Sonographic abnormalities in pregnancies conceived following IVF with and without preimplantation genetic testing for aneuploidy (PGT-A)

Prenatal diagnosis following preimplantation genetic testing (PGT): recommendations of the Italian Society of Human Genetics (SIGU)

This document aims to provide good practice recommendations in order to support maternal-foetal medicine specialists, clinical geneticists and clinical laboratory geneticists in the management of pregnancies obtained after the transfer of an embryo tested with preimplantation genetic testing (PGT). It was drafted by geneticists expert in preimplantation genetics and prenatal genetic diagnosis belonging to the "Working Group in Cytogenomics, Prenatal and Reproductive Genetics" of the "Italian Society of Human Genetics" (SIGU). In particular, the paper addresses the diagnostic algorithm to be applied in prenatal follow-up depending on the type of PGT performed, the results obtained and the related diagnostic value based on the most recent literature data and Italian and international recommendations.

Polygenic embryo screening: are there potential maternal and fetal harms?

Polygenic embryo screening (PES) and its derivate the Embryo Health Score (EHS) have generated interest in both infertile and fertile populations due to their potential ability to select embryos with a reduced risk of disease and improved long-term health outcomes. Concerns have been raised regarding the potential harms of IVF itself, including possible epigenetic changes that may affect the health of the offspring in late adulthood, which are not fully captured in the EHS calculation. Knowledge of the potential impacts of the trophectoderm biopsy, which is a key component of the PES procedure, on the offsprings' health is limited by the heterogeneity of the population characteristics used in the published studies. Nonetheless, the literature suggests a possible increased risk of preterm delivery, birth defects and pre-eclampsia after trophectoderm biopsy. Overall, the risks of PES for prenatal and postnatal health remain uncertain, and further research is needed. Counselling patients regarding these risks before considering PES is important, to provide an understanding of the risks and benefits. This review aims to highlight some of these issues, the need for continued investigation in this area, and the importance of informed decision-making in the context of PES.

Obstetric, neonatal, and child health outcomes following embryo biopsy for preimplantation genetic testing

BACKGROUND

Preimplantation genetic testing (PGT) of embryos developed in vitro requires a biopsy for obtaining cellular samples for the analysis. Signs of cell injury have been described in association with this procedure. Thus, the consequences of the biopsy on obstetric and neonatal outcomes have been the subject of some quantitative analyses, although the reliability of data pooling may be limited by important issues in the various reports.

OBJECTIVE AND RATIONALE

The present review identifies evidence for whether pregnancies conceived after embryo biopsy are associated with a higher risk of adverse obstetric, neonatal, and long-term outcomes. Available evidence has been summarized considering manipulation at various stages of embryo development.

SEARCH METHODS

We used the scoping review methodology. Searches of article databases were performed with keywords pertaining to the embryo biopsy technique and obstetric, neonatal, and postnatal outcomes. Studies in which embryos were biopsied at different stages (i.e. both at the cleavage and blastocyst stages) were excluded. We included data on fresh and frozen embryo transfers. The final sample of 31 documents was subjected to qualitative thematic analysis.

OUTCOMES

Sound evidence is lacking to fully address the issues on the potential obstetric, neonatal or long-term consequences of embryo biopsy. For polar body biopsy, the literature is too scant to draw any conclusion. Some data, although limited and controversial, suggest a possible association of embryo biopsy at the cleavage stage with an increased risk of low birthweight and small for gestational age neonates compared to babies derived from non-biopsied embryos. An increase in preterm deliveries and birth defects in cases of trophectoderm biopsy was suggested. For both biopsy methods (at the cleavage and blastocyst stages), an increased risk for hypertensive disorders of pregnancy was found. However, these findings may be explained by confounders such as other embryo manipulation procedures or by intrinsic patient or population characteristics.

WIDER IMPLICATIONS

Since there is inadequate evidence to assess obstetric, neonatal, and long-term health outcomes following embryo biopsy, an invasive PGT strategy should be developed with a cautious approach. A non-invasive approach, based on the analysis of embryo cell-free DNA, needs to be pursued to overcome the potential limitations of embryo biopsy.

