BACKGROUND AND PURPOSE:

• Ficara et al. (Ultrasound Obstet Gynecol., 2019) determined the types and incidence of previously undetected fetal abnormalities that could by identified using ultrasound at 35 to 37 weeks

METHODS:

• Prospective cohort study
• Participants
  • Singleton pregnancy, resulting in a live birth or stillbirth
  • Exclusion: Known chromosomal abnormalities
• Study design
  • Previous ultrasound exams
    • 11 to 13 weeks (90% of patients)
    • 18 to 24 weeks (100% of patients)
    • Ultrasound between 35w0d and 36w6d  
  • Anatomical abnormalities classified based on organ system
  • Type and incidence of new abnormalities were determined

RESULTS:

• 52,000 participants were included | Overall fetal abnormality incidence was 1.9%
• Among the 995 fetal anomalies
  • Detected in first or second trimester: 67.7%  
  • First diagnosis at 35–37 weeks: 24.8%
  • Postnatal detection: 7.4%
• Most common abnormalities diagnosed during all 3 trimesters included  
  • Cardiac: VSD
  • CNS: Ventriculomegaly
  • Face: Cleft lip and palate
  • Abdomen: Gastroschisis
  • Renal: Unilateral renal agenesis | Pelvic kidney | Hydronephrosis | Duplex kidney | Unilateral multicystic kidney
  • Extremities: Polydactyly | clubfoot

Ultrasound at 35 to 37 weeks

• Incidence of abnormalities first seen at 35–37 weeks: 0.5%
• Most common abnormalities seen for the first time at 35–37 weeks included
  • CNS: Mild ventriculomegaly | Arachnoid cyst
  • Renal: hydronephrosis | Duplex kidney
  • CNS: VSD
  • Abdomen: Ovarian cyst
• Abnormalities seen exclusively during this time period include
  • Ovarian cyst | Microcephaly | Achondroplasia | Dacryocystocele | Hematocolpos

Postnatal Detection

• Incidence of abnormalities first seen postnatally: 0.1%
• The most common anomalies included
  • Isolated cleft palate | Polydactyly or syndactyly | Ambiguous genitalia or hypospadias

CONCLUSION:

• Approximately 25% of all fetal abnormalities were identified at routine ultrasound between 35 and 37
• The authors suggest that based on results of this study, routine ultrasound at this time could help identify fetal anomalies and potentially improve outcomes by preparing adequately for delivery and postpartum care

Learn More – Primary Sources:

Value of routine ultrasound examination at 35–37 weeks’ gestation in diagnosis of fetal abnormalities

Related ObG Topics:

Mild Cerebral Ventriculomegaly on Prenatal Ultrasound – Next Steps and Clinical Implications

Microcephaly – Definitions and Key Points

Cleft Lip and Palate – Considerations and Discussion Points

Can Whole-Exome Sequencing Help Diagnose Otherwise Unexplained Fetal Structural Anomalies?