Researchers in a 2023 study performed a meta-analysis and combined the results of 21 studies that compared the impact of the COVID-19 vaccine on IVF and pregnancy outcomes, and found no differences.
The COVID-19 pandemic lasted for about 3 years beginning in 2019, with billions of people receiving the mRNA vaccine to combat infection. Vaccine hesitancy among women trying to conceive was common due to a lack of data on its effect on reproductive health.
Huang et al. (2023) performed a systematic review and meta-analysis that combined the results of 21 studies that compared IVF outcomes for COVID-19 vaccinated and unvaccinated women.
Key information:
- Studies were observational (cohort, cross-sectional, or case-control studies).
- Eligible studies included women who had been vaccinated partially, fully or boosted (received a full dose plus an additional booster).
- Studies were published between 2021 and 2022, took place in 5 countries (Israel, China, the US, Italy and Spain), and used different vaccine types (subgroup analyses were performed).
- Most studies were comparable in terms of female age.
- The primary outcome was egg retrieval numbers and clinical pregnancy rate.
🔗 Original studies are referenced in this post or within the linked Remembryo posts.
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No difference in IVF cycle characteristics for COVID-19 vaccinated vs unvaccinated women
This study found no difference in the number of days women were stimulated, gonadotropin dose uses, peak estradiol (E2) levels and endometrial thickness.
Two of the studies had higher heterogeneity (I2 of 72% and 56%), indicating that these studies weren’t very consistent in their outcomes. For gonadotropin doses, there was no heterogeneity, so these studies had consistent results.
No difference in IVF outcomes for COVID-19 vaccinated vs unvaccinated women
This study found no difference in the number of eggs retrieved, mature egg rate, fertilization rate, blastocyst formation rate, good quality embryo rate and euploidy rate. You can see the results below.
There was no heterogeneity in several of the studies, indicating that the results for that outcome were consistent between studies. There was a lot of heterogeneity for the “good quality embryo rate” outcome, so these studies varied in their results.
No difference in IVF pregnancy outcomes for COVID-19 vaccinated vs unvaccinated women
They also didn’t find any differences in biochemical (hCG positive) pregnancy rates, clinical pregnancy rates and ongoing birth rates. The heterogeneity was low for these studies, so the results were consistent between the studies.
No differences in egg retrieval numbers or clinical pregnancy rate based on type of COVID-19 vaccine used
In this study, their primary outcome was the number of eggs retrieved and clinical pregnancy rate. They did a subgroup analysis and compared these outcomes against the type of COVID-19 vaccine used.
For the number of eggs retrieved, they found no differences in studies involving women who were COVID-19 vaccinated with the mRNA vaccine, inactivated vaccine, protein-based vaccine or mixed.
Similarly, they found no difference for the clinical pregnancy rate and the type of vaccine used.
Some information on miscarriage from the studies
This is an updated section that I added due to the large number of people who were concerned that this study didn’t include miscarriage data. I did some light digging into the 6 studies that reported on ongoing pregnancy rates (since those studies probably have the potential to include miscarriage rates).
- 2 of the 6 studies didn’t include miscarriage data
- Aharon et al. (2022) found no difference in biochemical losses for vaccinated vs unvaccinated (17.1% vs 13.8%, aOR 1.21, 95% CI 0.69-2.14), or clinical pregnancy loss (18.0% vs 12.0%, aOR 1.02, 95% CI 0.51-2.06).
- Jacobs et al. (2022) found no difference in miscarriage rate (7.1% vs 5.0%, aOR, 2.15; 95% CI, 0.62-7.47).
- Wu et al. (2022) found no difference in early miscarriage before 12 weeks (15.0% vs 12.1%, P = 0.399).
- Cao et al. (2022) found no difference in early miscarriage (11.1% vs 11.2%; aOR, 1.003 (0.643–1.563).
I’m not sure why they didn’t include this data, but it may have to do with how each study defines miscarriage (some report miscarriage, early miscarriage or clinical pregnancy loss). In some cases the study didn’t define miscarriage at all. This makes it difficult to pool the data.
Conclusions
For women who were vaccinated or unvaccinated against COVID-19, this study found no differences in IVF cycle characteristics:
- Number of days stimulated
- Amount of gonadotropins used
- Peak E2 levels
- Endometrial thickness
IVF outcomes:
- Number of eggs retrieved
- Mature egg rate
- Fertilization rate
- Blastocyst formation rate
- Good quality embryo rate
- Euploidy rate
Or in pregnancy outcomes:
- Biochemical pregnancy rate
- Clinical pregnancy rate
- Ongoing birth rate
Subgroup analyses found no differences in the number of eggs retrieved and clinical pregnancy rates based on the type of vaccine used.
Limitations of this meta-analysis include that the included studies were observational and may contain bias, most studies investigated mRNA vaccines and not other types of vaccines, and some studies were small. There was also no data on miscarriage rates. The researchers call for more larger and multicenter studies.
“In conclusion, our work did not find significant differences in cycle characteristics, laboratory parameters, and fertility outcomes between vaccinated and unvaccinated women during assisted reproductive treatment.”
Huang et al. (2023)
Reference
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About Embryoman
Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Master’s in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.
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