A Case report of a false positive NIPT result due to vanished twin

Abstract

We report a case of a 30 year-old primipara who conceived after IVF due to primary infertility. At 10th week of pregnancy during an ultrasound scan (US) DC/DA twins were confirmed. Also during the US vanished twin syndrome was diagnosed, fetus A was alive, meanwhile fetus B stopped developing. The patient decided to perform a non-invasive prenatal test (NIPT). NIPT results showed an increased risk of 21st chromosome trisomy and showed male sex. Test was performed when twin B stopped developing. After the NIPT results, the patient was consulted in the perinatology centre in the Hospital of Lithuanian University of Health Sciences Kaunas clinics. At the 15th week of pregnancy during an US DC/DA twins were confirmed: fetus A was alive, there were no abnormalities of the fetal anatomy, meanwhile fetus B stopped developing at the 10th week of pregnancy. The decision was made to perform an invasive prenatal diagnostic procedure amniocentesis. However, after discussion with the patient about the possible false positive NIPT results caused by vanished twin syndrome, also in the NIPT result there was confirmed the male sex meanwhile during an ultrasound scan the female sex organs were confirmed. Amniocentesis was performed in a typical way, without complications. Amniocentesis was done only for twin A because the patient did not want to increase the risk of miscarriage. The sample of fetus A ’s amniotic fluids were tested, the genetic molecular testing was performed - there were no chromosome number abnormalities, also the test confirmed female sex (XX chromosomes). After evaluation of the genetics test and US results, the decision was made that NIPT showed the vanished twin increased risk of 21st chromosome trisomy. At 38th week of pregnancy an elective caesarean section was made because of the fetal breech presentation.