Real-time monitoring reveals the effects of low concentrations of volatile organic compounds in the embryology laboratory

STUDY QUESTION Could real-time monitoring of volatile organic compounds (VOCs) in the embryology laboratory provide meaningful early warning for potential harm from the environment? SUMMARY ANSWER Even in a laboratory environment with a total VOC concentration lower than the recommendation of the Cairo Consensus, the real-time monitored VOC concentrations are associated with changes in embryo morphological parameters. WHAT IS KNOWN ALREADY VOCs have been considered a key environmental detriment in embryology laboratories. However, the current VOC thresholds established by the Cairo consensus were based on the practical experience of air pollution cases, and a scientifically derived threshold is lacking. STUDY DESIGN, SIZE, DURATION The study included 7076 oocyte collection (OPU) cycles carried out between June 2020 and December 2022 in the Center for Reproductive Medicine of the affiliated Chenggong Hospital of Xiamen University, 6306 of which resulted in at least one embryo transfer (ET) attempt during the study. VOC monitoring data were recorded every 10 min. The average and peak concentrations of total VOCs and formaldehyde during culture were associated with embryo parameters and implantation following the first ET attempt of the cycle in generalized estimating equations and generalized additive models. MAIN RESULTS AND THE ROLE OF CHANCE Real-time monitoring of VOCs showed a dynamic of VOC concentration in the laboratory. The concentration reached peaks during the working hours of the days and working days of the week and fell quickly at night and on weekends. The average concentrations of VOCs during the culture period were linearly associated with decreased early cleavage (OR 0.92, 95% CI: 0.85, 0.99), decreased Day 3 compaction (OR 0.51, 95% CI: 0.32, 0.83), increased asymmetry (OR 1.13, 95% CI: 1.01, 1.25), and increased grade C trophectoderm (TE) (OR 1.99, 95% CI: 1.32, 3.01). On the other hand, increased Day 3 arrest, delayed blastocyst formation, and decreased grade A TE showed a non-linear association with VOCs, suggesting a possible threshold of effect. In the first transfer attempt, negative associations were observed between maximal formaldehyde concentrations and pregnancy in both fresh transfer (RR 0.971, 95% CI: 0.94, 0.99) and freeze-all frozen-thawed ET (RR 0.959, 95% CI: 0.92, 0.99) cycles. LIMITATIONS, REASONS FOR CAUTION The sensitivity and specificity of the monitor are not comparable to the standard protocols, such as chromatography-mass spectroscopy. Due to the lack of ability to identify the chemical nature of the components of VOCs, the toxicity and source of the VOCs were largely unknown. The representative sampling of the laboratory air may not necessarily reflect the exposure of embryos. WIDER IMPLICATIONS OF THE FINDINGS While the environment of the embryology laboratory has been significantly improved, the data suggested that a low VOC level could still be a concern. Due to the dynamic of VOC concentration in the laboratory air, periodic monitoring may fail to capture the increased VOC levels and give an early alarm. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the National Natural Science Foundation of China [grant number 22176159], the Xiamen Medical Advantage subspecialty construction project [grant number 2018296], and the Wu Jieping Medical Foundation [grant number 320.6750.2024-6-14]. All authors declare no competing interests. TRIAL REGISTRATION NUMBER N/A.