Delivery Management in Morbid Obesity

Karin A. Fox

GENERAL PRINCIPLES

Definition (1)

Obesity is defined by the Centers for Disease Control (CDC) and the World Health Organization (WHO) as a body mass index (BMI) of 30 kg/m² or more for adults.
Obesity is further subclassified as:
- Class 1: BMI >30 to <35
- Class 2: BMI 35 to < 40
- Class 3: BMI ≥40
Class 3 obesity is sometimes referred to as “extreme” or “severe” obesity.
Obesity is defined as a BMI >95th percentile for age and sex in children.
The prevalence of obesity in both adults has tripled and in children has quadrupled worldwide in the last four decades (WHO).
Obesity is a metabolic disease that is associated with an increased relative risk of hypercholesterolemia, diabetes, hypertension, cardiovascular disease, gallbladder disease, obstructive sleep apnea, certain cancers, osteoarthritis, and all causes of death. In pregnancy, obesity is associated with an increased relative risk for gestational or overt diabetes, chronic hypertension, preeclampsia, preterm birth, or postterm birth.
It is important to acknowledge that social attitudes about obesity vary widely. Many people, including medical professionals, have negative biases toward obesity, whether implicit or explicit (2,3). Patients who have had past experiences of overt discrimination or in more subtle or insidious microaggressions may be less trusting of medical providers (4). Equally important is to recognize that although obesity increases risk, a majority of women with obesity will still have good pregnancy outcomes, especially when care is individualized and optimized (1).

Physical Examination

BMI is calculated by dividing weight in kilograms by the square of the height in meters. The BMI does not measure body fat content directly but is easily and inexpensively calculated, and it correlates moderately with more direct and accurate (but more difficult or expensive) methods of body fat measurement. This ease of use makes BMI a reasonable screening tool for excess body fat and risk for diseases associated with metabolism.
Body fat index, calculated as a sonographic measurement of preperitoneal fat (mm) × subcutaneous fat (mm)/height (cm), or other more direct measurements of adiposity although not widely used may be more accurate predictors of complications of pregnancy, including gestational diabetes, hypertensive disorders of pregnancy (5) than BMI, but further studies are needed before such measures are used widely.
It is important to recognize that BMI is calculated using bodyweight; therefore, athletes with a very high lean body mass may have a relatively high BMI, but a normal or low percentage of body fat and other factors, such as skinfold thickness, diet, and performance should be considered for some individuals; however, over a BMI of 30, the correlation of BMI with total body fat increases.
Visceral adiposity, or fat deposition within the abdominal cavity that leads to a high waist circumference, is associated with a higher risk for metabolic disease than compared to peripheral adiposity, in which excess fat tissue is deposited in the skin, buttocks, legs, and hips. It is plausible that increased subcutaneous or peripheral adiposity increases the risk of wound complications, even in the absence of diabetes; however, there is little to no available evidence specifically differentiating central versus peripheral deposition and wound complication rates.
A multidisciplinary team approach is recommended to optimize outcomes. Collaborative care includes expertise from obstetricians, anesthesiologists, nursing staff, dietitians, neonatologists, and other subspecialists as needed.

Nonoperative Management

Obesity occurs primarily when there is a relative excess of caloric intake compared to caloric expenditure through metabolism and physical activity. Although obesity indicates high relative caloric intake, it is not an indication of adequate nutrition, as highly refined modern diets may provide surplus calories but lack fundamental micronutrients and vitamins; therefore, careful dietary assessment for all patients is recommended.
Obesity can be difficult to reverse, as sustained lifestyle modifications are often required. Risk reduction for health outcomes occurs even with modest (5%-10%) weight loss.
Pregnancy is not considered an optimal time for active weight loss owing to the nutritional demands to support pregnancy. Rather than attempting weight loss, the Institute of Medicine recommends a lower total weight gain during pregnancy (limited to 11-20 lb), with a focus on healthy nutrition and moderate exercise. Referral to a registered dietitian is recommended to address overall nutrition and healthy eating.
Surgical weight loss techniques, such as Roux-en-Y gastric bypass and gastric sleeve, have been proven effective and longer-lasting than lifestyle management alone and have been shown to reduce disease risks. Patients who have had weight loss surgery before pregnancy have a reduction in risks for diabetes, hypertension, and preeclampsia, but have an increased risk for fetal growth restriction. Most experts recommend that women delay pregnancy until at least 1 year to ensure that the initial rapid weight loss period has stopped, and weight and dietary intake remain stable.
Screening of and treatment for obstructive sleep apnea has been shown to reduce risks of development of preeclampsia and improvement in overall sleep in some patients. Use of continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) may be necessary during hospital admission if nocturnal oxygen desaturation is evident, even in patients who have not undergone formal sleep studies.

