Seasonal fluctuation of in vitro fertilization encounters in the United States

PURPOSE: To examine patient and hospital characteristics related to seasonal fluctuation in in vitro fertilization (IVF). METHODS: This retrospective cohort study examined 33,077 oocyte retrievals identified in the National Ambulatory Surgery Sample. Exposure assignment was monthly IVF encounters: low-volume months (<25%ile), mid-volume months (≥25/<75%ile), and high-volume months (>75%ile). Main outcomes were patient and hospital characteristics related to the exposure groups, assessed with a multinomial regression model. RESULTS: The median IVF encounters were 977 per month, ranging from 657 to 1074 (absolute-difference 417). January, July, and December were the lowest-quartile volume months, ranging from 657 to 710 encounters per month (low-volume months). May, August, and November were the top-quartile volume months, ranging from 1049 to 1074 encounters per month (high-volume months). In a multivariable analysis, patients undergoing IVF in the low-volume months were younger and less likely to have infertility or comorbidities. Patients undergoing IVF in the high-volume months were more likely to have lower household income and receive IVF at urban teaching facilities. Northeastern residents were less likely to have IVF in the low-volume months but more likely to have IVF in the high-volume months. Sensitivity analyses showed that the lowest-to-highest variability in monthly IVF encounters was higher in Northeast region compared to other regions (320 vs 50–128); infertility patients compared to those without (317 vs 190); privately insured patients compared to self-pay (227 vs 156); and older patients compared to younger (234 vs 192). CONCLUSION: This study suggests substantial seasonal fluctuation in IVF oocyte retrieval in the USA based on patient and hospital factors. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10815-023-02777-0.