Higher morbidity in hospitals during off-hours such as holidays and nighttime has been reported in numerous medical specialties. Studies have suggested that the obstetrics often encounter severe adverse neonatal events at nighttime 10 and on weekends 11. In this study, we examined the monthly IVF outcome for fresh embryo transfer cycles retrospectively and found that the lowest monthly live birth rate resulted from procedures performed in January and February, apparently the CNY holiday season. Precisely, the embryo transfer month with the lowest live birth rate was February, even 15.1% lower than January. We have several speculations for this live birth rate decline in the CNY holiday season.
Owing to the long-lasting tradition, the vast majority, if not all, of Chinese people inevitably experience abrupt changes in their daily life, such as unhealthy diet, frequent tobacco and alcohol consumption related to family and social gatherings, and sleep deprivation, etc. Although such a lifestyle change just lasts two months, it may compromise overall health condition and therefore affect IVF success rates 12. People tend to gain weight from eating excessively during the holiday season 13,14 thus taking up more salt, sugar, and fatty food than usual, leading to imbalanced nutrition, which is no exception for the CNY. Fatty meals can have acute adverse effects on oocyte mitochondria 15, and high-fat diets are detrimental to male fertility 16. A prospective study concluded that five Chinese food patterns, and the western food style "Puffed food-Candy-Bakery" were related to a lower likelihood of achieving biochemical pregnancy 17. A primate study involving a short-term high-fat western-style diet before IVF treatment demonstrated that high-fat diet reduces blastocyst numbers, dysregulates RNA binding and mitochondrial function 18. Consumption of higher sugar-containing beverage is associated with lower number of total, mature, and fertilized oocytes as well as lower number of top-quality embryos after ovarian stimulation 19. Higher intake of supplemental folic acid, vitamin B12, vitamin D, produce with low pesticide residue, whole grains, dairy, soy foods and seafood were defined as pro-fertility diet, which was associated with an increased probability of live birth of women undergoing IVF 20. During the CNY holiday season, people tend to change their diet in order to acquire more tasty foods, which contain more fat, salt, sugar. Such diet pattern shift could therefore reduce the intake of pro-fertility nutriments.
Frequent family and social gatherings during the CNY holiday season create occasions for excessive tobacco exposure and alcohol consumption. On one hand, smokers typically smoke more as cigarette gifting and sharing is part of the CNY tradition. On the other hand, non-smokers increasingly suffer from secondhand smoke at many occasions. It has been suggested that sharing cigarettes in China is a significant impediment to smoking cessation 21. According to a previous study, exposure to tobacco by women increased the risk of implantation failure by 17% and reduced the live birth success by 19% following IVF 22. Such negative impacts of tobacco exposure depend on hormonal status, individual health conditions, the amount of tobacco exposure, the total length of exposure time, and personal sensitivity to cigarettes 23. Compelling evidence has demonstrated that smoking negatively influences IVF outcomes 24-26. Moreover, using of both e-cigarette and regular cigarette by women was associated with small-for-gestational-age birth 27,28. A meta-analysis across twenty different studies with 5,865 subjects in total showed that the exposure to smoking had negative impacts on semen 29, which may reduce the efficacy of assisted reproductive technology (ART). Also, smoking induces DNA damage in sperms 30,31 thereby influencing IVF outcomes 24,32. Altogether, increased tobacco exposure by both partners may contribute to the LBR decline from IVF performed during the CNY holiday season.
The CNY holiday celebration is widely linked to alcohol abuse 33. One study found that female and male alcohol consumption is a primary risk factor for IVF 34. Female alcohol consumption was associated with a decreased number of oocyte retrieval and an increased risk of miscarriage. For males, one additional drink per day increased the risk of not achieving a live birth and drinking one month before IVF increased the risk of spontaneous miscarriage. When both of the couple drink, as few as four alcoholic drinks per week may cause a decrease in IVF live birth rate 35.
