The assessment of optimal timing of oocyte retrieval based on LH surge in natural cycle IVF: a large scale retrospective study

Abstract

Natural cycle IVF is patient friendly, low-risk, cost-effective, useful for women who don’t react to controlled ovarian stimulation as a result of declined ovarian function. The aim of present study is to assess whether the differences of oocyte retrieval (OR) timing based on LH surge influences ART outcomes in natural cycle IVF. A retrospective single center cohort study of 5793 natural cycles. Patients aged 26-51 years whose oocytes retrieved from January 2013-December 2013 were enrolled. Natural cycles were divided into 4 groups (A, B, C, D) by OR timing considering LH surge. Nasal spray of gonadotropin-releasing hormone agonist (GnRHa) was used as a trigger to maturate oocyte and adjust OR timing. Primary outcomes were maturation status of oocyte per total OR cycles and fertilization and cleavage per inseminated oocyte cycles and secondary outcome was clinical pregnancy rate (CPR) per fresh single embryo transfer cycles. Group A; OR at the same day of examination (Descending curve of LH surge), Group B; OR at the following day of examination without spray (Halfway near the peak of LH surge), Group C; OR at the following day of examination with spray (Ascending curve of LH surge), Group D; OR at two days later of examination (Pre LH surge). Chi squared test was performed and a P-value<0.05 was considered statistically significant. The rate of MII oocyte in Group A (25.2% 172/682) was significantly lower than in Group B (67.0% 134/200), C (52.4% 1254/2389), D (59.3% 1495/2522). The rate of MI and GV oocyte per total cycles in Group A (36.4% 248/682, 2.6% 18/682) was significantly higher than in Group B (13.0%, 26/200, 1.5% 3/200), C (15.8% 379/2389, 1.2% 29/2522), D (7.4% 187/2522, 1.1% 29/2522), respectively. The rate of fertilized oocyte in Group A (78.8% 313/397) was significantly lower than in Group C (83.3% 1351/1622), D (85.6% 1454/1697) except for in Group B (82.5% 132/160). The rate of cleaved oocyte in Group A (70.5% 280/397) was significantly lower than in Group D (77.5% 1316/1697) except for in Group B (73.1% 117/160), Group C (75.2% 1221/1622). When 1453 cycles with fresh embryo transfer were analyzed, CPR in Group A (26.4% 34/129) was significantly lower than in Group B (47.1% 32/68), C (39.7% 261/658) and D (40.1% 240/598). Our results revealed that OR at the same day of examination is difficult to take optimal OR timing. In addition, it is controversial whether GnRHa should be used or not in the inadequate size of follicle before entering descending curve of LH surge (Group A). Still acceptable CPR can be expected in Group A. Therefore, natural cycle IVF including OR at the same day of examination is a valuable method without wasting precious menstrual cycles or any drugs.