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OBSTETRICS FEATURE

Obesity in Pregnancy

Kara M. Coassolo, MD; Karen Tiedeken, MSN, CRNP

Obese pregnant women and their health care providers face a host of challenges. This article outlines the risks of pregnancy with obesity and offers tips for optimizing pregnancy outcomes.

The challenge of caring for the obese pregnant woman is common in typical obstetric practices. The National Health and Nutrition Examination Study from 2003 to 2004 reported an overall prevalence of obesity of 32.2%.1 For women ages 20 to 39, 28.9% were obese, and 8% had a body mass index (BMI) of 40 or higher. The most common method of assessing obesity is the BMI calculated by the weight in kg/height in m2. Typically, 25 kg/m2 or above is considered overweight, and 30 kg/m2 or higher obese. For a woman with the average height of 5'4", a weight of 146 lb classifies her as overweight, and 175 lb is considered obese.

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ASSESSING FOR UNDERLYING HEALTH PROBLEMS

Obese women are at increased risk for diabetes, chronic hypertension, and sleep apnea. A careful history and physical examination at the beginning of pregnancy should focus on signs or symptoms of these conditions, and consideration should be given to early screening for gestational diabetes.2 The prevalence of obstructive sleep apnea in pregnancy is unknown. A sleep study is reasonable in obese pregnant women with symptoms such as loud snoring and excessive daytime sleepiness, although it is not known if diagnosing and treating the disorder improve maternal or fetal outcomes (Table 1).

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TABLE 1. Surveillance in the First Half of Pregnancy for Obese Women

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FIRST AND SECOND TRIMESTERS

Several studies have noted an association between obesity and miscarriage. A meta-analysis combining both spontaneous and assisted pregnancies reported a significant increase in the odds of miscarriage in overweight and obese women compared with those of normal weight (odds ratio [OR], 1.67; 95% CI, 1.25-2.25).3

The risk of congenital anomalies is also increased. Several studies report not only an increased incidence of neural tube defects but also an incremental increase in the upper ranges of maternal BMI.4 Increased risks for various other defects have been described, including heart defects and facial clefting (Table 2).5 Diagnosing fetal anomalies prenatally remains challenging in the obese gravida, as a full anatomic survey is often incomplete or suboptimal.

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TABLE 2. Risk of Congenital Anomalies With Maternal Obesity5

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THIRD TRIMESTER

For obese women without underlying diabetes, the risk for gestational diabetes is increased. In a meta-analysis examining the association of gestational diabetes and maternal obesity, the odds increased incrementally for women who were overweight (OR, 2.14; 95% CI, 1.82-2.53), obese (OR, 3.56; 95% CI, 3.05-4.21), and severely obese (OR, 8.56; 95% CI, 5.07-16.04).6 Similarly, the risk of developing preeclampsia is increased almost 3-fold for obese women compared with those of normal weight.7

Several studies have reported an association with obesity and unexplained stillbirth. In a meta-analysis of 9 studies, the odds of stillbirth were 2.07 higher among obese women compared with those of normal weight.8 Increased fetal surveillance has not been tested as a strategy to decrease the risk.

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LABOR AND DELIVERY

The estimation of fetal weight is important in late pregnancy as the risk of macrosomia is increased. Maternal obesity has also been associated with an increased risk of shoulder dystocia after controlling for other factors.9

Obesity has been identified as a risk factor for cesarean delivery. In a meta-analysis incorporating 33 studies, the OR of a cesarean delivery for obese women was 2.05 (95% CI, 1.86-2.27).10 For women with a prior cesarean delivery attempting a vaginal birth after cesarean, success rates are inversely proportional to the prepregnancy BMI, with a success rate of 68.2% when the BMI is 30 or higher.11

Operating on the obese gravida can be challenging, and adjustments may be required to optimize the adequacy of the operating table, correct patient positioning, and the choice of surgical approach. No randomized trials have compared low transverse and supraumbilical abdominal incisions. Since the optimal approach is not known, each case should be considered individually.

Longer operative times and increased blood loss have been reported in obese women undergoing cesarean delivery.12 Despite the administration of prophylactic antibiotics, the risk of postoperative infections is increased.13 When the subcutaneous layer is greater than 2 cm, suture closure has been associated with a decreased risk of wound disruption, however subcutaneous drain placement has not demonstrated a significant reduction in postoperative wound complications.14,15

Anesthesia risks increase in obese parturients due to maternal comorbidities and obstetric complications. Regional anesthesia is preferred in these patients, but difficult or failed catheter placement and accidental dural puncture have been reported. Early assessment of the patient and preparation for a possible difficult airway may decrease potential complications (Table 3).16

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TABLE 3. Risks for Obese Women in the Third Trimester of Pregnancy

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POSTPARTUM PERIOD

Obesity is a risk factor for venous thromboembolism during pregnancy and in the puerperium. Early mobilization and mechanical prophylaxis (graduated compression stockings or intermittent pneumatic compression) are recommended to decrease the risk after cesarean delivery. There are insufficient data to determine whether the benefits of pharmacologic prophylaxis (ie, heparin) outweigh the risks.17

