Seasonal influences on in vitro fertilization and embryo transfer

Season at the time of oocyte collection and frozen embryo transfer outcomes

STUDY QUESTION

Does the meteorological season at the time of oocyte retrieval affect live birth rates in subsequent frozen embryo transfers?

SUMMARY ANSWER

Frozen embryo transfers resulting from oocytes retrieved in summer have 30% increased odds of live birth compared to frozen embryo transfers resulting from oocytes retrieved in autumn, regardless of the season at the time of embryo transfer.

WHAT IS KNOWN ALREADY

Season at the time of frozen embryo transfer does not appear to be associated with live birth rate. One study in the northern hemisphere found increased odds of live birth with frozen embryo transfer resulting from oocytes collected in summer when compared to those collected in winter.

STUDY DESIGN, SIZE, DURATION

Retrospective cohort study including all frozen embryo transfers performed by a single clinic over eight years, from January 2013 to December 2021. There were 3659 frozen embryo transfers with embryos generated from 2155 IVF cycles in 1835 patients. Outcome data were missing for two embryo transfers, which were excluded from analysis. Outcomes were analysed by the season, temperatures, and measured duration of sunshine at the time of oocyte collection and at the time of frozen embryo transfer.

PARTICIPANTS/MATERIALS, SETTING, METHODS

There were no significant differences between patients with oocyte collection or embryo transfers in different seasons. Meteorological conditions on the day of oocyte collection and the day of frozen embryo transfer, and in the preceding 14- and 28-day periods, were collected including mean, minimum, and maximum temperatures, and recorded duration of sunshine hours. Clinical and embryological outcomes were analysed for their association with seasons, temperatures, and duration of sunshine with correction for repeated cycles per participant, age at the time of oocyte retrieval, and quadratic age.

MAIN RESULTS AND THE ROLE OF CHANCE

Compared to frozen embryo transfers with oocyte retrieval dates in autumn, transfers with oocyte retrieval dates in summer had 30% increased odds of live birth (odds ratio (OR): 1.30, 95% CI: 1.04-1.62) which remained consistent after adjustment for season at the time of embryo transfer. A high duration of sunshine hours (in the top tertile) on the day of oocyte retrieval was associated with a 28% increase in odds of live birth compared to duration of sunshine hours in the lowest tertile (OR 1.28, 95% CI: 1.06-1.53). Temperature on the day of oocyte retrieval did not independently affect the odds of live birth. The odds of live birth were decreased by 18% when the minimum temperature on the day of embryo transfer was high, compared with low (OR: 0.82, 95% CI: 0.69-0.99), which was consistent after correction for the conditions at the time of oocyte retrieval.

LIMITATIONS, REASONS FOR CAUTION

This was a retrospective cohort study, however, all patients during the study period were included and data was missing for only two patients. Given the retrospective nature, causation is not proven and there are other factors that may affect live birth rates and for which we did not have data and were unable to adjust, including pollutants and behavioural factors. We were also not able to stratify results based on specific patient populations (such as poor- or hyper-responders) nor report the cumulative live birth rate per commenced cycle.

WIDER IMPLICATIONS OF THE FINDINGS

These findings may be particularly relevant for patients planning oocyte or embryo cryopreservation. Given the increasing utilization of cryopreservation, identification of factors that influence outcomes in subsequent frozen embryo transfers has implications for future therapeutic and management options. Further studies to clarify the physiology underlying the influence of sunshine hours or season on subsequent frozen embryo transfer outcomes are required, including identification of specific populations that may benefit from these factors.

STUDY FUNDING/COMPETING INTERESTS

No funding was provided for this study. S.L. has received educational travel assistance from Besins, Merck and Organon outside the submitted work. R.H. is National Medical Director of City Fertility and Medical Director of Fertility Specialists of Western Australia, has received honoraria from MSD, Merck Serono, Origio and Ferring outside the submitted work, and has equity interests in CHA SMG. C.R., M.W., and E.N. declare that they have no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Are ICSI results affected by months and seasons? A retrospective cohort study of fresh and frozen cycles

