Trophectoderm biopsy is associated with lower risks of moderate to extreme prematurity and low birthweights: a national registry cohort study of singleton livebirths from frozen-thawed blastocyst transfers

Background: Trophectoderm biopsy has become the mainstay assisted reproductive technique performed for preimplantation genetic testing, accounting for 43.8% of embryo transfer cycles in the United States in 2019 alone. Despite its prevalence, data on the obstetric and perinatal outcomes post-trophectoderm biopsy remains sparse and mixed. Objective: This study aimed to examine the risks of adverse perinatal outcomes in birthweights and prematurity after transfers of the vitrified-thawed blastocyst with trophectoderm biopsy for preimplantation genetic testing. Study Design: This was a retrospective observational cohort study of 45,712 singleton livebirths resulting from autologous vitrified-thawed blastocyst transfer cycles with or without trophectoderm biopsy for preimplantation genetic testing, reported by participating member clinics to the Society for Assisted Reproductive Technology national registry between 2014 and 2017. Adverse perinatal outcomes of preterm births and low birthweights were analyzed. Multivariable regression analyses were performed to control for covariates. Comparing the trophectoderm biopsy (n=21,584) and no trophectoderm biopsy (n=24,128) groups, adjusted odds ratios were calculated for the outcomes of small-for-gestational-age, large-for-gestational-age, low birthweight <2500 g, very low birthweight <1500 g, extremely low birthweight <1000 g, late preterm births <37 weeks, moderate preterm births <34 weeks, and extremely preterm births <28 weeks. Results: Women in the trophectoderm biopsy group were older and more likely to have prior pregnancies, deliveries, and a history of spontaneous abortions. Tobacco use, diminished ovarian reserve, and recurrent pregnancy loss were also more prevalent in the trophectoderm biopsy group. Trophectoderm biopsy was not associated with small-for-gestational-age (adjusted odds ratio, 0.97; 95% confidence interval, 0.85–1.12; P=.72) or large-for-gestational-age newborns (adjusted odds ratio, 1.10; 95% confidence interval, 0.99–1.22; P=.09). Risks of preterm births <37 weeks gestation were similar between the biopsy and nonbiopsy groups (adjusted odds ratio, 0.93; 95% confidence interval, 0.85–1.02; P=.11). Trophectoderm biopsy was associated with a significantly lower risk of low birthweight <2500 g (adjusted odds ratio, 0.80; 95% confidence interval, 0.70–0.92; P<.001), very low birthweight <1500 g (adjusted odds ratio, 0.62; 95% confidence interval, 0.46–0.83; P<.001), extremely low birthweight <1000 g (adjusted odds ratio, 0.48; 95% confidence interval, 0.31–0.74; P<.001), moderate preterm birth <34 weeks (adjusted odds ratio, 0.76; 95% confidence interval, 0.64–0.91; P=.003), and extreme preterm birth <28 weeks (adjusted odds ratio, 0.63; 95% confidence interval, 0.43–0.92; P=.02). Conclusion: Trophectoderm biopsy is not associated with increased risks of small-for-gestational-age, large-for-gestational-age, or late preterm birth. Risks of low birthweight, very low birthweight, and extremely low birthweight from moderate and extreme preterm births are lower after trophectoderm biopsy, possibly by selecting against confined placental mosaicism or inducing placental epigenetic changes, the mechanisms of which warrant further investigation.