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Myths and truths about obesity during pregnancy
Last reviewed: 01.07.2025
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Ironically, despite their excessive calorie intake, many obese women are deficient in vitamins that are vital for a healthy pregnancy.
In the December issue of Seminars in Perinatology, expert Lorelei L. Thornburgh looks at the many challenges obese women may face during pregnancy. The following myths and facts highlight some of the issues women should consider before, during, and after pregnancy.
Myth or truth?
Many obese women suffer from vitamin deficiencies.
Is it true
40% of women suffer from iron deficiency, 24% from folate deficiency and 4% from vitamin B12 deficiency. This is a concern because some vitamins, such as folate, are very important even before conception, reducing the risk of heart disease and spinal cord defects in newborns. Other micronutrients, such as calcium and iron, contribute to the physical development of the baby.
Thornburgh says vitamin deficiencies are linked to the quality of the diet, not the quantity of food consumed. Obese women tend to avoid fortified cereals, fruits and vegetables and eat more processed foods that are high in calories and low in nutritional value.
"Just like everyone else, women planning to become pregnant or who are currently pregnant should get a balanced combination of fruits and vegetables, lean protein and good quality carbohydrates. Women should also make sure they take a vitamin containing folic acid before and during pregnancy.
Obese patients should gain at least 7 kg during pregnancy.
Myth
In 2009, the Institute of Medicine revised its gestational weight recommendations for obese women from 7 kg to 5 kg. Previous research has shown that obese women who gain excessive weight during pregnancy have a very high risk of complications, including preterm birth, cesarean section, labor insufficiency, large-for-gestational-age babies, and babies with low blood sugar.
If an obese woman does not gain a lot of weight during pregnancy, her pregnancy outcome will be better than that of someone who has gained extra pounds. Talking to your doctor about acceptable weight gain during pregnancy is a key part of pregnancy management.
The risk of preterm birth is higher in obese women compared to non-obese women.
Is it true
Obese women who are obese during pregnancy are 20% more likely to have preterm labor, diabetes, or high blood pressure. Thornburgh says this is likely due to hormonal changes in obese women.
Respiratory diseases in obesity, including asthma and obstructive sleep apnea, increase the risk of extrapulmonary complications of pregnancy, such as cesarean section and preeclampsia.
Is it true
Women who are obese are up to 30% more likely to experience asthma flare-ups during pregnancy than women who are not obese.
Breastfeeding in obese women lasts longer than in women of normal weight.
Myth
The duration of breastfeeding in women suffering from obesity in 80% of cases does not exceed half a year.
Thornburgh confirms that breast size has nothing to do with how much milk you produce. Premature births can delay the start of breastfeeding because babies are admitted to the neonatal intensive care unit.
"Because of these issues, mothers need to be educated, motivated and work with their doctors. Even if you can partially breastfeed, it's better than not breastfeeding at all," Thornburgh said.
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