P–304 The endometrial preparation protocol does not affect the live-birth-rate after vitrified-warmed euploid single blastocyst transfers: an analysis of 1884 procedures

Study question

Is the live-birth-rate (LBR) different when comparing artificial (AC) and modified-natural (M-NC) cycle for endometrial preparation to vitrified-warmed euploid blastocyst transfer?

Summary answer

The LBR after vitrified-warmed euploid blastocyst transfer seem independent of the endometrial preparation administered.

What is known already

Only the transfer of a competent embryo on a receptive endometrium might result in successful implantation. Three main protocols for endometrial preparation to vitrified-warmed embryo transfer exist: NC, M-NC, and AC. None among them, though, has been shown more appropriate than the others to date, especially since, only in a few studies, the analysis was restricted to single euploid blastocyst transfers to limit the impact of embryonic issues on implantation. In conclusion, no clear consensus exists and the choice is still largely based on menstrual/ovarian cycle characteristics and patient’s needs.

Study design, size, duration

All first vitrified-warmed single euploid blastocyst transfers performed between April–2013 and March–2020 were included in the analysis. Endometrial preparation was conducted with either an AC (N = 1211) or a M-NC (N = 673). The protocol was chosen based on patients’ logistical reasons. The primary outcome was the LBR per transfer. Sub-analyses based on blastocyst quality and day of development were conducted. Birthweight, gestational age, gestational and perinatal issues were secondary outcomes.

Participants/materials, setting, methods

AC: oral estradiol-valerate 3-times/day from day2–3 of the cycle until the endometrial thickness reached ≥7mm, then 600 mg/day of micronized progesterone. The transfer was conducted on day6 of progesterone administration. M-NC: an intramuscular dose of 10,000IU hCG was administrated when the leading follicle was >17 mm and the endometrium was thicker than 7mm and trilaminar, plus 400 mg/day of micronized-progesterone as luteal phase support starting 36–40hr post-hCG. The transfer was conducted on day7 after trigger.

Main results and the role of chance

The two groups were similar for maternal age at retrieval (38.0±3.3yr) and transfer (38.3±3.3yr), reproductive history, embryological outcomes of the IVF cycle, body-mass-index, basal hormonal levels, and blastocyst features (Gardner’s classification: AA = 73%, AB/BA=11%, BB/AC/CA=8%, CC/BC/CB=8%; day5=48%, day6=47%, day7=5%). The LBR was 46.7% (N = 565/1211) and 49.9% (N = 336/673) after AC and M-NC, respectively, resulting in an odds-ratio 1.14, 95%CI:0.94–1.37. The absence of significant differences was confirmed also when adjusted for blastocyst quality and day of full-development (1.16, 95%CI:0.96–1.41). Among the 565 and 336 deliveries, the birthweight was similar (3290.3±470.7 versus 3251.7±521.5 g, Mann-Whitney-U-test=0.5), the gestational age was similar (38.5±1.7 versus 38.4±1.9 weeks, Mann-Whitney-U-test=0.5). Also, the rates of newborns who were normal (81% versus 82%), large (8% versus 9%), and small (11% versus 9%) for gestational age were similar (Chi-squared-test=0.5). The rates of patients experiencing gestational (6% versus 7%) and/or perinatal issues (3% versus 3%) were also similar (Fisher’s-exact-tests=0.4).

Limitations, reasons for caution

This is a retrospective study conducted in poor prognosis patients indicated to preimplantation genetic testing for aneuploidies. Future randomized controlled trials and cost-effectiveness analysis are desirable, as well as studies in different patient populations. Lastly, each gestational/perinatal issue shall be analyzed per se (e.g. different placentation disorders).

Wider implications of the findings: The absence of clinical and perinatal differences between the two protocols for endometrial preparation supports the adoption, whenever needed, of AC. This approach, in fact, allows a higher flexibility in patients’ and daily workload management.

