Decline in pregnancy rate (PR) with insemination of high motile sperm numbers for intrauterine insemination (IUI)

Abstract

To determine pregnancy rates following IUI based on total motile sperm counts (TMSC) and the impact of high motile sperm numbers on IUI success. A retrospective analysis of 9865 cycles of IUI for infertility treatment from 2001 to 2006. Four thousand four hundred ninety eight women undergoing IUI treatment for infertility from January 2001 through December 2006 were retrospectively analyzed for total motile sperm recovery after density gradient separation or sperm wash and the resulting clinical pregnancy outcome. In order to determine the relationship between the TMSC and the IUI outcome, patients were grouped according to their TMSC as: (1) <1.0 million (n = 221), (2) 1.0–5.0 million (n = 1074), (3) 5.1–10 million (n = 1628), (4) 10.1–20 million (n = 1958), (5) 20.1–50 million (n = 2558), (6) 50.1–100 million (n = 1794), (7) 100.1–200 million (n = 486) and (8) >200 million (n = 146). Differences in PR between the groups were determined statistically by Chi-Square Analysis. The mean age of women who underwent 9865 cycles of IUI at our center was 37.5 years. The combined overall PR for IUI was 11.4%. The PR for the groups was 1.4, 8.6, 10.1, 11.9, 12.1, 13.0, 16.0 and 9.6 respectively. Overall PR was strongly related to increasing TMSC (P=0.0001). The exception to this relationship occured only in the group of >200 million sperm (PR = 9.6%, P=0.052). Our findings confirm that the PR in infertility patients undergoing IUI is strongly related to the TMSC. Insemination with <1 million motile sperm after density gradient separation resulted in a PR of 1.4%. With increasing counts the PR reached a plateau at 5.1–200 million TMSC. However, when more than 200 million sperm were inseminated, the PR appeared to decline. This decrease in PR may reach statistical significance with a larger sample size in that group. Inseminating high numbers of motile sperm may have a negative impact on PR for patients undergoing treatment with IUI.