Chlorpheniramine
MedicationChlor-Trimeton, Aller-Chlor, Chlo-Amine, Polaramine, Teldrin
Antihistamine
Research strength: 3 / 5
ACOG includes chlorpheniramine among over-the-counter allergy medicines that studies support using during pregnancy, but advises checking with an obstetrician before taking one. MotherToBaby says most studies found no overall increase in birth defects, though two reported small increases in different defects with no consistent pattern; these sources emphasize different parts of the evidence. Li et al. (2013) found previously suggested associations were not supported by stable estimates; several exploratory findings had few exposed cases and did not remain significant after adjustment for many comparisons. Aldridge et al. (2014) did not detect a link between first-trimester antihistamine use as a group and miscarriage, but did not study chlorpheniramine alone. MotherToBaby does not give a separate chlorpheniramine-specific first-trimester risk estimate. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
- MotherToBaby: Chlorpheniramine fact sheetTeratology service
- ACOG: What medicine can I take for allergies while I'm pregnant?Professional society
- Li et al., 2013: Assessment of antihistamine use in early pregnancy and birth defectsUS government
- Aldridge et al., 2014: First-trimester antihistamine exposure and pregnancy outcomesUS government
Research strength: 3 / 5
ACOG includes chlorpheniramine among over-the-counter allergy medicines that studies support using during pregnancy, but advises checking with an obstetrician before taking one. MotherToBaby reports most studies found no overall increase in birth defects, though two reported small increases in different defects without a consistent pattern; the sources emphasize different parts of the evidence. The case-control studies by Gilboa et al. (2009) and Li et al. (2013) mainly examined early pregnancy and do not give a separate second-trimester estimate for chlorpheniramine. Aldridge et al. (2014) did not detect a link between first-trimester antihistamine use as a group and preterm birth; that finding does not answer second-trimester exposure. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
- MotherToBaby: Chlorpheniramine fact sheetTeratology service
- ACOG: What medicine can I take for allergies while I'm pregnant?Professional society
- Gilboa et al., 2009: Antihistamine use during early pregnancy and birth defectsUS government
- Li et al., 2013: Assessment of antihistamine use in early pregnancy and birth defectsUS government
- Aldridge et al., 2014: First-trimester antihistamine exposure and pregnancy outcomesUS government
Research strength: 3 / 5
ACOG includes chlorpheniramine among over-the-counter allergy medicines that studies support using during pregnancy, but advises checking with an obstetrician before taking one. MotherToBaby reports most studies found no overall increase in birth defects, while two described small increases in different defects without a consistent pattern; ACOG and MotherToBaby emphasize different parts of the evidence. The main primary pregnancy studies reviewed here focus on early pregnancy and do not give a chlorpheniramine-specific third-trimester estimate. MotherToBaby says studies have not examined later behavior or learning outcomes after chlorpheniramine exposure. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
- MotherToBaby: Chlorpheniramine fact sheetTeratology service
- ACOG: What medicine can I take for allergies while I'm pregnant?Professional society
- Li et al., 2013: Assessment of antihistamine use in early pregnancy and birth defectsUS government
- Gilboa et al., 2009: Antihistamine use during early pregnancy and birth defectsUS government
Chlorpheniramine — Breastfeeding
Research strength: 2 / 5
According to LactMed, occasional small doses are considered acceptable, but larger or longer use might affect an infant or reduce milk supply, particularly before milk supply is established or with pseudoephedrine. NHS SPS prefers non-sedating antihistamines overall; if a sedating antihistamine is needed, it names chlorphenamine as its preferred option. NHS SPS says normal doses of antihistamines are unlikely to affect milk supply once lactation is established, while LactMed's caution focuses on larger or longer use and early lactation. NHS SPS advises monitoring for infant drowsiness, irritability, dry mouth, poor feeding, and slow weight gain; NHS also advises against bed-sharing while taking chlorphenamine. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
- LactMed (NIH): ChlorpheniramineUS government
- NHS Specialist Pharmacy Service: Using antihistamines during breastfeedingUK government
- NHS: Pregnancy, breastfeeding and fertility while taking chlorphenamineUK government