IMAGING AND OTHER DIAGNOSTICS

Ultrasound remains the mainstay and primary modality for fetal imaging and can often be used as an initial imaging modality for maternal conditions during pregnancy. It is noninvasive, readily accessible in most obstetrical units, and relatively inexpensive compared to other imaging techniques.
X-ray and computed tomography (CT) imaging are reserved for maternal indications, such as pneumonia, evaluation for pulmonary embolism. Appropriate abdominal shielding is recommended to reduce fetal radiation exposure. Contrast may be used if clinically indicated; however, gadolinium-containing contrast agents are often avoided during pregnancy.
Magnetic resonance imaging (MRI) is used as adjunctive fetal and placental imaging, if abnormalities, such as fetal brain anomalies or placenta accreta spectrum are suspected, as well as for maternal indications, such as for appendicitis.
Every imaging modality has technical limitations, and accurate interpretation of imaging findings is dependent upon the operator’s experience and expertise (the person reading and interpreting the images).
Increased adiposity increases tissue depth through which ultrasound waves and radiation must penetrate, therefore potentially attenuating signals from ultrasound, x-ray, and CT imaging, and rendering these diagnostic imaging modalities more technically challenging.
Extreme obesity may inhibit a patient’s ability to fit within some CT and MRI scanners, for which open scanners have been developed. Motion artifact may be increased in some cases. If a patient is unable to lie flat owing to obesity-induced apnea, the ability to complete scanning may also be compromised.
Antenatal ultrasound screening: In observational studies, the ability to adequately visualize the fetal anatomy as described by standardized guidelines and “clear” the fetal anatomy survey inversely correlates with BMI. While in nonobese patients, as low as 4.2% require additional ultrasound appointments at 20 weeks to adequately visualize important fetal anatomical structures (6), this rate approaches 40% to 65% for patients with Class 3 obesity for standard and detailed anatomical scans, respectively (7). Additionally, the total time required to perform ultrasound scans increases with increasing BMI (8), highlighting the technical challenges that increasing adiposity poses for antenatal imaging and prenatal diagnosis.
- Some techniques that have been proposed to improve fetal ultrasound imaging are to perform transvaginal imaging for anatomy in the late first or early second trimester (9,10) to allow additional scan time, optimize ultrasound settings (use “penetration” mode), and utilize a transvaginal scanning transducer through the umbilicus (11) to image structures near the maternal mid-abdomen.

PREOPERATIVE PLANNING

As for all patients, any concomitant medical conditions should be optimized. For patients with hypertension, diabetes, autoimmune, or other disorders, these conditions should be medically optimized before delivery and/or surgery.
Consultation with the anesthesiology team is recommended. Increasing skin thickness makes the placement of regional analgesia more difficult, with an approximate 20% failure rate of epidural placement in some studies. Up to 33% of patients with obesity will have a difficult airway, which may be further exacerbated by laryngeal edema associated with
pregnancy, and may require awake intubation, should intubation be required.
Ensure adequate staff are available to assist with patient lifting and movement, especially if surgery is needed. Although there is no strict weight limit that any one individual may lift, frequent lifting, asymmetric loads, and lifting requiring bending, twisting, and stretching motions, all of which are potentially required while engaged in patient care, may lead to occupational injury for staff members. For heavier patients, more assistance is required for the safety of both the patient and staff. This is especially important if urgent movement may be needed, as with an urgent or emergent cesarean delivery that arises during labor.
Ensure that you have adequate equipment available to facilitate the surgical management of larger patients. Examples are listed in Table 6.5.1.
Some recommend increasing the dose of preoperative prophylactic antibiotics. In some studies, using a 3-g dose of cefazolin (standard is 2 g) in women over 120 kg (265 lb) (12) difference in tissue concentrations at the time of skin closure does not appear to differ significantly based on a double-blind, randomized controlled trial (13). Alternatively, a double-blinded randomized trial of the addition of postoperative prophylactic oral cephalexin 500 mg every 8 hours plus oral metronidazole 500 mg every 8 hours for 48 hours to a standard 2-g cefazolin intravenous preoperative prophylaxis demonstrated a significant risk reduction for surgical site infections but not in wound seromas or wound separation. The number needed to treat to reduce this risk of one surgical site infection was 12, and no adverse reactions were identified (14).