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PREGNANCY AFTER BARIATRIC SURGERY

Bariatric surgery has proved to be an effective weight-loss treatment for the morbidly obese patient. Women should be advised to delay pregnancy for 12 to 24 months after the procedure to accommodate the rapid weight loss and allow the patient to reach her goal weight. Once pregnant, these women should be monitored for adequate nutrition, maternal weight gain, and fetal growth. An evaluation for micronutrient deficiencies should be considered, and supplementation with iron, vitamin B12, folic acid, and calcium may be necessary.18 Surveillance for adequate fetal growth is warranted, with serial fundal height measurements and ultrasound as needed. Alternative testing for gestational diabetes should be considered, due to the increased risk of dumping syndrome. Strategies include fasting and assessing postprandial glucose levels either on 1 occasion or over the period of 1 week by home glucose monitoring (Table 4).

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TABLE 4. Recommendations for Pregnant Women After Bariatric Surgery

There have been several case reports of complications during pregnancy following bariatric surgery, including bowel obstructions, band slippage, gastric ulcers, and staple line strictures. In some cases, maternal or fetal/neonatal deaths occurred.19 There should be a high index of suspicion when a pregnant woman who has had these procedures presents with significant abdominal symptoms.

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MATERNAL OBESITY AND CHILD HEALTH

Multiple studies have examined the effect of the intrauterine environment on health complications that occur later. Maternal obesity has been found to increase the risk of childhood obesity 2-fold at ages 2 through 4, even after controlling for race, birth weight, and socioeconomic status.20

So how do we best care for these patients? Ideally we should counsel the nonpregnant woman about the health consequences of obesity and encourage weight loss prior to conception. In the early part of pregnancy, women should be counseled about the increased risk of pregnancy complications. Recommendations for nutrition and targeted weight gain are essential. The Institute of Medicine recently released new recommendations for weight gain in pregnancy (Table 5).21 Contrary to the prior recommendations in which no upper limit of weight gain was recommended, the new guidelines state that 11 to 20 lb is the goal for obese women. A targeted ultrasound should be done in the mid-trimester, and limitations for the detection of fetal structural malformations should be reviewed. Careful screening for gestational diabetes and surveillance for preeclampsia and macrosomia are warranted. A multi-disciplinary approach in the labor unit involving nursing and anesthesia can help prepare for potential complications surrounding delivery and in the postpartum period. Women should be encouraged to adapt a healthy lifestyle postpartum to minimize risk in a subsequent pregnancy.

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TABLE 5. Institute of Medicine Recommendations for Weight Gain in Pregnancy by Prepregnancy BMI21

The authors report no actual or potential conflicts of interest in relation to this article.

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Kara M. Coassolo, MD, is Attending Perinatologist, and Karen Tiedeken, MSN, CRNP, is Perinatal Nurse Practi-tioner, both in the Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Lehigh Valley Health Network, Allentown, PA.

References

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2. American College of Obstetricians and Gynecologists. ACOG Committee Opinion No 315: Obesity in pregnancy. Obstet Gynecol. 2005;106(3):671-675.
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4. Ray JG, Wyatt PR, Vermeulen MJ, Meier C, Cole DE. Greater maternal weight and the ongoing risk of neural tube defects after folic acid flour fortification. Obstet Gynecol. 2005;105(2):261-265.
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6. Chu SY, Callaghan WM, Kim SY, et al. Maternal obesity and risk of gestational diabetes mellitus. Diabetes Care. 2007;30(8): 2070-2076.
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9. Mazouni C, Porcu G, Cohen-Solal E, et al. Maternal and anthropomorphic risk factors for shoulder dystocia. Acta Obstet Gynecol Scand. 2006;85(5):567-570.
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15. Ramsey PS, White AM, Guinn DA, et al. Subcutaneous tissue reapproximation, alone or in combination with drain, in obese women undergoing cesarean delivery. Obstet Gynecol. 2005;105(5 Pt 1):967-973.
16. Vallejo MC. Anesthetic management of the morbidly obese parturient. Curr Opin Anaesthesiol. 2007;20(3): 175-180.
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18. American College of Obstetricians and Gynecologists. ACOG Practice Bulletin No 105: Bariatric surgery and pregnancy. Obstet Gynecol. 2009;113(6):1405-1413.
19. Maggard JA, Yermilov I, Li Z, et al. Pregnancy and fertility following bariatric surgery: a systematic review. JAMA. 2008;300(19):2286-2296.
20. Whitaker RC. Predicting preschooler obesity at birth: the role of maternal obesity in early pregnancy. Pediatrics. 2004;114(1):e29-e36.
21. Rasmussen KM, Yaktine AL, eds. Weight Gain During Pregnancy: Reexamining the Guidelines. Washington, DC: National Academies Press. In press.

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