Partial molar pregnancy after intracytoplasmic sperm injection occurring as a result of diploid sperm usage

Partial molar pregnancies are rare conceptions characterized by having 69 rather than 46 chromosomes, the additional chromosome complement usually occurring as a result of fertilization of the ovum by two sperm. Although assisted conception with intracytoplasmic sperm injection (ICSI) should prevent the development of a partial molar pregnancy, occasional cases have been described after assisted conception using ICSI. The objective of this study was to investigate the cause of partial molar pregnancy in a couple who had undertaken assisted conception with ICSI. Fluorescent microsatellite genotyping of DNA from the couple and tissue from their partial molar pregnancy was performed in order to confirm diagnosis and investigate the origin of the additional chromosome set. Genotyping confirmed that the partial molar tissue was triploid with an additional chromosome complement from the father. Genotyping of additional loci proximal to the centromere demonstrated that the two paternal sets of chromosomes originated in a single sperm with a double complement of paternal DNA resulting from non-reduction at the second meiotic division. This study confirms that partial molar pregnancy may occur after assisted conception with ICSI and that this occurs as a result of fertilization with a diploid sperm.