Shockingly, it was recently reported that for the very first time in all of human history, the number of obese individuals in the world exceeds the number of those who are underweight. Large segments of our population are at high risk for a multitude of serious maladies, perinatal morbidity and mortality, and ultimately, premature death. Despite the widely described negative health consequences of obesity, the obesity epidemic continues to challenge clinicians, researchers, public health policy makers, and the healthcare system. The problem is not solely limited to the developed world, as obesity has become a World Health Organization focus as it relates to global health improvement initiatives. Globally, more than 1 billion people are overweight with more than 300 million being obese. Cancer, orthopedic complications, diabetes, hypertension, stroke, heart disease, premature death, and other serious complications (Table 6-1) have been well described, and yet the public health goal of the populace achieving a normal body mass index (BMI) has been elusive. Sadly, obesity is a well-recognized “common denominator” to preventable mortality, and obese (as well as overweight) adults have been shown to be at significantly higher risks for any-cause mortality, than their leaner counterparts. The unfortunate trend toward a sedentary lifestyle and unhealthful eating habits has likely contributed to this unfortunate and costly situation, although unquestionably, myriad psycho-socio economic, genetic, and environmental factors are likely contributory. Ironically, despite the decades-long availability of dietetic, fat-free, low-fat, sugar-free, and low-calorie foods and beverages, not to mention the ubiquitous presence of health clubs in our communities, there are more obese Americans today than at any previous time in our history. In the CDC’s most recent analysis (2015), it was found that more than 72 million American adults are obese, which constitutes more than 36% of the adult population, and accounts for a staggering $150 billion of annual obesity-related healthcare expenditures. In just the 2 years between 2007 and 2009, 2.4 million more adult Americans became obese! While obesity is now recognized in 12.5 million American children and adolescents (17% of this population), sadly, nearly 1/3rd of all children ages 2 to 19 years are now either overweight or obese. Relevant to the practitioner of obstetrics, the prevalence of obesity is higher in women (38.3%) than in men (34.3%). Despite some differences in obesity prevalence based upon levels of education, income, and ethnicity/race, it is clear that over the past decades, obesity rates have increased for both men and women of all socioeconomic strata. While the number of obese Americans stood at just 13% in 1962, presently, approximately two in three US women are either overweight or obese, with the highest prevalence of 57% noted among non-Hispanic Black women aged 20 and over. Colorado remains the “leanest” state, with just 18% of its population obese, while the “heaviest” state is Mississippi, with nearly 35% of its adult population obese. At least nine states have obesity rates of at least 30%, as compared to none in 2000. Clearly, the Healthy People 2010 goals for 15% obesity among adults and 5% in children were not met, and with 2020 nearly upon us, it is unlikely that we will see the Healthy People 2020 goals of an adult obesity rate of 30.6%. This unfortunate “state of the weight” in the United States may ultimately undo the steady gains in overall health we have enjoyed as Americans since the dawn of the 20th century, and now contributes to the deaths of 300,000 Americans annually. The remarkably high prevalence of this condition and its significant negative impact on overall health makes its prevention and treatment a top priority for all healthcare disciplines.

Coexisting diabetes is a particularly significant comorbidity and affects nearly 10 million US obese women, with its prevalence having increased 61% since 1991. Nearly 4% of the overall adult female population is both obese and diabetic, and among diabetic women, 90% are either overweight or obese. This is significant in that obesity in persons with diabetes is associated with poorer control of blood glucose levels, blood pressure, and cholesterol, placing obese individuals with diabetes at higher risk for both cardiovascular and microvascular disease.

As with many other adverse health measures, disparity in obesity exists. African-American women have the highest prevalence of obesity (57%), as compared to Hispanic women (46%), and non-Hispanic white women (36%). This is particularly poignant as African-American women incur the greatest numbers of years of life lost to obesity-related premature mortality. Our patients with limited economic means appear to be disproportionally affected by obesity, given a relatively low prevalence of 29% for those at or 350% above poverty, while those women with income below 130% of the poverty level have an increased prevalence to 42%. Additionally, disparity in obesity rates amongst children is noted with the startling finding that one in seven low-income preschool-aged children are now obese. Nearly 1/3rd of 3.7 million children aged 2 to 4 years are either obese or overweight. The percentage of overweight children (ages 6-11) has doubled since the early 1980s, while the percentage of overweight adolescents has nearly tripled! Fortunately, recent data would indicate a plateauing of obesity prevalence for youth between 2003 and 2014. A provocative, startling statistic worthy of our attention in this matter, is that the obesity rate among children of parents without a high-school diploma is threefold greater than for those children whose parents who have earned a college degree (30.4% vs 9.5%).

