Overnight maturation of a metaphase I oocyte retrieved from a natural cycle using human tubular fluid: a case report

Abstract

Since the first successful pregnancy and live birth was achieved through natural cycle in vitro fertilization (IVF) in 1978 [1], there have been many technological advancements and refinements of protocols and techniques through the years [2]. Ovarian hyperstimulation was favored over unstimulated cycles, due to the increased number of embryos available for transfer and hence increased success rate. However, stimulated IVF is also associated with side effects such as ovarian hyperstimulation syndrome [3] and it is costly [4]. For patients who have failed to conceive after repeated stimulated IVF cycles, natural cycle IVF may be a cost-saving alternative [5, 6] which allows patients to avoid further exposure to the side effects associated with stimulated IVF cycles [7, 8]. However, one of the drawbacks of pure natural cycle IVF is its higher cancellations rates (28.9 % per cycle) and lower pregnancy rate (0 to 12.5 % per cycle) [5]. The main reasons for cancellation are premature ovulation before oocyte retrieval, failure to retrieve oocytes and retrieval of immature oocytes. The stage of maturation of the oocyte cannot be determined before retrieval as well. When an immature oocyte is retrieved, it is usually discarded and the cycle is cancelled. To maximize the utilization of the immature oocytes collected from unstimulated cycles, our centre evaluated our protocol and started incubating the immature oocytes overnight in human tubular fluid (HTF) (Irvine Scientific, USA) instead of discarding them. Standard IVF culture media has been shown to be as efficacious as specialized IVM media in ‘rescuing’ immature oocytes retrieved from standard stimulated IVF cycles [9]. When fully matured, the oocytes are fertilized, allowed to develop into embryos in culture and eventually transferred. We report the first case of a successful implantation and pregnancy achieved from this ‘rescue’ protocol in a natural IVF cycle.