Obesity and Pregnancy Clinical Presentation

Updated: Oct 18, 2021
  • Author: Dawn M Palaszewski, MD; Chief Editor: Edward H Springel, MD, FACOG  more...
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Weight loss before pregnancy, whether achieved via surgical or nonsurgical methods, has been shown to be the most effective intervention to improve medical comorbidities, especially diabetes and hypertension. Obese women who have even small weight reductions before pregnancy may have improved pregnancy outcomes if they can avoid excessive weight gain once pregnant. [3, 4] Unfortunately, many women present for obstetrical care with an elevated body mass index (BMI).

It is recommended that women with a history of bariatric surgery wait 12-24 months before conceiving so that the fetus is not exposed to a rapid maternal weight loss environment and so that the patient can achieve full weight loss goals. Unfortunately, pregnancy may occur prior to this recommended time frame. The number of bariatric surgical procedures performed annually has dramatically increased, with many performed in reproductive-aged women. [4] Obstetric care providers can expect to manage increasing numbers of pregnancies in women with a history of bariatric surgery. (Refer to the Medscape article on bariatric surgery for additional information.)


Physical Examination

Calculating BMI and weight gain counseling

A thorough history taking and physical examination are completed at the first obstetrics visit. A woman’s BMI is also calculated at the initial visit. Obesity class I is defined as a BMI of 30-34.9 kg/m2, obesity class II as a BMI of 35-39.9 kg/m2, and obesity class 3 as a BMI greater than or equal to 40 kg/m2. This BMI is used to provide counseling guided by Institute of Medicine (IOM) recommendations for gestational weight gain during pregnancy. The IOM guidelines recommend a total weight gain of 15-25 lb for overweight women and 11-20 lb for obese women. [5]

These recommendations have some limitations. As mentioned earlier, a pregnancy-specific definition of obesity has not been standardized; thus, the pre-pregnancy BMI is typically used. BMI is imperfect, as it does not tell the whole story about the composition of a patient's body. One also needs to realize that weight gain is used simply as a proxy measure for the nutritional status of the woman. It is the actual nutritional quality of food intake that is critical and not simply the act of gaining weight. Women tend to gain the amount of weight they feel that they should. Unfortunately, obese women expect that a weight exceeding IOM recommendations is appropriate and in turn gain in excess of the recommendations. [6]

Nutritional status before and during early pregnancy may play an important role in ensuring successful pregnancy outcomes. Preconceptional and periconceptional intake of vitamin and mineral supplements is associated with a reduced risk of low birth weight and/or small-for-gestational-age infants and preterm deliveries. [7]  Although inadequate weight gain and weight loss have been associated with small-for-gestational-age infants and even decreased lean body mass in the neonate, some studies have shown that in the pregnant woman with morbid obesity (BMI >40 kg/m2), weight gain of less than 10 lb and even weight loss in the setting of good balanced meals with appropriate caloric and nutritional intake may be acceptable. [8]  Careful evaluation of the patient's diet is key in this situation.

Increased maternal and fetal risks

Obese pregnant women are at increased risk for many maternal and perinatal complications, and the risks are amplified with increasing degrees of maternal obesity. For this reason, a detailed history and physical examination are critical at the initial obstetrics visit, with ongoing monitoring as needed.