The impact of preimplantation genetic testing on first- and second-trimester maternal serum analyte levels

OBJECTIVE

To determine whether preimplantation genetic testing (PGT) is associated with a change in maternal serum analyte levels in pregnancies conceived via in vitro fertilization (IVF).

METHODS

Retrospective cohort of singleton and twin IVF pregnancies with available first- or second-trimester serum analyte data from 01/2014 to 09/2019. Multiple of the median (MoM) values for free β-human chorionic gonadotropin (β-hCG), pregnancy-associated plasma protein A (PAPP-A), alpha-fetoprotein (AFP), inhibin A, and unconjugated estriol, were compared between two groups: pregnancies conceived after transfer of PGT screened euploid embryos vs. those conceived after transfer of untested embryos. Multiple linear regression of log MoM values with F test was performed to adjust for potential confounders.

RESULTS

Nine hundred and sixty-two singleton and 165 twin IVF pregnancies with serum analyte data available for analysis were included. PGT was associated with a higher median first- and second-trimester AFP compared to no PGT in singletons (1.23 MoM vs. 1.13 MoM; parameter estimate [PE] 1.08, 95% CI 1.00-1.17, p= .04, and 1.21 MoM vs. 1.07 MoM; PE 1.07, 95% CI 1.01-1.13, p= .01, respectively). PGT was also associated with a lower median PAPP-A compared to no PGT in twins (0.75 MoM vs. 1.18 MoM, PE 0.74, 95% CI 0.60-0.92, p= .006).

CONCLUSIONS

Our data suggest that PGT is associated with higher maternal serum levels of second-trimester AFP in singleton and lower levels of first-trimester PAPP-A in twin pregnancies conceived via IVF.

The impact of preimplantation genetic testing for aneuploidy on prenatal screening

OBJECTIVES

To determine whether preimplantation genetic testing for aneuploidy (PGT-A) is associated with a reduced risk of abnormal conventional prenatal screening results in singleton pregnancies conceived using in vitro fertilization (IVF).

METHODS

This was a retrospective cohort study of singleton IVF pregnancies conceived from a single tertiary care center between January 2014 and September 2019. Exclusion criteria included mosaic embryo transfers, vanishing twin pregnancies, and cycles with missing outcome data. Two cases of prenatally diagnosed aneuploidy that resulted in early voluntary terminations were also excluded. The primary outcome of abnormal first or second-trimester combined screening results was compared between two groups: pregnancy conceived after transfer of a euploid embryo by PGT-A vs. transfer of an untested embryo. Multivariable backwards-stepwise logistic regression with Firth method was used to adjust for potential confounders.

RESULTS

Of the 419 pregnancies included, 208 (49.6%) were conceived after transfer of a euploid embryo by PGT-A, and 211 (50.4%) were conceived after transfer of an untested embryo. PGT-A was not associated with a lower likelihood of abnormal first-trimester (adjusted OR 1.64, 95% CI 0.82-3.39) or second-trimester screening results (adjusted OR 0.96, 95% CI 0.56-1.64). The incidences of cell-free DNA testing, fetal sonographic abnormalities, genetic counseling, and invasive prenatal diagnostic testing were similar between the two groups.

CONCLUSIONS

Our data suggest that PGT-A is not associated with a change in the likelihood of abnormal prenatal screening results or utilization of invasive prenatal diagnostic testing. Counseling this patient population regarding the importance of prenatal screening and prenatal diagnostic testing, where appropriate, remains essential.

Utility of polygenic embryo screening for disease depends on the selection strategy

Polygenic risk scores (PRSs) have been offered since 2019 to screen in vitro fertilization embryos for genetic liability to adult diseases, despite a lack of comprehensive modeling of expected outcomes. Here we predict, based on the liability threshold model, the expected reduction in complex disease risk following polygenic embryo screening for a single disease. A strong determinant of the potential utility of such screening is the selection strategy, a factor that has not been previously studied. When only embryos with a very high PRS are excluded, the achieved risk reduction is minimal. In contrast, selecting the embryo with the lowest PRS can lead to substantial relative risk reductions, given a sufficient number of viable embryos. We systematically examine the impact of several factors on the utility of screening, including: variance explained by the PRS, number of embryos, disease prevalence, parental PRSs, and parental disease status. We consider both relative and absolute risk reductions, as well as population-averaged and per-couple risk reductions, and also examine the risk of pleiotropic effects. Finally, we confirm our theoretical predictions by simulating 'virtual' couples and offspring based on real genomes from schizophrenia and Crohn's disease case-control studies. We discuss the assumptions and limitations of our model, as well as the potential emerging ethical concerns.

