P-147 Comparison of Fertilization rate, Blastocyst rate and number of Top Quality Embryo with Short (2 hours) and conventional co-incubation (16-20 hours)of gametes
Authors: Ghumman S , Choudhury D , Khanna S , Patel S , Batra A 
Published: June 2023

Abstract

Study question
Does short Co-incubation of gametes increase quality and quantity of embryos by eliminating suboptimal culture conditions like increased reactive oxygen species seen with overnight incubation?

Summary answer
Although short co-incubation group had lower fertilization rate it yielded more blastocysts and top quality embryos on day 3 and 5.

What is known already
Successful fertilization can occur 20 minutes after co-incubation of gametes. Incubation time of 18 hours has been used as a routine combining it with fertilization check. However it is known to produce reactive oxygen species (ROS) released by cellular metabolism of inseminated sperms which affect embryo development and cause zona pellucida hardening. Studies have shown reduced oocyte exposure time caused improved embryo development. However, other studies have reported lower fertilization rate with no such advantage. Not many studies have been done with short co-incubation without denudation which might allow optimum fertilization and at the same time prevent increase in ROS.

Study design, size, duration
It is prospective controlled study. 62 patients (921 oocytes) were recruited. The sibling oocytes from each patient were divided into 2 groups. Group 1( Control) conventional co-incubation of gametes (16-20 hours) and group 2 short co-incubation (2 hours) after which they were transferred to a fresh media. Study period was from January 2022 to September 2022. Institutional scientific and ethical committee approval and written consent of couple taken.

Participants/materials, setting, methods
Couples undergoing IVF in tertiary infertility centre were recruited. Women under 40 years who yielded minimum 6 oocytes and males with normal semen parameters were included. Those excluded were couples requiring ICSI, poor responders with &lt;6 oocytes retrieved and couples requesting day 3 transfer. Primary outcome was number and percentage of top quality embryos (TQE) and blastocyst rate. Secondary outcome was fertilization rate. SPSS used for data analysis. Results expressed as mean +/-SD or percentage

Main results and the role of chance
Total oocytes studied 921 in 62 patients. Since control and study group were from sibling oocytes of same patient they were matched for age BMI, ovarian reserve, stimulation protocol, semen parameters and laboratory handling. Extra oocytes in odd number oocytes were randomized to 2 groups. Mean age was 31 years. Group 1 had 425 out of 455 (93.4%) oocytes fertilized and group 2 had 412 out of 466 (88.4%) oocytes fertilized (p value&lt;0.05). TQE on day 3 were 251 of 425 (59.05%) fertilized in group 1 and 277 of 412 (67.23%) fertilized in group 2 (p = 0.013). Blasts formed in group 1 were 41 of 425 (9.64%) and in group 2 were135 of 412 (32.76%) (p = 0.001). TQE on day 5 were 28/425 (6.67%) in group 1 (0.45 +/−0.9 blasts per patient) and 95/412 (23.05%) in group 2 (1.53+/-1.86 blasts per patient). (P = 0.001) Percentage of grade 2 embryos on day 3 and 5 was significantly higher in short co-incubation group. Although fertilization was higher in group 1 many embryos did not progress beyond day 2 as both grade 1 and 2 embryos on day 3 and 5 were less in percentage and absolute per patient value in this group.

Limitations, reasons for caution
Pregnancy rate could not be calculated as some patients wanted 2 embryos transferred and one group had only a single blast. For their transfer blasts were taken from both groups. Very poor responders (&lt;6 oocytes) not studied. Further studies needed to establish best time duration for short co-incubation (1-8 hours)

Wider implications of the findings
Practice for co-incubation after 16-20 hours needs to be re-evaluated. The study shows more top quality blasts with short insemination period. This may become the practice if it is established by further studies assuming that TQE are known to yield better pregnancy rates and IVF results

Trial registration number
not applicable