Management Overview of Pregnancy Complicated by Maternal Obesity

| March 26, 2014

by Jarin Leavitt, MD, and Jordan H. Perlow, MD

Dr. Jarin Leavitt is from the Department of Obstetrics and Gynecology, Banner Good Samaritan Medical Center, Phoenix, Arizona. Dr. Jordan H. Perlow is Director of the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Banner Good Samaritan Medical Center, Phoenix, Arizona, and Partner, Phoenix Perinatal Associates, Obstetrix Medical Group of Phoenix, Phoenix, Arizona.

Funding: No funding was provided.
Disclosures: The authors report no conflicts of interest relevant to the content of this article.

Bariatric Times. 2014;11(3):8–14.

Abstract
The overall trend toward a higher incidence of obesity in the general population naturally results in an increased prevalence of obesity complicating pregnancy. Rates of obesity vary by geographic region, and disparity is also noted among different socioeconomic and racial/ethnic groups. Obesity imparts an ever-present risk for adverse health outcomes for the woman who becomes pregnant and is not of a normal body mass index. Given the clinical risk issues with which the obese gravida presents, special attention and care is required in the rendering of prenatal care so as to achieve the best perinatal outcome possible. Obesity places a pregnant patient at risk for many serious complications of pregnancy, including maternal and fetal mortality. Management of the obese gravida requires special consideration and treatment adjustment to minimize these risks.

Background
The overall trend toward a higher incidence of obesity in the general population naturally results in an increased prevalence of obesity complicating pregnancy.[1] A sedentary lifestyle combined with poor dietary choices and a lack of regular exercise creates a situation in which the current obesity epidemic thrives. Despite increased awareness, obesity continues to grow in prevalence. New “quick fix” diet plans seem to appear every day with no improvement in the incidence of obesity. According to the Centers for Disease Control and Prevention (CDC), United States obesity (body mass index [BMI] >30kg/m2) prevalence varies by region with higher prevalence noted in states in the Midwest and South, and a lesser prevalence seen in the northwest and western states. However, even among the “healthier” states prevalence is still noted to be greater than 20 percent.[2] According to 2012 data from the CDC, the state with the lowest prevalence of obesity is Colorado at 20.5 percent, and the highest is Louisiana at 34.7 percent.

The differentiation of obesity “degrees” into classes helps stratify risk and estimate complication occurrence, and furthermore, allows for appropriate comparisons in health outcomes to be reached within populations. Definitions of obesity and the degree to which it has an effect on health are used as an important indicator of risk. Overweight is defined as BMI between 25.0 and 29.9kg/m².

Obesity is defined as BMI greater than or equal to 30kg/m². Subcategories of obesity as follows: class I—BMI 30.0 to 34.9kg/m2, class II—BMI 35.0 to 39.9kg/m2, and class III (also termed extreme obesity)—BMI greater than or equal to 40.0kg/m2. The term super-obesity is used to define a BMI greater than 50.3kg/m2.

Obesity and Pregnancy: Overview
Currently, obesity complicates up to 28 percent of pregnancies, with eight percent categorized as extremely obese (BMI greater than 40kg/m²). The obese gravida is at increased risk for many serious complications, including gestational diabetes, hypertensive disorders in pregnancy, fetal macrosomia, shoulder dystocia, birth trauma, fetal malformations, protracted labor, emergent cesarean delivery, postpartum hemorrhage, venous thromboembolism, and infection risk.[4–7] Also, those who undergo cesarean delivery are at increased risk of significant operative morbidity that may include greater blood loss, longer operative times, anesthetic complications, and postoperative wound infections.[5,7,8] Data has also shown a trend of an increased risk for childhood obesity and diabetes for those born to individuals with overweight and obesity.[9] Obesity complicating pregnancy has also been noted to independently increase the risk for spontaneous preterm birth[10] In fact, essentially every potential pregnancy complication is, to varying degrees, increased in the setting of obesity.