In present study, we aimed to investigate the effect of seasonal variation on ICSI results both in fresh and frozen embryo transfer cycles. Between January 2007 and December 2019, a total of 4039 ICSI cycles (3227 fresh and 812 frozen ET) which resulted in embryo transfer were included in the study. We found no significant difference in the pregnancy outcome among different seasons and months. The best results were obtained for spring (41.0%) and the least for winter (37.1%) in fresh cycles and the best for spring (42.5%) and the least for winter (29.7%) in FET cycles. In monthly distribution, the best results were obtained for September (57.0%) and the least for November (24.1%) in fresh cycles and the best for October (49.3%) and the least for December (20.2%) in FET cycles. Our study did not show any significant influence of the months or seasons on clinical pregnancy rates in either fresh and frozen embryo transfers. However, the difference among months in frozen cycles was notable although it did not reach statistical significance. It can be suggested that the strict control of reproductive hormones especially in fresh cycles as well as the standardized laboratory temperature minimize the influence of seasonal effect on ICSI outcome.

Circadian Rhythms in the Neuronal Network Timing the Luteinizing Hormone Surge

For billions of years before electric light was invented, life on Earth evolved under the pattern of light during the day and darkness during the night. Through evolution, nearly all organisms internalized the temporal rhythm of Earth's 24-hour rotation and evolved self-sustaining biological clocks with a ~24-hour rhythm. These internal rhythms are called circadian rhythms, and the molecular constituents that generate them are called molecular circadian clocks. Alignment of molecular clocks with the environmental light-dark rhythms optimizes physiology and behavior. This phenomenon is particularly true for reproductive function, in which seasonal breeders use day length information to time yearly changes in fertility. However, it is becoming increasingly clear that light-induced disruption of circadian rhythms can negatively impact fertility in nonseasonal breeders as well. In particular, the luteinizing hormone surge promoting ovulation is sensitive to circadian disruption. In this review, we will summarize our current understanding of the neuronal networks that underlie circadian rhythms and the luteinizing hormone surge.

The association between season, day length, and temperature on clinical outcomes after cryopreserved embryo transfer

OBJECTIVE

To investigate whether there is an association between season, temperature, and day length at oocyte retrieval and/or embryo transfer (ET) and clinical outcomes in frozen ET cycles.

DESIGN

Retrospective cohort study.

SETTING

Large academically affiliated research hospital.

PATIENT(S)

A total of 3,004 frozen ET cycles from 1,937 different women with oocyte retrieval and transfer between 2012 and 2017.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Implantation, clinical pregnancy, spontaneous abortion, and live birth.

RESULT(S)

Frozen ETs with oocyte retrieval dates in summer had 45% greater odds of clinical pregnancy (odds ratio [OR], 1.45; 95% confidence interval [CI], 1.15-1.82) and 42% greater odds of live birth (OR, 1.42; 95% CI, 1.13-1.79) compared with those with oocyte retrieval dates in winter. A 41% greater odds of clinical pregnancy (OR, 1.41; 95% CI, 1.16-1.71) and 34% greater odds of live birth (OR, 1.34; 95% CI, 1.10-1.62) were observed among transfers with an average temperature at oocyte retrieval in the highest tertile (17.2-33.3 °C) compared with those in the lowest tertile (-17.2-6.7 °C). There were no consistent associations between clinical outcomes and day length at oocyte retrieval or between season, day length, or temperature at transfer of thawed embryos.

CONCLUSION(S)

Warmer temperatures at oocyte retrieval are associated with higher odds of clinical pregnancy and live birth among frozen ET cycles. The consistent associations seen with oocyte retrieval dates and the lack of associations observed with ET dates suggest that any seasonality effects on in vitro fertilization success are related to ovarian function and not uterine receptivity.

Seasonal Influence on Assisted Reproductive Technology Outcomes: A Retrospective Analysis of 1409 Cycles

Background:

It is well known that seasonal variations influence natural conception and birth rates variably in different populations. It has been hypothesised that similar seasonal influences may affect treatment outcomes following assisted reproductive technology (ART). However, most studies report conflicting results.

Aim:

The aim of the study is to elucidate whether seasonality had any impact on the treatment success of the ART program.

Study Setting and Design:

We conducted a retrospective cohort study at a university-level tertiary care hospital in South India.

Materials and Methods:

All couples who underwent ART between January 2012 and December 2016 were included in the study. We divided the study population into three groups based on the seasonal differences experienced in our region. The primary outcome was live birth rate (LBR).

