胚盤胞移植(生殖)

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Infertile women undergoing IVF treatment face a 20-fold increased risk of twin and 400-fold increased risk of higher order pregnancies compared to the women not received IVF treatment. This is related to the current practice of transferring multiple embryos into the uterus. The medical, social and economic consequences of multiple gestation have been the subject of recent discussion and several preventive strategies have been identified. To avoid multiple gestation the brastocyst transfer has been expected for just a few years. In a reproductive tract, an embryo is thought to be carried into the uterine cavity at the stage of morulaor blastocyst. Considering this phenomenon, blastocyst stage might be suitable for implantation in the ART program. In a last decade it was very difficult for an embryo to be incubated to the blast ocyst stage in vitro. Before an improvement of culture medium, an embryo was co-cultured with several kinds of cells, such as Vero cells, oviductal epitherial cells or grananulasa cells, to obtain a blastocyst. But recently, culture medium (sequential medium) is well improved and suitable for long-term incubation. The characteristics of sequential medium are as follow ; 1) decrease of glucose concentration and increase of lactate forearly embryo cleavage, 2) increase of glucose concentration and decrease of pyruvate for late embryo development, 3) supplementation of essential and/or non-essential amino acids for late embryo development. Recently there were many reports about clinical outcomes of blastocyst transfer. They showed that blastocyst formation, implantation and pregnancy rates (/ET) were about 30-66%, 18.9-48%, and 40-68%, respectively. Although blast cyst transfer has achieved high pregnancy rate, it has not obtained the significant benefit as to the pregnancy and implantation rates compared to the day 3 embryo transfer. However, in the patients having failed IVF treatments many times, blastocyst transfer still increases implantation and pregnancy rates. The blastocyst formation rate in ICSI trial is significantly smaller than that in conventional IVF. Because oocytes were denuded during ICSI procedure and sperm findings in ICSI cases were worse than those in IVF cases. Although it has little meaning to apply the blastocyst transfer to all ART patients, a good quality of embryo could be selected among many embryos by the longterm incubation of embryos in vitro. Considering this merit the blastocyst transfer replacing a single embryo may be one of strategies to avoid a multiple pregnancy.
社団法人日本産科婦人科学会の論文
2003-08-01

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