Impact of preimplantation genetic testing for aneuploidies (PGT-A) on first trimester biochemical markers - PAPP-A (placenta-associated plasma protein) and free β-hCG (human chorionic gonadotropin)

Prenatal screening after preimplantation genetic testing for aneuploidy: time to evaluate old strategies

RESEARCH QUESTION

How does first-trimester aneuploidy screening perform in pregnancies achieved through IVF with preimplantation genetic testing for aneuploidy (PGT-A) in a medical setting?

DESIGN

This retrospective cohort study was undertaken in a single tertiary care centre between January 2013 and June 2022. In total, 20,237 women had prenatal follow-up at the study centre and were included in the study. The women were divided into three groups: singleton pregnancies conceived through the transfer of a PGT-A-screened euploid embryo (n = 510); singleton pregnancies conceived through IVF without PGT-A (n = 3291); and singleton pregnancies conceived naturally (n = 16,436).

RESULTS

The conventional combined screening test for pregnancies conceived through IVF with PGT-A had specificity of 91%; sensitivity could not be calculated as there were no cases of fetal aneuploidy in this group. In 89.1% of pregnancies conceived through IVF with PGT-A with high risk for trisomy 21, 18 or 13, the result was related to advanced maternal age (>35 years at time of screening).

CONCLUSIONS

The current screening strategy for trisomies 21, 18 and 13 can generate unnecessary tests in pregnancies achieved through IVF with PGT-A. A new protocol is needed for these patients, with greater weight given to ultrasound markers.

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.

Trophectoderm Biopsy Differentially Influences the Level of Serum β-Human Chorionic Gonadotropin With Different Embryonic Trophectoderm Scores in Early Pregnancy From 7847 Single-Blastocyst Transfer Cycles

OBJECTIVE

To evaluate whether trophectoderm (TE) biopsy differentially influence the level of serum β-human chorionic gonadotropin (β-hCG) with different TE-scored blastocysts transferred in early pregnancy.

METHODS

This retrospective cohort study contained 7847 single-blastocyst transfer cycles executed between January 2019 and June 2020, including 2657 preimplantation genetic testing (PGT) cycles and 5190 in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) cycles. All cycles were classified into biopsy and control groups, and further stratified based on the TE morphological scores into three subgroups: grades A, B, and C for TE scores, respectively. Intra-group and inter-group analyses were performed on serum β-hCG levels on the 12th day after blastocyst transfer (HCG₁₂), and obstetric and neonatal outcomes.

RESULTS

For cycles with a live birth, in grade A TE score subgroups, the HCG₁₂ level did not exhibit statistical significance between the control and biopsy groups after adjustment (769 mIU/mL vs. 753 mIU/mL, P=0.631). In contrast, in grade B and C TE score subgroups, the control group showed a significantly higher level of HCG₁₂ relative to the biopsy group (690 mIU/mL vs. 649 mIU/mL, P=0.001; 586 mIU/mL vs. 509 mIU/mL, P<0.001, respectively). We observed no statistically significant differences in obvious adverse obstetric and neonatal outcomes between the same TE-score subgroups of the biopsy group and control group.

CONCLUSIONS

While blastocysts with higher TE grades produced higher serum β-hCG levels in early pregnancy, TE biopsy might exert a negative impact on serum β-hCG levels by blastocysts with a grade-B TE score and below. TE biopsy did not increase the risk for adverse obstetric and neonatal outcomes.