Statistical Analysis:

Univariate and multiple logistic regression models were used to compare outcomes and results reported as odds ratio (OR) and 95% confidence interval (CI).

Results:

Univariate analysis revealed no significant difference in LBR in monsoon season (174/651, 26.7% vs. 83/319, 26.0%; OR 1.04, 95% CI 0.77,1.41; P = 0.81) as compared to summer. However, LBR was significantly higher in winter season (114/341, 33.4% vs. 83/319, 26.0%; OR 1.43; 95% CI: 1.02, 2.00; P = 0.04). Further, multivariate analysis following adjustment for various confounding factors revealed no significant statistical difference in LBR in monsoon (adjusted odds ratio [aOR], 0.92; 95% CI: 0.66, 1.26; P = 0.59) or winter (aOR 1.32; 95% CI: 0.92, 1.88; P = 0.13) as compared to summer season.

Conclusion:

The current study found no significant effect of seasonal variation on LBR following ART.

Seasonal variation, temperature, day length, and IVF outcomes from fresh cycles

PURPOSE

It is known that delivery rates from spontaneous conception vary according to season which may be due to cultural or environmental factors; however, conflicting data exist regarding whether outcomes from IVF are also seasonally dependent. The present study was designed to test the hypothesis that the season at oocyte retrieval is associated with livebirth after fresh transfer.

METHODS

Dates of oocyte retrieval for all autologous cycles in our IVF program between January 2012 and December 2017 were categorized by season. Dates were linked to local temperature (min, max, average) and day length obtained from meteorological records. Average maximum temperature and day length were categorized into tertiles. Multivariable logistic regression, adjusted for age and quadratic age, were used to model odds (aOR) of implantation, clinical pregnancy, spontaneous abortion, and livebirth.

RESULTS

Patient characteristics were similar across seasons. As expected, temperature and day length varied by season. When compared with cycles started during winter, there was no difference in the age-adjusted odds of livebirth for the other three seasons (spring: aOR: 0.97, 95% CI: 0.82-1.13; summer: aOR: 1.05, 0.90-1.23; fall: aOR: 0.98, 0.84-1.15). There was a positive linear trend between temperature and odds of implantation, and clinical pregnancy (p value, test for linear trend (implantation, p = 0.02; clinical pregnancy, p = 0.01)) but no association with livebirth for temperature or day length.

CONCLUSIONS

We found that season at oocyte retrieval was not associated with livebirth, contrary to patterns seen in naturally conceived populations. However, our data did suggest modestly higher odds of clinical pregnancy for retrievals in June and July, and that higher temperature at time of retrieval was associated with higher odds of clinical pregnancy but not livebirth.

The influence of seasonal variations on in vitro fertilization and fresh/frozen embryo transfer: a retrospective study

PURPOSE

To evaluate whether seasonal variations can affect the outcomes of in vitro fertilization (IVF) and embryo transfer (ET).

METHODS

The data of 2868 IVF-ET cycles over 5 years from patients treated for fallopian tube factors, oligospermia, and asthenospermia were collected retrospectively. The cycles were divided into four seasonal groups based on the day of ET. All cycles were performed using the gonadotropin-releasing hormone agonist and antagonist protocols. The ovarian response, embryo quality, and pregnancy outcomes were compared among groups. In addition, 4106 frozen embryo transfer (FET) cycles performed during the same period were analyzed, and the pregnancy outcomes were compared among the four seasonal groups.

RESULTS

The total dose of gonadotropin in the winter group (2106.04 ± 705.57 IU) was higher than the doses in the spring and summer groups (1994.06 ± 674.95, 2009.07 ± 742.26 IU, P < 0.05). The numbers of total oocytes, matured oocytes, fertilizations, cleavages, and high-quality embryos were comparable among seasonal groups (P > 0.05). Significant differences were not observed among seasonal groups in ET or FET for the implantation rate, clinical pregnancy rate, live birth rate, and miscarriage rate (P > 0.05).

CONCLUSION

Seasonal variations have little influence on the outcomes of IVF-ET and FET. IVF-ET or FET treatment can be performed during any season.

