Impact of different menstrual lengths in antagonist regimens on IVF assistance and pregnancy outcomes
Authors: Lan Yunzhu , Sun Xingyu , Liu Ling , Fu Li , Huang Guiying , Feng Xinjian 
Published: April 2022

Abstract
Objective:To compare whether there is a difference between the two groups of patients with different menstrual lengths in the antagonist regimen in terms of controlled ovarian stimulation（COS） and pregnancy outcome.Methods:In a retrospective analysis, case data of patients receiving IVF/ICSI assisted conception in the Department of Human Assistive Technology at the Affiliated Hospital of Southwestern Medical University from August 2018 to August 2021 were included and classified as having periods ≤4 days (n=103) and periods >4 days (n=442) based on the length of menstrual periods. basic information, ovulation procedures, laboratory data, and pregnancy outcomes were compared between the different menstrual length groups. Patients who achieved pregnancy were further divided into 2 groups according to the length of menstruation, and the mode of delivery and complications were recorded separately between the groups. Women were followed up until delivery and divided into different menstrual groups, the number of weeks of delivery, infant length, and infant weight were analyzed in both groups.Result(s):A total of 545 patients were assisted with antagonist regimens for pregnancy, based on the length of periods, divided into those with periods ≤4 days (n=103), those with periods >4 days (n=442).With no difference in age, the patients with periods >4 days had lower FSH/LH than those with periods ≤4 days (2.60 (1.80 to 3.58) vs. 3.57 (2.58 to 8.33), p<0.05) ,In contrast, AMH was higher (2.25 (1.18-3.83) vs. 1.73 (1.12-3.17), p < 0.05).We could deduce that ovarian reserve function may be better in patients with >4 days of menstruation than in those with ≤4 days of menstruation.We could deduce that ovarian reserve function may be better in patients with >4 days of menstruation than in patients with ≤4 days of menstruation, as evidenced by the fact that the initiation dose (bottles) (4(3-4) vs 3(2-4), p<0.05) and total Gn dose (bottles) (36.00(28.00-40.00) vs 32.00(24.92-40.00), p<0.05) were significantly higher in patients with ≤4 days of menstruation than in patients with >4 days of menstruation during in vitro fertilization. While the number of eggs obtained (7.00 (5.00-10.00) vs. 8.00 (6.00-11.25), p < 0.05), the number of MII (7.00 (4.00-10.00) vs. 8.00 (5.00-11.00), p < 0.05), and the number of 2PN (4.00 (3.00-6.00) vs. 5.00 (3.00-8.00 ), p < 0.05) yet lower than in patients with periods >4 days.During transplantation and post-transplantation follow-up, it was found that patients with periods >4 days had thicker endometrium (mm) at transplantation day than those with periods ≤4 days (9.10 (7.60-10.10) vs. 10.80 (9.50-12.30), p < 0.05), clinical pregnancy and biochemical pregnancy with periods >4 days were higher than those with periods ≤4 days (169 (38.2%) vs. 34 ( 33.0%)), (59(13.3%) vs 6(5.8%)), and non-pregnant patients with periods ≤4 days were higher than those with periods >4 days (63(61,.2%) vs 214(48.4%)) with statistical significance (p=0.027, <0.05). There was no statistically significant difference between the two groups with different menstrual periods for mode of delivery, ectopic pregnancy, early miscarriage, late miscarriage, week of gestation of delivery, fetal weight and fetal length in patients after fresh embryo transfer with antagonist regimen.Conclusions:From this retrospective study,it can be deduced that the sensitivity of patients with <4 days of menstruation to pro-ovulatory drugs,the number of eggs obtained by pro-ovulation,the thickness of the endometrium on the transplantation day,and the pregnancy outcome (clinical pregnancy, biochemical pregnancy) are lower than those with ≥4 days of menstruation during IVF.