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Nuchal translucency in multiple pregnancies
1Department of Obstetrics and Gynecology, Prenatal and Preimplantation Genetic Diagnosis, Fetal Therapy, Ospedale Regionale per le Microcitemie, Via Jenner 09121 Cagliari, Italy. prenatalmonni@tiscalinet.it
Aim:
To evaluate the prevalence of increased nuchal translucency (NT) in multiple pregnancies and its relation to fetal karyotype and pregnancy outcome.
Methods:
We measured fetal nuchal translucency (NT) in 6,338 women pregnant from 10+3 to 13+6 weeks by ultrasound and evaluated the prevalence of NT=95th centile in 115 multiple pregnancies, including 100 pairs of twins (70 dichorionic and 30 monochorionic placentas), 9 triplets, 5 quadruplets, and one quintuplet. Chorionicity, fetal karyotype, and pregnancy outcome were also evaluated in 400 singleton pregnancies.
Results:
NT=95th centile in a single fetus was found in 10/70 cases of dichorionic twin pregnancies (14%), in two quadruplets, in 7/30 monochorionic twin pregnancies (23.3%), and in both fetuses in one dichorionic twin pregnancy. In the control group, NT=95th centile was found in 17/400 (4.2%) cases. In multiple pregnancies, two cases of trisomy 21 and one of 47, XXY were found. NT=95th centile was found in 2/2 fetuses with trisomy 21 (one dichorionic twin pregnancy and one tetrachorionic pregnancy), but not in the 47, XXY trisomy (trichorionic triplet pregnancy). A skeletal dysplasia and a Goldenhar syndrome were found among the 10 dichorionic pregnancies with increased NT. Three intrauterine deaths of both fetuses, one congenital heart disease, and a case of twin-to-twin transfusion occurred in 7 monochorionic pregnancies with increased NT.
Conclusion:
Increased NT in multiple pregnancies indicates fetuses at risk of chromosomal abnormalities and fetal malformation, and monochorionic twin pregnancies at higher risk of adverse outcome.