- MotherToBaby: Chlorpheniramine fact sheetTeratology service
- Ito et al., 1993: Follow-up of breastfed infants exposed to maternal medicationUS government
Pregnancy
Evidence is mostly observational and often analyzes antihistamines as a group rather than chlorpheniramine alone. Aldridge et al. (2014) followed 2,685 pregnancies in a prospective cohort; 377 participants reported antihistamine use. The study did not detect an association between first-trimester antihistamine use and miscarriage or preterm birth, but its exposure analysis was class-wide and did not test chlorpheniramine alone. Li et al. (2013) used a North American case-control study with 13,213 infants with malformations and 6,982 nonmalformed controls. Chlorpheniramine was reported by 1.7% of controls. The authors found no stable support for previously proposed antihistamine-defect links; several exploratory chlorpheniramine findings had few exposed cases and were no longer significant after adjustment for multiple comparisons. Gilboa et al. (2009) studied 14 antihistamines and 26 birth-defect groups; the authors described the overall results as generally consistent with no association, while noting that selected findings needed further study. MotherToBaby reports two studies with small increases in different defect types and no consistent pattern. A 2026 case report described one intentional multidrug overdose at 6 weeks that included chlorpheniramine and dexketoprofen and paracetamol; the pregnancy ended by elective termination at 10 weeks, so the case does not assess outcomes after usual chlorpheniramine use. MotherToBaby says studies have not examined later behavior or learning outcomes after chlorpheniramine exposure.
Breastfeeding
Human lactation evidence is limited. LactMed reports no published chlorpheniramine milk-level or infant-level measurements and says larger doses or longer use might affect the infant or milk supply, particularly with pseudoephedrine or before lactation is established. The 1993 prospective follow-up included 838 breastfed infants whose mothers used medications. The abstract reports no major reactions requiring medical attention and minor symptoms in 8 of 85 infants exposed to antihistamines as a group; it does not give a chlorpheniramine-specific outcome count. MotherToBaby and LactMed report no side effects in five infants exposed to chlorpheniramine, but the published abstract does not identify that drug-specific subgroup. NHS SPS's February 2026 review says studies are very limited, milk and infant serum levels have not been measured, and infant monitoring is needed. NHS SPS prefers non-sedating antihistamines overall and identifies chlorphenamine as its preferred sedating option when one is needed.
Chlorpheniramine is an antihistamine used for allergy, hay fever, and common cold symptoms. NHS sources describe it as a sedating antihistamine and use the name chlorphenamine. MotherToBaby lists Chlor-Trimeton, Aller-Chlor, Chlo-Amine, Polaramine, and Teldrin as brand names.
What was tested
Pregnancy evidence includes retrospective case-control studies of first-trimester exposure and a prospective cohort of antihistamine use as a class. The case-control studies examined many antihistamine and birth-defect combinations, with some analyses based on small exposed groups. Breastfeeding evidence includes a prospective telephone follow-up of infants exposed to maternal medicines and clinical summaries; LactMed and NHS SPS report that published milk levels and infant serum levels have not been measured for chlorphenamine.
How to weigh isolated birth-defect signals against broader pregnancy guidance
- Source A says
- MotherToBaby reports that most studies found no overall increase in birth defects, but two studies found small increases in different defects. Li et al. reported exploratory chlorpheniramine associations, but their intervals did not remain significant after adjustment for multiple comparisons. (MotherToBaby: Chlorpheniramine fact sheet, Li et al., 2013: Assessment of antihistamine use in early pregnancy and birth defects)
- Source B says
- ACOG includes chlorpheniramine among over-the-counter allergy medicines supported by pregnancy studies, and the NHS says there is no good evidence that it harms the baby. Both advise discussing medicine use with a clinician or pharmacist. (ACOG: What medicine can I take for allergies while I'm pregnant?, NHS: Pregnancy, breastfeeding and fertility while taking chlorphenamine)
- Why they differ
- MotherToBaby highlights isolated defect-specific signals, while ACOG and NHS summarize the broader evidence and clinical use. The primary studies include many comparisons and sparse exposed groups; some exploratory associations were imprecise or did not remain significant after adjustment.
