acyclovir

Not known to be harmful; limited absorption from topical preparations

amoxicillin

No evidence of teratogenicity

ampicillin

Not known to be harmful

azithromycin

Limited data in pregnancy; use only if potential benefit outweighs risk.

benzathine benzylpenicillin

Not known to be harmful

benzylpenicillin

Not known to be harmful

cefixime

Single dose of cefixime is considered safe in pregnancy

ceftazidime

Not known to be harmful

ceftriaxone

Not known to be harmful

chloramphenicol

Third trimester: neonatal "grey baby" syndrome

ciprofloxacin

Avoid�arthropathy in animal studies; safer alternatives available

clindamycin

Not known to be harmful

clotrimazole

Not studied in first trimester. Used vaginally during second and third trimester not shown to cause birth defects.

cloxacillin

Not known to be harmful

doxycycline

Contraindicated in pregnancy and breastfeeding:

First trimester: effects on skeletal development in animal studies

Second and third trimesters: dental discoloration in children; maternal hepatotoxicity with large parenteral doses

erythromycin

Not known to be harmful

famciclovir

Animal studies did not show any risk for fetus�use only when potential benefit outweighs risk

fluconazole

Avoid in first trimester�multiple congenital abnormalities reported with long-term high doses

gentamicin

Second and third trimesters: auditory or vestibular nerve damage; risk probably very small, but use only if potential benefit outweighs risk (if given, monitoring of serum gentamicin concentration essential)

metronidazole

First trimester: avoid

Second and third trimesters: avoid high-dose regimens (>1g)

nystatin

No information available, but absorption from gastrointestinal tract negligible

ofloxacin

Avoid�arthropathy in animal studies; safer alternatives available

podophyllum resin

Avoid�neonatal death and teratogenesis have been reported

streptomycin

Second and third trimesters: auditory or vestibular nerve damage; avoid unless essential (if given, monitoring of serum streptomycin concentration essential)

sulfamethoxazole + trimethoprim

First trimester: theoretical teratogenic risk (trimethoprim is a folate antagonist)

Third trimester: neonatal haemolysis and methaemoglobinaemia; suggestion of increased risk of kernicterus in neonates appears to be unfounded

tinidazole

Manufacturer advises to avoid in first trimester

Second and third trimesters: avoid high-dose regimens (>1g)

tetracycline

Contraindicated in pregnancy and breastfeeding:

First trimester: effects on skeletal development in animal studies

Second and third trimesters: dental discoloration in children; maternal hepatotoxicity with large parenteral doses

trimethoprim

First trimester: theoretical teratogenic risk (folate antagonist)

valaciclovir

Animal studies did not show any risk for fetus�use only when potential benefit outweighs risk;

vancomycin

Use only if potential benefit outweighs risk�monitoring of plasma vancomycin concentration essential to reduce risk of fetal toxicity

zidovudine and other antiretrovirals

Avoid if possible in first trimester; benefit of treatment considered to outweigh risk in second and third trimesters