ENDOMETRIAL THICKNESS AND OBSTETRICAL OUTCOME IN ASSISTED REPRODUCTIVE TECHNOLOGY

Abstract

Mounting evidence suggests that assisted reproductive technology (ART) alters certain obstetrical parameters as compared to natural pregnancies. Endometrial thickness (EMT) is one possible parameter which could impact on the depth of placentation – either too shallow, or too deep. While the impact of EMT on actual pregnancy rates has been studied in ART, little is known on whether EMT affects the quality of placentation. Therefore, we studied the impact of EMT on obstetrical outcomes following fresh and frozen embryo transfers (ET). Retrospective cohort study including patients who obtained a live birth (LB) after autologous ART in our center, between January 2017 and December 2019. Single and double blastocyst transfers were included. Fresh and frozen ET with singleton and twin pregnancies were analyzed separately. We divided them into 4 groups according to the last measured EMT before ET : <7mm,7 to 9 mm; 9 to 12 mm; ≥ 12 mm. Primary outcome was pregnancy duration in days. Secondary outcomes were the birth weight, obstetrical complications and the delivery mode. Associations between the 4 EMT groups were assessed using ANOVA and Fisher tests. 120 patients obtained single LB after fresh ET and 19 patients obtained twin LB. After frozen ET 571 patients had single LB and 75 patients had twin LB. No significant difference was reported between the 4 EMT groups when compared for pregnancy duration in fresh or frozen ET, and in singleton or twin pregnancies. In fresh ET with singleton pregnancies, more obstetrical complications and medically induced deliveries before 41 gestational weeks (GW) were reported in the groups<7 mm and >12mm.Table 1Results for singleton pregnancies<7 mm7-9 mm9-12 mm≥12 mmpvalueFresh ETN=5N=25N=68N=22Pregnancy Duration256.7±20.3262.7±13.4260.7±18.5263.3±10.20.78Birth Weight3153±744.73263.7±407.13196.1±509.23128.2±507.70.83SpontaneousInduced<41GWInduced≥41GW1 (20)2 (40)2 (40)19 (76)5 (20)1 (4)49 (72)14 (21)5 (7)9 (41)10 (45)3 (14)0.01Complications4 (80)4 (16)20 (29)7 (32)0.04Frozen ETN=19N=324N=202N=26Pregnancy Duration256.7±20.3262.7±13.4260.7±18.5263.3±10.20.23Birth Weight3139.2±777.03326.7±535.73271.3±635.23422.7±469.50.29SpontaneousInduced<41GWInduced≥41GW9 (47)7 (37)3 (16)147 (45)126 (39)51 (16)89 (44)78 (39)35 (17)12 (46)10 (38)4 (15)0.99Complications4 (21)87 (27)49 (24)7 (27)0.88 Open table in a new tab Our findings report no difference in the pregnancy duration (in days) or in birth weight related to endometrial thickness at the time of fresh or frozen ET. This suggests that EMT does not impact the quality of placentation.