Serum pregnancy-specific beta1-glycoprotein before embryo transfer is related to endometrial thickness and to outcome prognosis in women undergoing in-vitro fertilization treatment

We have previously observed the repeated presence of low but detectableamounts of the trophoblast marker pregnancy-specific beta1-glycoprotein(SP1) in the serum of some women undergoing in-vitro fertilization (IVF)treatment around the time of oocyte retrieval. The occurrence of thesesignals seemed to be restricted to a defined group of patients which alsoshowed a lower pregnancy success rate in a preliminary study. To test ourhypothesis we have analysed 173 consecutive cycles leading to an embryotransfer. Fifty-four cycles (31%) had a serum SP1 level of at least 0.1ng/ml between days embryo transfer -5 and embryo transfer (group A). Fivepregnancies were obtained in this group (pregnancy rate = 9.3%), while ingroup B, defined by the absence of detectable SP1 before embryo transfer(119 cycles), 36 ongoing pregnancies were achieved (30.3%). Ten of the 41pregnancies were achieved in 33 first-time non-pregnant patients undergoingfurther attempts during the study period. Again the pregnancy rate washigher in the first-time group B women (9/23 versus 1/10 for group A).Patients tended to remain in their groups A or B, the latter beingassociated with a better immediate as well as subsequent chance forpregnancy. Group A cycles had a significantly lower endometrial thicknesstwo days before oocyte retrieval than group B (P = 0.0011). We postulatethat the presence of an unknown, maternal and progesterone- or folliclestimulating hormone-independent factor in some patients could stimulatetonic ectopic SP1 synthesis and at the same time negatively influenceendometrial development.