By Ahizechukwu C. Eke, MD, PhD, MPH
Obesity during pregnancy, defined by the International Classification of Diseases, 11th Revision (ICD-11), as a chronic complex disease characterized by excessive adiposity that can impair health at the onset of pregnancy, has become increasingly prevalent among women in the United States and represents the most common health challenge faced by women of childbearing age.1,2 Over the last two decades, there has been a significant rise in obesity rates among pregnant women, particularly with a notable 33% increase from 2001 to 2018 in women aged 20 to 39 years.2
Factors Affecting Obesity
According to the World Health Organization’s classification, obesity is categorized into three classes: Class I (body mass index [BMI] 30 kg/m² to 34.9 kg/m²), Class II (BMI 35 kg/m² to 39.9 kg/m²), and Class III (BMI ≥ 40 kg/m²).3 Presently, more than half of pregnant women in the United States fall into one of these obesity categories, with the prevalence of obesity varying by demographic factors such as age, race, and socioeconomic status.4,5 Given the increasing rates of obesity among pregnant women, there is an urgent need for effective management strategies to mitigate these risks and improve maternal and neonatal outcomes.
Obesity in pregnancy can be attributed to multiple factors that include genetic predispositions, lifestyle factors (such as diet and physical activity), and socioeconomic conditions.6 Genetically, individuals are predisposed to obesity through the heritability of BMI, which ranges from 40% to 70%.7 Environmental factors, such as high caloric intake and sedentary lifestyle, exacerbate these genetic predispositions. Moreover, certain medications and medical conditions also contribute to weight gain, which can persist or escalate during pregnancy.8
The pathophysiology of obesity in pregnancy involves a chronic state of positive energy balance leading to excessive fat storage in adipocytes.9,10 This state induces metabolic and inflammatory changes, which increase the storage of triglycerides and promote adipocyte hypertrophy and hyperplasia.9,10 These changes are associated with increased secretion of inflammatory cytokines and a state of insulin resistance, which affect metabolic functions across multiple organ systems, thereby influencing both maternal and fetal outcomes throughout the course of pregnancy.9,10
Maternal and Fetal Effects
Maternal obesity has a profound effect on both the mother and fetus, leading to a variety of adverse pregnancy outcomes. These include an increased risk of gestational diabetes, hypertensive disorders of pregnancy, cesarean delivery, preterm birth, fetal macrosomia, congenital anomalies, stillbirth, and infant mortality.11,12 Moreover, maternal obesity sets the stage for long-term health issues in offspring, such as metabolic syndrome and cardiovascular diseases, and also contributes to chronic conditions such as type 2 diabetes and cardiovascular diseases in the mother post-delivery.13
Effective management of obesity during pregnancy is crucial for improving maternal and fetal outcomes. This begins with rigorous screening for metabolic conditions during the first trimester, including gestational diabetes and hypertension. Screening for diabetes typically is conducted using a one-hour, 50-gram oral glucose tolerance test (OGTT) or hemoglobin A1c (HbA1c), with values greater than 200 mg/dL or an HbA1C over 6.5% being diagnostic of diabetes. If the one-hour OGTT result exceeds 140 mg/dL, a follow-up three-hour OGTT is indicated for diagnosis.
Monitoring During Pregnancy
Monitoring blood pressure at home and during prenatal visits also is critical. In addition, obesity can influence the accuracy of prenatal diagnostic tests, making early fetal aneuploidy screening (typically between 11-14 weeks of gestation) vital.14 The fetal fraction of cell-free deoxyribonucleic acid (DNA), which decreases with increasing maternal weight but rises with advancing gestational age, suggests that delaying cell-free fetal DNA testing in obese patients until late in the first trimester could optimize results. However, this delay might restrict options for chorionic villus sampling.14 Furthermore, an anatomical evaluation via a transvaginal approach is preferable late in the first trimester rather than early in the second trimester for women with obesity.15 Early intervention through lifestyle modifications and nutritional counseling is essential to manage weight gain and mitigate associated risks.
