ObjectiveTo define the appropriate number of embryos to be transferred at day 5.MethodsRetrospective analysis of 784 consecutive fresh day-5 embryo transfers
performed between 2007 and 2015, divided in three groups: Group A (N = 219):
received the only 2 embryos that reached a transferable stage; Group B (N =
357): received 2 selected embryos among several that reached a transferable
stage; Group C (N = 208): received the only 3 developing embryos. Clinical
pregnancy, implantation, multiple pregnancy and delivery rates were
registered. Kruskal-Wallis and Fisher Exact tests were applied as
appropriate.ResultsAge and previous attempts were comparable in the 3 groups. Compared with
Group A, Groups B and C had a higher oocyte recovery (10.7 ± 5.6
vs. 14.7 ± 8.0 vs. 13.8
± 6.6), fertilization rate (75.97% vs. 81.60%
vs. 83.29%) and percentage of embryos reaching a
transferable stage on day 5 (39.98% vs. 63.99%
vs. 60.97%), as well as a significantly higher clinical
pregnancy (42.92% vs. 61.06% vs. 58.17%)
and implantation rates (21.09% vs. 40.98%
vs. 36.97%). The multiple pregnancy rate was higher in
Groups B and C than in Group A (11.70% vs. 31.19%
vs. 37.19%). The high order multiple pregnancy rate
(> 2) was significantly increased in group C (1.06% vs.
0.92% vs. 14.05%).ConclusionsIn patients with 3 or more day 5 developing embryos, delivery rates are
similar if 2 or 3 embryos are transferred. The transfer of 3 embryos carries
an unacceptable increase in the risk of high order multiple pregnancy, with
its known consequences. According to our data, we should not exceed the
number of 2 day-5 fresh embryos transferred.