Is untreated streptococcal pharyngitis dangerous to a fetus in the late stages of pregnancy?

Untreated Streptococcal Pharyngitis in Late Pregnancy: Risk Assessment

Untreated streptococcal pharyngitis in late pregnancy should be treated promptly with appropriate antibiotics, as the potential for serious maternal and fetal complications—though rare—far outweighs any risks of antibiotic therapy.

Direct Fetal Risk from Group A Streptococcus Pharyngitis

The evidence provided focuses predominantly on Group B Streptococcus (GBS) colonization and neonatal disease prevention, not Group A Streptococcus (GAS) pharyngitis 1. This is a critical distinction: GBS causes neonatal sepsis through vertical transmission during delivery, while GAS pharyngitis is an upper respiratory infection that poses different risks 1.

However, untreated GAS pharyngitis can lead to life-threatening maternal complications that indirectly threaten the fetus:

• A documented case report describes a 28-year-old pregnant woman at 33 weeks gestation who developed pharyngitis with high fever, initially treated inadequately, which progressed to fulminant streptococcal infection resulting in stillbirth of twins and maternal death 2.
• The autopsy revealed systemic dissemination with numerous cocci and fibrin thrombi throughout circulation, demonstrating that streptococcal pharyngitis can progress to invasive disease during pregnancy 2.
• The causative organism (Streptococcus pyogenes) was producing streptococcal pyrogenic exotoxin A, which can trigger toxic shock-like syndrome 2.

Rare but Severe Complications of Untreated Streptococcal Pharyngitis

Beyond immediate maternal sepsis risk, untreated streptococcal pharyngitis can cause:

• Pulmonary-renal syndrome (PRS): A recently reported case describes a 26-year-old male whose untreated streptococcal pharyngitis progressed to post-streptococcal glomerulonephritis, then to diffuse alveolar hemorrhage requiring ICU admission and intubation 3.
• This represents the sixth documented case of streptococcal-induced PRS, which carries high morbidity and mortality rates 3.
• While this case was not in pregnancy, the pathophysiology demonstrates the potential for severe systemic complications from untreated infection 3.

Treatment Recommendations for Pregnant Women

Safe and effective antibiotics are available for streptococcal pharyngitis during pregnancy:

• Penicillin and cephalosporins are the safest antibiotic classes in pregnancy and should be used when endoscopic or clinical evidence of bacterial pharyngitis is present 1.
• Penicillin treatment shortens the acute illness, reduces risk of spread, prevents suppurative complications, and prevents acute rheumatic fever 4.
• Antibiotics that put the fetus at risk—including tetracyclines, aminoglycosides, trimethoprim-sulfamethoxazole, and fluoroquinolones—should be avoided during pregnancy 1, 5.

Clinical Algorithm for Management

When evaluating streptococcal pharyngitis in late pregnancy:

1. Confirm diagnosis with rapid antigen detection test or throat culture to distinguish bacterial from viral pharyngitis 4.

2. Initiate treatment immediately with penicillin or a first-generation cephalosporin if penicillin-allergic (without history of anaphylaxis) 1, 4.

3. Ensure compliance with the full antibiotic course, as pregnant women may be more reluctant to complete prescribed medications 5.

4. Monitor for warning signs of systemic progression: persistent high fever, worsening symptoms despite treatment, respiratory distress, or signs of preterm labor 2.

5. Do not delay treatment waiting for culture results if clinical suspicion is high, as the case report demonstrates rapid progression can occur 2.

Common Pitfalls to Avoid

• Underestimating severity: The documented case of maternal and fetal death from pharyngitis progression demonstrates that seemingly minor infections can become life-threatening in pregnancy 2.
• Inadequate treatment duration: Switching antibiotics due to minor side effects (like pruritus) without completing therapy can lead to treatment failure and progression to serious complications 3.
• Assuming viral etiology without testing: Clinical diagnosis alone is insufficient; bacterial confirmation guides appropriate antibiotic use 4.
• Using contraindicated antibiotics: Fluoroquinolones, while effective for many infections, are contraindicated in pregnancy despite good safety records after accidental use 5.