A greater number of euploid blastocysts in a given cohort predicts excellent outcomes in single embryo transfer cycles

Predicting frequency distributions of blastocyst biopsy genotypes by their discrete cohort size using the binomial theorem

RESEARCH QUESTION

How are blastocyst biopsy genotypes distributed as a function of cohort size, and how well does the binomial theorem predict the specific distribution of euploid genotypes across different cohort sizes?

DESIGN

This retrospective observational study included 1065 autologous blastocyst biopsies from 206 consecutive biopsy cases at a single centre. Cohorts were classified into three mutually exclusive categories: euploid+ (containing at least one euploid), euploid-mosaic/segmental+ and meiotic (containing whole chromosome errors alone), stratified by patient age (<37 years versus ≥37 years) and cohort size (10 discrete groups). 'Observed' distributions of individual euploid blastocysts/cohort were compared with binomially 'expected' distributions using the overall probability for euploidy for each age group.

RESULTS

For patients aged <37 years, cohorts were predominantly euploid+ (85.7%). The odds of being euploid increased for each 1-unit increase in cohort size. For each size group, the observed distribution of euploid blastocysts/cohort was closely concordant with distributions predicted binomially in the largest three cohort size quartiles. In contrast, cohort categories in the smallest quartile showed greater discordance. For patients aged ≥37 years, 48.5% of cohorts were euploid+ cohorts. While the odds of being euploid also increased for each 1-unit increase in cohort size, the observed peak number of euploid blastocysts/cohort was lower than predicted binomially in all size quartiles.

CONCLUSIONS

The binomial theorem can predict the probability distributions of euploid genotypes in cohort sizes exceeding four in patients aged <37 years without a biopsy. However, in smaller cohort sizes for patients aged >37 years and all cohort sizes in patients aged ≥37 years, there were fewer euploid blastocysts/cohort than predicted binomially; thus, untransferred mosaic/segmental genotypes represent a repository of pregnancy potential.

Effect of ovarian stimulation on embryo aneuploidy and mosaicism rate

There is a high incidence of chromosome abnormalities in human embryos that leads to a failed IVF cycle. Different studies have shown that maternal age is the determining factor in the appearance of chromosomal alterations in the embryo. However, the possible influence of ovarian stimulation on oocyte and embryo aneuploidies and mosaicism is controversial. A retrospective study was carried out in which 835 embryos from 280 couples undergoing reproductive treatment using their oocytes were chromosomally analyzed. A binary logistic regression analysis was performed to evaluate the relationship between different parameters characterizing controlled ovarian stimulation (COS) and the rate of aneuploidy and embryonic mosaicism. The embryo aneuploidy rate showed no association with the use of oral contraceptives, type, total and daily doses of gonadotropins, stimulation protocol type, and drugs used for ovulation trigger (p > 0.05). In contrast, the duration of the ovarian stimulation treatment was correlated with the aneuploidy rate: patients requiring more days of stimulation presented a lower rate of aneuploid embryos (p = 0.015). None of the variables studied showed any association with the rate of embryo mosaicism. However, the duration of COS showed association with the appearance of aneuploidy, suggesting that faster recruitment could be deleterious for those reassuming meiosis, yielding more abnormal karyotype.Abbreviations: IVF: in vitro fertilization; COS: controlled ovarian stimulation; PGT-A: preimplantation genetic test for aneuploidy; hCG: human chorionic gonadotropin; GnRH: gonadotropin-releasing hormone; LH: luteinizing hormone; FSH: follicle-stimulating hormone; NGS: next-generation sequencing; a-CGH: comparative genomic hybridization; TUNEL: Terminal transferase dUTP Nick End Labeling; FISH: fluorescent in situ hybridization.

Is more better? A higher oocyte yield is independently associated with more day-3 euploid embryos after ICSI

STUDY QUESTION

Is the number of oocytes retrieved after ovarian stimulation for ICSI independently associated with the number of day-3 euploid embryos (EE)?

SUMMARY ANSWER

A larger oocyte yield is independently associated with more day-3 EE, although the expected benefit decreases significantly with advancing age.

WHAT IS KNOWN ALREADY

Although traditionally ovarian stimulation aims at collecting more than one oocyte in order to increase the chance of pregnancy, there is evidence suggesting that excessive ovarian response leads to lower live birth rates. Whether a larger oocyte yield after ovarian stimulation is associated with the genetic composition of the resulting embryos and therefore with their reproductive potential is still largely unknown.

