Manniche, V., Furst, T., Schmeling, M., Gilthorpe, J., & Hansen, P. R. (2025). Rates of successful conceptions according to COVID-19 vaccination status: Data from the Czech Republic. The International journal of risk & safety in medicine, 36(4), 302-306. https://doi.org/10.1177/09246479251353384
Manniche V, Furst T, Schmeling M, Gilthorpe J, Hansen PR. Rates of successful conceptions according to COVID-19 vaccination status: Data from the Czech Republic. Int J Risk Saf Med. 2025;36(4):302-306. doi:10.1177/09246479251353384
Manniche, Vibeke, et al. "Rates of successful conceptions according to COVID-19 vaccination status: Data from the Czech Republic." The International journal of risk & safety in medicine, vol. 36, no. 4, 2025, pp. 302-306.
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Adverse effects of COVID-19 vaccination on human menstrual cycle characteristics have been observed, but limited data are available on the relationship between COVID-19 vaccination status and birth rates.
Objectives
Therefore, we used nationwide data from the Czech Republic to examine rates of successful conceptions (SCs), that is, conceptions leading to live births 9 months later, for women who were either vaccinated or unvaccinated against COVID-19 before SC.
Methods
Summary monthly COVID-19 vaccination and birth data for women in the Czech Republic aged 18-39 years were retrieved for the period from January 2021 to December 2023. The numbers of SCs per month per 1000 women were calculated for preconception-vaccinated or unvaccinated women, respectively, as well as the number of SCs per month per 1000 women for all women aged 18-39 years.
Results
During the study period, there were approximately 1,300,000 women aged 18-39 years in the Czech Republic, and the proportion of COVID-19-vaccinated women increased from January 2021 until reaching a steady state of around 70% by the end of 2021. At least from June 2021, SCs per 1000 women were considerably lower for women who were vaccinated, compared to those that were unvaccinated, before SC. Furthermore, SC rates for the vaccinated group were much lower than expected based on their proportion of the total population.
Conclusions
In the Czech Republic, SC rates were substantially lower for women vaccinated against COVID-19 before SC than for those who were not vaccinated. These hypothesis-generating and preliminary results call for further studies of the potential influence of COVID-19 vaccination on human fecundability and fertility.
Eckler R et al., 2025·PloS one·Free full text on PubMed Central
To investigate the impact of the COVID-19 pandemic's onset on clinical and demographic characteristics, pregnancy complications, and monthly conception rates resulting in births through spontaneous conceptions and in-vitro fertilization (IVF) in British Columbia (BC), Canada.
This retrospective population-based cohort study examined individuals who gave birth (both live births and stillbirths) in BC between June 1, 2010, and March 31, 2021, with estimated conception dates from January 1, 2010 to June 30, 2020. Data were obtained from the BC Perinatal Data Registry. Two groups were identified based on the estimated conception date: the pre-pandemic conception group (conception from January-1-2010 to February-29-2020) and the pandemic conception group (conception from March-1-2020 to June-30-2020). A time series forecasting method (ARIMA) was employed to observe trends in conception rates during the study period.
304,244 individuals with pregnancies resulting in live births or stillbirths during the study period were evaluated. A total of 429,843 such conceptions were included in the study: 417,753 (97.2%) occurring before the onset of the pandemic and 12,090 (2.8%) in the pandemic period. In June 2020, conceptions resulting in births decreased by 26.6% compared with June 2019. Trends in conceptions resulting in live births were similar, with a conception rate of 235.2 per 100,000 women of reproductive age in June 2020, compared with the expected rate of 305.0 per 100,000. In March 2020, 0.5% of conceptions that resulted in births ended in stillbirths, compared to 1.7% in March 2019. IVF conceptions ending in births declined during the pandemic, dropping to 2.5 and 2.8 per 100,000 in March and April 2020, respectively, compared with the expected 13.1 per 100,000. However, by June 2020, these rates began to recover toward the expected levels. Rates of gestational diabetes mellites (GDM), gestational hypertension (GHTN), and postpartum intensive care unit (ICU) admissions were similar before and during the COVID-19 pandemic.
During the challenging period of the COVID-19 pandemic in BC, couples may have chosen to delay conception. Rates of conceptions resulting in stillbirths remained relatively unchanged. IVF conception rates were impacted by the suspension of elective procedures. Preterm birth rates slightly exceeded expected levels but remained within normal fluctuations, and small increases in GDM and GHTN prevalence were also observed.
Bouchard TP et al., 2022·J Womens Health (Larchmt)
Some studies have suggested minor changes in the menstrual cycle after COVID-19 vaccination, but more detailed analyses of the menstrual cycle are needed to evaluate more specific changes in the menstrual cycle that are not affected by survey-based recall bias. Using a pretest-post-test quasi-experimental evaluation of menstrual cycle parameters before and after COVID-19 vaccination, we conducted an anonymous online survey of two groups of North American women who prospectively monitor their menstrual cycle parameters daily including bleeding patterns, urinary hormone levels using the ClearBlue Fertility Monitor, or cervical mucus observations. The primary outcome measures were cycle length, length of menses, menstrual volume, estimated day of ovulation (EDO), luteal phase length, and signs of ovulation. Perceived (subjective) menstrual cycle changes and stressors were also evaluated in this study as secondary outcome measures. Of the 279 women who initiated the survey, 76 met the inclusion criteria and provided 588 cycles for analysis (227 pre-vaccine cycles, 145 vaccine cycles, 216 post-vaccine cycles). Although 22% of women subjectively identified changes in their menstrual cycle, there were no significant differences in menstrual cycle parameters (cycle length, length of menses, EOD, and luteal phase length) between the pre-vaccine, vaccine, and post-vaccine cycles. COVID-19 vaccines were not associated with significant changes in menstrual cycle parameters. Perceived changes by an individual woman must be compared with statistical changes to avoid confirmation bias.