Culture systems: physiological and environmental factors that can affect the outcome of human ART

Many aspects of the embryo culture environment have been shown to affect embryo development and the subsequent outcomes of human ART. It is now becoming increasingly evident that embryo and later development can be affected by events and conditions that occur before, perhaps long before, the oocytes and sperm are collected and brought together in the ART laboratory. These include diet and metabolic disorders, general health and disease, physical and psychological stress, exposure to environmental estrogens and other toxins, pharmaceuticals, alcohol, smoking, and drug abuse. This paper discusses the known and potential effects of season of the year (or temperature) and environmental air pollution on the outcomes of human ART. It may be useful to advise ART patients to avoid high environmental temperature and air pollution. In addition, it is important for clinical embryologists to recognize that adverse outcomes may result from such exposures, and to incorporate this into the analysis of clinic data for the purposes of quality management.

Seasonal variation in assisted conception cycles and the influence of photoperiodism on outcome in in vitro fertilization cycles

The effect of seasonality and daylight length on mammalian reproduction leading to spring births has been well established, and is known as photoperiodism. In assisted reproduction there is much greater uncertainty as to the effect of seasonality. This was a 4-year retrospective analysis of 2709 standardised cycles of IVF/ICSI. Data was analysed with regard to the 1642 cycles occurring during the months of extended daylight (Apr-Sept) and those 1067 cycles during winter months of restricted light length (Oct-Mar). The results showed that there was significant improvement in assisted conception outcomes in cycles performed in summer (lighter) months with more efficient ovarian stimulation 766iu v880iu/per oocyte retrieved (p=0.006). There was similarly a significantly improved implantation rate per embryo transferred 11.42% vs 9.35% (p=0.011) and greater clinical pregnancy rate 20% vs 15% (p=0.0033) during summer cycles. This study appears to demonstrate a significant benefit of increased daylight length on outcomes of IVF/ICSI cycles. Whilst the exact mechanism of this is unclear, it would seem probable that melatonin may have actions at multiple sites and on multiple levels of the reproductive tract, and may exert a more profound effect on outcomes of assisted conception cycles than has been previously considered.

Lack of seasonal variations in fertilization, pregnancy and implantation rates in women undergoing IVF

BACKGROUND

Several studies have investigated seasonal variations during IVF. Their results are contradictory, especially concerning fertilization and pregnancy rates. The aim of the present study was to re-evaluate these parameters using a large number of IVF cycles.

METHODS

A total of 7368 IVF cycles conducted in Switzerland between 1995 and 2003 were retrospectively analysed. To avoid a bias in the evaluation of the fertilization rate, only IVF cycles without ICSI were considered for analysis. Cycles were assigned to seasons according to the date of the beginning of stimulation.

RESULTS

There were no statistically significant differences between the seasons concerning the fertilization, the pregnancy and the implantation rates. However, statistically significant variables deciding on the outcome of an IVF cycle are age, centre, aetiology of infertility and day of transfer.

CONCLUSIONS

There were no statistically significant seasonal differences in central Europe (Switzerland) that influenced the outcome of IVF treatment. The only statistically significant variables of IVF outcome were age, centre, aetiology of infertility and day of transfer. A change to routine fertility treatment concerning the different seasons should therefore not be taken into account.

Seasonality and human in vitro fertilization outcome

Seasonal changes in spontaneous fecundity have been observed in several human populations, but it is not clear whether the same applies to human in vitro fertilization-embryo transfer (IVF) procedures. In the present study, 2067 patients undergoing their first IVF attempt between the years 1998 and 2003 were grouped into four 'seasons' (December-February, March-May, June-August, September-November) according to the day on which they were administered human chorionic gonadotropin. Several parameters known to affect IVF outcome (including ovarian response to gonadotropins, sperm and oocyte quality, fertilization rate, embryo quality, pregnancy and implantation rates) were considered and potential changes among the four seasonal periods were analyzed. Moreover, some confounding variables (sperm quality, age, duration of infertility, indications for IVF) were controlled for. Overall, pregnancy rate per oocyte pick-up and per embryo transfer of 32.5% and 35.8%, respectively, as well as implantation rate of 18.9%, were recorded. None of the observed IVF-related parameters showed any significant change clearly related to a specific seasonal period, their fluctuations throughout the year being randomly determined. Ovarian responsiveness to gonadotropins, quality of gametes and embryos, and fertilization and implantation processes were apparently not significantly affected by seasonality. It is concluded that the results of a good-quality IVF program in humans are not significantly affected by the season of the year in which the IVF attempt is accomplished; therefore, season is not a relevant factor to be considered when planning an IVF treatment.

