[Fetal nuchal translucency measurement at 11-13 weeks and risk assessment for fetal aneuploidy and cardiac anomalies.].
Ultrasound is currently an integral part of prenatal care. In Iceland, all women are offered one ultrasound examination at 18-20 weeks, to assess fetal health, number of fetuses, placental location and to calculate the estimated due date. Also, about one third will have an early ultrasound examination due to pain, bleeding or uncertain dates. All women, aged 35 and older, are offered an amniocentesis for fetal karyotyping, due to the increased rate of chromosomal abnormalities with advancing maternal age. Younger women are not routinely offered fetal karyotyping. In this review, a method is described that can estimate the risk of chromosomal abnormalities based on an ultrasound examination at 11-13 weeks. The fetal crown rump length and nuchal translucency are measured in a sagittal view. Based on these measurements as well as maternal age, risk assessment for fetal aneuploidy is performed. A screen positive rate of 8% is expected if risk assessment for fetal aneuploidy is 1:300 or higher. This translates into 8% procedure rate for fetal karyotyping. This approach leads to the diagnosis of the majority of all fetal trisomies. The method was developed by the Fetal Medicine Foundation, London, and is now widely used throughout Europe and Canada. The institution teaches the methodology and offers continuous audit for quality assurance. If this methodology were to be applied in Iceland the procedure rate for fetal karyotyping could be reduced from 13% to 8% while improving diagnosis of trisomy 21 from 30% to 80%. The option of offering all expecting couples an early ultrasound and risk assessment for fetal trisomies should be considered.
Harðardóttir
H
H
Obstetrics and Prenatal Diagnosis Unit, Landspitali University Hospital, Hringbraut, 101 Reykjavík, Iceland. hhard@landspitali.is.