ABSTRACT
OBJECTIVE: To determine the effect of mechanical assisted hatching on the pregnancy rate (PR). DESIGN: A retrospective comparative analysis of hatched versus nonhatched consecutive assisted reproductive technology (ART) cycles. SETTING: A hospital-based ART program. PATIENT(S): Patients undergoing ART treatment with assisted hatching (1994-1996) were compared with patients who did not have assisted hatching (1990-1993). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Pregnancy rate, multiple PR, and rate of monozygotic twinning. RESULT(S): With hatching, the clinical PR per ET increased from 25.2% to 37.1% and the multiple PR per ET increased from 6.8% to 13.1%. In the nonhatched series, there were no monozygotic twins compared with eight cases in the hatched series (1.2% per ET). CONCLUSION(S): Mechanical assisted hatching increases the PR but concomitantly elevates the rate of multiple gestation and multiple gestation of high order. There is a particularly high risk of monozygotic twinning with mechanical hatching.