Trial registration number

None

P–519 Investigation of embryo chromosomal constitution and live birth rate after vitrified-warmed euploid single blastocyst transfer across ranges of maternal body-mass-index

Study question

Does maternal body-mass-index (BMI) associate with blastocysts’ chromosomal constitution and clinical outcomes in infertile patients undergoing preimplantation genetic testing for aneuploidies (PGT-A)?

Summary answer

A higher euploidy rate per biopsied blastocyst was reported among underweight women. Overweight women were instead subject to higher miscarriage (MR) and lower live-birth-rates (LBR).

What is known already

Different studies in the literature revealed an association between BMI and infertility, suggesting a J-shaped relationship: both underweight and overweight women can suffer from infertility issues. Even if IVF might increase the success rate in both these categories of patients, it seems insufficient per se to overcome the complex and multifactorial fertility impairment derived from unbalanced nutritional intakes. Miscarriage, in particular, is common in both underweight and overweight women. However, most of the literature is based on chromosomally-untested embryos. Study design, size, duration: Retrospective observational study. Only the first IVF cycle with ≥1 biopsied blastocyst from each woman was included. The primary outcome was the association between maternal BMI (underweight, BMI<18.5, n = 160; normal-weight, BMI=18–25, N = 1392; overweight, BMI>25, N = 259) and the mean euploidy rate per cohort of biopsied blastocysts (m-ER). The secondary outcomes were the association between maternal BMI with clinical (mainly MR and LBR), gestational and perinatal outcomes after first vitrified-warmed single euploid blastocyst transfers.

Participants/materials, setting, methods

We included 1811 women undergoing PGT-A at a private IVF center between April–2013 and March–2020. The secondary outcomes were investigated on 1125 first vitrified-warmed single euploid blastocyst transfers from all patients obtaining ≥1 transferable blastocyst. Only ICSI with ejaculated sperm and continuous culture in standard incubators were performed. Logistic regressions were conducted to identify putative confounders and adjust the results accordingly.

Main results and the role of chance

Except for a lower maternal age among underweight women (38.3±3.1 versus 38.9±3.4 yr, p < 0.01) and higher among overweight ones (39.3±3.6 yr, p = 0.04), no difference was reported with respect to normal-weight women in terms of duration of infertility, hormonal levels, main cause of infertility, sperm quality, and reproductive history. The mean number of biopsied blastocysts was ∼3 in all groups. The m-ER shows a decreasing trend as the maternal BMI increases between 17 and 22–23, to then plateau. In fact, a significant difference was reported between underweight (50.8%±36.4%) and normal-weight women (41.4%±37.5%, p < 0.01). A linear regression adjusted for maternal age confirmed this moderate association between increasing BMI and m-ER (unstandardized-coefficient-B –0.6%, 95%CI:–1.1% to –0.1%, p = 0.02).

Morphological quality and day of full-blastulation among transferred euploid blastocysts was similar in the three groups. Overweight women showed higher MR per pregnancy (N = 20/75, 26.7%, 95%CI:17.4%–38.3% versus N = 67/461, 14.5%, 95%CI:11.5%–18.2%; OR 2.0, 95%CI:1.1–3.6, p = 0.01) and lower LBR per transfer (N = 55/154, 35.7%, 95%CI:28.3%–43.8% versus N = 388/859, 45.2%, 95%CI:41.8%–48.6%; OR adjusted for euploid blastocysts’ features 0.67, 95%CI:0.46–0.96, p = 0.03). Clinical outcomes were instead similar among underweight and normal-weight women. All gestational and perinatal outcomes were comparable in the tree groups.

Limitations, reasons for caution

Our study is limited by its retrospective nature, and the fact that maternal BMI was measured only before oocyte retrieval and not before embryo transfer. Moreover, the reduced sample size did not allow for further relevant sub-analyses among solely obese women.

Wider implications of the findings: When possible nutritional/lifestyle modifications should be encouraged to adjust maternal BMI before IVF. Overweight patients should be especially informed of their higher risk for miscarriage. Yet, BMI is just a gross marker, future studies based on body fat localization and percentage (e.g. by bioelectrical impedance analyses) are desirable.

Trial registration number

None