Ongoing monitoring of the mother’s weight and metabolic health is crucial throughout the second and third trimesters of pregnancy. During these stages, the focus is on nutritional management to control gestational weight gain and address any metabolic issues, such as gestational diabetes, that may arise. Tailored dietary recommendations are crucial to ensure both maternal and fetal health while maintaining adequate nutritional intake. Women who passed the initial OGTT testing in the first trimester undergo repeat OGTT testing between 24 and 28 weeks of gestation. Additionally, antenatal fetal monitoring typically begins around the 36th week of gestation to assess fetal well-being. However, in obese women, the increased visceral fat can make it difficult for electronic fetal monitoring to accurately detect fetal heart rates. In such cases, biophysical profile testing can be a valuable supplementary tool for antenatal testing.16
The Institute of Medicine (IOM) guidelines recommend a more restricted range of weight gain for women with obesity compared to those with a normal BMI to optimize health outcomes.17 Specifically, the IOM advises that obese women aim to gain between 11 and 20 pounds throughout the pregnancy, with a suggested rate of about 0.5 pounds per week during the second and third trimesters.17 Effective weight management involves collaboration with nutritionists who provide specialized dietary plans. These plans cater to the increased metabolic demands of pregnancy while controlling excessive weight gain, thereby reducing the risk of gestational diabetes and other metabolic disorders.
GLP-1 Agonists
The use of glucagon-like peptide-1 (GLP-1) agonists during pregnancy in women with obesity presents a promising therapeutic avenue, given their efficacy in weight management and glycemic control in nonpregnant populations.18 GLP-1 agonists, such as liraglutide and semaglutide, have been shown to reduce HbA1c levels by 0.5% to 1.5% and promote weight loss of up to 3% to 5% of body weight in obese individuals with type 2 diabetes.19 Despite these benefits, the safety and efficacy of GLP-1 agonists during pregnancy remain underresearched.18
Current data are derived primarily from animal studies and limited human observational studies because of ethical and safety concerns. For instance, studies in rodents have shown an increased risk of fetal growth alterations and skeletal changes, although these findings have not been consistently replicated in human studies.18 The available human data, largely from pregnancy registries and retrospective analyses, suggest no significant increase in major congenital malformations with the use of GLP-1 agonists.18 However, as a result of the limited sample size and lack of controlled trials, these findings are preliminary. Because of the limited safety data regarding the use of GLP-1 agonists in pregnant women with obesity, it is advisable to avoid prescribing these medications until more comprehensive data support their safety and efficacy in this population.
Delivery and Postpartum Management
Delivery plans for pregnant women with obesity should be meticulously planned to manage potential complications effectively. This involves careful decision-making regarding the mode of delivery, with a comprehensive plan for either induction of labor or cesarean delivery based on the obstetric indications associated with obesity. In situations where fetal monitoring during labor proves challenging, the use of a scalp electrode can enhance intrapartum monitoring accuracy. However, this method necessitates the rupture of membranes, which can be a concern, since labor tends to be prolonged in obese patients, potentially increasing the risk of infection.
Additionally, given the extended time required from the decision to perform a cesarean delivery to the actual delivery of the fetus in obese patients, safety concerns during labor necessitate careful planning. Healthcare providers must maintain a low threshold for action on borderline fetal heart-rate tracings to mitigate risks. Furthermore, obese patients considering a trial of labor after a prior history of cesarean (TOLAC) delivery should be thoroughly counseled about the potential for prolonged labor and the risks associated with TOLAC. Prolonged labor in the setting of TOLAC in this population can increase the risk of maternal and fetal complications, particularly if an emergency cesarean delivery becomes necessary.
Postpartum management is centered on assisting mothers in returning to their pre-pregnancy weight and addressing ongoing metabolic issues, such as diabetes and hypertension, as well as breastfeeding issues. Obese postpartum patients often face unique challenges with breastfeeding, including difficulties in latching, reduced milk supply, and delayed onset of lactation. These issues may be compounded by anatomical variations, such as larger breasts and increased adipose tissue, which can hinder the baby’s ability to achieve a proper latch.
Management strategies focus on providing tailored lactation support, such as using specific breastfeeding positions that accommodate excess body weight and ensure comfort for both mother and baby. Additionally, frequent lactation consultations can help to monitor milk supply and provide interventions, such as expressing milk to stimulate production. Education on diet and hydration also is crucial to support milk production.
Ultimately, a multidisciplinary approach involving lactation consultants, obstetricians, and nutritionists is essential to address these breastfeeding challenges effectively and support the nutritional needs of the newborn. Also, psychological support is essential to help manage potential postpartum depression. It also is crucial to provide long-term health counseling and interventions to mitigate the increased risks of chronic conditions that can persist after childbirth.
Ahizechukwu C. Eke, MD, PhD, MPH, is Associate Professor in Maternal Fetal Medicine, Division of Maternal Fetal Medicine, Department of Gynecology & Obstetrics, Johns Hopkins University School of Medicine, Baltimore.
References
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