Early pregnancy wastage following late implantation of embryos after in-vitro fertilization and embryo transfer

Human embryo implantation: current knowledge and clinical implications in assisted reproductive technology

A pregnancy rate of approximately 15% per cycle renders the process of human reproduction inefficient. The cycle-dependent expression of molecules involved in the embryo-endometrial dialogue has lead to the identification of a 'window of implantation'. This is the unique temporal and spatial expression of factors that allows the embryo to implant (via signalling, appositioning, attachment and invasion) in a specific time frame of 48 h, 7-10 days after ovulation. Integrin molecules, L-selectin ligands, mucin-1, heparin-binding epidermal growth factor and pinopodes are involved in appositioning and attachment. The embryo produces cytokines and growth factors [interleukins, prostaglandins, vascular endothelial growth factor (VEGF)] and receptors for endometrial signals (leukaemia inhibitory factor receptor, colony stimulating factor receptor, insulin-like growth factors and heparin binding epidermal growth factor receptor). The immune system plays an important role. Immunomodulatory factors such as glycodelin, inhibin and interleukin prevent a graft-versus-host reaction. Angiogenesis controlled by VEGF and prostaglandins is needed for formation of a receptive endometrium and a placenta. Identification of these factors has led to their use as markers of implantation that may identify defects causing subfertility. An ideal marker of implantation is sensitive and specific, and easy to obtain without disturbing implantation. Glycodelin and leukaemia inhibitory factor (serum) and integrins and pinopodes (biopsies) are promising candidates.

Human chorionic gonadotropin levels in successful implantations after assisted reproduction techniques

To assess successful implantation and early post-implantation embryonic development in assisted reproduction techniques, serum human chorionic gonadotropin (hCG) levels in early gestation in pregnancies with a singleton live birth as the outcome were evaluated. The study was performed as a prospective cohort study of patients undergoing in vitro fertilization (IVF) or artificial insemination by husband (AIH) following ovarian stimulation. Serum hCG levels on days 14, 16, 20 and 27 following ovulation induction with hCG were examined. Serum hCG values were significantly lower in early gestation in IVF compared with AIH, but no difference in hCG doubling times was observed. No difference in serum hCG values between IVF treatment with or without gonadotropin-releasing hormone agonist (GnRHa) was observed. Significantly lower hCG values but no difference in doubling times in early gestation in IVF compared with AIH may be explained by late but successful implantation in IVF. The mechanism for this assumed late implantation is not clear. Altered endometrial receptivity or factors of embryonic origin might explain the observed variation in hCG values and the assumed late implantation.

Do human concepti have the potential to enter into diapause?

Although there is no direct evidence as to whether human concepti have the potential to enter into diapause before implantation, the possibility that human concepti may be capable of following this developmental pathway if exposed to an appropriate environment cannot be ruled out. Direct evidence remains elusive because of the ethical restraints associated with research activities within this area of knowledge. If conceptus diapause has evolved in primates and persists at the present time despite its apparent limited or no adaptive advantage, artificial induction of diapause in humans may have clinical implications for increasing: (i) the viability of concepti after biopsy, freezing-thawing or any other experimental procedure that tends to decrease cell numbers or division rate of concepti; and (ii) the relatively low implantation rates obtained at the present time after uterine transfer of human concepti fertilized in vitro. Furthermore, conceptus diapause may be a good paradigm to understand the interplay between the different genetic/molecular components of both the conceptus and endometrium at implantation.

Embryo implantation during menstruation in the absence of adequate estradiol and progesterone support, with subsequent normal response to ovulation induction and superfetation

OBJECTIVE

To report an unusual case of embryo implantation and superfetation.

DESIGN

Retrospective case analysis.

SETTING

Oak Brook Fertility Center.

PATIENT(S)

A 41-year-old woman underwent two consecutive ovarian stimulation cycles interrupted by a normal menstrual period. Ovulation and implantation occurred during both cycles. The first embryo conceived developed normally until term; the second failed to develop.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Retrospective analysis of stored blood samples for serum E2, P, and beta-hCG levels.

RESULT(S)

Rising beta-hCG levels during menstruation indicated normal embryonic implantation in the absence of adequate E2 and P support. During subsequent ovarian stimulation, there was a normal follicular and E2 response and normal ovulation in spite of the ongoing pregnancy. The second embryo, conceived during the second cycle of stimulation, implanted but failed to develop.

CONCLUSION(S)

This unusual case indicates that E2, P, and endometrial thickness requirements for successful implantation may not always be as critical as postulated previously. The absence of a decidual response might have facilitated superfetation.