You will be provided with the titles and abstracts of a collection of medical RCT reports studying a clinical question -- for instance, the efficacy of an intervention on some medical outcome. Please write a few sentences synthesizing the findings of these reports, which could serve as a conclusion section for a systematic review article. Your response should not include any other text. The RCT reports are below.



Title 1:
A prospective, randomized study comparing day 2 and day 3 embryo transfer in human IVF.
Abstract 1:
It is believed that delayed transfer of embryos after IVF allows for a better selection of good quality embryos. Hence, the number of embryos and all other prognostic factors being equal, transfer of day 3 embryos should be associated with higher implantation and pregnancy rates than transfer of day 2 embryos. To investigate this hypothesis, a prospective randomized study was carried out to compare implantation and pregnancy rates between day 2 and day 3 transfers. The relationship between the embryo quality score of day 2 and day 3 embryos and their respective implantation rates was also analysed. In a 2 year period all patients undergoing infertility treatment and in whom at least seven normally fertilized oocytes were obtained were included in the study. A minimization procedure was performed taking into account the patient's age and the method of fertilization (IVF or intracytoplasmic sperm injection). By using a uniform policy of embryo transfer, the number of embryos transferred was similar in both groups. The outcome parameters were embryo quality, implantation and pregnancy rates. No difference was observed in implantation and pregnancy rates between transfers on day 2 versus day 3 (23.8 versus 23.8% and 47.9 versus 46.8% respectively). The incidence of embryos of moderate to poor quality was higher in embryos cultured for 3 days compared with those cultured for 2 days. It is concluded that the outcomes of embryo transfer in terms of implantation and pregnancy rates are comparable for day 2 and day 3 embryos, although the overall embryo quality score decreases when embryos are kept in culture till day 3.


Title 2:
Early, late, and sequential embryo transfer in in vitro fertilization program: a preliminary report.
Abstract 2:
The timing of ET was evaluated by transferring four embryos at 44 to 48 hours, 68 to 72 hours, or equally dividing and sequentially transferring at 44 to 48 and 68 to 72 hours after insemination. Fifty-one patients were randomly allocated to one of the above protocols. The mean number of blastomeres of embryos transferred at 68 to 72 hours after insemination was significantly (P less than 0.0001) higher than those transferred at 44 to 48 hours. The number of embryos with good morphology was similar in all study groups. The pregnancy rate was similar in the three protocol groups, 53% at 44 to 48 hours, 59% at 64 to 72 hours, and 47% by sequential transfer. There probably is no advantage in delaying the transfer or dividing the embryos into two sequential transfers. It seems that sequential transfer is not associated with any harmful effect.


Title 3:
Clinical outcome of day 2 versus day 3 embryo transfer using serum-free culture media: a prospective randomized study.
Abstract 3:
The objective was to evaluate whether extending the embryo culture period from 2 to 3 days would yield a more optimal selection of viable embryos, thereby increasing the implantation and live birth rates.
                Patients undergoing in vitro fertilization with at least one oocyte fertilized were prospectively randomized to 2 or 3 days of embryo culture in serum-free media. On the basis of their morphology and cleavage rate, a maximum of three embryos was selected for transfer.
                Embryos transferred on day 2 or day 3 were similar morphologically, however, a higher proportion of retarded embryos was observed on day 3. The implantation rate was 15.8 and 14.3% for day 2 and day 3 transfers, respectively. The increase in live birth rate from 18.5 to 22.6%, possibly suggesting a better embryo selection on day 3, was not statistically significant.
                Extending the embryo culture period from 2 to 3 days had no effect on implantation and live birth rates.


Title 4:
Day 2 vs. day 3 embryo transfer after intracytoplasmic sperm injection. A prospective, randomized study.
Abstract 4:
To compare, in a prospective, randomized study, implantation and pregnancy rates between day 2 and day 3 embryo transfer intracytoplasmic sperm injection (ICSI).
                A total of 106 patients undergoing ICSI cycles who had at least 1 embryo suitable for cryopreservation were prospectively randomized into 2 groups: group I, embryo transfer performed on day 2; group II, embryo transfer performed on day 3.
                Patient ages did not differ (P = .58) between groups I (33.1 +/- 4.5) and II (32.7 +/- 4.4). The number of oocytes retrieved from group I (13.7 +/- 5.2) was similar (P = .82) to that retrieved from group II (13.7 +/- 5.4). In addition, there was no difference (P = .30) in the number of oocytes retrieved at metaphase II between groups I (10.6 +/- 4.4) and II (9.7 +/- 4.2). Fertilization and cleavage rates were also similar (P = .58 and P = .50, respectively) between groups I (78.2 +/- 14.0% and 98.7 +/- 4.3%) and II (76.2 +/- 14.8% and 99.8 +/- 1.24%, respectively). The total number of embryos and of embryos transferred were similar (P = .22 and P = .36; respectively) for groups I (8.0 +/- 3.0, 2.8 +/- 0.7) and II (7.16 +/- 3.2, 2.6 +/- 0.8). Pregnancy rates per transfer, implantation rates and abortion rates were also similar for groups I (43.4%, 20.8% and 8.7%, respectively) and II (41.5%, 24.1% and 23%, respectively) (P = 1.0, P = .57 and P = .24, respectively).
                The results suggest that extending the embryo culture period from 2 to 3 days for patients who had at least 1 embryo left for cryopreservation had no effect on implantation, pregnancy or abortion rates in an ICSI program.
Although an increase in clinical pregnancy rate with day three embryo transfer was demonstrated, at present there is not sufficient good quality evidence to suggest an improvement in live birth when embryo transfer is delayed from day two to day three.