Birth defects surveillance after assisted reproductive technology in Beijing: a whole of population-based cohort study

OBJECTIVES

To compare the differences in the prevalence of birth defects among offspring conceived by assisted reproductive technology (ART) and conceived spontaneously (non-ART), and assess the contribution of ART to birth defects.

DESIGN

A population-based retrospective cohort study.

SETTING

Beijing.

PARTICIPANTS

Pregnant women whose expected date of childbirth was verified as occurring between October 2014 and September 2015, and were registered on the Beijing Maternal and Child Health Information Network System, were the recorded pregnancy outcomes. 2699 ART offspring and 191 368 non-ART offspring (live births, stillbirths and medical terminations) were included in our study.

INTERVENTIONS

None.

OUTCOME MEASURES

Risk ratios (RR) for birth defects were calculated among ART conceptions and non-ART conceptions with confounding factors by using logistic regression models.

RESULTS

194 067 offspring were included in the present study, and 2699 (1.4%) were conceived using ART. Among all the births, the prevalence of any birth defect in the ART offspring (5.5%) was significantly higher than in the non-ART offspring (3.8%) (crude RR, 1.49, 95% CI 1.26 to 1.76). After adjusting for confounding factors, ART use was still associated with an increased risk of any birth defect (5.4% vs 3.5% in ART and non-ART group, adjusted RR (aRR), 1.43, 95% CI 1.08 to 1.90), especially for chromosomal abnormalities (0.5% vs 0.2% in ART and non-ART group, aRR, 3.11, 95% CI 1.28 to 7.58), in singleton births to mothers <35 years. Circulatory system malformations and musculoskeletal system malformations were observed to have a non-significant increase in offspring conceived by ART. However, the associations between ART and birth defects were not detected in multiple births or mothers ≥35 years.

CONCLUSIONS

This study confirmed a small but significant association between ART and birth defects. However, the risk tends to be non-significant under the conditions of advanced maternal age or multiple pregnancies.

Noninvasive prenatal testing in women undergoing in vitro fertilization with preimplantation genetic testing

PURPOSE OF REVIEW

To discuss the utilization, performance, and interpretation of noninvasive prenatal testing (NIPT) results in women achieving pregnancy through in vitro fertilization (IVF) and preimplantation genetic testing for aneuploidy (PGT-A).

RECENT FINDINGS

Although PGT-A is a highly accurate method for the selection of euploid embryos the possibility for error still exists. Many women pursue NIPT after conception via IVF with or without PGT-A, whereas some forgo prenatal screening all together. Recent evidence suggests that the prevalence of a positive NIPT following PGT-A is low, and the positive predictive value is altered in this population.

SUMMARY

NIPT is a valuable prenatal screening tool that should be offered to pregnant women regardless of prior PGT. In women who conceive following IVF and PGT-A through the transfer of euploid embryos, positive test results should be interpreted with caution.

Adding new ingredients to the recipe for successful embryo transfers

The success of a pregnancy and the birth of a heathy baby following embryo transfer are conditioned by many factors, including embryo quality and the uterine environment. While we keep looking for more indicators of embryo quality, it also is critical to understand what constitutes a favorable uterine environment leading to a successful pregnancy and birth. This issue of JARG offers new insights on both components-so called by some "the seed and the soil"-and also highlights the critical interactions between the two. Collectively, these publications are contributing to a better understanding of basic embryology and reproductive biology. They could lead to multiple applications to mitigate infertility issues; however, our knowledge base remains rudimentary when it comes to sorting out the 'soil or seed' dilemma. The call from all authors for more research in their respective areas resonates within the ART community. Recognizing the practical and ethical limitations of studies in human patients also reemphasizes the need for solid research in multiple animal models to better understand what constitutes the best recipe for successful embryo transfer outcomes.