SUMMARY:

Obesity is an epidemic in the United States. Bariatric surgery can improve some pregnancy outcomes, but nutritional and surgical complications can occur and result in adverse perinatal outcomes. The rate of obesity has increased by 70% from 1994 to 2003 and the rate of pre-pregnancy obesity is 29% in the United States in 2019

Maternal and Reproductive Effects

• Increased risk for
  • Reduced fertility
  • Gestational diabetes
  • Preeclampsia
  • Cesarean delivery | Operative morbidity (excessive blood loss and infectious morbidity)
  • Indicated preterm birth
  • Less likelihood of TOLAC
• More likely to
  • Be admitted earlier in labor
  • Require labor induction and additional oxytocin
  • Undergo longer labor

Fetal and Neonatal Effects

• Increased risk for
  • Congenital abnormalities
  • Growth abnormalities
  • Miscarriage | Stillbirth
  • LGA and macrosomia | Childhood obesity
• Impaired visualization of ultrasound images may compromise prenatal diagnosis but does not appear to compromise fetal weight estimations

Bariatric Surgery

• Available to patients with BMI ≥ 40 kg/m² or ≥ 35 kg/m² with comorbidities
• The most effective therapy for morbid obesity
• Two surgical approaches: Restrictive and malabsorptive
  • Roux-en-Y gastric bypass: Combination restrictive and malabsorptive
  • Adjustable gastric band: Restrictive
• Procedures have increased dramatically
  • Majority of patients are female | 50% are reproductive-aged women | Increasing in adolescents

Effects of Bariatric Surgery

• Future fertility
  • Weight loss improves PCOS, anovulation, irregular menses leading to higher fertility rates
  • Effect on miscarriage rates uncertain
• Maternal morbidity and mortality
  • Weight loss outside of pregnancy improves medical comorbidities (i.e., hypertension, diabetes)
  • Lower average weight gain during pregnancy
  • Reduced incidence of gestational diabetes, pregestational diabetes, and preeclampsia (may vary with surgical type)
• Cesarean Delivery Rates
  • Higher rates of cesarean delivery when compared to nonobese patients
  • No difference when compared to obese or severely obese
  • May be attributed to previous cesarean delivery in obese patients
• Significant late surgical complications include
  • Intestinal obstruction and gastrointestinal hemorrhage
  • High index of suspicion warranted for gastrointestinal surgical complications when patient presents with symptoms
• Effect on fetal and infant morbidity and mortality
  • Congenital abnormalities are not increased
  • Trend towards lower mean birth weights
    • More appropriately grown infants | Fewer LGA infants | More SGA infants
    • Maternal weight gain is likely a predictor of birth weight
  • Perinatal death not increased
  • Limited data on other neonatal outcomes

Preconception Recommendations

• Contraceptive counseling after surgery, especially for adolescents
  • Consider non-oral administration of hormonal contraception due to malabsorption of OCP risk
• Wait 12 to 24 months after bariatric surgery before conceiving
  • Reduces fetal exposure to rapid maternal weight loss
  • Allows patient to achieve full weight loss goals
  • If pregnancy occurs before this time
    • Provide closer surveillance of maternal weight and nutritional status
    • Perform ultrasound for serial growth monitoring

Nutritional Recommendations

Common Nutritional Deficiencies After Bypass Surgery (Roux-En-Y) Include

•  Protein | Iron | Vitamin B | Folate | Vitamin D | Calcium
  • Broad evaluation for micronutrient deficiencies at beginning of pregnancy
    • If proven deficit: Begin appropriate treatment
    • In absence of deficit: Monitor micronutrients every trimester
  • Begin supplementation with oral forms
  • Change to parenteral forms if laboratory studies do not improve
  • Daily recommendation for protein intake remains 60 g regardless of surgery status
• Caloric and protein restriction during pregnancy may impair fetal growth
  • No benefit reducing pregnancy comorbidities
  • Not recommended even if patient continues to be overweight after surgery
• Women who become pregnant after bariatric surgery should take a prenatal vitamin in addition to a multivitamin
  • Excess of vitamin A (>500 IU/day) during pregnancy is associated with birth defects
• Appropriate to consult with nutritionists, bariatric surgery team to assist with nutrition, achieve appropriate weight gain goals
• Nutrient deficiencies can also occur after restrictive procedures because of decreased food intake, intolerance to certain foods or both

Active band management

• If patient has had an adjustable gastric banding (Lap-Band®)
  • Fluid from the gastric band is removed or lessened during pregnancy allowing for less gastric constriction and increased oral intake
  • May also relieve nausea and vomiting in first trimester
• Early consultation with bariatric surgeon is recommended

Gastrointestinal Complications

• There may be a delay in diagnosis of bariatric-related complications
  • Anastomotic leaks | Bowel obstruction | Internal and ventral hernia |
  • Band erosion or migration
• All gastrointestinal problems should be evaluated with high index of suspicion for surgery related complications
  • Early involvement of bariatric surgeon

Dumping Syndrome

• Ingestion of refined sugars or highly glycemic carbohydrates shifts volume from intravascular to bowel lumen
• Symptoms include
  • Abdominal cramps | Bloating | Nausea | Vomiting | Diarrhea
• Hyperinsulinemia and hypoglycemia can occur later and cause
  • Tachycardia | Palpitations | Anxiety | Diaphoresis
• 50-g glucose screen for gestational diabetes may not be tolerated
  • Consider alternative measures for screening
    • Home glucose monitoring for 1 week between 24 to 28 weeks

Medication Dosages

• Due to decreased absorptive surface of the intestine
  • Extended-release preparations are not recommended vs oral solutions or rapid release formulations
• Caution against NSAIDs to avoid gastric ulceration
• When therapeutic drug level is critical, drug level testing may be necessary

Mode of Delivery

• Bariatric surgery
  • Does not alter course of labor or its management
  • Should not be considered an indication for cesarean delivery
• Cesarean delivery rates are higher after bariatric surgery but there is no known physiological reason
• If extensive and complicated abdominal surgery is present, prelabor consultation with bariatric surgeon should be considered

KEY POINTS:

• Bariatric surgery can positively affect fertility as well as impact maternal, fetal and infant morbidity risks
• Broadly evaluate micronutrient deficiencies in pregnancy
• Maintain a high index of suspicion for post-bariatric surgical complications

Learn More – Primary Sources:

ACOG Practice Bulletin 105: Bariatric Surgery in Pregnancy

CDC MMWR: Increases in prepregnancy obesity: United States, 2016-2019

Related ObG Topics:

Obesity in Pregnancy: Classification and Clinical Implications

Increasing BMI and Adverse Pregnancy Outcomes: What Are the Risks?

Maternal Overweight, Obesity and Congenital Malformations – How Strong is the Link?

Recommended Weight Gain and Obesity Management in Pregnancy