A Randomized Double Blinded Controlled Study Comparing a Shorter Exposure of Oocyte to Spermatozoa Versus a Standard Incubation on the Live Birth Rate of In-vitro Fertilization Treatment

1. Background

In vitro fertilization (IVF) technique is now commonly used for the treatment of infertile couples. To obtain better outcomes of IVF, it is important to enhance embryo quality by optimizing IVF techniques. In IVF procedures, oocytes and sperm are routinely co-incubated overnight, which may expose oocytes and zygotes to suboptimal culture conditions with increased reactive oxygen species (ROS) produced by sperm in this long term culture[1]. High levels of reactive oxygen species (ROS) can adversely affect the quality of the embryos, result in hardening of the zona pellucida and impair the implantation capacity of embryos [2-4]. Studies shows successful fertilization of a mamamal oocyte occurs 20mins after gametes meet [5]. Sperm can penetrate through the cumulus cells within 15min, and 80% of oocytes can be fertilized when they are exposed to a large number of spermatozoa within 1hrs[1]. As an attempt to avoid possible detrimental effects on the oocytes from long exposure to sperm, the brief co-incubation insemination protocol was developed. It implies that long-term co-incubation of oocytes and sperm may not be necessary and may even be harmful. Some reports suggest that a sperm-oocyte exposure time of 1-6 h improves IVF outcomes[1,2,6,7] However, other studies report no such advantage with a short insemination time[8,9,10] .

Recent published Meta analysis shows[11] brief co-incubation of gametes was associated with significantly higher rates of clinical pregnancy (RR: 1.84, 95% CI: 1.24-2.73), ongoing pregnancy (RR: 1.73, 95%CI: 1.27-2.33) and higher rate of implantation (RR: 1.80, 95% CI: 1.43-2.26) than standard insemination. But the rates of normal fertilization (RR: 0.98, 95% CI: 0.93-1.02), good quality embryos (RR: 1.24, 95% CI: 1.0-1.53) and polyspermy (RR: 0.84, 95% CI: 0.7-1.01) were not significantly different compared with standard insemination. In another Cochrane meta-analysis[12] eight RCTs with 733 women were included, and got the similar results. But it only reported clinical pregnancy rate, ongoing pregnancy rate which was significantly higher in brief co-incubation group than standard insemination. For the miscarriage rate, there were six miscarriages in one trial including 167 women. This low quality evidence suggested no significant difference in the odds of miscarriage between brief co-incubation and standard insemination (OR 1.98, 95% CI 0.35 to 11.09; P = 0.44). And live birth was not reported in the included studies, it is unclear whether brief co-incubation improves the life birth rate compared with the standard overnight insemination protocol.

Drawbacks inherent to the quality of these studies, such as lack of allocation concealment and no blinding, limit the quality of the available evidence. To better evaluate these issues, more well designed RCTs are required to assess whether brief co-incubation would contribute to a higher live birth rate and a lower miscarriage rate compared to the standard overnight insemination protocol. 2. Objectives:

The objective of the present randomized, double blinded controlled study is to compare clinical effectiveness (especially on live birth rate) of a shorter exposure of oocyte to spermatozoa compared to a standard incubation in women undergoing IVF treatment. 3. Trial design: