What tests and interventions are recommended at 24 weeks of pregnancy?

Recommended Tests and Interventions at 24 Weeks of Pregnancy

Screening for gestational diabetes mellitus (GDM) should be performed in all pregnant women at 24 weeks of gestation. 1

Gestational Diabetes Screening

• The USPSTF strongly recommends screening for GDM in asymptomatic pregnant women after 24 weeks of gestation (B recommendation) 1
• The most common screening approach in the United States is the 2-step method: 1
  • Initial 50-g oral glucose challenge test (OGCT) in a non-fasting state
  • If screening threshold is met or exceeded (130 mg/dL, 135 mg/dL, or 140 mg/dL), proceed to the oral glucose tolerance test (OGTT)
• Alternative 1-step approach uses a 75-g glucose load with evaluation of fasting glucose and plasma glucose levels after 1 and 2 hours 1
• Early detection and treatment of GDM significantly reduces the risk for preeclampsia, fetal macrosomia, and shoulder dystocia 1

Risk Factors for GDM

• Women at higher risk for GDM include those who: 1
  • Are obese
  • Are older than 25 years
  • Have a family history of diabetes
  • Have a history of previous gestational diabetes
  • Belong to certain ethnic groups (Hispanic, Native American, South or East Asian, African American, or Pacific Island descent)

Fetal Assessment

• Routine ultrasound assessment is typically performed between 18-22 weeks (anatomy scan), but may be repeated or performed at 24 weeks if not done earlier 2
• Ultrasound at this stage can help with: 2
  • Confirming gestational age
  • Detecting multiple pregnancies
  • Identifying major fetal abnormalities
  • Assessing placental location

Additional Laboratory Tests

• For RhD-negative women, a second antibody screen test should be performed at 24-25 weeks of gestation 3
• Non-invasive fetal RhD prediction is recommended for RhD-negative women at approximately 25 weeks 3
• Consider checking hemoglobin/hematocrit to assess for anemia 1
• For women who have had bariatric surgery, additional monitoring is recommended: 1
  • Full blood count, serum ferritin, and iron studies
  • Serum folate and vitamin B12
  • Serum vitamin A
  • Vitamin E assessment

Fetal Viability Considerations

• 24 weeks marks an important milestone for fetal viability 4
• At 24 weeks, the chance of survival with intensive care is approximately 50%, with the odds favoring normal development in survivors 4
• This information may influence management decisions if complications arise at this gestational age 4

Potential Pitfalls and Caveats

• False positive results from GDM screening can cause unnecessary anxiety and inconvenience 1
• The 50-g OGCT has variable sensitivity and specificity depending on the threshold used 1
• There is insufficient evidence to recommend universal screening for GDM before 24 weeks of gestation (I statement) 1
• Women with risk factors for type 2 diabetes may benefit from earlier screening, though evidence for this practice is limited 1
• Routine late pregnancy ultrasound (after 24 weeks) in low-risk populations has not been shown to improve overall perinatal outcomes 5

Follow-up Care

• For women diagnosed with GDM, management includes: 1
  • Dietary modifications
  • Moderate physical activity
  • Glucose monitoring
  • Support from diabetes educators and nutritionists
  • Medication (insulin or oral hypoglycemic agents) if glucose is not controlled with lifestyle interventions
• For RhD-negative women carrying an RhD-positive fetus, Rh immunoglobulin should be administered at 29 weeks 3