Pregnancy management
The approach to management of the obese gravid woman is multifaceted. Further complicating the picture are historic misperceptions regarding weight gain during pregnancy. For example, as cited by Flick and Artel,[11] traditional thought has been that even in the patient population with obesity, maternal weight gain should be “net positive” to reflect the weight of the products of conception and increased uterine size. Studies have shown, however, that women with overweight and obesity are able to generate the necessary increase in caloric intake needed from their own reserves.[11,12]

Preconception
Women with obesity who desire to become pregnant should be counseled regarding the increased risk to their health and future offspring should pregnancy occur in the setting of obesity. Measures should be taken to initiate weight loss and achieve a normal BMI before conception. Women should be thoroughly counseled regarding the higher likelihood for serious adverse health outcomes, including maternal mortality, preterm birth and its sequelae, hypertensive disorders of pregnancy, fetal growth aberrations, congenital malformation, and stillbirth.[13] Several large studies have demonstrated that weight reduction is an important factor for these women to reduce risk for perinatal complications. For example, an increase in pregravid weight between the first and second pregnancies was shown to increase the risk of development of preeclampsia with the subsequent pregnancy, while a decrease in pregravid weight between pregnancies resulted in a decreased risk for cesarean delivery and large for gestational age infants.[14–16] In addition, increased pregravid BMI is associated with many maternal metabolic disorders, including diabetes mellitus, hypertension, and hyperlipidemia.[17] The increased incidence of these and other potential maternal health factors undoubtedly places the patient at risk during her pregnancy.

It is important to note that patients with overweight and obesity often have higher rates of infertility, and thus, when seeking treatment for such, are found to require increased doses of medication to stimulate successful ovulation.[18] The infertility specialist is found in an ideal situation because the patient will seek medical attention prior to conception providing opportunity for improvement in maternal weight. They should in no uncertain terms be counseled that attainment of a normal BMI prior to conception is recommended to achieve the best pregnancy outcome possible. Furthermore, the patient with obesity conceiving a multiple gestation, certainly more likely in the setting of assisted reproductive technology, will face even further increased risks for adverse perinatal outcome, and thus, a goal of management should undoubtedly be the avoidance of multiple gestation. In otherwise healthy individuals, preconception counseling is nearly nonexistent as the typical first prenatal visit occurs in the first trimester. Fertility specialists should include maternal weight loss recommendations in their routine counseling and consider successful weight loss a prerequisite to intervention. The American College of Obstetricians and Gynecologists (ACOG) recommends a healthy diet with daily aerobic exercise to achieve those goals.[13] Referral to a bariatric physician should be considered to discuss all options for management to achieve normal weight.

Patients who have undergone bariatric surgery require special attention. General considerations for pregnancy after bariatric surgery are that the patient should wait 12 to 18 months prior to conception to decrease fetal exposure to rapid weight loss.[19] It should also be noted that patients who have undergone Roux-en-Y bypass or similar surgery are at increased risk for malabsorption syndromes. It is all the more important for these patients to have adequate vitamin supplementation, including vitamins B12, B6, B1, D, folic acid, calcium, and iron.[19] It has also been suggested that four high-protein meals are preferred over six meals daily.[19] Pregnancy related changes in upper GI function may necessitate evaluation of adjustable gastric bands to determine if such changes may help alleviate symptoms. Laparoscopic adjustment of gastric bands is generally considered safe, particularly in the second trimester.[20]

Post-bariatric surgery complications, including bowel obstruction and maternal and fetal death, have been reported during pregnancy.[21,22] Most cases occurred in women who had Roux-en-Y bypass surgery and involved internal herniation; however, other cases have included volvulus, band slippage, and intussusception with bowel necrosis.[23–25] Problems with detecting such complications in pregnancy are due to symptoms mimicking common pregnancy complaints, such as nausea, gastro-esophageal reflux, generalized abdominal discomfort, and contractions. Experts suggest a low threshold for surgical evaluation and computed tomography (CT) imaging in patients with a history or physical exam concerning for possible bowel obstruction in the setting of a history of prior bariatric surgery. Even with negative imaging studies, providers should maintain a high degree of suspicion in these patients and early consultation with a general or bariatric surgeon is recommended.[26]