Edelman A et al., 2022·Obstetrics and gynecology·Free full text on PubMed Central
To assess whether coronavirus disease 2019 (COVID-19) vaccination is associated with changes in cycle or menses length in those receiving vaccination as compared with an unvaccinated cohort. We analyzed prospectively tracked menstrual cycle data using the application "Natural Cycles." We included U.S. residents aged 18-45 years with normal cycle lengths (24-38 days) for three consecutive cycles before the first vaccine dose followed by vaccine-dose cycles (cycles 4-6) or, if unvaccinated, six cycles over a similar time period. We calculated the mean within-individual change in cycle and menses length (three prevaccine cycles vs first- and second-dose cycles in the vaccinated cohort, and the first three cycles vs cycles four and five in the unvaccinated cohort). We used mixed-effects models to estimate the adjusted difference in change in cycle and menses length between the vaccinated and unvaccinated cohorts. We included 3,959 individuals (vaccinated 2,403; unvaccinated 1,556). Most of the vaccinated cohort received the Pfizer-BioNTech vaccine (55%) (Moderna 35%, Johnson & Johnson/Janssen 7%). Overall, COVID-19 vaccine was associated with a less than 1-day change in cycle length for both vaccine-dose cycles compared with prevaccine cycles (first dose 0.71 day-increase, 98.75% CI 0.47-0.94; second dose 0.91, 98.75% CI 0.63-1.19); unvaccinated individuals saw no significant change compared with three baseline cycles (cycle four 0.07, 98.75% CI -0.22 to 0.35; cycle five 0.12, 98.75% CI -0.15 to 0.39). In adjusted models, the difference in change in cycle length between the vaccinated and unvaccinated cohorts was less than 1 day for both doses (difference in change: first dose 0.64 days, 98.75% CI 0.27-1.01; second dose 0.79 days, 98.75% CI 0.40-1.18). Change in menses length was not associated with vaccination. Coronavirus disease 2019 (COVID-19) vaccination is associated with a small change in cycle length but not menses length.
Karaman E et al., 2025·Vaccines (Basel)·Free full text on PubMed Central
This study aimed to elucidate the effects of messenger RNA (mRNA) and inactivated coronavirus disease 2019 (COVID-19) vaccines on ovarian histology and reserve in rats. Thirty female Wistar albino rats, aged 16-24 weeks, were randomly divided into three groups (n = 10): control, mRNA vaccine, and inactivated vaccine groups. Each vaccine group received two doses (on day 0 and day 28) at human-equivalent doses. Four weeks post-second vaccination, ovarian tissues were harvested for analysis. Immunohistochemical analysis was performed to evaluate the expression of transforming growth factor beta-1 (TGF-β1), vascular endothelial growth factor (VEGF), caspase-3, and anti-Müllerian hormone (AMH) in ovarian follicles. Both vaccines induced significant increases in TGF-β1, VEGF, and caspase-3 expression, with more pronounced effects in the mRNA vaccine group. Conversely, AMH expression in the granulosa cells of primary, secondary, and antral follicles showed marked reductions (p < 0.001). The counts of primordial, primary, and secondary follicles decreased significantly in the inactivated vaccine group relative to controls and further in the mRNA vaccine group compared to the inactivated group (p < 0.001). Additionally, the mRNA vaccine group exhibited a decrease in antral and preovulatory follicles and an increase in atretic follicles compared to the other groups (p < 0.05). The serum AMH level was diminished with the mRNA vaccination in comparison with the control and inactivated groups. Our findings suggest that both mRNA and inactivated COVID-19 vaccines may detrimentally impact ovarian reserve in rats, primarily through accelerated follicular loss and alterations in apoptotic pathways during folliculogenesis. Given these observations in a rat model, further investigations into the vaccines' effects on human ovarian reserve are needed.
Tomáš Fürst, Jonathan D Gilthorpe, Peter Riis Hansen, Vibeke Manniche, Max Schmeling
T Fürst, Jon Gilthorpe, J Gilthorpe, Pete Hansen, P Hansen, V Manniche, M Schmeling
PMID 40534497 40534497 DOI 10.1177/09246479251353384 10.1177/09246479251353384 Manniche et al. 2025, Manniche 2025
Cite this article
Manniche, V., Furst, T., Schmeling, M., Gilthorpe, J., & Hansen, P. R. (2025). Rates of successful conceptions according to COVID-19 vaccination status: Data from the Czech Republic. The International journal of risk & safety in medicine, 36(4), 302-306. https://doi.org/10.1177/09246479251353384
Manniche V, Furst T, Schmeling M, Gilthorpe J, Hansen PR. Rates of successful conceptions according to COVID-19 vaccination status: Data from the Czech Republic. Int J Risk Saf Med. 2025;36(4):302-306. doi:10.1177/09246479251353384
Manniche, Vibeke, et al. "Rates of successful conceptions according to COVID-19 vaccination status: Data from the Czech Republic." The International journal of risk & safety in medicine, vol. 36, no. 4, 2025, pp. 302-306.
