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Strong Link Between Obesity and High Blood Pressure During Pregnancy

Note: The Pregistry website includes expert reports on more than 2000 medications, 300 diseases, and 150 common exposures during pregnancy and lactation. For the topic Hypertension, go here. For the topic Obesity, go here. These expert reports are free of charge and can be saved and shared.

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Pregnancy-induced hypertension, called gestational hypertension, is high blood pressure that occurs after 20 weeks of pregnancy. In most cases, blood pressure returns to normal after delivery, but this condition can be dangerous for a pregnancy, for the mother, and for the baby.

Gestational hypertension that occurs before 34 weeks (early-onset) can lead to pregnancy complications, including loss of the pregnancy. Gestational hypertension later in pregnancy can lead to toxemia of pregnancy, which is also called preeclampsia.

Preeclampsia can cause headache, nausea and vomiting, and swelling of your hands and face. It can also cause preterm birth and a low birthweight baby. The most dangerous complication is eclampsia, which is rare, but can cause seizures and be life-threatening. You can read about these conditions here.

Risk factors for pregnancy-induced hypertension include:

  • Your first pregnancy
  • Previous preeclampsia or a family history of preeclampsia
  • High blood pressure before pregnancy
  • Carrying twins or multiple babies
  • Being pregnant through IVF
  • Having diabetes
  • Being over age 40
  • Being overweight

A new study from researchers at University of Texas McGovern Medical School shows just how big a risk factor obesity is for gestational hypertension. Their study is published in the July 2020 edition of Obstetrics & Gynecology.

The study found that women with obesity had a significantly increased risk of gestational hypertension. Obesity was defined as having a body mass index (BMI) over 30. BMI is a measure of body mass based on your height and weight.

Gestational hypertension that occurs before 34 weeks (early-onset) can lead to pregnancy complications, including loss of the pregnancy. Gestational hypertension later in pregnancy can lead to toxemia of pregnancy, which is also called preeclampsia.

Key Findings From the Study

Researchers went back and looked at gestational hypertension and BMIs for women having a single baby in the U.S. between 2014 and 2017. Women who had hypertension before pregnancy were excluded. Obesity was defined as class 1 (BMI 30 to 34.9), class 2 (BMI 35 to 39.9), and class 3 (BMI 40 or more).

Fourteen million women were included in the study of which about 6 percent developed gestational hypertension. The researchers divided these women into early and late gestational hypertension. Early onset gestational hypertension is more dangerous for a pregnancy and occurs before 34 weeks. Compared to women in the study who were not obese (BMI of 18.5 to 29.9), the risk of early-onset gestational hypertension was:

  • 13 percent higher for class 1 obesity
  • 57 percent higher for class 2 obesity
  • Double the risk for class 3 obesity

For late-onset gestational hypertension, the increased risk was even higher:

  • 71 percent for class 1
  • 5 times higher for class 2
  • Four times higher for class 3

Importance of the Study

Gestational hypertension can be treated, but it is better to prevent it. Since obesity is one of the greatest risks for this condition, it is also one of the best ways to prevent it. Think about getting your BMI below obesity level before you try to get pregnant. If you become pregnant, work closely with you pregnancy care provider to make sure you don’t gain too much weight. If you are struggling with your weight and thinking about a future pregnancy, ask your doctor to help you start an exercise and diet program to achieve and maintain a healthy weight.

Christopher Iliades
Dr. Chris Iliades is a medical doctor with 20 years of experience in clinical medicine and clinical research. Chris has been a full time medical writer and journalist since 2004. His byline appears in over 1,000 articles online including EverydayHealth, The Clinical Advisor, and Healthgrades. He has also written for print media including Cruising World Magazine, MD News, and The Johns Hopkins Children's Center Magazine. Chris lives with his wife and close to his three children and four grandchildren in the Boston area.

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