Objective: To evaluate and compare the risk of early pregnancy loss in patients stimulated with GnRH antagonist protocols according to oral contraceptive pill (OCP) pretreatment.
Design: Retrospective case-control study.
Setting: Instituto Valenciano de Infertilidad. University of Valencia. Spain.
Patient(s): One thousand five hundred thirty-nine patients, aged <36, stimulated with GnRH antagonists for IVF between January 1, 2000 and November 1, 2005.
Intervention(s): Reproductive outcome was compared based on the application (or not) of OCP pretreatment: 944 women were included in the OCP group and 595 in the non-OCP group. The Student's t test was used for statistics.
Main outcome measure(s): Pregnancy, biochemical pregnancy, ectopic pregnancy, early clinical pregnancy loss, early pregnancy loss, and ongoing pregnancy rates.
Result(s): No significant differences were observed in any of the outcome parameters. Early pregnancy loss rates were similar: 23% in the OCP pretreatment group versus 19.2% in the non-OCP pretreatment group. However, longer periods of ovarian stimulation and higher doses of gonadotropins needed to be employed in the OCP group.
Conclusion(s): There is not sufficient evidence to confirm OCP pretreatment as a risk factor for miscarriage in patients stimulated with GnRH antagonist protocols.