title: Screening and Invasive Testing in Twins.
abstract: Prenatal screening and testing for trisomy 21 in twin pregnancies poses a number of challenges: the exact estimate of the a priori risk of trisomy 21, the choice of prenatal screening test and/or invasive techniques to employ for the diagnosis and the impact of the result on the options of treatment in case of discordant results within a twin pair or among multiples. These different aspects are discussed below while recognizing that many issues remain unresolved.
authors.affiliation: Department of Obstetrics and Gynecology, Prenatal and Preimplantation Genetic Diagnosis, Fetal Therapy, Ospedale Microcitemico, via Jenner, 09121 Cagliari, Italy. prenatalmonni@tiscali.it.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Monni
authors.affiliation: Department of Obstetrics and Gynecology, Prenatal and Preimplantation Genetic Diagnosis, Fetal Therapy, Ospedale Microcitemico, via Jenner, 09121 Cagliari, Italy. ambraiuc@tiscali.it.
authors.forename: Ambra
authors.initials: A
authors.lastname: Iuculano
authors.affiliation: Department of Obstetrics and Gynecology, Prenatal and Preimplantation Genetic Diagnosis, Fetal Therapy, Ospedale Microcitemico, via Jenner, 09121 Cagliari, Italy. angelica.zoppi@tiscali.it.
authors.forename: Maria Angelica
authors.initials: MA
authors.lastname: Zoppi
keywords: invasive diagnosis; screening; therapy; twins