Rocky Mountain Spotted Fever Treatment in Pregnancy: A Case Report
RMSF in pregnancy may resemble HELLP syndrome
A rash or known tick bite may be absent
Prompt doxycycline treatment can be critical
Rocky Mountain spotted fever treatment in pregnancy requires prompt clinical recognition because the infection can progress rapidly and become life-threatening. Although doxycycline use during pregnancy has historically raised concerns, current CDC guidance recommends doxycycline for suspected Rocky Mountain spotted fever (RMSF), including in pregnant women.
A case report describes a 37-year-old pregnant woman who was admitted to the hospital at 31 weeks gestation because of severe headaches and a fever that had persisted for 1 week.
A few days before admission, she developed night sweats, chills, sweating, shortness of breath, and diarrhea.
Her symptoms began while she was traveling in Washington state. She reported briefly walking in the woods but did not recall a tick bite and had not noticed a rash.
“This is the first case to our knowledge to report RMSF in pregnancy without a significant rash or tick history,” the authors state.
RMSF was initially mistaken for atypical HELLP syndrome
The woman had thrombocytopenia, elevated liver enzymes, anemia, protein in her urine, and a severe headache. She was initially treated for atypical HELLP syndrome, a potentially life-threatening pregnancy complication generally considered a variant of preeclampsia.
Because she also had a fever, clinicians continued investigating an infectious cause and prescribed broad-spectrum antibiotics.
However, 6 hours after the initial antibiotics were started, her condition worsened. She remained febrile and developed severe tachypnea, tachycardia, and a new need for supplemental oxygen.
She was transferred to the intensive care unit. After both maternal respiratory distress and fetal heart rate abnormalities developed, she was intubated and an urgent cesarean section was performed.
“The patient was started on doxycycline immediately after vancomycin was discontinued,” the authors state.
Why doctors suspected Rocky Mountain spotted fever
RMSF became the presumed diagnosis based on the combination of severe headache, fever, malaise, rapidly worsening illness, thrombocytopenia, elevated liver enzymes, and cerebrospinal fluid findings consistent with aseptic meningitis.
“RMSF became the presumed diagnosis due to the clinical criteria of headache, fever, and malaise, laboratory findings notable for thrombocytopenia, transaminitis, acutely worsening disease, and cerebrospinal fluid analysis consistent with aseptic meningitis,” the authors point out.
The patient improved substantially after doxycycline was started. She was extubated 3 days later and discharged home on postoperative day 6.
The infant was born at 31 weeks, remained stable in the neonatal intensive care unit, and showed no evidence of RMSF during the neonatal period.
Early RMSF testing may be negative
The patient’s acute RMSF antibody test was negative. However, later convalescent serology was positive at a titer greater than 1:256.
This illustrates an important diagnostic limitation. Antibodies may not be detectable during the early stage of RMSF, and clinicians should not delay treatment while waiting for confirmatory test results when the clinical suspicion is high.
In the first few days of illness, RMSF is generally a presumptive clinical diagnosis based on symptoms, laboratory abnormalities, exposure risk, and the course of the illness.
RMSF can occur without a rash or known tick bite
RMSF is commonly associated with fever, severe headache, and a spotted rash. However, the classic combination may not be present early in the illness.
The 2024 case report notes that the classic triad of fever, headache, and rash is observed in only 3% of patients during the first 3 days of illness. The authors also report that up to 20% of patients may have an atypical or absent rash.
A separate series of four pregnant women with RMSF reported that the rash may not appear until several days after symptoms begin and cited estimates that 12% to 32% of RMSF cases may occur without a rash.
Patients may also be unaware of a tick bite. Ticks can attach in locations that are difficult to see, and the bite itself may not be noticed.
The absence of a rash or recalled tick bite should therefore not exclude RMSF when a pregnant patient develops an unexplained fever, severe headache, thrombocytopenia, elevated liver enzymes, or rapidly progressive multisystem illness.
RMSF can resemble pregnancy-related complications
Diagnosing RMSF during pregnancy can be especially difficult because several manifestations overlap with pregnancy-related illnesses.
Respiratory distress, acute kidney injury, neurologic changes, thrombocytopenia, and elevated liver enzymes may also occur with preeclampsia or HELLP syndrome.
The presence of fever may raise concern for an infectious diagnosis, particularly when the patient is normotensive, has possible outdoor exposure, or continues to deteriorate despite treatment directed at a pregnancy-related disorder.
Four additional RMSF cases during pregnancy
A 2017 case series described four pregnant women with confirmed RMSF in Sonora, Mexico. All four women presented with fever and a petechial rash and were treated with doxycycline.
All four women survived. However, the three patients infected during the first trimester experienced spontaneous abortions. The fourth patient developed RMSF at 36 weeks gestation and delivered a healthy infant by cesarean section.
The authors proposed that hypotension and placental ischemia, rather than direct fetal infection, may have contributed to pregnancy loss. Available evidence remains limited, and the precise effects of RMSF on the placenta and fetus are not fully understood.
These cases underscore the potential severity of RMSF during pregnancy while also showing that pregnant patients have been treated successfully with doxycycline.