- What the evidence shows overall
- The available studies do not establish a repeated defect pattern. ACOG and NHS guidance supports clinician discussion rather than an avoid rating, while the limited and mostly early-pregnancy data justify retaining uncertainty.
Possible milk-supply effects during breastfeeding
- Source A says
- LactMed says larger doses or longer use might decrease milk supply, particularly before lactation is established or with pseudoephedrine. (LactMed (NIH): Chlorpheniramine)
- Source B says
- NHS SPS says evidence on antihistamines and milk production is limited and conflicting, and normal therapeutic doses are unlikely to affect milk production, especially after lactation is established. (NHS Specialist Pharmacy Service: Using antihistamines during breastfeeding)
- Why they differ
- LactMed highlights larger or longer use, early lactation, and combination with pseudoephedrine; NHS SPS describes normal therapeutic doses and established lactation. The sources address different dose and timing conditions.
- What the evidence shows overall
- LactMed says the effect of lower oral chlorpheniramine doses on prolactin or breastfeeding success has not been studied. The summary keeps both sources' dose and lactation-stage context and does not state that occasional use is known to reduce milk supply.
- ACOG advises checking with an obstetrician before taking an over-the-counter allergy medicine. (ACOG)
- NHS SPS prefers cetirizine or loratadine as non-sedating options during breastfeeding. If a sedating antihistamine is needed, it names chlorphenamine as its preferred choice and advises infant monitoring and the lowest effective dose for the shortest time. (NHS Specialist Pharmacy Service)
- The NHS says a non-drowsy antihistamine may be preferable during pregnancy or breastfeeding. (NHS)
General research, not specific to pregnancy.
The NHS says chlorphenamine can cause drowsiness and advises against bed-sharing with a baby while taking it.
- MotherToBaby says chlorpheniramine can cause sleepiness in adults. (MotherToBaby: Chlorpheniramine fact sheet)
- The NHS advises not sharing a bed with a baby while taking chlorphenamine. (NHS: Pregnancy, breastfeeding and fertility while taking chlorphenamine)
- MotherToBaby: Chlorpheniramine fact sheetTeratology serviceSecondary
- LactMed (NIH): ChlorpheniramineUS governmentSecondaryPage dated 2026-04-15
- ACOG: What medicine can I take for allergies while I'm pregnant?Professional societySecondaryIndependent check
- NHS: Pregnancy, breastfeeding and fertility while taking chlorphenamineUK governmentSecondaryPage dated 2025-05-14Independent check
- NHS Specialist Pharmacy Service: Using antihistamines during breastfeedingUK governmentSecondaryPage dated 2026-02-05Independent check
- Aldridge et al., 2014: First-trimester antihistamine exposure and risk of spontaneous abortion or preterm birthUS governmentPrimaryIndependent check
- Li et al., 2013: Assessment of antihistamine use in early pregnancy and birth defectsUS governmentPrimaryIndependent check
- Gilboa et al., 2009: Use of antihistamine medications during early pregnancy and isolated major malformationsUS governmentPrimaryIndependent check
- Ito et al., 1993: Prospective follow-up of adverse reactions in breast-fed infants exposed to maternal medicationUS governmentPrimaryIndependent check
- Uysal et al., 2026: Intentional dexketoprofen overdose during pregnancy, three casesUS governmentPrimary
Last reviewed 2026-10-16
Independent check 2026-10-16
Not yet clinician-reviewed
Ask your provider about your situation.
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