STUDY DESIGN, SIZE, DURATION

This is a multi-centered retrospective cohort study analyzing 724 cycles of preimplantation genetic testing for aneuploidy (PGT-A) cycles using day-3 biopsy and array-comparative genomic hybridization between March 2011 and December 2016 in three laboratories.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The primary outcome measure was the number of EE on day-3. Statistical analysis was performed using the generalized estimating equations (GEE) framework and multivariate regression models to control for the clustered nature of the data while adjusting for potential confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

A multivariate regression GEE model including all significant population and stimulation characteristics as covariates as well as an interaction term between female age and number of oocytes revealed that the number of oocytes retrieved was still positively associated with the number of EE (coeff: +0.40, 95% CI: 0.24-0.56). The interaction term was highly significant (coeff: -0.01, P < 0.001) indicating an effect modifying role of female age on the association of oocytes retrieved with the number of EE. The number of oocytes retrieved was also positively associated with cumulative live birth rates (odds ratio: 1.07, 95% CI: 1.03-1.12).

LIMITATIONS, REASONS FOR CAUTION

This study is retrospective and the presence of residual unknown bias cannot be excluded. Furthermore, the population analyzed in this study might not be completely representative of the general population undergoing ICSI.

WIDER IMPLICATIONS OF THE FINDINGS

These results provide an explanatory mechanism for the recently published positive association between the number of oocytes retrieved and cumulative live birth rates.

STUDY FUNDING/COMPETING INTEREST(S)

CAV is supported by a NHMRC Early Career Fellowship (GNT1147154)/ No competing interests to declare.

A Higher Ovarian Response after Stimulation for IVF Is Related to a Higher Number of Euploid Embryos

This study has analysed the relationship between ovarian response and the number of euploid embryos. This is a post hoc analysis of a subset of data generated during a prospective cohort study previously published. Forty-six oocyte donors were subjected to ovarian stimulation with 150 IU of rFSH and 75 IU of hp-hMG in a GnRH agonist long protocol. Preimplantation genetic screening was performed in all viable embryos. We observed a positive relationship between ovarian response and the number of euploid embryos. When ovarian response was above the median (≥17 oocytes), the mean number of euploid embryos per donor was 5.0 ± 2.4, while when <17 oocytes were obtained the mean number of euploid embryos was 2.7 ± 1.4 (p = 0.000). Aneuploidy rate did not increase with ovarian response or gonadotropin doses. Also, the number of euploid embryos was inversely related to the amount of gonadotropins needed per oocyte obtained (ovarian sensitivity index). These results suggest that the number of euploid embryos available for embryo transfer increases as the number of oocytes obtained does. Considering the total number of euploid embryos seems more relevant than the aneuploidy rate.

Predictors of twin pregnancy after ovarian stimulation and intrauterine insemination in women with unexplained infertility

Multi-foetal gestation is a well-known, adverse outcome of infertility treatment. Maternal and obstetrical complications are more frequent in multiple pregnancies compared to singletons. The aim of this study was to determine parameters that affect the risk for multiple pregnancies after ovarian stimulation (OS) with intrauterine insemination (IUI). We retrospectively evaluated all cases of OS with IUI cycles that ended with successful clinical pregnancy. A total of 259 pregnancies were analysed (175 singletons, 63 twins and 21 triplets). Significant parameters predicting multiple pregnancies were gravidity and number of follicles at least 15 mm in diameter on day of hCG. A previous pregnancy increased the risk for multiple gestation by a factor of 1.86 (95% CI 1.03-3.37, p = 0.04). Each follicle ≥15 mm increased the odds ratio for multiple gestation by 1.3 (95% CI 1.03-1.65, p = 0.027). In conclusion, women with more than one previous pregnancy and three or more than three follicles ≥15 mm at hCG are at risk for multi-foetal pregnancy after OS and IUI.

