even after pregnancy.
Between 2% and 10% of mothers develop gestational diabetes during pregnancy. A mama with gestational diabetes during one pregnancy is more likely to have it again during a future pregnancy—or go on to develop another type of diabetes after pregnancy. The American Diabetes Association recommends that women with a history of gestational diabetes should have lifelong screening for the development of type 1 and type 2 at least every 3 years.
Kaisu Luiro-Helve, MD, PhD, at the University of Helsinki in Finland explained at the European Congress of Endocrinology that, “Type 1 diabetes is not just a disease of the young. Type 1 usually occurs within 10 years of gestational diabetes, and that is the time when we need to stay alert and perhaps conduct another oral glucose tolerance test. Do not forget about these women after delivery.”
Chuang YC, et al. The association between weight gain at different stages of pregnancy and risk of gestational diabetes mellitus. Journal of Diabetes Investigation. 20 Aug 2021; doi:10.1111/jdi.13648
Luiro-Helve K, et al. Abstract #1479. Presented at European Congress of Endocrinology; May 22-26, 2021 (virtual meeting).
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