ABSTRACT
We present a case of a fetus acquiring two different balanced translocations from each parent and subsequent uniparental isodisomy from postzygotic loss of a paternal chromosome. Balanced chromosomal translocations occur in 0.14% of the population and increase the risk of other genetic abnormalities, such as uniparental disomy (UPD) and mosaicism. Preimplantation genetic testing (PGT) can identify some genetic abnormalities. Translocations t(6;21) and t(5;15) have been reported individually but never together in a viable fetus. A non-consanguineous couple who were known carriers of two different balanced translocations conceived via classic in vitro fertilization (IVF). They had a normal PGT completed. Chorionic villus sampling (CVS) revealed that the fetus had received t(6;21) from the mother and t(5;15) from the father. The probability of the fetus acquiring both translocations was 2.8%. CVS also revealed UPD of chromosome 14. Amniocentesis was performed, which was consistent with the CVS in detecting the balanced translocations but provided more information about the UPD, determining that it was a mosaic maternal uniparental isodisomy of chromosome 14 (UPD(14)mat). The couple underwent genetic counseling to discuss the above findings and ultimately decided on dilation and evacuation at 17 weeks of gestation. The likelihood of conception of this fetus and survival past the first trimester is extremely rare. These specific chromosomal translocations and (UPD(14)mat) have never been reported before. This case emphasizes the concomitant nature of imprinted genes, resulting in multiple genetically unique alterations. This report also highlights the limitations of PGT, CVS, and amniocentesis in being reproducibly consistent, which is important to discuss prior to IVF conception.
ABSTRACT
BACKGROUND: We present a case of monochorionic-triamniotic pregnancy that developed after embryo transfer following in vitro fertilization (IVF). METHODS: After controlled ovarian hyperstimulation and transvaginal retrieval of 22 metaphase II oocytes, fertilization was accomplished with intracytoplasmic sperm injection (ICSI). Assisted embryo hatching was performed, and two embryos were transferred in utero. One non-transferred blastocyst was cryopreserved. RESULTS: Fourteen days post-transfer, serum hCG level was 423 mIU/ml and subsequent transvaginal ultrasound revealed a single intrauterine gestational sac with three separate amnion compartments. Three distinct foci of cardiac motion were detected and the diagnosis was revised to monochorionic-triamniotic triplet pregnancy. Antenatal management included cerclage placement at 19 weeks gestation and hospital admission at 28 weeks gestation due to mild preeclampsia. Three viable female infants were delivered via cesarean at 30 5/7 weeks gestation. CONCLUSIONS: The incidence of triplet delivery in humans is approximately 1:6400, and such pregnancies are classified as high-risk for reasons described in this report. We also outline an obstetric management strategy designed to optimize outcomes. The roles of IVF, ICSI, assisted embryo hatching and associated laboratory culture conditions on the subsequent development of monozygotic/monochorionic pregnancy remain controversial. As demonstrated here, even when two-embryo transfer is employed after IVF the statistical probability of monozygotic multiple gestation cannot be reduced to zero. We encourage discussion of this possibility during informed consent for the advanced reproductive technologies.
