Kamis, 11 Januari 2018

No Benefit in Frozen Embryo Transfer in Nonpolycystic Women

No Benefit in Frozen Embryo Transfer in Nonpolycystic Women


Frozen embryo transfer showed no clear benefit over fresh embryo transfer among infertile women who do not have polycystic ovary syndrome (PCOS), according to two studies published online January 10 in the New England Journal of Medicine.

In the first study, Yuhua Shi, MD, PhD, from the Center for Reproductive Medicine, Shandong Provincial Hospital–Shandong University, China, and colleagues randomly assigned 2157 women across 19 sites to receive either a fresh-embryo transfer or a frozen-embryo transfer during their first cycle of in vitro fertilization. Enrolled women were 20 to 35 years of age, and those with a diagnosis of PCOS or medical condition associated with adverse pregnancy outcomes were excluded. The primary outcome was live birth.

Dr Shi and colleagues found no significant difference in the rate of live births between the frozen-embryo group and the fresh-embryo group (48.7% and 50.2%, respectively; relative risk [RR], 0.97; 95% confidence interval [CI], 0.89 to 1.06; P = .50).

The authors did note, however, that women undergoing frozen-embryo transfer had a lower risk for moderate or severe ovarian hyperstimulation syndrome compared with those undergoing fresh-embryo transfer (0.6% vs. 2.0%; RR, 0.32; 95% CI, 0.14 to 0.74; P = .005).

Of note, a study conducted by this same group of researchers previously demonstrated that frozen embryo transfer had a favorable effect on the rate of live births among women with PCOS. The authors hypothesize that one of the reasons for this difference may be “the unfavorable uterine environment after fresh-embryo transfer in women with [PCOS,] as shown by a much lower rate of live birth overall in the previous trial than in the present trial.”

The second study, led by Lan N. Vuong, MD, PhD, from the University of Medicine and Pharmacy at Ho Chi Minh City, Vietnam, included 782 women undergoing their first or second in vitro fertilization cycle and who were infertile for reasons other than PCOS. The women were randomly assigned to receive either a frozen-embryo or a fresh-embryo transfer. The primary outcome of this study was ongoing pregnancy, with live birth being a secondary outcome.

The researchers found no significant difference in the rates of live birth between the frozen-embryo group and the fresh-embryo group (33.8% and 31.5%, respectively; RR, 1.07; 95% CI, 0.88 to 1.31).

Similarly, there was no significant difference in the rate of ongoing pregnancy, which occurred in 36.3% of women (142/391) in the frozen-embryo group and in 34.5% of women (135/391) in the fresh-embryo group (P = .65).

Dr Vuong and colleagues also found no difference between the groups in the rate of pregnancy complications, including ovarian hyperstimulation syndrome. They do note, however, that “the rate of this complication was very low in our trial,” and that women at high risk for this complication were not included.

Dr Vuong and colleagues acknowledge that the single-center nature of the trial may limit the generalizability of the study findings.

The researchers in both trials also suggest that differences in embryo characteristics, preservation techniques, uterine conditions, and introduction of bias resulting from lack of blinding may make comparison among studies difficult.

Dr Shi’s study was funded via grants from the National Key Research and Development Program of China, the Major Program of the National Natural Science Foundation of China, and the State Key Program of the National Natural Science Foundation of China. Dr Vuong’s study was funded by the My Duc Hospital, Ho Chi Minh City, Vietnam. The authors have disclosed no relevant financial relationships.

N Engl J Med. 2018;378:126-136, 137-147. Shi article abstract, Vuong article abstract

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