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Ampicillin Pregnancy and Breastfeeding Warnings

Medically reviewed by Last updated on Apr 24, 2023.

Ampicillin is also known as: Omnipen, Omnipen-N, Principen, Totacillin-N

Ampicillin Pregnancy Warnings

Animal studies have failed to reveal evidence of fetal harm/teratogenicity. This drug crosses the placenta into fetal circulation. There are no controlled data in human pregnancy; however, this drug has been in clinical use for many years and its use in human pregnancy has shown no evidence of harmful effect.

Most retrospective data available indicate that this drug is not likely to be a human teratogen.

A case report of the prophylactic use of this drug to reduce the chances of miscarriage secondary to group B streptococci infection in a high-risk patient, has been described in the medical literature. A 38-year-old patient with history of 3 prior pregnancy losses due to second trimester chorioamnionitis was treated prophylactically in an attempt to carry her fourth pregnancy to term. Beginning at 14 weeks of gestation, the patient received 250 mg orally 4 times a day for the first 10 days of each calendar month. Because the patient also had diabetes, the obstetrician performed a cesarean section at 40 weeks of gestation, delivering a healthy, 3630 g male infant whose Apgar scores at 1 and 5 minutes were 9 and 9.

Oral ampicillin-class antibacterials have poor absorption during labor. In animal studies (guinea pigs), IV administration slightly decreased uterine tone and frequency of contractions, but moderately increased height and duration of contractions. It is not known if use of such drugs in humans during labor or delivery has immediate/delayed adverse effects on the fetus, prolongs labor duration, or increases the prospect that obstetrical intervention (e.g., forceps delivery) or resuscitation of neonate will be needed.

AU TGA pregnancy category A: Drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.

US FDA pregnancy category B: Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women.

This drug should be used during pregnancy only if clearly needed and the benefit outweighs the risk to the fetus.
-According to some authorities: Use is considered acceptable.

AU TGA pregnancy category: A
US FDA pregnancy category: B

See references

Ampicillin Breastfeeding Warnings

Use is considered acceptable; caution is recommended.
-According to some authorities: Breastfeeding is not recommended during use of this drug.
-According to some authorities: A decision should be made to discontinue breastfeeding or discontinue the drug, taking into account the importance of the drug to the mother and the benefit of breastfeeding for the child.

Excreted into human milk: Yes (in small amounts)

-Low levels in milk are not expected to cause harmful effects in the nursing infant.
-Disruption of infant's gastrointestinal flora (resulting in diarrhea or thrush) reported occasionally with penicillins; such effects have not been adequately evaluated.
-Sensitization of the infant may occur and should be considered; according to some authorities, an alternative feeding method is recommended to avoid possible sensitization of the neonate.
-This drug is considered compatible with breastfeeding by the WHO and other experts.
-Some other penicillins (amoxicillin, ticarcillin) are considered compatible with breastfeeding by the American Academy of Pediatrics.

After 500 mg orally every 6 hours for 3 days, milk levels fluctuated little and ranged from 0.575 to 1 mg/L at various times in 1 mother and ranged from 0.014 to 0.0675 mg/L in another.

In 10 mothers given 1.5 or 2 g/day orally for 3 doses, milk levels ranged from 0.03 to 0.2 mg/L; in 1 mother given 3 g/day orally, milk levels ranged from 0.08 to 0.3 mg/L. In 3 mothers administered 2 g/day IM, milk levels ranged from 0.3 to 0.9 mg/L; in 3 mothers administered 4 g/day IM, milk levels ranged from 0.4 to 0.9 mg/L. In all cases, peak milk levels were reached 3 hours after dosing. It was estimated that the breastfed infant received 0.08 to 0.2 mg of this drug daily with such doses.

In a study, postpartum women with endometritis received 1 or 2 g IV (infused over 20 minutes); milk levels averaged 1.7 mg/L and the highest level was 3 mg/L.

In 15 women administered 500 mg IM 4 times a day, milk drug levels averaged 0.11, 0.21, 0.17, 0.27, and 0.26 mg/L at 30 minutes, 1 hour, 2 hours, 4 hours, and 6 hours after the dose, respectively.

In 13 women with mastitis given 1 g orally 4 times a day, average milk levels ranged from 0.6 to 1.05 mg/L. Urine samples were obtained from 8 of their breastfed infants; drug was detectable in samples from 2 infants.

In 15 women administered a single 2 g dose IV, milk levels averaged 1.1 mg/L at 2 hours after dosing.

An uncontrolled observation of breastfed infants of mothers taking this drug showed an apparent increase in diarrhea and candidiasis cases that was ascribed to this drug in breast milk.

In a prospective follow-up study, 5 nursing mothers reported taking this drug (dose not provided). One mother reported diarrhea in her infant. Neither rash nor candidiasis was observed in exposed infants.

During a small and controlled prospective study, mothers monitored their infants for signs of side effects (furring of the tongue, feeding difficulties, changes in stool frequency and consistency, diaper rash, skin rash), weight change, and jaundice. These parameters were not statistically different when infants of control mothers and of mothers taking this drug were compared.

See references

References for pregnancy information

  1. "Product Information. Omnipen (ampicillin)." Wyeth-Ayerst Laboratories (2002):
  2. "Product Information. Polycillin-PRB (ampicillin-probenecid)." Apothecon Inc
  3. Czeizel AE, Rockenbauer M, Sorensen HT, Olsen J "A population-based case-control teratologic study of ampicillin treatment during pregnancy." Am J Obstet Gynecol 185 (2001): 140-7
  4. Marinoff DN, Chinn A "Preventing recurrent second trimester group B streptococcus chorioamnionitis by intermittent prophylactic ampicillin." Obstet Gynecol 98(5 Pt 2) (2001): 918-9
  5. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  6. TGA. Therapeutic Goods Administration. Australian Drug Evaluation Committee "Prescribing medicines in pregnancy: an Australian categorisation of risk of drug use in pregancy." (2007):
  7. Cerner Multum, Inc. "Australian Product Information." O 0
  8. Melbourne: Therapeutic Guidelines Limited "eTG complete [Online]" (2015):

References for breastfeeding information

  1. Campbell AC, McElnay JC, Passmore CM "The excretion of ampicillin in breast milk and its effect on the suckling infant." Br J Clin Pharmacol 31 (1991): p230
  2. Matheson I, Samseth M, Sande HA "Ampicillin in breast milk during puerperal infections." Eur J Clin Pharmacol 34 (1988): 657-9
  3. "Product Information. Omnipen (ampicillin)." Wyeth-Ayerst Laboratories (2002):
  4. "Product Information. Polycillin-PRB (ampicillin-probenecid)." Apothecon Inc
  5. American Academy of Pediatrics Committee on Drugs "The transfer of drugs and other chemicals into human milk" Pediatrics 108 (2001): 776-789
  6. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  7. Cerner Multum, Inc. "Australian Product Information." O 0
  8. United States National Library of Medicine "Toxnet. Toxicology Data Network." (2013):
  9. Melbourne: Therapeutic Guidelines Limited "eTG complete [Online]" (2015):

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.