Sensitivities of nuchal translucency with different cut-offs for screening chromosomal abnormality in Korean population

Abstract

SCREENING CHROMOSOMAL ABNORMALITY IN KOREAN POPULATION JAE HYUG YANG, MIN HYOUNG KIM, JIN HOON CHUNG, HYUN KYONG AHN, MOON YOUNG KIM, HYUN MEE RYU, JUNE SEEK CHOI, Samsung Cheil Hospital and Women’s Healthcare Center, Sungkyunkwan University, School of Medicine, Obstetrics and Gynecology, Seoul, South Korea, Samsung Cheil Hospital and Women’s Healthcare Center, Sungkyunkwan University, School of Medicine, Obstetric and Gynecology, Seoul, South Korea OBJECTIVE: This study was aimed to compare the sensitivities and false positive rates of screening test for chromosomal abnormality using ultrasonographic measurement of nuchal translucency(NT) with different cut-offs in Korean population. STUDY DESIGN: Between January 2001 and December 2001, 2688 singleton pregnancies undergoing ultrasound between 11 and 14 weeks of gestation were involved in this study. We reviewed the obstetrical and neonatal medical records and analyzed the sensitivities and false positive rates of NT for screening chromosomal abnormalities using three cut-offs such as 2.5 mm, 3.0 mm, and 95th percentile for each crown-rump length (CRL). RESULTS: There were 32 chromosomal abnormalities (1.2%) including 12 cases of trisomy 21. The numbers of chromosomal abnormalities detected by NT with different cut-offs of 2.5 mm, 3.0 mm and 95th percentile were 22, 18 and 23 respectively. By using cut-off as 95th percentile, we could detect additional one more case of trisomy 18 than using fixed cut-off, 2.5 mm. The sensitivities and false positive rates for all chromosomal abnormalities were 68.8%, 56.3%, 71.8% and 6.4%, 3.6%, 5.7% respectively according to each cut-off, 2.5 mm, 3.0 mm and 95th percentile. The sensitivities of trisomy 21 were 75.0%, 50.0%, and 75.0%, respectively. CONCLUSION: The cut-off using 95th percentile for each fetal CRL increases the sensitivity and decreases false positive rate to detect the chromosomal abnormality compared with a fixed cut-off. CRL dependent cut-off of NT may be the more rational one than a fixed cut-off for screening chromosomal abnormality in Korean population. 644 MULTIFETAL PREGNANCY REDUCTION EFFECT OF NUCHAL TRANSLUCENCY ASSESSMENT: THE THOMAS JEFFERSON UNIVERSITY EXPERIENCE, 2001-2004 SHARON BYUN, SURASITH CHAITHONGWONGWATTHANA, WARALAK YAMASMIT, KEITH RYCHLAK, STUART WEINER, Thomas Jefferson University, Department of Obstetrics and Gynecology, PHILADELPHIA, Pennsylvania OBJECTIVE: To report our experience of pregnancy outcome after multifetal reduction (MFR) with the routine use of nuchal translucency (NT) measurements. STUDY DESIGN: We performed a retrospective review of all patients who underwent MFR at Thomas Jefferson University Hospital between 1/1/01-2/13/ 04 (N = 142). Reduction selection criteria were by fetal position, CVS, abnormal NT, or other indications. Pregnancy outcome data were obtained for preterm labor, preterm premature rupture of membranes, gestational hypertension, and gestational diabetes; gestational age at delivery, birth weight, mode of delivery, maternal postpartum complications and neonatal complications. RESULTS: 142 patients underwent MFR during this time period. 16/391 fetuses had abnormal NT measurements (4.09%). Of the 375 fetuses that had normal NT measurements, 23.9% underwent CVS. Of the 16 fetuses that had increased NTs, 20.0% had CVS (P = NS). CVS was performed on 116 fetuses. 8/102 CVS results that were available had an abnormal karyotype (7.8%). Reduction selection was by fetal position in 47.4%, by CVS in 25.2%, by increased NT in 4.4%, due to anomalies in 4.4%, by selecting the monochorionic pair in 7.4%, and by some combination in 11.0%. Pregnancy outcome data were obtained for the delivered 94 pregnancies. There was one first trimester loss (1.1%). The overall mean gestational age at delivery was 34.9 weeks. The mean birth weight was 2192 g (SD 711 g). CONCLUSION: There was a low rate of pregnancy loss following multifetal reduction. There was not a statistically significant difference in maternal complications rates, mean gestational age at delivery, and neonatal birth weight when reduction was by NT, CVS, and position. There was not a statistically significant decrease in the number of CVSs performed when there was an increased NT measurement. However, further investigation is needed to determine whether NT measurements alone could be used to aid in selective multifetal reduction by directing CVS toward the more likely euploid embryo and/or directing MFR toward the more likely abnormal one.