Advances in Embryo Transfer

Embryo transfer refers to a step in the process of assisted reproduction in which one or several embryos are placed into the uterus of a female with the intent to establish a pregnancy. Currently this biotechnology has become one of the prominent high businesses worldwide. This technique, which is often used in connection with in vitro fertilization (IVF), has widely been used in animals or human, in which situations the goals may vary. In animal husbandry, embryo transfer has become the most powerful tool for animal scientists and breeders to improve genetic construction of their animal herds and increase quickly elite animal numbers which have recently gained considerable popularity with seedstock dairy and beef producers. In human, embryo transfer technique has mainly been used for the treatment of infertile couples to realize their dream to have their children. The history of the embryo transfer procedure goes back considerably farther, but the most modern applicable embryo transfer technology was developed in the 1970s (Steptoe and Edwards, 1978). In the last three decades, embryo transfer has developed into a specific advanced biotechnology which has gone through three major changes, “three generations”---the first with embryo derived from donors (in vivo) by superovulation, non-surgical recovery and transfer, especially in cattle embryos, the second with in vitro embryo production by ovum pick up with in vitro fertilization (OPU-IVF) and the third including further in vitro developed techniques, especially innovated embryo micromanipulation technique, which can promote us to perform embryo cloning involved somatic cells and embryonic stem cells, preimplantation genetic diagnosis (PGD), transgenic animal production etc. At the same time, commercial animal embryo transfer has become a large international business (Betteridge, 2006), while human embryo transfer has spread all over the world for infertility treatment. Just only in the United States of America there are 442 assisted reproductive technology (ART) centers with IVF programs in 2009 report of the Centers for Disease Control and Prevention. Embryo transfer, besides male sperm, involves entire all process from female ovarian stimulation (start) to uterine receptivity (end). During this entire process, many new bio-techniques have been developed (Figure 1). These techniques include optimal ovarian stimulation scheme, oocyte picking up (OPU) or oocyte retrieval, in vitro maturation (IVM) of immature oocytes, in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), preimplantation genetic diagnosis (PGD), blastocyst embryo culture technology, identification of optimal uterine environment etc. Here, we will review some key newly developed biotechnologies on human embryo transfer.