Polyethylene Glycol
MedicationMiraLAX, GaviLAX
Osmotic laxative
Research strength: 2 / 5
MotherToBaby lists polyethylene glycol as an osmotic laxative and says very little is expected to reach the bloodstream, so pregnancy exposure is expected to be small. It says only a few studies have examined laxatives during pregnancy and that over-the-counter laxatives used as directed are not expected to raise the chance of birth defects. This is a group-level finding, not a polyethylene-glycol-specific estimate. MotherToBaby does not give a first-trimester estimate for this medicine. Ask your provider about your situation.
Last reviewed: 2026-10-16
Research strength: 3 / 5
MotherToBaby says polyethylene glycol is poorly absorbed and expected pregnancy exposure is small. Its limited birth-defect evidence covers over-the-counter laxatives as a group, not polyethylene glycol by trimester. A 2024 Japanese cohort found no significant difference in perinatal prognosis between polyethylene glycol and magnesium oxide, but only 12 participants were prescribed polyethylene glycol and outcomes were not separated by trimester. These data do not settle uncommon outcomes. Ask your provider about your situation.
Last reviewed: 2026-10-16
Research strength: 3 / 5
MotherToBaby says polyethylene glycol is poorly absorbed and expected pregnancy exposure is small. It does not give a third-trimester estimate for this medicine. In a 2024 Japanese cohort of 211 people, 12 were prescribed polyethylene glycol; the authors reported no significant difference in perinatal prognosis or side effects compared with magnesium oxide, but trimester-specific outcomes were not reported. A 2024 trial studied constipation symptoms with polyethylene glycol 4000 in weeks 28 to 32, not birth defects or infant outcomes. Ask your provider about your situation.
Last reviewed: 2026-10-16
Polyethylene Glycol — Breastfeeding
Research strength: 1 / 5
LactMed says polyethylene glycol is very poorly absorbed, does not enter breast milk, and requires no special precautions; it describes the medicine as a possible laxative of choice during breastfeeding. LactMed also reports that relevant published information on milk levels and infant effects was not found. NHS Specialist Pharmacy Service says macrogol 3350 can be used, but advises precautionary monitoring for infant diarrhea, vomiting, or irritability; its guidance applies to full-term, healthy infants. These sources differ on infant monitoring, while both support use. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
- LactMed: Polyethylene GlycolUS government
- NHS Specialist Pharmacy Service: Using laxatives during breastfeedingUK government
- MotherToBaby: LaxativesTeratology service
Pregnancy
MotherToBaby lists polyethylene glycol (PEG) as an osmotic laxative and says very little is expected to enter the bloodstream. Its birth-defect statement covers over-the-counter laxatives as a group and is not a PEG-specific estimate. Ishibashi et al. (2024) conducted a prospective cohort study of 211 perinatally managed people; 12 were prescribed PEG, identified as macrogol 4000 in the discussion, and only 8 PEG users were in the reported side-effect analysis. Questionnaires were completed around 28 weeks and after delivery. The authors reported no significant difference in perinatal prognosis or side effects between PEG and magnesium oxide; outcomes were not broken down by trimester, and the study was too small to assess uncommon outcomes reliably. Raj et al. (2024) randomized 360 pregnant participants at 28 to 32 weeks to PEG 4000 or lactulose for four weeks; 247 who completed the study were analyzed. The trial measured constipation symptoms, quality of life, stool form, and gastrointestinal side effects, not fetal malformations, miscarriage, or infant effects. The 2015 Cochrane review found no data for osmotic laxatives; its search ended in 2015 and predates the later cohort and trial. The sources reviewed do not provide a PEG-specific miscarriage estimate.
Breastfeeding
LactMed, revised February 15, 2026, says PEG is very poorly absorbed and does not enter breast milk, and that no special precautions are required. It reports that relevant published information was not found for maternal levels, infant levels, infant effects, or effects on lactation. NHS Specialist Pharmacy Service, updated November 10, 2023, says macrogol 3350 can be used during breastfeeding and advises precautionary monitoring of a full-term, healthy infant for diarrhea, vomiting, or irritability. It also says there is no evidence for use in breastfeeding and expects milk transfer and infant effects to be negligible. MotherToBaby's occasional loose-stool reports concern laxatives as a group and do not establish an effect from PEG. LactMed reports no relevant published PEG-specific milk-level or infant-outcome information as of its revision date.
