The detrimental effect of increased endometrial thickness on implantation and pregnancy rates and outcome in an in vitro fertilization program.

OBJECTIVE: To determine whether there is a maximal value for endometrial thickness, as measured on the day of hCG administration, above which implantation and pregnancy are unlikely to occur.
DESIGN: Retrospective analysis.
SETTING: A university-based tertiary care center for assisted reproductive technology. PATIENT(S): A total of 809 IVF cycles in 623 patients resulting in ET. INTERVENTION(S): Endometrial thickness was measured by means of transvaginal ultrasound on the day of hCG administration. Cycles were divided into two groups based on endometrial thickness. Group A consisted of 680 cycles with "normal" endometrial thickness (7-14 mm), and group B included 37 cycles with "increased endometrial thickness" (>14 mm). MAIN OUTCOME MEASURE(S): Implantation, clinical pregnancy and miscarriage rates. RESULT(S): Group B cycles had significantly lower implantation and pregnancy rates compared with group A (3% versus 15% and 8.1% versus 29.7%, respectively). Two of 3 pregnancies (66.6%) from group B miscarried, compared with 44 of 202 (21.8%) pregnancies in group A. CONCLUSION(S): Patients with endometrial thickness of > 14 mm on the day of hCG administration comprise approximately 5% of the patients who undergo ET in our program. Our experience suggests that implantation and pregnancy rates are significantly reduced, and miscarriage rates may be increased in this group.