356 Is placental mosaicism identified by CVS associated with higher rates of adverse obstetric outcomes?

Abstract

Placental mosaicism is identified in approximately 1-2% of women who undergo CVS. While high rates of adverse obstetric outcomes have been described, data is inconsistent. Our objective was to compare outcomes in pregnancies with and without mosaicism identified at CVS. All women who underwent CVS followed by amniocentesis from 2010-2020 were identified. Those who underwent amniocentesis due to mosaicism on CVS were compared to those who underwent amniocentesis after CVS for other reasons. Pregnancies terminated for genetic abnormalities were excluded. Obstetric outcomes were compared between the two groups. Student t test and Fisher’s exact test were used for statistical comparison. During the study period 2539 women underwent CVS, and 66 (2.6%) subsequently underwent amniocentesis: 29 (44%) due to mosaicism, 22 (33%) due to sampling/laboratory issues, and 15 (23%) for additional diagnostic testing. The most common forms of mosaicism were for sex chromosome abnormalities (n=4), tetraploidy (n=4), and Trisomy 9 (n=4). Mean maternal age was 36.7 ± 3.5-yrs, and 41% of women were nulliparous. Age and parity were similar between groups. There were no pregnancy losses or stillbirths. Obstetric outcomes are in Table 1. Those who had placental mosaicism did not have higher rates of adverse outcomes compared to those who underwent amniocentesis following CVS due to other reasons. Placental pathology was performed in 41% of cases, and placental mosaicism was not associated with higher rates of lesions of malperfusion (45.5% vs. 37.5%, p=0.71). We did not observe an association between placental mosaicism and adverse obstetric outcomes. As our study cohort consisted of small numbers of different forms of mosaicism, it is unclear if specific mosaic karyotypes have higher rates of adverse outcomes.