First Trimester Care
The National Institutes of Health (NIH) recommends initiating prenatal care in the first trimester with the goal of 90 percent of all first visits occurring during this important time.[27] According to The National Vital Statistics report published in 2011, it was estimated that overall rate of first trimester presentation to prenatal care was only 71 percent, significantly less than the goal of 90 percent.[28] Screening for maternal disorders early in pregnancy is of particular importance in the population with obesity, as evidenced by the plethora of comorbidities with which they present and which can complicate perinatal outcome. Early ultrasound to verify intrauterine gestation and plurality of pregnancy, and to establish pregnancy dating is important on entry to obstetric care. Increased rates of ovulatory dysfunction in individuals with overweight and obesity make dating of the pregnancy particularly important.[29,30] Screening for pregestational medical conditions is also an important undertaking early in prenatal care. Screening should be employed for diabetes, hypertension, thyroid disorders, sleep apnea, and cardiac disease along with any other medical comorbidity for which there exists a high degree of suspicion. Experts also recommend routine baseline lab work to include uric acid, creatinine, hepatic transaminases, and 24-hour urine protein.[31] It has also been suggested that individuals with extreme obesity (class III) could benefit from maternal echocardiography, to determine the existence of cardiomyopathy, especially for those patient with longstanding history of obesity comorbidities (diabetes and/or hypertension).[32,33]

In patients who have undergone bariatric surgery, baseline chemistry and nutritional status evaluation should be accomplished.[19] Individualized counseling regarding pregnancy risks should be discussed with the patient early in pregnancy. Goals of care and a management plan should be reviewed. Given the significantly increased risk for preeclampsia, patients should be counseled on the potential benefits of daily low-dose aspirin in reducing this in high-risk groups.[34]

Second Trimester Care
During the second trimester, full and adequate evaluation of fetal anatomy should be attempted. A multitude of congenital malformations occur more commonly in pregnancies complicated by obesity. Fetal malformations, including cardiac and neural tube defects, have been shown to be associated with obesity. Other malformations, including omphalocele, diaphragmatic hernia, cystic kidney, and orofacial clefts, have also shown significant correlation with obesity.[35–39] Given the difficulty in achieving adequate sonographic visualization due to the suboptimal image clarity, expert opinion suggests imaging no earlier than 20 to 22 weeks gestation.31 Some have suggested that only about 50 percent of ultrasound studies of women with obesity result in complete and adequate fetal assessment.[40] In the non-obese gravid patient, serial fundal height measurement provides some indication that fetal growth is adequate.[41] This is typically initiated in the second trimester during routine prenatal checkups. In the population with obesity, however, fundal height is difficult to accurately assess given the degree of abdominal adipose tissue. Therefore, serial ultrasounds for the evaluation of fetal growth should be performed at approximate monthly intervals to accurately assess appropriateness of fetal growth, or aberrations thereof. Given the marked increased risk for fetal neural tube defects, maternal serum alpha-feto-protein evaluation is recommended.[42]

Third Trimester Care
As a BMI greater than 30kg/m2 significantly increases the risk for virtually all adverse outcomes, third trimester care differs between women with and without obesity. A focus on the avoidance of stillbirth, detection of diabetes and preeclampsia, and ongoing monitoring for the adequacy of fetal growth are key components of third trimester prenatal surveillance. Compared to normal weight women, women with obesity are at increased risk of stillbirth with an odds ratio of 2.8.[43] Intrauterine fetal death is more common even after correctioning for coexisting medical complications. Unfortunately, the specific mechanism for this increased risk of stillbirth has yet to be identified.[43,44] Although the reason for this increased risk is poorly understood, hypotheses include poorly controlled undiagnosed diabetes mellitus, predisposition to fetal anomalies as well as increased risk of hypoxic-apneic episodes due to undiagnosed sleep apnea.[44,45] Some experts, therefore, suggest increased third trimester surveillance including initiation of antenatal fetal testing.[31]

