摘要：INTRODUCTION: CONTROLLED OVARIAN HYPERSTIMULATION (COH) MAY HAVE A NEGATIVE IMPACT UPON THE ENDOMETRIAL ENVIRONMENT, THUS, A "FREEZE-ALL" (FET) STRATEGY WAS CONSIDERED. METHODS: REVIEW INCLUDING 44 STUDIES EVALUATING 278.000 NEWBORNS AFTER ART, COMPARING THE RESULTS OF THE CLASSIC VERSUS FREEZE-ALL STRATEGY. RESULTS: THE CUMULATIVE LIVE BIRTH RATE (LBR) AND PREGNANCY RATE (PR) WERE SIGNIFICANTLY HIGHER IN THE "FREEZE-ALL" (FET) VERSUS ET (LBR: 60.55% VS. 45%, PR: RR 1.30 [CI 95%]). FET IS ASSOCIATED WITH A LOWER OBSTETRIC RISK [CI 95%]: THE FETUS HAS A LOWER RISK OF BEING SMALL FOR GESTATIONAL AGE RR: 0.59, LOW GESTATIONAL WEIGHT RR: 0.74, PREMATURE BIRTH RR: 0.74 BUT MORE INCREASED RISK OF CESAREAN RR: 1.10 AND LARGE FOR GESTATIONAL AGE RR: 1.49. WITH REGARD TO THE RISKS OF ANTEPARTUM HAEMORRHAGE, PLACENTA PRAEVIA, PERINATAL MORTALITY, CONGENITAL ANOMALIES AND SPONTANEOUS ABORTION RATE, THERE ARE NO CONSISTENT FINDINGS: SOME STUDIES CONCLUDED THAT THE RISK IS LOWER IN FET (0.67, 0.68, 0.8 AND, RESPECTIVELY 0,83), BUT MOST CONSIDER THAT THERE IS NO SIGNIFICANT STATISTICAL DIFFERENCE. GESTATIONAL HYPERTENSION IS CONTROVERSIAL, SOME STUDIES HAVE FOUND THAT IT IS MORE COMMONLY LINKED TO FET (RR: 1.29), BUT THE RESULTS ARE INSIGNIFICANTLY STATISTICALLY DIFFERENT. HOWEVER, FET IS AN INDEPENDENT RISK FACTOR FOR PLACENTA ACCRETA, 3 TIMES HIGHER THAN ET. MONOZYGOTIC MONOCHORIONIC PREGNANCY AFTER SINGLE-EMBRYO IS LOWER IN FET IN GENERAL (0.8%), BUT MATERNAL AGE BELOW 35 YEARS IS A RISK FACTOR IN FET CYCLES. CONCLUSIONS: "FREEZE-ALL" IS AN ELIGIBLE PROTOCOL.
