First trimester fetal reduction: its role in the management of twin and higher order multiple pregnancies

Multiple pregnancy may be the result of stimulated or non-stimulated, and of assisted or natural conception. As observed in the past decade, assisted conception technologies have significantly increased the prevalence of multiple pregnancy. The increase has been much more marked for triplets and higher order births. Rates of perinatal mortality and fetal and maternal complications are higher in twins than in singletons, and the adverse outcome rises with increasing number of multiples. Unplanned multiple pregnancy may be felt to be emotionally and physically so stressful an experience as to drive patients to refusal of pregnancy itself, or to want to reduce the number of fetuses to an acceptable standard. Fetal reduction techniques have emerged as a very effective medical approach to improve pregnancy outcome and a key option of patients trying to carry a pregnancy to term. Multiple fetuses are most frequently heterozygotes; therefore the risk of each of them being affected by a Mendelian disease or sporadic chromosomal aberration is an independent probability. Thus, the incidence of genetic defects in at least one fetus is increased and directly related to the order of multiples, and this makes it worthwhile to offer karyotyping of the fetus(es) to be spared, before the reduction procedure takes place. When a multiple pregnancy is established, one may conclude selective reduction is the most effective therapeutic approach for reducing risks.