It is important to monitor fetal growth as women with obesity are at increased risk for fetal macrosomia as well as fetal growth restriction. Serial growth ultrasounds as well a sonographic estimation of fetal weight near delivery are recommended to accurately plan delivery route. ACOG recommends counseling regarding the option for a scheduled cesarean delivery if the estimated fetal weight is greater than 4,500 grams at time of delivery in a woman with diabetes and 5,000 grams in a non-diabetic individual.[46] There is no specific recommendation with respect to route of delivery pertaining to BMI criteria. Close surveillance for preterm labor is suggested given the significantly increased risk for premature birth,[10] and antenatal steroids should be administered when the risk for preterm birth within seven days exists.[47,48]

Intrapartum
Labor and delivery poses unique challenges for the parturient with obesity and the obstetrical provider. Mothers with obesity are more likely to carry a pregnancy past their scheduled due date and often have indications for induction of labor.[49,50] This population is at increased risk of failed induction despite attempts at augmentation of labor with oxytocin.[51,52] This places them at increased need for cesarean delivery, and the inherent morbidities of a surgical delivery. These morbidities, including venous thromboembolism, gastric aspiration, anesthesia complications, pneumonia, wound infection and dehiscence, and others, are further complicated by maternal obesity with respect to risk. Women with obesity who undergo cesarean delivery are at increased risk for wound complications including infections and wound breakdown.[8,53] One study estimates the risk of cesarean delivery in the patient with obesity (BMI 30–34.9kg/m²) at 33.8 percent, compared with 20.7 percent in the non-obese control group. The same study showed that women with extreme obesity (BMI >35kg/m²) had a cesarean delivery rate of up to 50 percent,4 (see “cesarean section” in following section).

Anesthetic considerations
Parturients with obesity are at significantly greater risks for anesthesia related complications. Up to 75 percent of anesthesia-related maternal deaths are complicated by maternal obesity, the majority of which are related to the inability of obtaining an endotracheal airway,[54] thus emphasizing the benefit of regional anesthesia when possible. Anesthetic consultation should ideally be sought during the third trimester of pregnancy or upon admission to labor and delivery.[31] The anesthesiologist should be made aware of obesity-related comorbidities and the presence of preeclampsia, as airway edema may further compromise successful intubation.[55] Experts suggest placement of an epidural catheter early in the labor process even if it is not yet necessary for pain control, so as to reduce the probability of need for general anesthesia should emergent delivery be required.[56–58] If general anesthesia is anticipated, then consideration for an “awake” intubation is appropriate. Also video laryngoscopes should be available. If providers and institutions find themselves without these resources, then maternal transport to a tertiary care center should be considered.[31] The environment that provides resources contributing to the greatest element of patient safety should be sought. Prior to intubation, preoxygenation is particularly important in this patient population. In the typical healthy nonobese patient it takes nine minutes for oxygen saturation to fall from 100 to 90 percent, while the patient with obesity reaches the same level of desaturation within three minutes. Oxygen desaturation may be even more drastic in individuals with extreme obesity.[59,60] Physiologic changes of pregnancy result in a 20-percent increase in oxygen consumption and a 20 to 30-percent decrease in functional residual lung capacity in pregnancy. This change is the result of an upward shift of the diaphragm as well as increases to the residual and expiratory reserve volumes.[61] Relaxation of the lower esophageal sphincter and increased intra-abdominal pressure make aspiration of gastric contents a genuine threat during pregnancy. Aspiration is compounded by both the physiological changes of pregnancy as well as obesity. Therefore, it is recommended to give 30mL of nonparticulate antacid, such as sodium citrate, to decrease gastric content acidity. Also, an H2 blocker can be given as well as a prokinetic agent such as metoclopramide.[57]

Antibiotics
Women with obesity undergoing cesarean section should receive higher doses of prophylactic antibiotics than women of normal weight.[62] In general and specifically related to cesarean section, preoperative antibiotic administration has been shown to decrease the risk of infectious morbidity. Patients undergoing bariatric surgery were studied to evaluate efficacy of antibiotic dosage among individuals with extreme obesity . The evidence showed that therapeutic tissue levels were achieved in only 10 to 48 percent of cases. Those patients with BMI greater than 60kg/m² had the lowest levels of adequate antibiotics while those with BMI 40 to 49.9kg/m² achieved therapeutic levels in only about 48 percent of cases.[63] Guidelines established for 2013 by the American Society of Health-system Pharmacists, the Infectious Disease Society of America, the Surgical Infection Society, and the Society for Healthcare Epidemiology of America recommend cefazolin 2 grams for women less than 120kg undergoing cesarean delivery and 3 grams for those greater than 120kg.[64] If the patient has a history of severe penicillin allergy then the alternative regimen of clindamycin 900mg plus gentamicin 5mg/kg of actual body weight should be considered. If actual body weight is greater than 20 percent more than ideal body weight then dosage should be adjusted accordingly.[64]

