Babesia pregnancy transmission is real and underrecognized. In this Inside Lyme case study, I discuss two mothers who unknowingly passed this tick-borne parasite to their babies.

Saetre and colleagues first described these cases in the Journal of the Pediatric Infectious Disease Society in 2017.

This parasite can be contracted from the bite of a deer tick, a blood transfusion, or during pregnancy. The CDC recognizes that transmission can occur in utero.

First Mother with Babesia Pregnancy

The first mother lived in Westchester County, New York, an area endemic for Lyme disease. I live and practice medicine in the same county.

The mother was diagnosed with Lyme disease in her third trimester at 32 weeks gestation. She presented with an erythema migrans rash (EM). She was treated with amoxicillin.

I advise mothers that neither amoxicillin nor azithromycin is effective against other common tick-borne infections such as Ehrlichia, Anaplasmosis, and Babesia.

The doctors followed the mother. She was positive by IgM laboratory testing two weeks after her diagnosis of Lyme disease. A positive IgM test would be consistent with an early infection. I would have treated the mother.

The mother was not treated. The mother and her baby boy went home.

The mother’s baby boy was diagnosed and treated 4½ weeks after going home.

The mother was again positive. The tests were now positive by an IgG western blot. The conversion from a positive IgM western blot test to a positive IgG western blot test was further evidence that the mother contracted this infection during her third trimester. I would still have treated the mother.

Again the mother was not treated—an example of how tick-borne infections get dismissed even with clear evidence.

Second Mother with Babesia Pregnancy

The second mother lived in Putnam County, New York, an area endemic for Lyme disease. Putnam County is located just north of Westchester County.

The mother initially had muscle soreness and a fever for two weeks. She was diagnosed with Lyme disease in her third trimester at 37 weeks gestation. She presented with an EM rash and was treated with amoxicillin.

The mother’s laboratory tests for a tick-borne infection were not positive at the time of her EM rash.

Her baby girl was tested after delivery. Her girl’s blood test was positive for Babesia microti by PCR. The doctors did not look for the parasite in her baby girl’s red blood cells under the microscope. The doctors concluded that the baby girl showed no symptoms. Her baby girl was not treated.

The mother and her baby girl went home.

Her baby girl had evidence of this parasite in her red blood cells when she was 18-days-old. Her girl was hospitalized and treated with a series of antibiotics, antiparasitic medications, and a blood transfusion.

The mother’s blood tests were now positive by PCR, IgM, and IgG tests. The conversion from a positive IgM to a positive IgG was further evidence that the mother contracted this infection during her third trimester.

The mother was not treated. The baby girl was.

Clinical Takeaway

Congenital Babesia transmission occurs when mothers acquire infection during pregnancy, yet both mothers in these cases remained untreated despite positive serology while their infants required delayed treatment weeks after birth. Critical maternal-fetal medicine considerations:

• Amoxicillin treats Lyme disease but not Babesia or other tick-borne coinfections (Ehrlichia, Anaplasmosis)—pregnant women with erythema migrans rash in endemic areas require coinfection screening and consideration of antiparasitic therapy
• IgM to IgG seroconversion during third trimester confirms acute maternal infection with high vertical transmission risk—both mothers showed this pattern yet received no treatment while their infants developed parasitemia
• Neonatal symptoms can be delayed weeks after birth—one infant appeared asymptomatic initially but required hospitalization with blood transfusion at 18 days of age when parasitemia became apparent
• Medical dismissal of maternal infection despite positive serology creates preventable infant morbidity—both mothers had laboratory confirmation but were denied treatment while their infants subsequently required intensive intervention

Frequently Asked Questions

Can Babesia be passed from mother to baby during pregnancy?

Yes. Babesia pregnancy transmission can occur in utero. Both mothers in this case passed the infection to their babies during the third trimester.

Does treating Lyme disease treat Babesia too?

No. Amoxicillin and doxycycline treat Lyme disease but are not effective against Babesia, which requires different medications like atovaquone and azithromycin.

Should pregnant women with Lyme disease be tested for Babesia?

Yes. Pregnant women diagnosed with Lyme disease should be tested for co-infections including Babesia, especially if they live in or traveled to endemic areas.

Why weren’t the mothers treated?

Despite positive test results, both mothers were left untreated—an example of how babesia pregnancy cases can be dismissed even with clear laboratory evidence.

What happened to the babies?

Both babies were eventually diagnosed and treated, but not until weeks after going home. One baby required hospitalization and a blood transfusion at 18 days old.

For comprehensive Babesia information organized by topic—including symptoms, testing, treatment, blood transfusion risks, and special populations—visit our complete Babesia guide.

Related Reading

• Babesia and Lyme: What Patients Need to Know
• Congenital Babesia: When Only One Twin Gets Infected
• Babesia Treatment Protocol: What Works When Standard Therapy Fails

References

1. Saetre K, Godhwani N, Maria M, et al. Congenital Babesiosis After Maternal Infection With Borrelia burgdorferi and Babesia microti. J Pediatric Infect Dis Soc. 2017.