Polyethylene glycol 3350, also called macrogol 3350, is an osmotic laxative. The Bayer MiraLAX label lists 17 g of PEG 3350 per adult dose.
What was tested
Ishibashi et al. (2024) studied 211 people receiving perinatal care in Japan; 12 were prescribed PEG, identified as macrogol 4000 in the discussion, with side-effect data reported for 8 PEG users. The study compared perinatal prognosis and constipation treatment, but did not provide trimester-specific PEG outcomes. Raj et al. (2024) randomized 360 pregnant participants at 28 to 32 weeks, 180 to each arm, to PEG 4000 or lactulose for four weeks; 247 participants completed the study and were analyzed. Outcomes included complete spontaneous bowel movements, constipation symptom and quality-of-life scores, stool form, diarrhea, and other side effects. The trial did not test fetal malformations, miscarriage, or breastfeeding outcomes. The Cochrane review searched evidence through April 30, 2015, and found no included data for osmotic laxatives.
Whether infants need special monitoring when a parent uses PEG while breastfeeding
- Source A says
- LactMed says PEG is very poorly absorbed, does not enter breast milk, and requires no special precautions. (LactMed: Polyethylene Glycol)
- Source B says
- NHS Specialist Pharmacy Service says macrogol 3350 can be used during breastfeeding, but advises precautionary monitoring for infant diarrhea, vomiting, or irritability. Its recommendation applies to full-term, healthy infants. (NHS Specialist Pharmacy Service: Using laxatives during breastfeeding)
- Why they differ
- Both sources describe very low expected absorption and no direct evidence of infant effects. LactMed says no special precautions are needed; NHS SPS adds monitoring as a precaution, rather than in response to a reported PEG-related infant effect.
- Other sources
- The Bayer MiraLAX label tells breastfeeding users to ask a health professional before use; it does not give a PEG-specific infant monitoring instruction. (DailyMed: Bayer MiraLAX Drug Facts label)
- What the evidence shows overall
- LactMed and NHS SPS both support use during breastfeeding, while differing on monitoring. NHS SPS describes monitoring as precautionary, and LactMed reports no relevant published information on infant effects. The evidence about infant effects remains very limited.
- MotherToBaby notes that dietary changes, fluids, high-fiber foods, and regular activity may help with constipation, and that a provider may review these before discussing medicine. (MotherToBaby)
- The Bayer MiraLAX label lists a 17 g once-daily adult dose, says not to take more than directed, and says not to use the product for more than 7 days unless advised by a doctor. (DailyMed: Bayer MiraLAX label)
- The MHRA advises against directly mixing PEG laxatives with starch-based thickeners because the mixture can become thin and may increase aspiration risk for people with swallowing difficulties. (UK MHRA)
General research, not specific to pregnancy.
The MiraLAX label says PEG 3350 may cause loose, watery, more frequent stools. The label and MHRA warn that mixing PEG with starch-based thickeners can undo thickening and may increase aspiration risk for people with swallowing difficulties.
- The label says users may have loose, watery, more frequent stools and directs them to stop use and ask a doctor if diarrhea occurs. (DailyMed: Bayer MiraLAX Drug Facts label)
- The Bayer label says not to combine PEG with starch-based thickeners used for difficulty swallowing. The MHRA explains that mixing can make the liquid thin and watery, which may increase aspiration risk in people with swallowing difficulties. (DailyMed: Bayer MiraLAX Drug Facts label, UK MHRA: PEG laxatives and starch-based thickeners)
- MotherToBaby: LaxativesTeratology serviceSecondary
- LactMed: Polyethylene GlycolUS governmentSecondaryPage dated 2026-02-15
- NHS Specialist Pharmacy Service: Using laxatives during breastfeedingUK governmentSecondaryPage dated 2023-11-10Independent check
- Ishibashi et al., Evaluation and treatment of constipation in pregnancy (2024)US governmentPrimaryIndependent check
- Raj et al., Polyethylene glycol compared to lactulose for constipation in pregnancy (2024)US governmentPrimary
- Cochrane Review: Interventions for treating constipation in pregnancyUS governmentPrimaryPage dated 2015-09-04Independent check
- DailyMed: Bayer MiraLAX Drug Facts labelDrug company labelTertiaryPage dated 2026-05-06
- UK MHRA: PEG laxatives and starch-based thickenersUK governmentSecondaryPage dated 2021-04-27Independent check
Last reviewed 2026-10-16
Independent check 2026-10-16
Not yet clinician-reviewed
Ask your provider about your situation.
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