What is the recommended monitoring protocol for a pregnant woman with a pre‑pregnancy body mass index of ≥30 kg/m²?

Monitoring Protocol for Obese Pregnant Women (BMI ≥30 kg/m²)

Pregnant women with BMI ≥30 kg/m² require intensified surveillance including early glucose screening, enhanced ultrasound protocols, anesthesia consultation for BMI >40, thromboprophylaxis assessment, and structured weight gain monitoring at every prenatal visit. 1, 2

Initial Assessment and Baseline Monitoring

First Prenatal Visit

• Calculate and document BMI from pre-pregnancy height and weight to establish baseline and guide all subsequent counseling 2, 3
• Provide diet and exercise counseling immediately based on Institute of Medicine recommendations, targeting approximately 7 kg total weight gain for obese women 2, 4
• Prescribe 5 mg folic acid daily (higher than standard dose) to continue until end of first trimester 1
• Screen for vitamin D deficiency and supplement if confirmed deficient 1
• Assess for pre-existing type 2 diabetes with fasting plasma glucose or glucose challenge test at initial visit 1

Weight Monitoring Throughout Pregnancy

• Measure and document weight at every prenatal visit to track gestational weight gain against targets 2
• Target total weight gain of approximately 7 kg for obese women, substantially less than normal-weight women 2
• Recommend 30 minutes of moderate-intensity exercise daily or 150 minutes per week unless contraindications exist—obesity alone does not contraindicate exercise 2, 4

Metabolic and Medical Surveillance

Glucose Screening

• Perform early glucose screening at 12 weeks gestation using either fasting plasma glucose or 50-g glucose challenge test 1
• Repeat standard gestational diabetes screening at 24-28 weeks even if early screening was normal 1
• For women with history of malabsorptive bariatric surgery, consider alternative testing with 1 week of home glucose monitoring (fasting and 2-hour postprandial) between 24-28 weeks instead of oral glucose tolerance test 1

Preeclampsia Prevention

• For BMI ≥35 kg/m², prescribe low-dose aspirin (75-180 mg daily) starting at 12 weeks until delivery, provided gastrointestinal hemorrhage risk is low 1, 4

Ultrasound Surveillance Protocol

First Trimester

• Nuchal translucency scan between 11 weeks 4 days and 13 weeks 6 days for women with BMI >40 kg/m² 1, 5

Second Trimester

• Early anatomy assessment at 14-16 weeks gestation to overcome acoustic window limitations from adipose tissue 1, 5
• Routine morphology scan at 20-22 weeks gestation as standard anatomical survey 1, 5

Third Trimester

• Growth scan at 28-32 weeks gestation when clinical assessment is limited by obesity to detect late-onset fetal growth restriction 1, 5
• Maintain high index of suspicion for fetal growth abnormalities throughout pregnancy given increased risk of both macrosomia and growth restriction 1

Specialist Consultations

Anesthesia Referral

• Refer all women with BMI >40 kg/m² to anesthesiologist during antenatal period for consultation 1
• During consultation, discuss limitations and risks of anesthesia during delivery, including potential difficulties with regional anesthesia placement 1

Additional Specialist Involvement

• Refer to dietician for nutritional consultation for all obese pregnant women 1, 4
• For women with history of bariatric surgery, establish communication between obstetrician and bariatric surgery team and provide nutritional supplements beyond usual pregnancy requirements 1

Thromboprophylaxis Assessment

Risk Stratification

• Assess venous thromboembolism risk at multiple time points throughout pregnancy 1, 3
• Consider thromboprophylaxis for women with extreme obesity who are hospitalized prior to delivery 1
• Consider thromboprophylaxis for obese women on bed rest or requiring surgery during antenatal period 1
• Plan for mechanical thromboprophylaxis (pneumatic compression devices) before cesarean section if possible 1

Labor and Delivery Preparation

Intrapartum Planning

• Establish early venous access during labor for women with BMI >40 1
• Alert operating room staff if weight exceeds 120 kg to ensure adequate staffing and equipment availability 1
• Plan for active management of third stage of labor due to increased postpartum hemorrhage risk 1

Critical Monitoring Pitfalls to Avoid

• Do not assume obesity alone indicates need for cesarean delivery or induction of labor—these decisions require additional obstetric or medical indications 1
• Do not recommend weight loss during pregnancy except in exceptional cases with serious comorbidities like uncontrolled diabetes or hypertension requiring intervention 2, 4
• Do not skip early anatomy scan at 14-16 weeks for BMI >40—waiting until 20-22 weeks alone may result in inadequate visualization 1, 5
• Do not overlook bariatric surgery history—these patients require modified glucose screening and enhanced nutritional monitoring 1