In vivo development of transferred mouse embryos conceived in vitro in simple and complex media

Ovulated mouse ova were fertilized in vitro and cultured to the four-cell stage in simple medium (modified Earle's balanced salts solution, EBSS) supplemented with bovine serum albumin (BSA) and in complex media (modified Ham's F-10 medium, Gibco, Grand Island, NY) with and without human cord serum supplementation. Fertilization and cleavage to the four-cell stage were the same for the three groups. Embryos in cohorts of six were transferred into oviducts of 14 to 16 pseudopregnant recipients per group. Pregnancy rates were higher for the EBSS/BSA and Ham's F-10 groups (36%) than for the Ham's F-10/cord serum group (19%). The percentage of embryos that developed into fetuses in the pregnant recipients was also higher for the Ham's F-10 group (47%) and the EBSS/BSA group (33%) than for the Ham's F-10/cord serum group (22%). The average fetal weights 17 days after transfer for the EBSS/BSA embryo group was 659 +/- 40 mg and for the Ham's F-10 group was 666 +/- 20 mg, higher (P less than 0.05 and P less than 0.003, respectively) than for the Ham's F-10/cord serum group, which was 522 +/- 30 mg. Although all developmental parameters were lower for the in vitro conceived embryos than for a control group of in vivo developed embryos transferred directly to pseudopregnant recipients, the cord serum culture conditions were the least supportive of normal embryo development.