CME: Obesity in pregnancy: prepare for unique challenges

November 1, 2008

Counsel obese patients that losing weight before pregnancy ups the odds of getting pregnant and can spare them and their child serious risks and complications.

It's estimated that at least one third of all pregnant women in this country are obese, and a separate survey has identified nearly 60% of women of childbearing age as overweight or obese.2

Although BMI is strongly correlated with body fat, unlike complicated methods of determining fat content, BMI is not a diagnostic tool. For example, a lean muscular woman can have a high BMI. To determine if excess weight is a health risk, further assessments might include measuring skin-fold thickness and evaluating diet, physical activity, and family history.

The World Health Organization calls obesity "one of today's most blatantly visible, yet neglected, public-health problems," and adds that "it threatens to overwhelm both developed and developing countries."3 Some 312 million people worldwide are obese. At all ages and throughout the world, women generally have higher mean BMI and higher obesity rates than men for biological reasons.3

Increased BMI raises the risk of impaired carbohydrate tolerance. Fasting and postprandial plasma insulin concentrations are higher in obese pregnant women than in the nonobese. Even in overweight subjects, the incidence of gestational diabetes is up to 6.5 times greater than for normal women, and in obese women (BMI >30) the incidence is up to 20-fold higher than normal.4-8

Maternal hemodynamic changes in obese gravidas include higher arterial blood pressure, hemoconcentration, and altered cardiac function. And obese pregnant women have significantly more hypertensive disorders (gestational hypertension, preeclampsia). In addition, their incidence of hypertension is 2.2 to 21.4 times higher than in controls and preeclampsia occurs up to 9.7 times more often.4,7

Obesity also slightly raises the risk of urinary tract infections and respiratory disorders and places these women at moderate risk for developing thromboembolisms.8 There are also 37.5% more congenital malformations (chiefly neural tube and cardiac defects) when mothers are obese compared to nonobese controls.4