Why doxycycline treatment should not be delayed
The authors of the 2024 case note, “Prompt and timely treatment with doxycycline significantly limits the morbidity and mortality of RMSF in both children and adults.”
The CDC identifies doxycycline as the treatment of choice for RMSF. Treatment is most effective at preventing severe complications when it begins within the first 5 days of illness.
The CDC has also advised clinicians that doxycycline is the recommended treatment for suspected RMSF in adults and children of all ages, including pregnant women. Treatment should begin immediately when RMSF is suspected and should not be delayed pending laboratory confirmation.
Broad-spectrum antibiotics commonly prescribed for other infections may not effectively treat RMSF. The woman in the 2024 case continued to deteriorate after receiving vancomycin and meropenem but improved after doxycycline was started.
How recommendations during pregnancy have changed
A 2001 review illustrates the historical concern surrounding doxycycline during pregnancy. At that time, the authors described chloramphenicol as the recommended treatment for pregnant women because tetracycline-class antibiotics were generally avoided.
Subsequent evidence led to a reassessment of doxycycline. The 2017 case series noted that concerns were largely based on reports involving prolonged courses of older tetracyclines rather than short courses of doxycycline.
The authors concluded that therapeutic doxycycline doses had not been shown to pose a substantial risk of fetal malformation or tooth staining and that the risks of untreated RMSF outweighed the potential medication risks.
Chloramphenicol has been used to treat RMSF in pregnancy, but it carries risks that include bone marrow suppression, aplastic anemia, and gray baby syndrome. It has also been associated with a higher risk of death among patients with RMSF than treatment with tetracyclines.
Is doxycycline safe during pregnancy?
No medication can be described as completely risk-free during pregnancy. However, current evidence has led to greater acceptance of a short course of doxycycline when it is needed to treat a potentially life-threatening rickettsial infection.
Earlier concerns about fetal tooth discoloration and impaired bone growth were primarily linked to older tetracycline drugs and prolonged exposure. Doxycycline binds calcium less readily than older tetracyclines, and available human data have not demonstrated the same pattern of harm with short treatment courses.
When RMSF is suspected, clinicians must weigh any potential medication risk against the immediate dangers of untreated infection. RMSF can progress rapidly, cause multisystem illness, and threaten both the mother and fetus.
The 2024 authors conclude, “Given the potentially dire implications in pregnancy, providers in endemic areas should consider RMSF in the differential of atypical presentations in pregnant women and those with a fever of unknown origin.”
Frequently Asked Questions
What is the recommended treatment for Rocky Mountain spotted fever during pregnancy?
Doxycycline is the recommended treatment for suspected Rocky Mountain spotted fever, including during pregnancy. Treatment should begin promptly when RMSF is suspected rather than waiting for laboratory confirmation.
Can Rocky Mountain spotted fever occur during pregnancy without a rash?
Yes. A rash may appear several days after other symptoms begin, and some patients never develop one. The absence of a rash should not rule out RMSF when the clinical findings suggest the infection.
Can RMSF occur without a known tick bite?
Yes. Many patients do not recall being bitten because ticks may be small, the bite may be painless, and the tick may attach in a location that is difficult to see.
Why can RMSF be mistaken for HELLP syndrome?
Both conditions may involve headache, thrombocytopenia, elevated liver enzymes, and rapidly progressive illness during pregnancy. Fever, possible outdoor exposure, neurologic findings, and deterioration despite treatment for HELLP syndrome may raise concern for an infection such as RMSF.
Can an early RMSF test be negative?
Yes. Antibody tests may be negative during the first days of illness because detectable antibodies have not yet developed. In the 2024 case, the acute antibody test was negative, while a later convalescent test was positive.
Should treatment wait until RMSF test results are available?
No. Delaying treatment can increase the risk of severe illness or death. Doxycycline should be started based on clinical suspicion while diagnostic testing is underway.
Has doxycycline been used successfully during pregnancy?
Yes. The 2024 case and a 2017 series of four pregnant women describe maternal survival following doxycycline treatment. Pregnancy outcomes varied, reflecting the potential severity of RMSF and the limited evidence available from reported cases.
Clinical Takeaway
Rocky Mountain spotted fever may be difficult to recognize during pregnancy when there is no rash, known tick bite, or classic presentation.
The infection may resemble HELLP syndrome because both can involve headache, thrombocytopenia, elevated liver enzymes, and rapidly progressive illness. Early antibody testing may also be negative.
When RMSF is clinically suspected during pregnancy, prompt doxycycline treatment may be critical for protecting both the mother and fetus.
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Why early Lyme disease tests can be negative
References
- Wu J, Dotters-Katz SK, Varvoutis M. Atypical presentation of Rocky Mountain spotted fever in pregnancy. AJP Rep. 2024;14(1):e40-e42.
- Licona-Enriquez JD, Delgado-de la Mora J, Paddock CD, et al. Rocky Mountain spotted fever and pregnancy: Four cases from Sonora, Mexico. Am J Trop Med Hyg. 2017;97(3):795-798.
- Stallings SP. Rocky Mountain spotted fever and pregnancy: A case report and review of the literature. Obstet Gynecol Surv. 2001;56(1):37-42.
- Centers for Disease Control and Prevention. Clinical care of Rocky Mountain spotted fever. CDC. 2025.
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
