Congélation lente et vitrification des ovocytes humains matures et immatures

Performance and security questions in human oocyte cryopreservation have been taking researchers for about two decades. Oocytes are usually frozen at metaphase II. Immature oocytes cryopreservation is still a research alternative. Two techniques are currently available for oocyte cryopreservation: slow freezing and vitrification. Experimental data suggest that vitrification has less impact on oocyte physiology than classical slow freezing. After slow freezing of mature oocytes, survival and fertilization rates reach 70 to 80% whereas cleavage rates are around 90%, leading to five implantations and 1.2 births per 100 thawed oocytes. After vitrification of mature oocytes, survival and cleavage rates reach 90% leading to 11 implantations and 1.8 births per 100 thawed oocytes. The obstetrical and neonatal prognosis of these pregnancies is reassuring. No increased risk of congenital anomalies has been observed. However, further evaluation is needed to guarantee the safety of cryopreservation procedures. Immature oocyte cryopreservation is not currently perfected but some indications appear of great interest.     

Malformations et facteurs environnementaux

The relationship between intrauterine exposure to environmental agents and the occurrence of congenital malformations has been the subject of numerous studies, leading to sometimes inconclusive results. To date, there are still many unknowns about the proportion of congenital malformations attributable to the effects of the environment and the nature of the substances likely to increase their occurrence. This article proposes to assess the current knowledge on this question. Once the concepts of “malformation”, “environment”, “mutagenic and teratogenic effects” have been defined, the article takes a census of the current sources of information used to study them (malformations registries, Pélagie cohorts, ELFE and Sépages cohorts, REACH regulation). An emphasis is placed on the criteria that are recognized as being decisive in the validation of studies aiming at evaluating these associations, such as using correct definitions, using an accurate measure of the malformations studied, as well as the exposure, co-exposure and biological data used. Finally, the article establishes an assessment of the most salient physical and chemical factors, in terms of known or suspected reprotoxic risk: endocrine disruptors, solvents, atmospheric pollutants, pesticides and electromagnetic fields.