**Embryo Implantation and Cryopreservation**

190 Advances in Embryo Transfer

[24] Tucker MJ, Wong CJ, Chan YM, Leong MK, Leong CK. Post-operative artificial insemination –does it improve GIFT outcome? Hum Reprod. 1990;5(2):189-192. [25] Qasim SM, Trias A, Karacan M, Shelden R, Kemmann E. Does the absence or presence of

[26] Coulam C.B and Stern, J.J. Effect of seminal plasma on implantation rates. Early

[27] Stern, J.J, Coulam, C.B, Wagenknecht, D.R, Peters AJ, et al. Seminal plasma treatment of

[28] Naeye RL. Coitus and associated amniotic-fluid infection. N Engl J Med.

[29] Fanchin R, Harmas A, Benaoudia F. Microbial flora of the cervix assessed at the time of

[30] Sharkey DJ, Macpherson Am, Tremellen KP, Robertson SA. Seminal plasma differentially

[31] Fox CA, Wolff HS, Baker JA. Measurement of intra-vaginal and intra-uterine pressures during human coitus by rodio-telemetery. J Reprod Fertill. 1970;22(2)243-251. [32] Fanchin R , Righini C , Olivennes F . Uterine contractions at the time of embryo transfer

[33] Fanchin R , Righini C , Ayoubi JM, Olivennes F , de Ziegler D . Uterine contractions at the

[34] Barker JN, Mitra RS, Griffiths CE, et al. Keratinocytes as initiators of inflammation. Lancet

[35] Quayle AJ. The innate and early immune response to pathogen challenge in the female genital tract and the pivotal role of epithelial cells. J Reprod Immunol 2002;57:61-79. [36] Sallusto F, Lanzavecchia A. Efficient presentation of soluble antigen by cultured human

[37] Burnham K, Robb L, Scott CL, et al. Effect of granulocyte-macrophage colony-stimulating

[38] Diehl S, Rincon M. The two faces of IL-6 on Th1/Th2 differentiation. Mol Immunol

[39] Thompson LA, Barratt CL, Bolton AE, et al. The leukocytic reaction of the human uterine

[40] Lim KJ, Odukoya OA, Ajjan RA, et al. The role of T-helper cytokines in human

[41] Jasper MJ, Tremellen KP, Robertson SA.Reduced expression of IL-6 and IL-1alpha

[42] Kunz G, Leyendecker G. Uterine peristaltic activity during the menstrual cycle:

recurrent spontaneous abortion. Am J Reprod Immunol, 1992;27,50.

insemination? Hum Reprod. 1996; 11(5):1008-1010.

epithelial cells. Mol Hum Reprod. 2007 Jul;13(7):491-501.

pregnancy: Biol. Med, 1995;1: 33 – 36.

1979;29;301(22):1198-200.

jul – Aug : 26(7 – 8 ): 498 – 505

1991;337:211-214

1994;179:1109-1118.

2000;20:1071-1076.

2002;39:531-536.

Suppl 3:5-9.

cervix. Am J Reprod Immunol 1992;28:85-89.

reproduction. Fertil Steril 2000;73:136-142.

Reprod Immunol 2007;73:74-84.

1998;70(5):866-870.

2009 ; 91:167 – 72

cycles – a double blind , placebo – controlled , randomized pilot study . Fertil Steril

seminal fluid matter in patients undergoing ovulation induction with intrauterine

embryo transfer adversely affects *in vitro* fertilization outcome. Fertil Steril.

regulates inflammatory cytokine gene expression in human cervical and vaginal

alter pregnancy rates after in vitro fertilization . Hum Reprod . 1998 ; 13(7):1968 – 1974

time of embryo transfer : a hindrance to implantration ? Contracept Fertil Sex . 1998

dendritic cells is maintained by granulocyte/macrophage colony- stimulating factor plus interleukin 4 and downregulated by tumor necrosis factor alpha. J Exp Med

factor on the generation of epidermal Langerhans cells. J Interferon Cytokine Res

mRNAs in secretory phase endometrium of women with recurrent miscarriage. J

characterization regulation function dysfunction. Reprod Biomed Online 2002;4

**14**

*USA* 

Russell A. Foulk

*University of Nevada, School of Medicine* 

**Implantation of the Human Embryo** 

Implantation is the final frontier to embryogenesis and successful pregnancy. Over the past three decades, there have been tremendous advances in the understanding of human embryo development. Since the advent of *In Vitro Fertilization*, the embryo has been readily available to study outside the body. Indeed, the study has led to much advancement in embryonic stem cell derivation. Unfortunately, it is not so easy to evaluate the steps of implantation since the uterus cannot be accessed by most research tools. This has limited our understanding of early implantation. Both the physiological and pathological mechanisms of implantation occur largely unseen. The heterogeneity of these processes between species also limits our ability to develop appropriate animal models to study. In humans, there is a precise coordinated timeline in which pregnancy can occur in the uterus, the so called "window of implantation". However, in many cases implantation does not occur despite optimal timing and embryo quality. It is very frustrating to both a patient and her clinician to transfer a beautiful embryo into a prepared uterus only to have it fail to implant. This chapter will review the mechanisms of human embryo implantation and

The human embryo enters the uterine cavity approximately 4 to 5 days post fertilization. After passing down the fallopian tube or an embryo transfer catheter, the embryo is moved within the uterine lumen by rhythmic myometrial contractions until it can physically attach itself to the endometrial epithelium. It hatches from the zona pellucida within 1 to 2 days after entering the cavity thereby exposing the trophoblastic cells of the trophectoderm to the uterine epithelium. Implantation occurs 6 or 7 days after fertilization. During implantation and placentation, a human embryo must attach itself to the uterus under conditions of shear stress. The embryo is rolling about within a mucus rich environment between the opposing surfaces of the endometrial walls of the uterus. This interactive process is a complex series of events that can be divided into three distinct

Once the human blastocyst hatches from the zona pellucida, the free-floating sphere of cells must orient itself as it approaches the endometrial surface and form an initial adhesion

**1. Introduction** 

**2.1 Apposition** 

discuss some reasons why it fails to occur.

**2. Phases of human embryo implantation** 

steps: apposition, attachment and invasion (Norwitz et al., 2001).
