Speaker

Dr. Tuangsit Wataganara

Chief of the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology,

Faculty of Medicaine Siriraj Hospital, Mahidol University, Thailand

Speaker's Biography

Dr. Wataganara is an Associate Professor in the Division of Maternal Fetal Medicine, Faculty of Medicine Siriraj Hospital, Bangkok, Thailand. He is board-certified in both Obstetrics and Gynecology and Maternal Fetal Medicine. He has a special research interest in non-invasive prenatal genetic diagnosis (Tufts-New England Medical Center, Boston, USA) and fetal interventions. He has over 30 publications related to fetal medicine in international peer-review journals in the past ten years. Among his several prestigious awards include an Outstanding Young Investigator Award from CNAPS III Meeting (the USA, 2003) and Shan S. Ratnam Young Gynecologist Award from 20th AOCOG Meeting (Japan, 2007). He is an executive director of Ian Donald Inter-University School of Medical His Fetal Therapy unit in Bangkok is one of the most active facilities of its kind in Asia.

Topic

Fetal and Extra-fetal Sonogenetic Assessment

Abstract

First-trimester (11 to 13 weeks of gestation) nuchal translucency (NT) is used in screening common aneuploidies, typically involving chromosomes 13, 18, 21, X, and Y. Regardless of gestational weeks, a fixed threshold of 3.0 or 3.5 mm (or >99 %tile for crown-rump length) is independently associated with chromosomal abnormalities, major anomalies (especially cardiac malformations), and genetic syndromes of the fetus. Recently, a practice-specific multiple of the median (MoM) threshold (i.e., 1.9 MoMs) has been shown to maintain the same detection rate (DR) at a screen-positive rate 31% lower than the traditional fixed-threshold approach. When a non-invasive prenatal test (NIPT) is offered as a primary test, NT does not offer added benefits in detecting atypical chromosome abnormalities (low DR, low positive predictive value; PPV) because most of the atypical aneuploidies have a normal NT. Although fetal anatomy scanning during the NT assessment is coming of age, the ultrasound DR of atypical aneuploidies not detectable by NIPT is still low (»50%). In fact, most major structural anomalies are not related to either chromosomal, sub-chromosomal, or single-gene aberrations. Especially in an era of prenatal genomic screenings and diagnostics, NT should not serve as a stand-alone test. The modern-day paradigm may be in the following orders; (1) a dating scan at 8 to 10 weeks of gestation, (2) NIPT at 10 to 12 weeks of gestation for singleton or at 12 weeks of gestation for twins, (3) fetal NT and anatomy surveillance at 12 to 13 weeks of gestation, (4) those with abnormal (or no-call) NIPT, NT >/= 1.9 MoMs, or major structural defects shall be offered either chorionic villus sampling or early amniocentesis for karyotype studies (conventional or molecular; employing array comparative genomic hybridization (aCGH)) or whole-exome sequencing (WES), and (5) repeated anatomy scan at 16 to 20 weeks of gestation can (1) improve the negative predictive value (NPV) of the fetal, and placental, abnormalities, as well as (2) allow for a chance for measurement of the cervical length in those with prior risks of preterm delivery.

The implementation of this paradigm needs to consider legal regulations, which are varied from one practice to another.