UBC Theses and Dissertations
Investigation of aneuploidy and mosaicism throughout pregnancies conceived through assisted reproductive technology (ART) Watt, Katherine
Assisted Reproductive Technology (ART) has been used for nearly four decades to help infertile couples achieve pregnancy. Such pregnancies are at a greater risk of restricted fetal growth and preterm birth, though whether these risks arise from environmental factors imposed on embryos cultured in vitro, or from genetic or epigenetic factors related to underlying infertility of the parents, remains unclear. Embryos generated using ART are frequently mosaic – having at least two genetically distinct cell populations within the same embryo. Mosaicism that persists in the cells that form the placenta can be observed as confined placental mosaicism (CPM), wherein genetic imbalances that may be fatal for a fetus are tolerated in the placenta, albeit with consequences such as restricted fetal growth, premature birth, and fetal demise. To investigate whether genetic imbalances and mosaicism occur more frequently for ART conceptions, term placentas from in-vitro fertilization (IVF) conceptions were analyzed at three distinct sites for large variations in chromosomal copy number. The incidence of CPM (4/82, 4.9%) was not significantly greater than what has previously been observed in term placentas from spontaneous conceptions (8/528, 1.5%, P=0.064, Fisher’s Test). The presence of constitutional genetic abnormalities and mosaicism were also investigated by karyotyping live-born infants from ART and natural conception pregnancies, and abnormalities were detected at similar rates between IVF (3/220, 1.36%), intracytoplasmic sperm injection (ICSI) (4/255, 1.57%), and naturally conceived cases (5/336, 1.49%). My results support observations that ART pregnancies are not at significantly greater risk of chromosomal abnormality or mosaicism than spontaneous pregnancies, and suggest that the poorer perinatal outcomes observed for ART conceptions may be attributable to other factors, such as small copy number variation or epigenetics.
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