Regimen of ovarian stimulation affects oocyte and therefore embryo quality

Without any doubt the regimen used to mature multiple capable oocytes for IVF impacts IVF outcomes. Studies have indicated that the inclusion of LH activity, adjuvant agents such as growth hormone (GH), and regimens providing for simultaneous action of both LH and FSH during final oocyte maturation may have beneficial effects on IVF outcomes. Because of the difficulty in improving IVF outcomes in poor responders, the studies on GH are of particular interest. As pointed out in this review, the apparent beneficial effects of GH on oocyte competence may also apply to older women or to normal responders with reduced embryo quality. A much more difficult question is whether and how much ovarian stimulation impacts on oocyte competence. Paradoxically it seems that there are not demonstrated differences between the stimulated and the natural unstimulated cycle, whereas studies in laboratory animals and IVF patients have shown deleterious effects of higher compared with lower doses of gonadotropins. Recent studies suggest that the use of high doses of gonadotropins as an independent factor correlates negatively with the probability of live birth, whereas a high ovarian response per se is associated with better cumulative pregnancy rates, owing to the availability of more euploid and good-quality embryos. Although adjunctive use of androgens has not been discussed here, it is briefly covered in the first review of this series.

How do patient perceived determinants influence the decision-making process to accept or decline preimplantation genetic screening?

OBJECTIVE

Identify the determinants that influence the patient's decision-making process when deciding to accept or decline preimplantation genetic screening (PGS) in a given IVF cycle.

DESIGN

Pilot, retrospective, cross-sectional study that used a questionnaire containing a combination of quantitative and qualitative items.

SETTING

Private practice IVF clinic.

PATIENT(S)

Patients and partners initiating an IVF treatment cycle, both autologous and donor, between October 2012 and January 2015.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Identification of patient perceived determinants and the importance of each on the decision to accept or decline PGS.

RESULT(S)

Responses from the questionnaire (N = 117) were returned, and of these, 60% accepted PGS. The female response rate was 75% (N = 88) and the male response rate was 25% (N = 29). Ninety-eight percent were Christian (N = 112) and 88% college educated (N = 102) with 39% (N = 40) having some postgraduate education. Sixty-eight percent (N = 79) had no knowledge of PGS before the IVF cycle; however, after provider education, 92% (N = 108) correctly identified that PGS was elective and 93% (N = 109) reported sufficient knowledge to make an informed decision to accept or decline PGS. The additional cost of screening, the provider information and influence, and social support or acceptance from partner, family, and/or friends, were the three statistically significant variables affecting the decision.

CONCLUSION(S)

This is the first study, to the authors' knowledge, to identify and assess the determinants of the patient decision-making process when presented with the choice of PGS. Several factors contribute to the patient-perceived determinants when choosing to accept or decline PGS, including cost, religious and ethical beliefs and values, social and family support, provider influences, and the past reproductive experience of the patient.

Why more is less and less is more when it comes to ovarian stimulation

PURPOSE

The purpose of the present study is to describe the possible mechanisms which may explain the apparent paradox of "less is more." Mild ovarian stimulation for in vitro fertilization (IVF) minimizes ovarian hyperstimulation syndrome (OHSS) and multiple gestations without compromising the pregnancy rate (PR).

METHODS

The pertinent English literature (PubMed) addressing mild stimulation for IVF/assisted reproductive technology (ART) and publications addressing "mild" or "soft" controlled ovarian stimulation (COS) vs conventional COS for IVF, OHSS, natural cycle IVF, and IVF outcome in association with COS was searched.

RESULTS

Four possible mechanisms can be put forward to explain the apparent paradox of "less is more." (1) In the natural or mild stimulation cycles, the healthiest follicles are selected by the principle of "quality for quantity"; (2) high estradiol (E2) in the late follicular phase significantly correlated with higher rates of small for gestational age (SGA) and low-birth-weight (LBW) neonates; (3) anti-Mullerian hormone (AMH), LH, testosterone, and E(2) are significantly higher in natural cycle (NC)-IVF than in stimulated IVF follicles, suggesting an alteration of the follicular metabolism in stimulated cycles; and (4) supraphysiological E(2) may increase the growth hormone-binding protein (GH-BP) bio-neutralizing GH and diminishing the resultant insulin-like growth factor (IGF) levels, necessary for optimal synergism with follicle-stimulating hormone (FSH).

CONCLUSIONS

It is suggested to aim at the retrieval of around eight to ten eggs. Mild stimulation should be the common practice for IVF. In cases where more than ten ova are retrieved or high E(2) levels are reached, either intentionally or unintentionally, "freeze-all policy" should be considered and embryo transfer (ET) done in a subsequent natural cycle.