It’s common that people change their sleep patterns drastically and even get sleep deprived due to festival celebration and holiday travel. The traditional celebration involves staying up late or even staying up all night long on New Year’s Eve. A systematic review showed female and male fertility and IVF outcomes may suffer from decreased sleep duration and chronotype 36.
Besides above-mentioned lifestyle changes, emotional stress is another critical factor for live birth of IVF performed during the CNY holiday season. During the CNY holiday season, patients feel stressed from making decisions about whether or not to interact with certain relatives or friends due to financial pressures as travel, gifts purchasing, entertaining, and alcohol consumption can be significant expenses. One study showed that holiday sedentary behavior can have an indirect impact on anxiety through neurobiological markers37. Stress also increased by traveling and interacting with visitors during the Chinese New Year holiday season. Patients receiving IVF during this period would be stressed from IVF itself and the CNY preparation and celebration. Several studies showed that stress had negative impacts on IVF outcomes, i.e., number of oocyte retrieval, fertilization, pregnancy, spontaneous abortion, live birth, multiple gestations, and low birth weight. A meta-analysis including 43 articles showed that psychological stress might diminish IVF success rates, possibly due to hypothalamic dysfunction either via neurotransmission alterations, catecholamine depletion, or interference with hypothalamic receptors for neurotransmitters 38. Elevated glucocorticoid levels due to stress could have inhibitory effects on steroidogenesis, spermatogenesis, and sperm maturation. A study indicated that psychological stress among men at the time of oocyte retrieval had negative impacts on sperm quality 39. Moreover, a cross-sectional study showed a negative association between self-reported stress and sperm parameters 40.
Many studies assessed the impact of psychological stress on IVF outcomes. Ebbesen demonstrated that stressful life-events have a negative impact on the chances of successful IVF outcome 41. A meta-analysis showed a small but significant association between stress and reduced pregnancy chances in female patients receiving ART 42 . A study on 160 infertile women undergoing IVF demonstrated that psychological stress was negatively linked to IVF outcomes 43. Women with excessive stress may have a very high risk of not achieving a successful live birth delivery 44. Several evaluation methods have been used for assessing psychological stress. PHQ-9 (Patient Health Questionnaire-9) and PHQ-2 (Patient Health Questionnaire-2) are easy-to-use measures of depressive symptoms that are suitable for infertility patients 45. Haimovici et al. evaluated psychological stress by questionnaires and visual analog scales, and analyzed cytokines in serum, semen, cervicovaginal, and follicular fluids. This study speculated that stress-induced cytokines in both partners may be indicative of IVF failure 46. A study testing the influence of psychological stress on embryo cleavage kinetics 47 demonstrated that a stress management program offered to the infertile couples, was able to retard first embryo cleavage and accelerate embryo compaction. Taken together, avoiding psychological stress on both partners receiving IVF is beneficial to increase the success rate.
Travel also affects IVF outcomes. People have many travel plans during the Chinese New Year holiday season, so patients tend to rush to have their IVF to be completed prior to traveling. On the other hand, medical staff may also travel, leading to work shift changes during the holiday season that may impact the IVF outcome 48,49. For instance, during the CNY holiday season, patients may have their follow-ups handled by doctors and nurses who may not be familiar with their situations. Future studies are warranted to assess the potential effect of medical staff changes on IVF outcomes.
Limitations
Firstly, as a retrospective study, some variables, which may have negative impact on the live birth rate, were not recorded, such as smoking, BMI changing, sleep quantity and quality, travel, and psychological stress. Secondly, our study focused on the live birth rate of the first fresh implantation cycle, while the cumulative live birth rate during the holiday season compared with the non-holiday season is still unknown. Thirdly, our results are only based on data from our IVF center. It’s unclear whether the holiday season impacts other cities as social cultures vary across China. Future prospective multi-center studies will provide new insights into those above factors that may affect the live birth rate.