348: The accuracy of prenatal ultrasound in the diagnosis of true microcephaly

in the diagnosis of true microcephaly Jennifer Wong, Casey Howe, Angela Bianco, Robert Green, Joanne Stone Mount Sinai School of Medicine, Maternal Fetal Medicine, New York, NY, Mount Sinai School of Medicine, Department of Obstetrics and Gynecology, New York, NY, Department of Pediatrics, New York, NY OBJECTIVE: To determine the accuracy of prenatal ultrasound in detection of microcephaly, defined as birth head circumference (HCbirth) 10%ile. STUDY DESIGN: This was a retrospective chart review of fetuses identified prenatally with a head circumference (HCfetal) of 3%ile. HCbirth were abstracted from the newborn medical chart, and Z-scores calculated for both. Sensitivity, specificity, false positive (FP) and false negative (FN) rates were calculated for HCfetal. An ROC curve was calculated to determine the accuracy of HCfetal in the detection of microcephaly. RESULTS: An ultrasound database search from Jan 2005 to July 2011 for HC 3% identified 730 ultrasounds of 455 fetuses in 433 patients. There were 375 live births in this group. Median Z-scores were similar between fetal and neonatal groups ( 1.16 [ 1.6, 0.9] and 1.2 [ 1.8, 0.7], respectively). The overall prevalence of microcephaly was similar in both groups using an HCfetal Z-score cutoff of 1.3 (40.1% and 49.6% respectively). A Z-score of 1.3 had 44.6% sensitivity, 35.1% specificity, 44.9% FP rate, and 45.9% FN rate for detection of microcephaly (p 0.08). Using a HCfetal Z-score cutoff of 1.7 yielded 28.8% sensitivity, 21% specificity, 62.6% FP and 28.2% FN rate (p 0.09). The area under the ROC curve was 0.6, indicating that HCfetal is an inaccurate test for microcephaly. Gestational age at time of ultrasound was not significantly associated with microcephaly (95% CI 0.27-0.01). CONCLUSION: Prenatal ultrasound was able to detect a population at risk for microcephaly as evidenced by the high prevalence in this group at birth; however, the ability of prenatal ultrasound to predict a specific HCbirth for an individual is poor. Sensitivity and specificity for prenatal ultrasound are low, and FP and FN rates are high. Factors which contribute to the inaccuracy of prenatal ultrasound include the variability of the microcephaly phenotype, heterogeneous etiologies, lack of consensus regarding the definition of microcephaly, high rate of concurrent growth restriction, and lack of genderor race-specific fetal growth curves. 349 Antenatal ultrasonographic findings to predict esophageal atresia in cases with visible stomach bubble Jeong Woo Park, Yeo rang Kim, Seung Mi Lee, Chan-Wook Park, Joong Shin Park, Jong Kwan Jun, Hee Chul Shin Seoul National University College of Medicine, Deptartment of Obstetrics and Gynecology, Seoul, Korea, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Obstetrics and Gynecology, Seoul, Korea, Seoul National University College of Medicine, Department of Obstetrics and Gynecology, Seoul, Korea OBJECTIVE: Becauses fetuses with esophageal atresia need an early postnatal surgery, they should be delivered in a tertiary center. However, prenatal diagnosis of esophageal atresia sometimes challenging. The aim of this study was to determine the antenatal ultrasonographic findings which offer the best diagnostic accuracy in fetal esophageal atresia with or without tracheoesophageal fistula (EA/TEF) with moderate to severe polyhydramnios and visible stomach bubble. STUDY DESIGN: We performed a retrospective analysis of 121 pregnant women who presented polyhydramnios (AFI 24) between March 1996 and April 2011. Of these, 3 cases in whom EA was suspicious but delivered stillbirth without autopsy, and those who were diagnosed as having other fetal gastrointestinal obstructions (e.g. duodenal atresia, jejunal atresia, or ileal atresia), hydrops fetalis, or congenital diaphragmatic hernia were excluded. A total of 87 cases were enrolled. Ultrasonographic findings evaluated were (1) small abdominal circumference (AC) less than 10 percentile for gestational age, (2) upper pouch sign, and (3) tiny stomach bubble. Predictive value of an individual sonographic marker was calculated. RESULTS: Of a total of 87 cases with polyhydramnios, 2 cases had upper neck pouch sign. Of these 85 cases, 8 cases showed absent stomach bubble. The remaining 77 cases were analysed. In the setting of polyhydramnios and visible stomach bubble (77 cases), the prevalence of EA/TEF was 6.5% (5/77). Small AC had higher sensitivity compared to tiny stomach bubble. Small AC and tiny stomach bubble were statistically significant sonographic findings for diagnosing esophageal atresia antenatally. After adjusting possible confounders, only small AC was remained significant (P 0.05). CONCLUSION: In polyhydramnios and visible fetal stomach bubble, small AC as an antenatal sonographic finding suggests that the fetus has EA/TEF. Clinicians should measure AC in this setting. Poster Session II Diabetes, Labor, Medical-Surgical-Disease, Obstetric Quality & Safety, Prematurity, Ultrasound-Imaging www.AJOG.org