[The effect of delayed insemination on fertilization in vitro and the development of human embryos]

Extracorporeal fertilization of 363 oocytes was applied in 148 patients with tubal infertility. The aspiration of the follicles was performed 36 to 38 hrs after the onset of the endogenous LH rise or 36 hrs after injection of hCG. Oocytes maturity was evaluated on the basis of the morphological appearance of the cumulus oophorus. The eggs were incubated in culture medium before insemination. The duration of delayed insemination had a marked effect on the proportion of fertilized oocytes and the development of embryos (X2 = 10.34, P = 0.05). After maturation of 1.5 to 3.5 hrs, minimal preovulatory oocytes were fertilized and developed to embryos. Maturation of 3.5 to 5.5 hrs increased the number of fertilized oocytes from 56% to 71.7% and the number of embryos from 50% to 55.1%. After 5.5 to 7.5 hrs of maturation significantly more fertilized oocytes (t = 2.4, P less than 0.02) and developed embryos (t = 2.41, P less than 0.02) were obtained. Preincubation of intermediary preovulatory or immature oocytes had no beneficial effect on the fertilization rate and the development of embryos.