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RESEARCH QUESTION: Does a freeze-all strategy improve live birth rates in women of different age groups? DESIGN: Retrospective cohort study of 1882 first embryo transfer cycles, performed between January 2013 and December 2015. Reproductive outcomes between fresh (FRESH) or frozen (FROZEN) embryo transfers were compared in patients stratified by age: 38 years. Student’s t test for independent samples and χ(2) analyses were used as needed. A multivariable logistic regression analysis was performed adjusting for age, triggering drug, number of retrieved oocytes, number of transferred embryos, and percentage of top-quality embryos. MAIN RESULTS AND THE ROLE OF CHANCE: Live birth rates (LBR) were significantly higher for FROZEN in the 38 years groups, LBR for FROZEN vs FRESH were not statistically different (30.9% in the FROZEN group vs 29.3% in the FRESH group, p = 0.70, and 19.8% in the FROZEN group vs 12.7% in the FRESH group, p = 0.07, respectively). The multivariate analysis found a significantly positive effect of performing FROZEN on LBR in the younger group (OR 2.46, 95% CI 1.31–4.62; p = 0.005) but had no impact in women between 35 and 38 years (OR 1.01, 95% CI 0.55–1.83; p = 0.98) or older (OR 0.96, 95% CI 0.43–2.13; p = 0.92). CONCLUSIONS: Performing a freeze-all strategy seems to result in better reproductive outcomes when compared with a fresh ET in women under 35 years, with no significant impact on older women.

STUDY QUESTION Does the time from ovum pick-up (OPU) to frozen embryo transfer (FET) affect reproductive outcomes in a freeze-all strategy? SUMMARY ANSWER Our study did not detect statistically significant differences between first and subsequent cycles, clinically relevant differences are not ruled out and further and larger studies are required. WHAT IS KNOWN ALREADY Following controlled ovarian hyperstimulation (COH) delaying FET until the endometrium has returned to an optimal pre-stimulation state may have a significant emotional impact on patients, which adds to the stress and anxiety accompanying a standard IVF cycle. Currently there is no agreement on the best time to perform a FET after a freeze-all cycle in order to maximize reproductive outcomes for the patient. STUDY DESIGN, SIZE, DURATION: Retrospective cohort study of 512 freeze-all cycles, performed between January 2012 and December 2014. COH was performed by either a GnRH antagonist (n = 397) or a long GnRH agonist protocol (n = 115). Ovulation was triggered using either a GnRH agonist (n = 258) or hCG (n = 254). Endometrial preparation was performed in an artificial cycle by either oral (n = 238) or transdermal (n = 274) oestrogen. Differences were considered significant if P < 0.05. PARTICIPANTS/MATERIALS, SETTING, METHODS Reproductive outcomes between FETs which took place either within the first menstrual cycle following OPU (Cycle 1; n = 263) or afterwards (Cycle ≥2; n = 249) were compared. Student's t-test for independent samples, Mann-Whitney U-test and Chi-square analysis were used where appropriate. A multivariable logistic regression analysis was performed adjusting for maternal age, drug used for ovulation trigger, number of retrieved oocytes, number of embryos obtained, day of embryonic development at transfer, number of embryos transferred and type of endometrial preparation. Differences were considered significant if P < 0.05. MAIN RESULTS AND THE ROLE OF CHANCE Live birth rate (LBR) was significantly higher in FET performed during Cycle 1 vs Cycle ≥2 (37.6% vs 27.3%, respectively; P = 0.01) before adjusting for confounding factors. We found no difference for biochemical pregnancy (49.8% vs 43.8%; P = 0.17), clinical pregnancy (44.1% vs 36.1%; P = 0.07) or pregnancy loss (11.8% vs 16.1%; P = 0.16). A multivariable analysis found no impact of timing of elective FET on LBR (odds ratio, OR 0.73; 95% CI 0.49-1.08). The impact remained not significant after adjusting for number of retrieved oocytes, drug used for ovulation trigger (hCG vs GnRH agonist) and reason for cryopreservation. The factors that significantly affected LBR were: maternal age in both age categories (women between 35 and 40 years vs women below 35 years, OR 0.63, 95% CI 0.4-0.95; and women over 40 years vs women below 35 years, OR 0.34, 95% CI 0.2-0.7), day of embryonic development at transfer (day +4 vs +3; OR 1.7, 95% CI 1.1-2.8) and number of transferred embryos (OR 2.2, 95% CI 1.4-3.3) and oestrogen used for endometrial preparation (transdermal vs oral; OR 0.62, 95% CI 0.4-0.9). LIMITATIONS REASONS FOR CAUTION The main limitation of our study is its retrospective nature. Although we adjusted our statistical analysis for a number of known and suspected confounders, we cannot exclude the possibility of residual confounding factors. WIDER IMPLICATIONS OF THE FINDINGS According to our results, clinicians might not need to wait more than one menstrual cycle before performing FET. This allows us to reduce unnecessary delays in FET, without compromising reproductive outcomes. STUDY FUNDING/COMPETING INTERESTS No funding was sought for this study. Authors declare no competing interests. TRIAL REGISTRATION NUMBER NA.

Objective To examine the available evidence to assess if cryopreservation of all embryos and subsequent frozen embryo transfer (FET) results in better outcomes compared with fresh transfer. Design Systematic review and meta-analysis. Setting Centers for reproductive care. Patient(s) Infertility patient(s). Intervention(s) An exhaustive electronic literature search in MEDLINE, EMBASE, and the Cochrane Library was performed through December 2011. We included randomized clinical trials comparing outcomes of IVF cycles between fresh and frozen embryo transfers. Main Outcome Measure(s) The outcomes of interest were ongoing pregnancy rate, clinical pregnancy rate, and miscarriage. Result(s) We included three trials accounting for 633 cycles in women aged 27–33 years. Data analysis showed that FET resulted in significantly higher ongoing pregnancy rates and clinical pregnancy rates. Conclusion(s) Our results suggest that there is evidence that IVF outcomes may be improved by performing FET compared with fresh embryo transfer. This could be explained by a better embryo-endometrium synchrony achieved with endometrium preparation cycles.

Purpose: To compare the efficacy of nifedipine and fenoterol in the management of threatened preterm labor (TPL). Methods: A randomized and multicenter study assessing the tocolytic effect of nifedipine versus fenoterol in patients admitted to the participating maternity units with a diagnosis of TPL and a cost-savings study for economic assessment. For a power of 80% and an α error equal to 0.05, 132 consecutive patients were recruited during the study period; 66 patients were assigned to each group. A χ2 analysis and a mean differences test were performed according to variable types and survival curves per intention-to-treat. Results: Demographics were similar in both groups. The latency period was similar in both groups (26.7 vs. 25.6; p = 0.3). There were no differences in the results obtained. Nifedipine failed more frequently to obtain tocolysis when used as a first-line agent (80 vs. 90%, p = 0.0001). The group treated with fenoterol showed more drug adverse events (57.8 vs. 19.0%, p = 0.0001). The economic assessment did not evidence a significant difference in terms of cost savings between groups treated with either drug. Conclusion: The present study failed to demonstrate either clinical or economic superiority of any of the two drugs used in TPL management. The highest failure percentage of nifedipine when used as a first-line agent should encourage further research.