[Comparison of pregnancies issued from frozen embryo transfers and pregnancies issued from fresh embryo transfers in fertilization in vitro. FIVNAT].

The French in vitro fertilization registry FIVNAT allowed us to describe the most important cohort of pregnancies resulting from the replacement of frozen-thawed embryos, and to compare them with pregnancies issued from fresh embryos transfers. From 1987 to 1992, 465 and 8,757 clinical pregnancies were respectively collected, and resulted in the birth of 386 et 8729 babies. Whereas the miscarriage rate was higher, pregnancy evolution was more normal after transfer of frozen-thawed embryos. Multiple pregnancies were less frequent; preterm birth rates and low birth rate were also significantly lower. Nevertheless, after cryopreservation of embryos, more complications were noted. However, further analysis involving more pregnancies after transfer of frozen-thawed embryos is necessary before reaching conclusion. Finally, congenital malformation rate was not different between the two groups.