Brief co-incubation of gametes benefits the outcomes of newborns.

Purpose: The objective of this study was to determine whether ammonium accumulates in IVF media during fertility process and whether the brief co-incubation of gametes (bIVF) benefited the outcomes of newborns.

Methods: Ammonium levels in IVF media during gamete co-incubation were measured and the effects of bIVF on neonatal outcomes were evaluated retrospectively in this study.

Results: A total of 609 live newborns cycles were included in this study. The results showed that ammonium levels in the conventional IVF (cIVF) media was significantly increased than that in bIVF and control media (27.32 ± 5.60 vs 20.71 ± 3.89, P = 0.03; 27.32 ± 5.60 vs 19.46 ± 1.31, P = 0.01, respectively). In the cIVF group, the mean gestational age was significantly lower (37.36 ± 2.29 vs. 37.74 ± 1.94 weeks, P = 0.031) and the incidence of preterm birth (< 37 weeks) was higher than that in the bIVF group (25.80 vs. 17.63%, P = 0.015). Singleton cycles and twin cycles were then analyzed respectively. The gestational age and birth weight of the singleton cycles were similar between the two groups. However, of the twin cycles, the gestational age was significantly decreased and the rate of preterm birth was increased significantly in the cIVF group (35.76 ± 2.31 vs. 36.48 ± 1.73, P = 0.013; 53.33 vs. 31.52%, P = 0.002, respectively).

Conclusions: There is an ammonium accumulation in IVF media during co-incubation of gametes. And bIVF reduces the risk of preterm birth (< 37 weeks), especially with regard to preterm birth of the twin cycles, and seems to be a safe alternative method for improving the neonatal outcomes compared with cIVF.