Partial zona dissection or subzonal sperm insertion: microsurgical fertilization alternatives based on evaluation of sperm and embryo morphology

Abstract

Objective: To establish guidelines for application of partial zona dissection, subzonal sperm insertion, and regular in vitro fertilization (IVF) in severe male factor patients.

Design: Two studies were performed: partial zona dissection and IVF was applied in 57 couples during the first period, and subzonal sperm insertion was also applied in a second group of 47 couples.

Setting: Procedures were performed in an academic research environment.

Patients, participants: Couples who failed fertilization previously, others not acceptable for IVF, and a third group in whom IVF was expected to fail.

Interventions: Oocytes were micromanipulated with either partial zona dissection or subzonal sperm insertion, or the zona pellucida was left intact. Embryos were replaced in patients prophylactically treated with methylprednisolone and antibiotics.

Main outcome measures: Because several microsurgical fertilization techniques are now available, this study was performed to compare sperm parameters, embryo morphology, fertilization, and implantation rates after application of two successful micromanipulation procedures.

Results: Twenty-one pregnancies were established in 104 patients, 5 definitely from subzonal sperm insertion and 4 from partial zona dissection. Patients who failed IVF before had a similar chance of pregnancy after the use of micromanipulation, as first time patients (9/53 versus 12/51). In a subgroup of 15 patients who failed IVF with insufficient numbers of motile sperm, fertilization was significantly higher after subzonal sperm insertion. Partially zona-dissected embryos from couples with severe teratozoospermia (less than or equal to 5% normal forms; strict criteria) had significantly more morphological abnormalities than those from patients with moderate teratozoospermia (6% to 10% normal forms). In severely teratozoospermic patients, significantly fewer partially zona-dissected than subzonally inserted embryos implanted.

Conclusions: The decision of which micromanipulation method to perform can possibly be based on careful analysis of sperm morphology.