J. Aguilar

The human first cell cycle: impact on implantation.

The morphology of fertilization events has been related to successful implantation by subjective criteria (pronuclei score, pronuclei symmetry and position). This work first described these events by time-lapse technology and then compared the timings of fertilization events (second polar body extrusion, first and second pronuclei appearance, abuttal and fading) in implanted versus nonimplanted embryos in a 2-year cohort retrospective study. A total of 1448 transferred embryos from 842 patients undergoing intracytoplasmic sperm injection with oocyte donation were monitored, 212 embryos from treatments where the number of gestational sacs matched the number of transferred embryos and 687 embryos from treatments no biochemical pregnancy was achieved. The timings at which second polar body extrusion (3.3-10.6 h), pronuclear fading (22.2-25.9 h) and length of S-phase (5.7-13.8 h) occurred were linked successfully to embryo implantation. The other parameters were apparently not related, as determined by image acquisition and time-lapse analysis.

Treatment of Luteal Phase Defects in Assisted Reproduction

Abnormal luteal function is a common issue in assisted reproduction techniques associated with ovarian stimulation probably due to low levels of LH in the middle and in the late luteal phase. This defect seems to be associated with supraphysiological steroid levels at the end of follicular phase. The luteal phase insufficiency has not got a diagnostic test which has proven reliable in a clinical setting. Luteal phase after ovarian stimulation becomes shorter and insufficient, resulting in lower pregnancy rates. Luteal phase support with progesterone or hCG improves pregnancy outcomes and no differences are found among different routes of administration. However, hCG increases the risk of ovarian hyperstimulation syndrome. In relation to the length of luteal support, the day of starting it remains controversial and it does not seem necessary to continue once a pregnancy has been established. After GnRHa triggering ovulation, intensive luteal support or hCG bolus can overcome the defect in luteal phase, but more studies are needed to show the LH utility as support.

Ovarian stimulation in patients with breast cancer.

Breast cancer is the most prevalent malignancy among women under 50. Improvements in diagnosis and treatment have yielded an important decrease in mortality in the last 20 years. In many cases, chemotherapy and radiotherapy develop side effects on the reproductive function. Therefore, before the anti-cancer treatment impairs fertility, clinicians should offer some techniques for fertility preservation for women planning motherhood in the future. In order to obtain more available oocytes for IVF, the ovary must be stimulated. New protocols which prevent exposure to increased estrogen during gonadotropin stimulation, measurements to avoid the delay in starting anti-cancer treatment or the outcome of ovarian stimulation have been addressed in this review. There is no evidence of association between ovarian stimulation and breast cancer. It seems that there are more relevant other confluent factors than ovarian stimulation. Factors that can modify the risk of breast cancer include: parity, age at full-term birth, age of menarche, and family history. There is an association between breast cancer and exogenous estrogen. Therefore, specific protocols to stimulate patients with breast cancer include anti-estrogen agents such as letrozole. By using letrozole plus recombinant follicular stimulating hormone, patients develop a multifollicular growth with only a mild increase in estradiol serum levels. Controlled ovarian stimulation (COS) takes around 10 days, and we discuss new strategies to start COS as soon as possible. Protocols starting during the luteal phase or after inducing the menses currently prevent a delay in starting ovarian stimulation. Patients with breast cancer have a poorer response to COS compared with patients without cancer who are stimulated with conventional protocols of gonadotropins. Although many centres offer fertility preservation and many patients undergo ovarian stimulation, there are not enough studies to evaluate the recurrence, breast cancer-free interval or mortality rates in these women.

Embryo s-phase length analysis on first and second cell cycle and its relationship with reproductive outcome

OBJECTIVE: to analyse the length of the s-phase (synthesis of DNA), in the first cell cycle (ECC1) and in each blastomere of the second cell cycle (ECC2) of known implantation data (KID) embryos, and to relate them with reproductive outcome. DESIGN: Observational retrospective study of 1679 transferred embryos from 940 ICSI patients from our egg donation program between January 2011 and January 2014 in IVI Vigo and IVI Valencia, cultured in Embryoscope. Sperm samples under 1 million/ml were used as an exclusion criteria. MATERIALS AND METHODS: Only non-multinucleated embryos which either failed to implant or fully implanted were included in the study. The s-phase was calculated as the period while nuclei were visible, being ECC1 S-phase1⁄4tPNfading-tPNappearance, and ECC2 S-phase1⁄4 t2MONO1(f)t2MONO1(a). ANOVA test and c2-test were performed when applicable to assess the influence of the length of S-phase in the implantation rate. RESULTS: S-phase in both cell cycles were calculated in 904 KID embryos out of 1679, and therefore were analyzed. 32,74% (n1⁄4296) fully implanted (KID+), and 67,25% (n1⁄4608) failed to implant (KID-). The average length of s-phase in the ECC1 in the KID+ embryos was longer than in KID-, 15,50h v.s. 14,38h, and slightly shorter in ECC2, 8,35 in KID+ v.s. 8,60h in KID-. 46,1% (n1⁄4112) of the embryos implanted when the difference between both s-phases was greater than 7.96h, being 29,1% for those where the difference is between 5,96h-7,95h; 23,1% for those between 3,61h-5,95h; and 30% for those below 3,6h. CONCLUSIONS: Results show that the s-phase ECC1, nearly double the length of s-phase ECC2, and the greater the difference between both s-phase, the greater the embryo implantation, suggesting that the replication in the first cell cycle may implicate particularities related to the genome combination, and that those embryos which do not implant may not complete the replication of its genome during the first cycle producing a larger reduction in the duration of the second.