WHAT IS A PRECLINICAL PREGNANCY LOSS

Purpose: To evaluate the contribution of embryo quality to preclinical loss rates after in vitro fertilization (IVF)/embryo transfer (ET) pr egnancy multiple gestation, and clinical loss rates rt ere compared to preclinical pregnancy loss rates over a 3-year period. Methods: The p regnancy outcomes after 1675 fresh ETs from 1994 to 1997 were studied. While establishment of a clinical pregnancy confirms uterine receptiv ity multiple gestation rates reflect embryo quality. Because the major ity of clinical losses are chromosomally abnormal, clinical loss rates serve as another indicator of embryo quality. Results: The overall pr eclinical pregnancy loss rate was 5%, (78/1675) of ETs and 17% (78/472 ) of pregnancies. During the 3-year period the pregnancy rates per ET increased from 19 to 36% (P < 0.0001), multiple gestation rates increa sed from 21 to 48% (P < 0.008), clinical loss rates decreased from 20 to 6% (P < 0.0001), and preclinical pregnancy loss rates remained unch anged from (3 to 19% (P = 0.1). Conclusions: Preclinical pregnancy los s more likely reflects abnormalities in uterine receptivity rather tha n embryo quality. If recurrent preclinical pregnancy loss occurs after IVF/ET evaluation for abnormalities of uterine receptivity should be performed.