Venous thromboembolism
Intrapartum risk of thromboembolic disease is increased in pregnancy, and further increased by obesity as well as cesarean delivery. Most experts recommend a minimum of intermittent pneumatic compression devices that are able to accommodate large legs. In the Cochrane review, metanalysis failed to show evidence for universal prophylaxis. Despite this lack of hard evidence, experts generally recommend pharmacologic thromboprophylaxis in the postpartum patient with obesity until they are fully ambulatory.[13,65–70] Recommendations from the Society for Maternal-Fetal Medicine are to consider low molecular weight heparin or unfractionated heparin for pharmacologic thromboprophylaxis in the postpartum patient with obesity after cesarean delivery.[62] Resumption of prophylactic anticoagulation should be held for 12 hours after cesarean delivery or removal of an epidural catheter, whichever is later.[62,71]

Vaginal birth after cesarean delivery
Vaginal birth after cesarean delivery (VBAC) has poor success in patients with obesity . In one large prospective multicenter study, nonobese women had a VBAC failure rate of 15 percent compared to 30 percent for women with obesity (BMI 25.0–29.9kg/m²) and 39 percent for women with morbid obesity (BMI >40kg/m²). The population with obesity also had increased rates of uterine scar dehiscence (1.4–2.1% compared to 0.9% in the nonobese population).[72] In those patients weighing over 300 lbs, VBAC success rates are noted to be as low as 10 percent.[73] Not only were they at increased risk of failure, but the higher rate of complications (risk of infection, uterine rupture, hemorrhage requiring blood transfusion) related to cesarean delivery after a failed trial of labor make it crucial that providers adequately counsel patients with obesity about the low likelihood of VBAC success, and the option of scheduled repeat cesarean section.[73]

Cesarean Delivery
Surgical approach to the patient with obesity undergoing cesarean delivery should be individualized based on each patient’s unique body habitus. It is important to note that in individuals with obesity , particularly those with an “apron-like” pannus of adipose tissue, the umbilicus is a poor landmark to identify pelvic organs. In these women the pubic symphysis and iliac crests are more reliable and consistent marks,[74] and should be examined and palpated in planning a successful surgical approach. In the nonobese patient, a pfannenstiel incision is generally made two finger breadths above the pubic symphisis. Even in individuals with extreme obesity, the adipose tissue in this location is not particularly thick, making it an option for incision placement; however the size, location, and retractability of the panniculus may limit its utility. Montgomery straps or an improvised approach using elastoplast tape to retract the pannus cephalad, may allow for improved access to the suprapubic region for pfannensteil incision placement. Care must be taken with cephalad pannus retraction as this potentially can exacerbate cardiorespiratory compromise due to excessive weight displacement onto the thorax.[75] One must also exercise care in not making the incision too low if the pannus is left in situ, as the incision could potentially be carried down into the subcutaneous tissue and then through the other side of the pannus, without entering the peritoneal cavity. Postoperative care of a pfannensteil incision among the patient with obesity must be attended to carefully and allow for the area to be kept clean and dry given that it is a relatively warm and moist environment. The transverse periumbilical incision may be considered, particularly for those women who are over 400 Lbs. as it provides the strength of a transverse repair without burying the incision under a large panniculus.[76] One disadvantage to this approach, however, is that exposure to the lower uterine segment can be suboptimal and require a vertical hysterotomy thus increasing risk of blood loss and uterine rupture during subsequent pregnancy.[65] Also, subcutaneous tissue will be at its greatest depth in this region, and care must be taken during subcutaneous tissue dissection, as large caliber veins are commonly noted within this fatty layer.[65]

