Reproductive Failure

Human conception and pregnancy is both a vulnerable and a robust process. It is vulnerable in that a large proportion of all conceptions are chromosomally abnormal, with the great majority of such pregnancies aborting. It is robust in that more than 99% of the time, a term pregnancy results in a chromosomally normal baby; unbalanced chromosomal abnormalities are seen in less than 1% of newborns. This chapter considers the somewhat surprising vulnerability of the human species to chromosome abnormality, from prior to, at, and following conception. A remarkable fraction of pregnancy loss is due to chromosomal imbalance, and there is an associated maternal age effect. This chapter considers the chromosomal contribution to miscarriage, fetal death in utero, and perinatal death. Recurrent pregnancy loss may have a chromosomal basis, and male and female infertility may relate to abnormality of, in particular, the sex chromosomes. The genetics of hydatidiform mole is reviewed.