Management of twin pregnancies with fetal trisomies.

OBJECTIVE: To examine options of management and outcome of twin pregnancies affected by fetal trisomies. DESIGN: Retrospective study. SETTING: Research Centre for Fetal Medicine. POPULATION: Twenty-seven twin pregnancies affected by fetal trisomy. METHODS: A computer search was made of our database for twin pregnancies concordant or discordant for trisomies. The data were reviewed for gestation at diagnosis of the chromosomal abnormality, management and pregnancy outcome. MAIN OUTCOME MEASURES: Pregnancy management and outcome in relation to type and gestation at diagnosis of the trisomies. RESULTS: There were seven cases where both fetuses were trisomies and in these the parents opted for termination of pregnancy; termination was also performed in another pregnancy where one fetus had trisomy 18 and the chromosomally normal co-twin had a major facial cleft. In 19 cases one fetus had either trisomy 21 (n = 14) or trisomy 18 (n = 5) and the other was normal. Selective fetocide was carried out in 13 of 14 pregnancies discordant for trisomy 21 and in one of the five with trisomy 18. In the four cases discordant for trisomy 18 that were managed expectantly, the trisomic baby died in utero or in the neonatal period, whereas the normal co-twin was liveborn at 33 to 40 weeks (median 37). In the 14 cases of selective fetocide, the chromosomally normal co-twin was live born at 24 to 41 weeks of gestation (median 38), and there was a nonsignificant inverse correlation between the gestation at fetocide and gestation at delivery. CONCLUSIONS: In twin pregnancies discordant for fetal trisomies the main determinant in deciding whether to perform selective fetocide or adopt expectant management is the degree of lethality of the chromosomal defect.

Fetal karyotyping in twin pregnancies: selection of technique by measurement of fetal nuchal translucency.

OBJECTIVE: To examine the usefulness of selecting the appropriate technique for fetal karyotyping in twin pregnancies by using maternal age and fetal nuchal translucency thickness to determine risk for chromosomal defects in each fetus. SETTING: Fetal Medicine Centre, London, United Kingdom. SUBJECTS: Sixty-seven twin pregnancies identified at the time of an ultrasound scan for determination of fetal nuchal translucency thickness, where the parents requested karyotyping. INTERVENTION: The risk for chromosomal defects in each fetus was calculated from the maternal age and fetal nuchal translucency thickness at 10 to 14 weeks of gestation. If the estimated risk for either fetus was 1 in 50 or greater, chorion villus sampling was the method of choice, whereas if the risk was less than 1 in 50 second trimester amniocentesis was performed. RESULTS: The estimated risk for trisomies was more than 1 in 50 in 34 pregnancies and 23.5% of these fetuses were found to be chromosomally abnormal. In contrast, in the 33 low risk pregnancies chromosomal abnormalities were found in only 1.5% of the fetuses. CONCLUSIONS: In twin pregnancies the technique for fetal karyotyping may by selected by calculating the risk for chromosomal abnormality based on maternal age and fetal nuchal translucency thickness.

Abnormalities of the heart and great arteries in chromosomally normal fetuses with increased nuchal translucency thickness at 11-13 weeks of gestation.

Pathological examination of trisomic fetuses with increased nuchal translucency thickness at 11-13 weeks of gestation demonstrated a high prevalence of cardiac defects and abnormalities of the great arteries. This study reports the pathological findings observed from the examination of the heart and great arteries of 21 chromosomally normal fetuses with increased nuchal translucency. In 19 of the 21 cases there were abnormalities; the commonest was narrowing of the aorta at the level of the isthmus and immediately above the aortic valve. This finding is different from that in case of trisomy 21, where narrowing of the isthmus is associated with an increased diameter of the aortic valve. These findings suggest that abnormalities of the heart and great arteries may be implicated in the pathogenesis of increased nuchal translucency not only in trisomic fetuses but also in chromosomally normal fetuses. It can be implied that increased nuchal translucency thickness at 10-14 weeks of gestation may prove to be a useful marker for the identification of fetal cardiac abnormalities.