Ideally be guided by urine culture and local resistance patterns.
| Antibiotic | Pregnancy Considerations |
|---|---|
| Nitrofurantoin | Widely used for cystitis. Generally safe in pregnancy. Usually avoided at term (especially near delivery) and in G6PD deficiency. Not suitable for pyelonephritis. |
| Fosfomycin | Often given as a single 3 g oral dose. Good safety profile throughout pregnancy. |
| Amoxicillin | Safe in pregnancy, but resistance rates may limit usefulness. Culture-guided use is preferred. |
| Amoxicillin/Clavulanate | Generally safe and commonly used. |
| Cephalexin | Excellent pregnancy safety record. |
| Cefuroxime | Commonly used and considered safe. |
Antibiotics generally avoided or used with caution
• Sulfamethoxazole/Trimethoprim: Avoid if possible in the first trimester and near term.
• Ciprofloxacin and other fluoroquinolones: Not first-line in pregnancy.
• Amikacin and other aminoglycosides: Reserved for serious infections, not routine cystitis.
• Tetracycline and related drugs: Avoid in pregnancy.
Practical approach
For an otherwise healthy pregnant woman with uncomplicated cystitis:
1. Send a urine culture if possible.
2. Common first-line choices are:
o Nitrofurantoin
o Fosfomycin
o Cephalexin
3. Repeat urine culture after treatment if clinically indicated, especially in pregnancy.
If a fluoroquinolone (Ciprofloxacin, Levofloxacin) or an aminoglycoside (Amikacin) was taken within 4 weeks post-conception (approximately 4–6 weeks gestational age by LMP), the overall fetal risk is generally considered low.
Timing is important
The first 2 weeks after conception are often called the "all-or-none" period:
• Significant injury usually results in failed implantation or miscarriage.
• Surviving embryos generally continue normal development.
• Structural malformations are uncommon during this phase.
By weeks 3–4 post-conception, organogenesis is beginning, but available human data for these antibiotics remain relatively reassuring.
Fluoroquinolones
Animal studies raised concerns about cartilage toxicity, but human pregnancy studies have not shown a consistent increase in:
• Major congenital malformations
• Skeletal abnormalities
• Miscarriage attributable to the drug itself
Current evidence does not support pregnancy termination or invasive testing solely because of first-trimester fluoroquinolone exposure.
Aminoglycosides
The theoretical concern is fetal ototoxicity and nephrotoxicity.
• Most reports of fetal hearing loss involved streptomycin.
• Data for amikacin, gentamicin, and similar agents do not demonstrate a major teratogenic effect.
• A short course early in pregnancy is unlikely to cause congenital malformations.
Relative concern
For a short course early in pregnancy:
1. Fosfomycin → most reassuring
2. Cephalosporins/Penicillins → very reassuring
3. Fluoroquinolones → generally reassuring, not preferred but inadvertent exposure is usually low risk
4. Aminoglycosides → more theoretical concern than fluoroquinolones, mainly hearing toxicity, but brief early exposure is still unlikely to cause fetal harm