Question special

“IVF is widely performed”, however there are “concerns about the safety of the procedures for women and for their infants”
Hypothesis: outcome after frozen-embryo transfer: “higher rate of singleton pregnancies”, “lower risks of preterm birth, low birth weight, and perinatal death”“However, data are lacking from randomized trials to determine any differences between the two procedures in live-birth rates and pregnancy complications.”
Then I expect a RCT on fresh versus frozen embryos for infertility, however why then in women with with polycystic ovary syndrome (POS)? Do we have robust data in the general population of subfertile women who need IVF? I refer to a recent (2 August 2016) editorial from dr Bhattacharya (Fertil Steril 2016;106:241): “Our confidence in the results of existing studies limited by the observational nature of the available data. A genuinely unbiased estimate of the advantages of a policy of elective ET can only be confirmed by a
definitive randomized controlled trial with an adequate length of follow-up of the offspring.” Thus, we need a robust RCT on fresh versus frozen embryos for infertility, not yet in P(C)OS women.