Obesity in Pregnancy

Obesity poses a significant maternal risk during pregnancy, after delivery, and for long-term health issues. Maternal obesity can also adversely affect outcomes for the fetus, neonate, and child. Evidence-based management of maternal obesity should be established before pregnancy and continued after delivery and over the course of a lifetime. This is a review of the factors associated with obesity in pregnancy and the management considerations for people with obesity who are considering getting pregnant, are pregnant, or have given birth. Epidemiology. Obesity is defined as a body mass index (BMI) of 30 kg/m2 or higher. Although this threshold balances the sensitivity and specificity for identifying those at risk of disease from excess body fat, it does not take into consideration individual differences in frame size, lean body mass, and fat distribution patterns. Over the past 2 decades, the prevalence of obesity in the United States has increased among women 20 to 39 years of age from 29.8% in 2001-2002 to 39.7% in 2017-2018. Of those who had a live birth in 2020, 26.7% were overweight, and 29.5% were obese. Prepregnancy obesity disproportionately affects American Indian or Alaska Native (40%), non-Hispanic Black (39%), and Hispanic (32%) women versus non-Hispanic White (26%) or non-Hispanic Asian (10%) women. Antepartum Conditions. Compared with women of normal weight, those with obesity are more likely to experience irregular or absent ovulation, less likely to conceive per cycle, and more likely to experience subfertility or infertility. Obesity has also been associated with delayed conception, increased rate of miscarriage, and poorer outcomes from assisted reproductive technology treatments.Women with obesity are also 3 to 4 times more likely to have gestational diabetes, which increases the risk of gestational hypertension, preeclampsia, and cesarean delivery (CD). Gestational diabetes is more prevalent in Hispanic, non-Hispanic Black, Native American, Alaska Native, or Pacific Islander women than non-Hispanic White women. Up to 70% of women with obesity can expect to develop diabetes 22 to 28 years after pregnancy. A small, but significant, positive association also has been found between obesity and maternal depressive symptoms and anxiety before and after childbirth. Stigma is associated with obesity, which can lead to more depressive symptoms, poor eating behaviors, and stress. In addition, women with poor mental health often struggle with weight management. Fetal Conditions. Maternal obesity has been associated with an increased risk of structural anomalies, including a strong causal relationship for congenital heart defects and moderate causal relationship for neural tube defects. Meta-analyses have also shown positive, dose-response associations between maternal BMI and macrosomia and large for gestational age. Among women with obesity, the risk of stillbirth is as high as 2.1 times as that in women with normal weight, although other mechanisms may be involved in reported associations. Labor, Delivery, and Postpartum Conditions. Compared with women of normal weight, those with a BMI of ≥50 kg/m2 have the highest risk of maternal morbidity during hospitalization (adjusted odds ratio [OR], 1.99; 95% confidence interval [CI], 1.57-2.54). The association between maternal obesity and preterm birth is unclear, but a recent meta-analysis found a significant overall pooled OR of 1.17 (95% CI, 1.13-1.21). Although the association between obesity and preterm birth is of higher magnitude at earlier gestational ages, a dose-response effect with BMI has not been established. In addition, a study has shown that women with obesity have higher rates of labor induction, oxytocin augmentation, failure of labor to progress, and instrumental delivery than those with normal weight. There is also a higher risk of postterm birth with increasing BMI in women with BMI ≥50 kg/m2 (OR, 1.75; 95% CI, 1.50-2.04). Women with obesity are at higher risk for CD and associated complications, such as anesthesia-related complications, wound complications, excessive blood loss, venous thrombosis, postpartum endometritis, and failure of vaginal birth after CD. A meta-analysis also found that women in labor, who are obese, are more likely to experience wound, urinary tract, perineum, or chest or breast infections (pooled OR, 3.34; 95% CI, 2.74-4.06). The risk of venous thromboembolism is 4 times as high in women with obesity who are in labor, but there is a less strong association with BMI at delivery. Management Considerations. Preferably before conception, but certainly during the antepartum period, health care providers should inform women about the risks of obesity and the benefits of weight loss before pregnancy and in the long term. Counseling should include recommendations to adopt healthy eating and exercise habits, as well as discussions around actual and appropriate ranges of weight gain. Obese patients should also be screened for high blood pressure, proteinuria, depression, and obstructive sleep apnea, as well as pregestational type 2 diabetes mellitus at the initial prenatal visit with a follow-up glucose challenge test if the initial test is normal. Forwomen with BMI ≥35 kg/m2, daily intake of aspirin (75mg) is recommended from 12 weeks' gestation until birth to reduce the risk of preeclampsia. The American College of Obstetricians and Gynecologists recommends weekly antenatal surveillance for fetal well-being, starting at 34 weeks of gestation for women with a prepregnancy BMI ≥40 kg/m2 and by 37 weeks for women with a prepregnancy BMI of 35 to 39 kg/m2. During labor and delivery, additional staff and equipment may be needed, depending on the patient's weight. Vaginal birth should be encouraged, and a history of bariatric surgery should not be an indication for CD. For women with obesity undergoing CD, some experts recommend increasing the preoperative dose of cefazolin, although there is mixed evidence on its clinical benefit. Some trials have assessed broadening or extending antibiotic coverage for women undergoing CD, such as adding azithromycin to standard antibiotic prophylaxis to reduce the risk of postoperative infection or a prophylactic 48-hour course of oral cephalexin and metronidazole postoperatively to reduce surgical site infections. Neuraxial anesthetic techniques should be used preferentially in patients with obesity. Mechanical thromboprophylaxis with pneumatic compression before and after CD is recommended.Weight-based dosing of pharmacologic options for thromboprophylaxis is consideredmore effective thanBMI-stratified dosage after CD in women with class III obesity. During postpartum care, women with obesity may need early breast-feeding support. Counseling should include information about the risks associated with obesity for women and infant along with recommendations for postpartum weight loss. Management of Obesity and Gestational Weight Gain. Both environmental and genetic factors play a role in positive weight balance and weight gain over time. Early obesitymanagement can minimize weight gain during pregnancy and reduce the prevalence of gestational diabetes. Studies show that when prenatal health care providers make these lifestyle recommendations, they are more successful. One study found that women who underwent motivational interviewing monthly for 7 to 8months had greater weight loss by 2 kg than a control group receiving only emotional support. However, these interventions often fail when people revert to previous eating and exercise habits after intensive management, suggesting that management of obesity requires a long-term approach.