OBJECTIVETo investigate the in vitro maturation of human oocytes (IVM) from pregnant late term, natural cycles and Gn stimulating cycles and the effect of granulose cells on IVM from pregnant late term.

METHODSA total of 1086 immature oocytes were obtained including 633 oocyte-cumulus complexes (OCCs) and 453 denuded oocytes (DOs). OCCs were divided into pregnant late term group, natural cycle group and IVM group, and DOs were divided into pregnant late term group, natural cycle group and controlled ovarian hyperstimulation (COH) group. All the oocytes were matured in IVM culture system and fertilized by ICSI. The embryos were cultured to blastocyst stage except that those in IVM group were transferred into the uterus. The main outcomes were assessed including maturation rate (MR), fertilization rate (FR), cleavage rate (CR), and blastulation rate (BR) (natural cycle group, pregnant late term group and COH group) and pregnancy rate per transfer cycle (PR) of IVM group.

RESULTSMR of OCCs in pregnant late term group, natural cycle group and COH group was 74.3%, 76.9% and 82.2%, respectively, showing statistical difference between pregnant late term cycle group and IVM group. No statistical difference was observed in FR, CR or BR between the three groups. For IVM cycle group, clinical pregnancy rate of 20% per aspiration was achieved. For DOs, MR of COH group (86.0%) was significantly higher than that of the natural cycle group (72.5%) and pregnant late term group (72.7%) (P<0.01). FR, CR and BR showed no statistical difference among the 3 groups. No difference was found in MR, FR, CR and BR between OCCs group and DOs group from pregnant late term.

CONCLUSIONSThe oocytes from pregnant late term have the same development potential as those from natural cycles or Gn stimulating cycles in vitro, and provide a new source of donor oocytes. Granulose cells do not affect the IVM from pregnant late term.