Prenatal Vitamin Contents: Folate, Iron, Iodine, Choline and DHA Explained
A nutrient-by-nutrient look at what prenatal vitamins list, what UK advice and research say about folate, iron, iodine, choline and DHA, and where official figures could not be checked.
Content last updated . This page has not been medically reviewed.
Urgent: iron is the ingredient that makes prenatal vitamins dangerous for small children. Very high doses can be fatal, particularly if taken by children. [1] In the US call Poison Help at 1-800-222-1222, or 911 if the child has collapsed or has trouble breathing. [2]
Nutrient by nutrient
| Nutrient | What the source says | Official figure we could verify | Evidence label |
|---|---|---|---|
| Folate / folic acid | Folic acid taken before and in early pregnancy reduces the chance of a neural tube defect. [3] Folate is the form in food; folic acid is the manmade form. [4] | UK (NHS, 2026): 400 mcg a day from before pregnancy until 12 weeks; 5 mg on prescription in higher-risk situations. [3] For adults generally, 1 mg or less a day of folic acid supplements is unlikely to cause harm (NHS, undated page read 2026). [4] | Established nutritional role |
| Iron | Needed to make red blood cells; levels are checked at the first midwife appointment and around 28 weeks. [3] If levels are low, a GP or midwife will recommend iron supplements. [3] | The NHS iron page gives figures for adult women (14.8 mg a day at 19 to 49) but not for pregnancy; 17 mg or less a day of supplements is unlikely to cause harm (NHS, 2020). [1] No pregnancy figure verified. | Established where deficiency is found |
| Iodine | Important for the baby's brain development, and requirements increase during pregnancy. [5] | Adults need 140 mcg a day; 0.5 mg or less a day of supplements is unlikely to cause harm (NHS, 2020). [6] No pregnancy figure verified. | Established nutritional role |
| Choline | Most pregnant women have intakes below recommendations, according to a 2025 review; that review found current evidence insufficient to support or refute that more choline in pregnancy improves a child's neurodevelopment. [7] | Could not be verified: the NIH and EFSA pages were not readable. | Insufficient evidence |
| DHA (an omega-3) | Important for the normal development of the baby's brain and eyes; oily fish is rich in it. [5] | No official amount verified. | See below |
US figures (RDA, AI and upper levels) for these nutrients are published by the NIH Office of Dietary Supplements. That site returned an access error this session, so we do not quote them. EFSA and Health Canada pages for pregnancy were not readable either. See RDA, AI, DV and UL explained for how the terms differ.
What research covers for DHA and omega-3
A Cochrane review of 70 trials (19,927 women) compared omega-3 long-chain fats, as supplements or foods, with no omega-3. Preterm birth before 37 weeks was lower with omega-3 (13.4% versus 11.9%), but prolonged pregnancy beyond 42 weeks was probably more common (1.6% versus 2.6%). [8] This is about omega-3 fats in general, not about the DHA in any particular prenatal vitamin. See omega-3 evidence by use and ALA, EPA and DHA.What is on the label versus in the bottle
A 2025 study analysed 47 prenatal products from US online and local pharmacies. Choline was listed on 12 products and iodine on 25. Of those listing iodine, 20 held more than 20% less than the label said. [9] Arsenic, lead and cadmium were measurable in some products but none exceeded United States Pharmacopeia limits. [9] The authors called for better regulation; this was a convenience sample and does not describe every product. See quality testing and certifications.Vitamin A is the one to check on the label
The NHS says not to take supplements containing vitamin A (retinol) or cod liver oil during pregnancy, and to check the label. [3] If you choose a multivitamin-mineral, it advises one made for pregnancy or without vitamin A. [5]Frequently asked questions
Does a prenatal vitamin need to contain choline?
There is no official amount we could verify. A 2025 systematic review found the evidence insufficient to say that extra choline in pregnancy improves a child's neurodevelopment. [7] In that study most products did not state a choline amount. [9]
Why do some prenatal vitamins have no iron?
The sources we read do not compare products with and without iron. The NHS says a clinician recommends iron if blood tests show low levels. [3] Ask your midwife or doctor.
Is the iodine on the label reliable?
In one US study, 20 of 25 products listing iodine contained over 20% less than claimed. [9]
Is folate the same as folic acid?
No. Folate is found in food; folic acid is the manmade form. [4] Advice to take a supplement before pregnancy refers to folic acid in the NHS wording. [3]
Is more always better?
No. The NHS warns that too much vitamin A can harm a baby's development, and that more than 100 mcg of vitamin D a day could be harmful. [3]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read the evidence labels
Labels used on this page: established nutritional role / deficiency treatment, evidence in adequately nourished people, mixed, insufficient evidence.
Safety and who should ask first
- Medicines: tell your doctor and pharmacist about everything you take. [2] See medication interactions.
- Doubling up: a separate iron, iodine or kelp product on top of a prenatal vitamin can add the same nutrient twice. Seaweed, especially brown seaweed such as kelp, can supply too much iodine. [5]
- Surgery and bleeding or anemia: tell your doctor, including a dentist. [2]
- Kidney and liver conditions, thyroid disease: not described in the sources we read for this page; ask a clinician.
Related: prenatal and postnatal vitamins overview, folate (vitamin B9), folate vs folic acid vs methylfolate, iodine, choline and iron.
References
- NHS: Iron. Read 2026-10-22.
- MedlinePlus: Prenatal Vitamins. Read 2026-10-22.
- NHS: Pregnancy vitamins and supplements. Read 2026-10-22.
- NHS: B vitamins and folic acid. Read 2026-10-22.
- NHS: Vegetarian and vegan diets during pregnancy. Read 2026-10-22.
- NHS: Iodine. Read 2026-10-22.
- Gould et al., Choline During Pregnancy and Child Neurodevelopment: systematic review (Nutrients 2025). Read 2026-10-22.
- Cochrane review, Omega-3 fatty acid addition during pregnancy (2018). Read 2026-10-22.
- Borgelt et al., Content of selected nutrients and heavy metals in prenatal multivitamins and minerals (Am J Clin Nutr 2025). Read 2026-10-22.