Second-trimester amniocentesis vs. chorionic villus sampling for prenatal diagnosis in multiple gestations.

Objective: To study the impact of invasive procedures for prenatal diagnosis on multiple pregnancies and compare first-trimester chorionic villus sampling with second-trimester amniocentesis.

Methods: Retrospective study of 347 second-trimester amniocenteses and 69 chorionic villus sampling procedures.

Results: Miscarriage occurred in 4.18% of women after amniocentesis and 4.54% of women after chorionic villus sampling. In the amniocentesis group the risk of miscarriage was higher in the cases with transplacental entry (4.54%) than in those with transamniotic entry (2.08%). The rates of preterm delivery < or = 32 weeks and preterm delivery < or = 35 weeks in the amniocentesis group were 11.8% and 32.4% and in the chorionic villus sampling group 16.66% and 23.8%, respectively. Total fetal loss rate was similar in the amniocentesis group (8.8%) and the chorionic villus sampling group (10.22%). In the 21 cases where selective feticide was carried out the total fetal loss rate was lower in the chorionic villus sampling group (8.3%) than in the amniocentesis group (11.1%), although the difference did not reach statistical significance.

Conclusions: Chorionic villus sampling appears to be a safe alternative to amniocentesis and should be considered as the method of choice particularly when there is a high risk of an affected fetus necessitating selective feticide.