Obstetric outcome of pregnancies after the transfer of cryopreserved and fresh embryos obtained by conventional in-vitro fertilization and intracytoplasmic sperm injection

This study reports the obstetric outcome of pregnancies obtained after the transfer of cryopreserved or fresh embryos where the initial procedure was standard in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), Pregnancies obtained after frozen IVF (n = 245) or frozen ICSI (n = 177) were compared with a control group of pregnancies after fresh embryo transfer in standard IVF (n = 245) acid ICSI (Iz = 177) cycles were selecte d as controls. The controls were matched according to maternal age, parity and date of embryo transfer. In the standard IVF group, the biochemical pre gnancy rates in the cryopreserved and fresh groups were 18.8 and 9.8% respe ctively (P < 0.01), In the ICSI group, the biochemical pregnancy rates in t he cryopreserved and fresh groups were 16.4 and 6.8% respectively (P < 0.01 ), The miscarriage rates were comparable between the cryopreserved and fres h groups. However, in the frozen ICSI group the miscarriage rate (26.0%) wa s significantly higher than in the frozen conventional IVF group (13.1%) (P = 0.001). The frequencies of preterm deliveries, infants with very low bir thweight and intrauterine deaths were similar in the groups, The low birthw eight rates in the frozen IVF (16.1%) and ICSI (12.1%) groups were signific antly lower than those in the fresh IVF (32.2%) and ICSI (32.7%) groups (P < 0.001). The major malformation rates in the frozen IVF (2.4%) and ICSI (2 .9%) groups were not different from the major malformation rates in the fre sh IVF (4.5%) and ICSI (2.4%) groups. In conclusion, the cryopreservation p rocess had no negative impact on the outcome of pregnancies over 20 weeks o f gestation. Longterm follow-up studies are needed in order to prove the sa fety of the freezing-thawing process.