Abstract
PurposeTo investigate the associations between blastocyst development and the sex ratio (male:female) among singleton live births resulting from single-blastocyst frozen embryo transfer (FET) cycles.MethodsPatients with singleton live births following the first autologous single FET of non- preimplantation genetic testing (PGT) blastocysts in a single reproductive medicine department between January 2015 and February 2019 were included in this retrospective study. The primary outcome measure was the singleton sex ratio. Multivariable logistic regression models were used to estimate the associations between blastocyst quality and singleton sex ratio after adjustment for some potential confounders.ResultsThere were 638 high-quality and 572 poor-quality single blastocyst FETs, and the blastocysts were conceived via 855 IVF and 355 ICSI treatments. A total of 1210 singleton live births were assessed. High-quality single blastocyst FET resulted in a significantly higher sex ratio than did poor-quality single blastocyst FET (60% vs. 49.7%, P < 0.001). The infertility cause was not associated with sex ratio among singleton live births (P = 0.537). The results of a multivariate analysis revealed that a high-quality blastocyst has a 150% higher probability of being male than a poor-quality blastocyst (adjusted odds ratio (aOR) 1.57; 95% CI 1.24–2, P < 0.001). Among the three blastocyst morphological parameters, Grade B trophectoderm was significantly associated with a higher sex ratio than Grade C (aOR 1.71; 95% CI 1.33–2.21. P < 0.001). Neither expansion degree nor inner cell mass degree were significantly associated with the singleton sex ratio.ConclusionsA single high-quality blastocyst FET has a higher chance of resulting in a male infant than a female infant. The results demonstrate that grade B trophectoderm confers benefits in improving the implantation potential of male blastocysts.
Highlights
Human-assisted reproductive technology (ART) aims to achieve a single live birth
We found that high-quality single blastocyst frozen embryo transfer (FET) resulted in a significantly higher sex ratio than did poor-quality single blastocyst FET (60% vs. 49.7%, P < 0.001, Fig. 2.)
The results of a multivariate analysis revealed that a high-quality blastocyst has a 150% higher probability of being male than a poor-quality blastocyst
Summary
Human-assisted reproductive technology (ART) aims to achieve a single live birth. Following improvements in blastocyst culture systems and freezing technology [1, 2], single blastocyst transfer (SBT) is considered the most effective means of avoiding multiple pregnancies subsequent to ART [3,4,5,6]. The sex ratio at birth is often calculated as the proportion of males among all live births or the number of male births per 100 female births [14]. Dean et al reported a significantly higher sex ratio at birth among infants born after SBT (54.1%) than among those born after cleavage-stage transfer cycles (49.9%) [15]. The details of the relationship between the characteristics of blastocysts and the sex ratio at birth remain unclear
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