“I always got pregnant very easily. Then suddenly, nothing worked anymore.”
Nathalie is a 38-year-old mom from Sweden. She and her partner have a 9-year-old child, and in July 2022 they lost their baby boy just 2 days after birth because of a blood clot caused by lack of oxygen during delivery. In her words, trying again felt like “a way to deal with the sorrow.”
From “I get pregnant easily” to “why is nothing working?”
For most of her life, Nathalie had never struggled to get pregnant. After their loss in 2022, she quickly conceived again, but that pregnancy ended in a chemical pregnancy in December 2022. That had never happened to her before.
Month after month went by with no pregnancy.
In March 2023, she and her partner sought help from a private doctor. She was prescribed Letrozole and used Ovidrel to trigger ovulation for 3 cycles—even though she already ovulated on her own, just a little later than average. Still, no success.
They tested her husband’s sperm. The results came back “normal/OK but not great.” Since they already had children together and had conceived before, they decided to move forward with IVF, thinking maybe egg quality or sperm quality had changed.
Two egg retrievals, good embryos… and still no baby
They did two egg retrievals:
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The first retrieval didn’t go very well.
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The second retrieval produced 17 eggs and 7 blastocysts with great quality.
They did one fresh transfer from the first retrieval—no pregnancy.
Then they prepared for frozen transfers from the second retrieval.
They had to wait two cycles before doing the first frozen transfer. In the month between the second retrieval and that first frozen transfer, they tried naturally and she actually got pregnant again (September 2023). That pregnancy also ended in a chemical pregnancy.
After that, they did two frozen transfers with good-quality embryos.
Both transfers failed—no pregnancy.
Nathalie kept feeling something very specific:
“I felt that the embryos were starting to implant. I recognized the ache from my other successful pregnancies. But I felt a very severe pain that I did not recognize. Now I know it was when the embryos were pushed away.”
She had normal workups, good embryos, and repeated failed transfers. She had been pregnant before. Something was missing.
The menstrual blood test that changed everything
In December 2023, after the second failed frozen transfer, Nathalie decided to do a menstrual blood test that looks for hidden problems in the uterine lining, including viruses.
The sample was simply menstrual fluid, which naturally contains the same endometrial cells that doctors sample in a biopsy.
When the results came back in early January 2024, they finally showed something new:
HHV-6 was detected in her uterus.
Nathalie had never heard of this virus before. She started searching and learned that Human Herpesvirus 6 (HHV-6) is a herpes-family virus that can hide inside the cells of the uterine lining and may be linked to infertility and early pregnancy loss in some women.
She immediately contacted her IVF clinic.
Antiviral treatment and calming the immune system
Her IVF doctor prescribed valaciclovir (an antiviral similar to valacyclovir/acyclovir).
Both Nathalie and her partner took valaciclovir for about one month.
Because she read that HHV-6 can activate natural killer (NK) cells, making the immune system more likely to attack embryos, she and her doctor also decided to add immune-calming treatments:
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She received 4 intralipid infusions.
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She took a low dose of valaciclovir for the first 8 weeks of pregnancy on medical advice.
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Her IVF doctor also prescribed Prednisolone, a steroid, “just in case” to further calm the immune response.
These decisions were made together with her doctors, based on her unique history and risk profile.
The next transfer… and a very different outcome
In early February 2024, after antiviral and supportive treatment, Nathalie had her third frozen embryo transfer.
This time, it worked.
She became pregnant and, at the time she shared her story, she was 35 weeks pregnant with a healthy pregnancy progressing well.
“Thanks to HHV-6 testing and antivirals, I finally got successfully pregnant.”
Looking back, Nathalie also learned that COVID-19 infection can sometimes reactivate HHV-6. She had COVID while she was 23 weeks pregnant with the baby they lost in July 2022. She believes this may have played a role in activating the virus in her uterus.
What Nathalie’s story shows
Nathalie’s journey shows how:
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You can have normal tests, good embryos, and repeated failed transfers,
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And still have a hidden virus in the uterus that standard fertility tests never check.
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A menstrual-fluid test that looks at cells from the uterine lining can uncover HHV-6.
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Antiviral treatment and careful immune support—under a doctor’s guidance—may help calm the virus and improve the chances of implantation.
Her story doesn’t mean every woman with infertility has HHV-6. But it does show that for some women with “unexplained” infertility and failed IVF, looking for hidden infections in the uterus can finally reveal a missed cause—and open the door to a very different outcome.
“It made me infertile. The virus did not allow any embryo to stay. When we finally found it and treated it, the embryo could stay.”
If Nathalie’s story feels familiar—normal tests, good embryos, but repeated losses or failed transfers—it may be worth asking your doctor whether HHV-6 testing of the uterine lining (including menstrual-fluid–based testing) could be a missing step in your journey.
(Always talk with your own doctor before starting or changing any treatment. Nathalie’s story is one woman’s experience, not a guarantee of results.)