Sex Ratio and Cleavage Rhythm in Embryos From ICSI

Abstract

There are some controversies related to the prevalence of male and female embryos after assisted reproductive techniques. This ratio called primary sex ratio is, in fact, the rate between XX and XY embryos at the time of fertilization. In accordance to Pergament et al in 2002, in humans this ratio differs remarkably from the theoretically expected equality of 1: 1, and may be as high as 170 XY (males) to 100 XX (females). Moreover, it has been supposed that the injection of a single sperm directly into the egg appears to slow down the growth rate of the resulting female (but not male) early embryos. The aims of this study had been access the rate between embryos XX and XY from ICSI cycles and evaluate their cleavage rhythm and development. Retrospective study This study included 452 embryos from 106 ICSI cycles with patients who had classical indications to PGD as: recurrent miscarriage, severe male factor, genetic familiar diseases and advanced maternal age. Four hundred seventy six blastomeres were submitted to biopsy for analyze by fluorescent in situ hybridization (FISH) technique and 432 (95.6%) had been shown results. Probes to chromosomes X and Y were used for screening in all embryos; moreover probes to chromosomes 13,18 and/or 21 were used for specific indications, so each embryo were analyzed for three to five probes. The embryo biopsy and FISH were performed in accordance with pre-established protocols. Two hundred and twenty (50.9%) embryos were diagnosed as XY and 212 (49.1%) as XX (primary sex ratio, 1,04 XY: 1,0 XX; p = 0,586). One hundred and eleven female embryos (52.3%) and 130 embryos XY (59.1%) had not been presented numerical abnormalities to chromosomes analyzed (P= 0.208). There were no statistical difference among the percentage of normal embryos that also showed normal cleavage rhythm, when XY and XX embryos were compared (53.0% vs. 49.0%, respectively, P = 0.692). This study suggests that the primary sex ratio observed in embryos from ICSI cycles and submitted to PGD could be compared to natural conception ratio. Moreover, XX and XY embryos seem to exhibit similar developmental conditions showing satisfactory good cleavage rhythm with good chance to be transferred.