Interpretation
We found no association between obesity and live birth when transferring
a single euploid blastocyst embryo. Our results suggest that the
negative impact of being overweight or obese may be related to embryonic
aneuploidy. A prior meta-analysis showed that a high BMI did not affect
the IVF clinical outcomes in donor oocyte recipients, which suggested
that oocyte quality may be the most important factor in obese women
[14]. Previous studies suggested metabolic alterations in the serum
are reflected in the follicular fluid and that some of these alterations
may affect oocyte quality with higher BMI both in vitro and in vivo
[15-17]. In addition, one prospective cohort study showed that
elevated follicular follicular free fatty acid (FFA) were associated
with poor cumulus oocyte complex (COC) morphology [18]. Moreover,
severe obesity is also associated with a greater prevalence of spindle
anomalies and non-aligned chromosomes in failed fertilized oocytes
[19].
Embryo aneuploidy, which is widely known to be the most important factor
for negative outcomes, was not given enough attention in previous
studies when comparing the live birth rate between obese and
normal-weight women. Obesity has been reported to alter the early embryo
metabolomic signature [20], raising the possibility of epigenetic
mediated impairment of clinical outcomes.