Obesity and Pregnancy

While the clinical reality of the profound negative impact of obesity on perinatal outcome is well recognized by the busy obstetrical practitioner “in the trenches”, a plethora of research into this subject does in fact support these unfortunate perceptions. Obesity negatively impacts virtually all adverse pregnancy outcomes, among which are increased risks for congenital malformations, diabetes, aberrations in fetal growth, stillbirth, hypertensive disorders of pregnancy, labor abnormalities, a higher cesarean section rate, and greater morbidities associated with cesarean delivery. In fact, the likelihood of super-obese women requiring ICU admission is increased significantly, with nearly 60% of ICU admission risk medicated by medical comorbidities, thus emphasizing the critical nature of well-coordinated multidisciplinary care. Newly emerging information would also suggest and support the additional burden of obesity in negatively impacting fetal programming, thus deleteriously impacting the long-term health of the next generation, as increased pre-pregnancy BMI is a known risk factor for childhood obesity. Obesity complicating pregnancy has also been recognized as a significant contributor to an increased use of perinatal healthcare resources, contributing to the ever-increasing costs of healthcare.

The complications and challenges posed by obesity in the care of these patients tests even the most “seasoned”, skilled practitioner, especially as it relates to prenatal diagnosis and intrapartum care. Tragically, most dreadful of obstetric complications, maternal death, appears to be on the rise in the 21st century, with obesity now recognized as a likely significant contributor. These patients are indeed high risk and deserving of intense efforts to minimize morbidity and mortality when possible, and thus achieve the best perinatal outcome possible. This chapter strives to inform the reader of the critical components of obstetric care for the obese gravida, reviewing selected antepartum, intrapartum, and postpartum considerations.

Definitions

Historically, obesity has been defined and described in a variety of descriptive ways, with terms such as severe, extreme, super, massive, morbid and even “grotesque” appearing in the literature to describe different degrees of obesity. Until relatively recently, standardized descriptive definitions for overweight and obesity were lacking; however, the BMI (Table 6-2) is now used throughout the literature to indicate the specific patient population being investigated, and thus is the standard measure utilized to determine categories of body weight. The terms overweight and obesity both describe ranges of weight that are greater than what is generally considered healthy for a given height. The terms also identify ranges of weight that have been shown to increase the likelihood of disease and other adverse health consequences. Importantly, while BMI correlates with the amount of body fat, BMI does not directly measure body fat. Thus, some individuals such as athletes may have a BMI that identifies them as overweight even though they do not have excess body fat. Other methods of estimating body fat and body fat distribution include measurements of skinfold thickness and waist circumference, calculation of waist-to-hip circumference ratios, and techniques such as ultrasound, computed tomography, and magnetic resonance imaging.

Obesity is most commonly associated with an excess of caloric intake versus expenditure or physical activity, although as noted above, a myriad of factors (psychosocial-economic genetic and environmental) may play roles as well. A small percent may be caused by a diverse group of neurologic and endocrine disorders (Table 6-3).

An adult with a BMI more than or equal to 30 is considered to be obese, while an individual with a BMI calculation between 25 and 29.9 is considered overweight. Classes of obesity have also been described, as noted in Table 6-2. Recent information indicates that just more than 50% of all pregnant women had pre-pregnancy BMIs consistent with being either overweight or obese, 8% of women of reproductive age are extremely obese (BMI > 40), and the percentage of women with a BMI of more than or equal to 50 (termed “super-obesity”) has increased fivefold over the past 20 years. This is somber data, as extreme obesity is associated with the most severe general health and perinatal complications.

Given the health implications of obesity, bariatric surgery has become quite common and is among patients of reproductive age not infrequently. In fact, of all these procedures, half are done in women of reproductive age. Pregnant patients with a history of gastric surgery for obesity should be counseled appropriately and surveillance during prenatal care heightened. It is generally recommended to delay childbearing for 12 months post surgery to provide time to optimize weight loss and reduce potential adverse effects of nutritional deficiencies. While some outcomes have been noted as improved with weight loss following bariatric surgery, such as preeclampsia, gestational diabetes, and fetal macrosomia, reports have shown an increased risk for gastric band complications during pregnancy and nutritional deficiencies. Gastrointestinal hemorrhage and other procedure related complications, including fetal and maternal death have been reported during pregnancy. Patients with this surgical history with abdominal complaints should be evaluated thoroughly and without delay, and physical findings consistent with an acute abdomen should be met with a low threshold for surgical consultation and exploration. A large percentage of post-bariatric surgery patients will still meet the criteria for being obese during pregnancy, and at continued risk of obesity related adverse perinatal outcomes. Preconception counseling is highly recommended, and achievement of a normal BMI (18.5-24.9) prior to pregnancy should be looked at as a primary goal to reduce risks for adverse outcomes. Patients should also be counseled that oral contraceptives may be less effective in patients post bariatric surgery with malabsorption, and alternative effective non-oral contraceptive options should be reviewed (Tables 6-4 and 6-5).

