Endometrial pattern, but not endometrial thickness, affects implantation rates in euploid embryo transfers

To evaluate the relationship of endometrial thickness (EnT) and endometrial pattern (EnP) to euploid embryo transfer (ET) outcomes.

Retrospective cohort.

Private academic clinic.

Patients (n = 277; age 36.1 ± 4.0 years) whose embryos (n = 476) underwent aneuploidy screening with fresh (n = 176) or frozen (n = 180) ET from July 2010 to March 2014.

The EnT and EnP were measured on trigger day and at ET. Patients were stratified by age and cycle type (fresh or frozen). Cycle data were combined at trigger day, but separated at ET day.

Outcome measures were implantation rate, pregnancy rate, and clinical pregnancy rate. Analysis was conducted using χ(2) analysis and Fisher's exact test.

A total of 234 gestational sacs, 251 pregnancies, and 202 clinical pregnancies resulted from 356 cycles. The EnT (9.6 ± 1.8 mm; range: 5-15 mm) at trigger day (n = 241 cycles), as a continuous or categorical variable (≤8 vs. >8 mm), was not associated with implantation rate, pregnancy rate, or clinical pregnancy rate. The EnT at day of fresh ET (9.7 ± 2.2 mm; range: 4.4-17.9 mm) (n = 176 cycles) or frozen ET (9.1 ± 2.1 mm; range: 4.2-17.7 mm) (n = 180 cycles) was not associated with implantation rate, pregnancy rate, or clinical pregnancy rate. Type 3 EnP at trigger day was associated with increased serum progesterone at trigger and a decreased implantation rate, compared with type 2 EnP. The EnP at fresh or frozen ET was not associated with implantation rate, pregnancy rate, or clinical pregnancy rate.

Within the study population, EnT was not significantly associated with clinical outcomes of euploid ETs. A type 3 EnP at trigger day suggests a prematurely closed window of implantation.