Prediction of human blastocyst development from morulas with delayed and/or incomplete compaction.

Objective: To determine the influence of delayed compaction and fragmentation on the developmental capacity of morulas.

Design: Prospective study.

Setting: University IVF center.

Patient(s): Intracytoplasmic sperm injection (ICSI) cycles with compact embryos on day 4 or day 5.

Intervention(s): The embryos were divided into day 4 (n = 329) and day 5 (n = 256) morulas and graded I, II, or III, according to the percentage of fragmentation (<5%, 5%-20%, or >20%). The embryos were measured using Cronus3 software.

Main Outcome Measurement(s): Blastocyst development rate, blastocoel expansion rate, and optimal blastocyst rate. In an optimal blastocyst: surface area, trophectoderm cell number, inner cell mass (ICM) surface area, ICM volume and ICM shape.

Result(s): Day 4 morulas in classes I-III developed into optimal blastocysts in 57.4%, 50%, and 35.6% of the total, respectively, and day 5 morulas in classes I-III in 43.3%, 29.1%, and 13.6% of the total, respectively. A negative association was identified between the amount of morula fragmentation, the blastocyst ICM size, and the number of trophectoderm cells. A delay of 1 day in compaction was associated with a reduced ICM volume.

Conclusion(s): The measurement of compaction timing and cytoplasmic loss in morulas assists in predicting their ability to develop into optimal blastocysts.