Development of embryos from natural cycle in-vitro fertilization: impact of medium type and female infertility factors.

Single embryos derived from natural cycle in-vitro fertilization (IVF) were graded during the pre-transfer culture period using morphological criteria. Most embryos developed well in culture with 96% showing continuing division and 68% showing good morphological appearance, although embryo quality tended to decline with an increased incidence of fragmentation and uneven cleavage as division proceeded. Both the pregnancy rate and the distribution of embryo grades were similar among four different culture media used, suggesting that choice of medium had little impact on outcome. In contrast, there were marked differences in pregnancy rate according to the type of infertility, which was not reflected in a decrease in embryo quality. However, although embryos from patients with tubal infertility implanted and formed viable pregnancies irrespective of morphological appearance, only 'good' quality embryos from patients with non-tubal (or 'unexplained') infertility were able to implant. Thus the appearance of the embryo derived from natural cycle IVF in women with unexplained infertility may be of clinical relevance.