VP28.07: Impact of confined placental mosaicism on outcome of pregnancy

Abstract

To assess the incidence of confined placental mosaicism (CPM) on CVS and amniocentesis in our population and to study the impact of CPM on the outcome of pregnancies with a structurally normal fetus at mid trimester anomaly scan and the association of abnormal first trimester serum biochemistry with CPM. This is a single centre study where all pregnancies that had an invasive procedure ie CVS or amniocentesis before 20 weeks of gestation from January 2011 till December 2020 were considered. The study included pregnancies that had mosaic pattern on CVS or amniocentesis. The incidence of CPM on CVS and amniocentesis was calculated. Fetal ultrasound in all trimesters, maternal serum biochemistry in the first trimester, presence of fetal growth restriction (FGR) and postnatal outcome were obtained. During the study period, of the 2081 Amniocentesis procedures 1 (0.05%) had CPM with tetraploidy mosaic confirmed by postnatal karyotype with normal outcome. Of 1144 CVS procedures performed 10/1144 (0.9%) were detected to have a mosaic pattern. 5/10 mosaic pattern obtained in pregnancies with fetal structural abnormalities were terminated before amniocentesis could be performed. 5/10 (0.44%) had structurally normal fetuses and hence Amniocentesis could be performed to confirm CPM. Of the four where first trimester serum biochemistry was available, three (75%) cases had low maternal serum PAPP-A (< 0.3). 2 of 5 cases had Trisomy 18, one had Trisomy 16 and one had Trisomy 21 mosaic pattern, all of which had normal antenatal and postnatal outcomes. 1/5 pregnancies had Trisomy 16 mosaic pattern which was found to have severe early onset FGR at 18 weeks and was terminated. Hence, 1/5 pregnancies with CPM had poor fetal outcome. The incidence of CPM in our study was about 0.44% on CVS and that on amniocentesis 0.05%. FGR was the only antenatal complication. We did not observe any maternal complications. Low maternal serum PAPP-A levels may indicate a higher possibility of obtaining a mosaic pattern on a CVS.