Obesity and weight gain in pregnancy
Myths, facts, and risks
Q. A 33-year-old G3P2002 presents at 16 weeks’ gestation with a history significant for morbid obesity (body mass index [BMI], 42), gestational diabetes with her most recent pregnancy, and chronic hypertension. What are the main risk factors for her during this pregnancy and how should she be counseled?
A. Over the last few decades, the prevalence of overweight (BMI, 25.0–29.9) and obesity (BMI >30) in women has more than doubled.1 This unabated epidemic has led to more than two-thirds of women being classified as overweight and obese. Approximately 8% of women are now considered to have extreme obesity, defined as a BMI of 40 or greater.2 Pregnancy is associated with permanent weight increases in every BMI category and is a major contributor to the obesity epidemic.3 Obesity itself is associated with an increased risk of hypertension, type 2 diabetes mellitus, obstructive sleep apnea, and hypercholesterolemia. These risks increase as BMI increases. Obesity in pregnancy is associated with risks to both the mother and the fetus. It also contributes significantly to escalating healthcare costs.
Q. What are the risks to the patient?
A. It cannot be emphasized enough that the ideal time for counseling is prior to conception. Pregnancy, however, provides a unique opportunity for lifestyle modification. Pregnant women are more prone to adopt healthy lifestyles, have better and more frequent access to medical care, and are under close medical supervision. Nevertheless, overweight and obese women have higher rates of menstrual irregularities and infertility. This means that they are more likely to delay prenatal care because they may not realize they are pregnant. Thus early ultrasounds should be performed to verify dating, to exclude multiple gestations, and for early diagnosis of congenital anomalies, such as anencephaly, via transvaginal ultrasound.
In spite of mounting evidence that obesity is a risk factor for various adverse outcomes in pregnancy, almost half of women becoming pregnant today are overweight or obese.4 Once pregnant, obese women are at increased risk for gestational diabetes mellitus (GDM) (odds ratio [OR], 2.6; 95% confidence interval [CI], 2.1–3.4), gestational hypertension (OR, 2.5; 95% CI, 2.1–3.0), preeclampsia (OR, 1.6; 95% CI, 1.1–2.25), and cesarean delivery (33.8% risk increase).5 Obese pregnant patients are also at significant risk for subsequent type 2 diabetes, multiple gestations, and chronic hypertension. These risks increase by obesity class.6 Studies have shown that early screening for GDM or type 2 diabetes and hypertension are beneficial, as these patients often do not realize they have any underlying medical conditions.7 Obese patients should undergo an early 50-g, 1-hour oral glucose challenge test. Studies are currently evaluating the screening/diagnostic values for hemoglobin A1c to diagnose GDM or pre-existing type 2 diabetes as early as possible in addition to routine follow-up testing. Previous studies have demonstrated that hemoglobin A1c correlates well with glucose tolerance test, however, the high incidence of false negative and positive for hemoglobin A1c as a screening test GDM requires further studying which is being done now.8 All obese patients should also be assessed for obstructive sleep apnea, because its prevalence correlates with weight (Table 1).