Pathophysiology

In pregnancy, blood volume and cardiac output increase approximately 40% with further increases of cardiac output during labor and delivery, reaching values 80% greater than pre-pregnancy values. Obesity accentuates these changes as blood volume and cardiac output expand in proportion to the increase in body fat and tissue mass. Pharmacodynamics for drug therapy may be altered because obese patients have a larger volume of distribution for lipophilic drugs, but a decrease in lean body mass and tissue water. These changes may predispose obese patients to both subtherapeutic and toxic responses to medications.

During pregnancy, a state of relative hyperventilation exists, which may be mediated through progesterone. Respiratory rate does not change, however with increased tidal volume, an approximate 50% increase in minute ventilation occurs, with a resultant increase in PaO₂ and decrease in PaCO₂. Therefore, when evaluating respiratory complaints, beware the “normal” PCO₂. Obese patients demonstrate significant abnormal changes in respiratory physiology. In fact, obese gravidae have markedly diminished functional residual capacity, and except for residual volume, all lung volumes, vital capacity, and total lung capacity are significantly reduced. In labor, PO₂ is diminished. Furthermore, heightened demand for ventilation, elevated work of breathing, respiratory muscle inefficiency, and diminished respiratory compliance have been shown. Ventilation to perfusion ratio abnormalities and hypoxemia, especially in the supine position further demonstrate the potential adverse impact of obesity on maternal respiratory physiology. Total compliance in obesity diminishes by an average of 50%, which is equivalent to placing a 50-lb. weight on the chest and abdomen of a non-obese patient! These respiratory changes in the obese parturient cause the work of breathing to be increased 3 times normal. Desaturation occurs more rapidly with apnea, as during apnea, oxygen requirements are provided by the functional residual capacity, which as noted, is significantly reduced. With diminished functional residual capacity and increased oxygen requirement, preoxygenation prior to intubation is particularly relevant.

Obesity may also be associated with obstructive sleep apnea (OSA), which refers to apnea (absent or severely reduced airflow) during sleep despite respiratory effort, which can predispose to right-sided heart failure and secondary pulmonary hypertension. Antepartum identification of OSA helps in planning interventions to reduce respiratory morbidity, which can be aggravated by immobility, body position, pain, and use of opioids. A low threshold for the evaluation of sleep disorders, pulmonology consultation, sleep medicine consultation, and maternal echocardiography is suggested when clinical history is suggestive. Treatment with continuous nasal positive airway pressure (CPAP) may improve outcome. The increase in cardiac work in these patients should also be considered in evaluation of underlying cardiac dysfunction. While data are limited, OSA may further increase the risk for preeclampsia and gestational diabetes. Even in the absence of OSA, consideration for performing maternal echocardiography is reasonable for patients with greater classes of obesity, especially in the presence of coexisting hypertension given the potential for preexisting hypertensive cardiomyopathy (Table 6-6).

The intrapartum management (Table 6-7) of the obese patient in labor is a multidisciplinary team effort. The obstetrician, nurse midwife, labor and delivery nurse, obstetric anesthesiologist, and nurse anesthetist should have the unified focus of achieving the best perinatal outcome possible. Maternal-Fetal Medicine specialists often serve as an integral component of this team. Medical consultants who have participated in evaluating and treating the patient for coexisting medical complications should be notified of the patient’s admission to labor and delivery, or such specialists (eg, cardiologist, pulmonologist, endocrinologist) called upon for consultation if previously unrecognized medical complications exist. Given the profound physiologic changes occurring in the obese gravid patient and the high probability of coexisting medical complications, it is suggested that patients at highest risk (higher classes of obesity) receive anesthesia consultation soon after admission to labor and delivery. Given the significant intrapartum risks that may occur in these patients, and the challenges intubation may pose, it would be reasonable to consider “in-house” anesthesia and obstetrical response capabilities as important in the management of those obese patients at highest risk (eg, extreme obesity, preexisting medical complications/comorbidities, prior abdominal surgery). Maternal transport or prenatal referral to physicians who work in a tertiary care environment may critical for such patients. Additionally, there may be specific equipment needs to accommodate the obese patient (eg, wider and stronger operating tables, wheelchairs, lifts, longer instruments, large blood pressure cuffs, large pneumatic compression devices), and as such, obstetrical departments should be prepared accordingly.