Background To evaluate the safety of cryopreservation in combination with IVF or ICSI, neonatal outcome was investigated in children conceived from frozen-thawed ICSI embryos (cryo ICSI) and frozen-thawed IVF embryos (cryo IVF).
Methods Questionnaire data and results of physical examination at 2 months of age of 547 cryo ICSI and of 390 cryo IVF children were also compared with those from 2889 ICSI and 2995 IVF infants born after transfer of fresh embryos.
Results Birth characteristics were comparable between cryo ICSI and cryo IVF. Cryo singletons showed a trend towards higher mean birthweight compared to fresh singletons, both in ICSI and IVF, reaching significance when all cryo (ICSI plus IVF) singletons were considered. Low birthweight rate according to multiplicity was comparable between fresh and cryo, both in ICSI and IVF. Very low birthweight and prematurity according to multiplicity were comparable between cryo and fresh, in ICSI but not in IVF. Cryo IVF twins showed a higher rate of prematurity and very low birthweight compared to fresh IVF twins. Major malformations were more frequently observed in cryo ICSI (6.4%) than in cryo IVF liveborns (3.1%) (RR 2.08; 95% CI 1.09 to 3.95) and fresh ICSI liveborns (3.4%) (RR 1.89; 95% CI 1.30 to 2.76).
Conclusion Singleton children conceived from cryopreserved embryos (ICSI or IVF) have no adverse neonatal outcome compared to children conceived from fresh embryos. However, more major malformations were found in cryo ICSI children than in cryo IVF children and than in the fresh cohorts. This new finding warrants further attention and understanding.