Obesity in Pregnancy: Classification and Clinical Implications

SUMMARY:

The prevalence of obesity in women of reproductive age (20 to 39) in the US is 39.7%. Prevalence is found to be lowest among non-Hispanic Asian women (17.2%) and higher in non-Hispanic White (39.8%), Hispanic (43.7%), and non-Hispanic black (56.9%) women (2017 to 2018 data). Obesity is commonly classified based on body mass index (BMI). BMI is defined as weight in kg divided by height in meters squared (kg/m²). Definitions are as follows

• Underweight: BMI <18.5
• Normal weight: BMI 18.5 to 24.9
• Overweight:  BMI 25 to 29.9
• Obesity class I: BMI 30 to 34.9
• Obesity class II: BMI 35 to 39.9
• Obesity class III: BMI ≥40

KEY CLINICAL POINTS:

Potential Fetal and Maternal Complications

Antepartum effects

• Increased risk of spontaneous abortion and recurrent miscarriage
• Increased risk of stillbirth
• Increased risk of fetal anomalies include:
  • Neural tube defects
  • Cardiovascular abnormalities
  • Cleft lip and palate
  • Anorectal atresia
  • Hydrocephalus
  • Limb reduction anomalies
• Increased risk of maternal cardiac dysfunction, proteinuria, sleep apnea, fatty liver disease, gestational diabetes , preeclampsia

Intrapartum effects

• Increased risk of
  • Cesarean sections
  • Failed trial of labor
  • Endometritis
  • Wound dehiscence
  • Deep venous thrombosis

Post-partum effects

• Weight retention
• Metabolic dysfunction
• Pregravid obesity in future pregnancies
• Early termination of breast feeding
• Post-partum anemia
• Depression

Fetal and childhood risks

• Increased risk of neonatal and infant death
• Macrosomia
• Impaired growth
• Metabolic syndrome
• Childhood obesity

Management Considerations

Preconception Care

• Behavioral interventions
  • Focus on diet and exercise to improve outcomes vs exercise alone
  • Encourage weight loss prior to pregnancy
• Refer to behavioral counseling with interventions focused on nutrition, diet and exercise

Note: USPSTF recommends clinicians offer behavioral counseling interventions to promote healthy weight gain and preventing excess gestational weight gain in pregnancy to all pregnant women (see ‘Learn More – Primary Sources’ below) | Table 2 includes a comprehensive summary of behavioral counseling interventions

Prenatal Care

• Calculate BMI to guide diet and exercise counseling at initial visit
• Counsel patients about limitations of identifying structural anomalies with ultrasound in obese patients
• Glucose intolerance
  • Assess for glucose intolerance risk factors including
    • ≥BMI 30 | Previous GDM | Impaired glucose metabolism
  • Recommend early glucose screening for those with risk factors (list for early screening factors can be found in ‘Related ObG Topics’ by tapping on ‘Updated ACOG Guidance on Gestational Diabetes’)
• Weekly antenatal fetal surveillance
  • BMI of 35 to 39.9: Consider initiating weekly surveillance at 37w0d
  • BMI ≥40 or greater: Consider initiating weekly surveillance at 34w0d

Intrapartum Care

• Labor pattern
  • First stage of labor may be prolonged in obese patients
  • Consider delaying cesarean delivery for labor arrest
• Cesarean incision
  • Optimal skin incision is unclear
  • Vertical may be associated with increased complications
  • Supraumbilical incision may be helpful in the presence of a large panniculus
• Prophylactic antibiotics prior to cesarean
  • Weight-based dosing may be considered
    • BMI ≥30 or weight ≥80 kg: 2 g cefazolin
  • Postoperative oral regimen in obese individuals who may not have received IV azithromycin
    • 500-mg oral cephalexin and 500-mg metronidazole every 8 hours for 48 hours
• Skin cleansing prior to cesarean
  • Use an alcohol-based solution such as chlorhexidine–alcohol
• Vaginal cleansing
  • Prior to both vaginal or cesarean delivery with either povidone–iodine or chlorhexidine gluconate

Postpartum Care

• VTE mechanical prophylaxis
  • Recommended prior to and after cesarean delivery
  • CMQCC recommends mechanical prophylaxis for BMI >40 for vaginal birth
• VTE chemoprophylaxis
  • LMW heparin: Enoxaparin 40 mg daily commonly used as prophylactic dose following surgery
  • Weight-based VTE chemoprophylaxis dosing may be considered in Class III obesity following cesarean
    • 0.5 mg/kg enoxaparin every 12 hours starting 12 hours after surgery (based on prospective cohort study)
  • Subcutaneous drains
    • Do not use routinely after cesarean due to increased risk for wound complications

Learn More – Primary Sources:

ACOG Practice Bulletin 230: Obesity in Pregnancy

ACOG Committee Opinion No. 548 :Weight Gain During Pregnancy

USPSTF: Behavioral Counseling Interventions for Healthy Weight and Weight Gain in Pregnancy