In vitro maturation of oocytes in women at risk of ovarian hyperstimulation syndrome-A prospective multicenter cohort study

Background: In vitro maturation (IVM) is an artificial reproductive technology in which immature oocytes are harvested from the ovaries and subsequently will be matured in vitro. IVM does not require ovarian hyperstimulation (OH) and thus the risk of ovarian hyperstimulation syndrome (OHSS) is avoided. In this study, we assessed the live birth rate per initiated IVM cycle in women eligible for in vitro fertilization/intracytoplasmic sperm injection (IVF/ ICSI) and at risk for OHSS. Furthermore, we followed women who were not pregnant after IVM and committed to a conventional IVF/ICSI procedure. Materials and Methods: In this multicenter prospective cohort study, we started 76 IVM cycles using recombinant follicle stimulating hormone (rFSH) priming in 68 patients. There were 66 oocyte retrievals, in which a total of 628 oocytes were collected. We incubated the immature oocytes for 24-48 hours and fertilized those that reached metaphase II by ICSI. Results: Three hundred eighty six (61% oocytes) achieved metaphase II. The fertilization rate was 55%. We performed 59 embryo transfers (1.9 embryos per transfer) in 56 women, including 3 frozen embryo transfers. There were four ongoing pregnancies (5.3% per initiated cycle) leading to the birth of a healthy child at term. None of the patients developed OHSS. The ongoing pregnancy rate of the first conventional IVF/ICSI cycle after an unsuccessful IVM cycle was 44%, which was unexpectedly high. Conclusion: We concluded that IVM led to live births but with low effectiveness in our study. Earlier reported IVM success rates are higher which can be caused by a more extended experience in these centers with the intricate laboratory process. However, a possible selection bias in these studies cannot be ruled out. Furthermore, IVM might have a beneficial effect on further IVF/ICSI treatments due to its “ovarian drilling” effect.