Differential growth of human embryos in vitro: role of reactive oxygen species.

Objective: To examine the relationship of early human embryonic development with the level of reactive oxygen species (ROS) in the culture media on the first day (day 1 ROS) after insemination.

Design: A prospective study.

Setting: Patients undergoing assisted reproduction in a teaching hospital.

Patient(s): Patients undergoing conventional IVF (n = 104; 115 cycles) and intracytoplasmic sperm injection (ICSI) (n = 91; 96 cycles) were included. Both fertilization and early cultures were performed in human tubal fluid with 5% serum substitute supplement.

Intervention(s): Day 1 ROS levels in the central well (sample) and the outer well (control) of each embryo culture dish were measured after overnight incubation by chemiluminescence assay using luminol as the probe.

Main Outcome Measure(s): Fertilization rate and embryo quality at day 3 and 5 were recorded for each cycle. Age, parity, and demographic features were also compared.

Result(s): High day 1 ROS levels in culture media were associated with low blastocyst rate, low fertilization rate, low cleavage rate, and high embryonic fragmentation with ICSI but not with conventional IVF. High day 1 ROS levels in culture media were associated with lower pregnancy rates in both IVF and ICSI cycles.

Conclusion(s): Reactive oxygen species generated in culture media by day 1 may be an important biochemical marker for early embryonic growth. Increased embryonic fragmentation and slow cleavage rate may be partially attributed to early exposure of embryos to high ROS levels in ICSI cycles. Differential growth of ICSI embryos incubated under identical conditions may be in part due to differences in ROS levels of the culture medium surrounding these embryos.