Natural cycle in-vitro fertilization in couples with unexplained infertility: impact of various factors on outcome

This study evaluated outcome in 117 couples with unexplained infertility who underwent 162 attempts at natural cycle in-vitro fertilization (NIVF) between 1991 and 1993. An egg was obtained in 138 cycles and a single embryo was transferred in 89 cycles. There were 16 implantations (four biochemical pregnancies, three clinical abortions and nine live births). The implantation rate per embryo was 16/89 (18.0%), which translated into a live birth rate per egg collection of 9/138 (6.5%). The impact factors that were assessed included oocyte quality, sperm quality, embryo quality and woman's age. The outcome measures used were fertilization/inseminated egg and implantation/replaced embryo. All embryo transfers were of single embryos. We conclude that, in couples with unexplained infertility, outcome following NIVF is affected by both egg and sperm quality and by the age of the woman. Embryo quality was independent of the above factors but was also critical for successful implantation.