Relationship of biochemical pregnancy to pre-ovulatory endometrial thickness and pattern in patients undergoing ovulation induction

In order to assess the relationship between pre-ovulatory endometrialthickness and pattern and biochemical pregnancy, the pregnancyoutcome was retrospectively analysed in 81 patients undergoingovulation induction evaluated by vaginal ultrasound on the dayof human chorionic gonadotrophin (HCG) administration or luteinizinghormone (LH) surge. Biochemical pregnancies occurred in 7/32(21.9%) pregnancies when endometrial thickness was <9 mm,compared to 0/49 when endometrial thickness was 9 mm on theday of HCG administration or LH surge (P < 0.0025). Clinicalabortions occurred in 5/32 (15.6%) pregnancies when endometrialthickness was 6–8 mm, compared to 6/49 (12.2%) when endometrialthickness was 6–8 mm (NS). Endometrial thickness was relatedto the cycle day of HCG or LH surge (r = 0.37, P < 0.001)but was unrelated to oestradiol level on the day of HCG administrationor LH surge (r = 0.12). Biochemical pregnancies were relatedto endometrial pattern (r = – 0.22, P = 0.02) but wereunrelated to maternal age or previous abortions. Clinical abortionswere related to age (r = 0.26, P = 0.01) and to previous abortion(r = 0.25, P = 0.013) but were unrelated to endometrial pattern.Neither biochemical pregnancy nor clinical abortion was relatedto oestradiol or LH levels on the day of HCG administrationor LH surge. These findings suggest that the majority of biochemicalpregnancies do not result from karyotypically abnormal embryos,as do clinical abortions.