Fascial closure is typically accomplished with delayed absorbable or nonabsorbable suture and utilizes the Smead-Jones technique (far-far-near-near) or an equivalent method that incorporates mass closure if a vertical incision was utilized. We tend to avoid placement of a vertical incision if possible, as they have been shown to be complicated by wound dehiscence and infection more frequently than transverse skin incisions.[77–78] Randomized trials have shown that closure of the subcutaneous space with a depth of greater than 2cm, reduces the risk of wound disruption by up to 33 percent.[79]

Subcutaneous drains have been shown in randomized controlled trials to increase rates of wound complications and are therefore not generally recommended.[80] Skin closure may be accomplished with either subcuticular stitches or staples. Studies in the general population have failed to prove one method superior to the other but they have not been compared directly in the population with obesity undergoing cesarean delivery.[62,81,82]

Hospital equipment capable of providing service for the patient with obesity must be available at hospitals where such patients are expected. Weight capacity of a standard hospital bed is generally 350 to 400 lbs., while specialized bariatric beds can accomidate 600 to 1,000 lbs.[62] Standard wheelchairs may also be insufficient for the patient with obesity and bariatric options should be available.

Postoperatively, additional assistance in moving the patient is often required in order to safely transfer an anesthetized patient from the operating table to a recovery bed. In addition to the above mentioned considerations, specialized surgical equipment, such as long instruments, deeper retractors, and the alexis-o retractor, should be immediately available to the operating suite.[62]

Postpartum
The postpartum period continues to infer risk to the recently delivered patient with obesity. As mentioned previously, obesity increases the risk for development of endomyometrisis, wound infection and venous thromboembolism among other potential complications.[4,5,7,8] Interventions to reduce these risks have also been discussed previously (see sections on antibiotics and venous thromboembolism). Postpartum evaluation 1 to 2 weeks to assess wound healing and resolution of pregnancy related complications, including hypertension, should be encouraged.

Postpartum depression has been shown to be positively correlated with BMI and in cases of extreme obesity, present in up to 40 percent of patients.[83] Patients should be made aware of the signs of postpartum depression and be provided with resources for adequate treatment should symptoms arise. Screening for postpartum depression should be accomplished using a proven depression screening method such as the Edinburgh Depression Scale.

Maternal weight retention postpartum will place the patient at increased risk for long-term health risks, including cardiovascular and metabolic diseases.[84] Weight loss in the postpartum period can be enhanced by resumption of physical activity and breastfeeding.[85] Breast feeding has long-known health benefits for the neonate, but it should be made known that maternal benefits including weight loss may also occur.[85]

Increased prevelance of gestational diabetes means that these patients should be counseled on the importance of appropriate follow up to screen for pregestational diabetes at the six-week postpartum checkup. Patients with a history of gestational diabetes have a seven-fold increased risk of development of diabetes later in life.[86] The Fifth International Workshop on Gestational Diabetes Mellitus recommends that women undergo a 75 gram, two-hour oral glucose tolerance test in the time period of 6 to 12 weeks postpartum.[87,88]

As discussed previously, adequate counseling on the relationship of obesity and maternal and fetal risk in subsequent pregnancies should be reviewed in great detail during the postpartum visit. It is precisely because of this increased risk that family planning be reviewed and course of action made in accordance with the patient’s long-term family planning goals. Providers must take advantage of the six-week postpartum visit to provide additional preconception counseling as in many cases the next time the patient returns to the office, the reason could be to initiate prenatal care once again.

Summary
Given the increased risks for a multitude of adverse pregnancy outcomes when pregnancy is complicated by obesity, women should be encouraged to achieve a normal BMI prior to conception. The obese gravida should be managed as a “high-risk” pregnancy, and surveillance heightened with interventions as outlined here. Hospitals should have proper bariatric certified equipment and other specialized equipment to care for the potential complications of obesity and pregnancy. Transfer of care to a tertiary care center should be considered on an individual basis, when degree of obesity, complicating comorbidities, and/or providers with limited provider experience creates the potential for a diminishment of patient safety.

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