Do lunar phases affect conception rates in assisted reproduction?

OBJECTIVES

To assess the effect of the phases of the moon on pregnancy rates in humans following in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) treatment.

DESIGN

Retrospective, observational study.

SETTING

Reproductive Medicine Unit, Liverpool Women's Hospital.

PATIENT

Complete data for all women undergoing assisted conception procedures over a period of 13 years (1995-2002).

INTERVENTION

Assisted conception procedures--IVF and ICSI.

MAIN OUTCOME MEASURES

Biochemical pregnancy that is positive pregnancy test result following embryo transfer.

RESULTS

There was no significant effect of any lunar phase on the incidence of biochemical pregnancy (p-value 0.71). Age of the woman significantly affects the chances of pregnancy, (OR 0.95, 95% CI 0.91, 0.998, and p-value 0.04). The chances of pregnancy rises significantly with increase in the number of embryos replaced from 1 to 2 (OR 2.97, CI 1.36, 6.48, and p-value 0.01).

CONCLUSION

Pregnancy rates in humans, following assisted conception, appears to be independent of the effect of the lunar phase during which embryo transfer is carried out.

The influences of weather on patients with different ovarian responses in the treatment of assisted reproductive technology

PURPOSE

The purpose of this study was to evaluate the influences of tropical weather on patients with different ovarian responses in the treatment of assisted reproductive technology.

METHODS

Six-hundred fourty-seven women underwent their first treatment cycles were retrospectively analyzed. Patients received embryo transfer either 3 days or 5 days after oocyte retrieval, depending on the number and quality of embryos on day-2.

RESULTS

Significant correlations were demonstrated in the top quality embryo rates of day-3 and day-5 embryo transfers with temperature, humidity, and atmosphere pressure. The cumulative light hours negatively correlated with the implantation and pregnancy rates of day-3 embryo transfer (-.282 and -.282, respectively), while they positively correlated with those of day-5 embryo transfer (.225 and .224, respectively).

CONCLUSIONS

These results clearly suggest that weather may exert influences on the outcome of assisted reproductive technology. Patients with different ovarian responses or blastocyst culture and transfer may modify weather influences.

Environmental and occupational factors affecting fertility and IVF success

Reproductive function has been shown to be sensitive to changes in the physical, psychosocial and chemical environments. Although reproductive effects of occupational exposure to hazardous chemicals have been well documented in the literature, the potential effects of chemical contaminants at levels representative of contemporary exposures in the general population are much less certain. Evidence for adverse effects of exposure to environmental contaminants is more conclusive among the lower animals than for humans where considerable controversy remains. In addition to potential reproductive hazards of exposure to environmental contaminants, there is also evidence for adverse reproductive effects of the physical and psychosocial environments. In this review we focus on the difficulties involved in linking exposure to putative hazardous substances in environmental and occupational settings to adverse reproductive outcomes, especially success of IVF procedures. We highlight the plausibility of adverse events through animal and cell studies and the application of these results to the interpretation of human data. We consider both the male and female partners since it is essentially their combined contributions of gametes which may be affected by chemicals, which lead to successful outcomes.

Do lunar cycles influence in vitro fertilization results?

PURPOSE

Our objective was to investigate the lunar influence on IVF-ET outcomes.

METHODS

Between 1992 and 1999 we have completed 7572 preprogrammed IVF-ET treatment cycles with the same stimulation protocol in two outpatient units. (Vienna, Austria and Budapest, Hungary) Multiple regression (SAS; proc Logistic) and two separate analyses were performed on pregnancy rates using a harmonic sinoidal trend based on the synodic and anomalistic lunar cycles respectively.

RESULTS

The overall pregnancy rate was 30.9%. The amplitude of harmonic sinoidal, trend for the synodic lunar cycles was chi2 = 1.63,2d.f., p = 0.44 and chi2 = 6.27,2d.f., p = 0.044 for the anomalistic moon periods. For the anomalistic lunar months the amplitude of harmonic sinoidal trend was borderline in terms of higher pregnancy rates with the moon in Perigee.

CONCLUSION

The cause of seasonal changes in IVF-ET outcomes is probably very complex. Our results indicate that lunar influence may only be one of the contributing factors. Further studies are needed to clarify unexplained fluctuations of pregnancy outcomes.