-Original-

Outcomes of 8 Years of Noninvasive Prenatal Testing at Nippon Medical School Hospital

Ikuno Kawabata^1,2, Tomoko Sahara¹, Sayuri Hiraoka¹, Mirei Yonezawa², Hidehiko Miyake^1,3, Shunji Suzuki² and Takeshi Yamada¹

¹Division of Clinical Genetics, Nippon Medical School Hospital, Tokyo, Japan
²Department of Obstetrics and Gynecology, Nippon Medical School Hospital, Tokyo, Japan
³Department of Genetic Counseling, Graduate School of Humanities and Science, Ochanomizu University, Tokyo, Japan

Background: Noninvasive prenatal testing (NIPT) is used to screen for fetal chromosomal abnormalities, such as fetal aneuploidy, and has been offered at our hospital since 2013. We analyzed data from our center to determine if NIPT screenees could be given more-accurate information on NIPT outcomes.
Methods: This retrospective observational study included 819 pregnant women who requested NIPT at Nippon Medical School Hospital from November 2013 to October 2021. We examined medical records for data on NIPT results and clinical outcomes.
Results: Of the 819 women, 764 (93.2%) underwent NIPT, and 55 (6.7%) did not. Of the 764 women who underwent NIPT, 17 received a positive result (2.2%), of whom 2 (11.8%), 4 (23.5%), and 11 (64.7%) received a positive result for trisomy 13, 18, and 21, respectively. The true-positive rates after definitive diagnoses of trisomy 13, 18, and 21 were 1 (50%), 3 (75%), and 11 (100%), respectively. Of the 17 positive results, there were two false-positive results (11.8%) (for trisomy 13 and trisomy 18). Eleven women with fetal aneuploidy terminated their pregnancies, and four cases resulted in intrauterine fetal death. Five neonates with negative NIPT results had congenital disease without chromosomal abnormality. Two patients had indeterminate results from the first blood sampling, possibly because of treatment with unfractionated heparin. The results of repeat testing after heparin cessation were negative.
Conclusions: Our results were generally similar to nationwide data for Japan. NIPT providers can provide more detailed and individualized genetic counseling for each situation by understanding their own medical facility's data in detail.

J Nippon Med Sch 2022; 89: 520-525

Keywords
noninvasive prenatal testing (NIPT), prenatal test, genetic counseling

Correspondence to
Ikuno Kawabata, Division of Clinical Genetics, Nippon Medical School Hospital, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan
ikawabata8512@nms.ac.jp

Received, February 12, 2022
Accepted, April 21, 2022