High-dose vitamin A can cause birth defects, and other pregnancy supplements carry their own risks

Key takeaways

• In a 1995 study of 22,748 pregnancies, researchers estimated that about 1 in 57 babies born to women taking more than 10,000 IU a day of preformed vitamin A from supplements had a birth defect attributable to it¹.
• Beta-carotene, the plant form of vitamin A, isn’t known to cause birth defects and has no set upper limit, so the form on the label matters as much as the amount³.
• A 2025 review of 51 studies tied prenatal cannabis use to higher odds of low birth weight and preterm birth even after accounting for tobacco, and the FDA advises avoiding THC and CBD in any form⁵⁶.
• Kratom, a plant that acts on opioid receptors, has been linked to newborn withdrawal, and routine opioid drug screens can miss it⁸.
• Eating dates late in pregnancy cut the need for induction by about half in pooled studies of low to moderate certainty, while castor oil made every woman who swallowed it in trials nauseous⁹¹⁰.

Between 1984 and 1987, nurses interviewed 22,748 pregnant women about what they ate and which supplements they took¹. They had been identified when they came in for a prenatal blood screening test or amniocentesis¹.

When researchers matched those answers to the babies’ health, one ordinary nutrient stood out. Among women whose supplements supplied more than 10,000 IU of preformed vitamin A a day, a group of defects tied to how the face, head and heart form was 4.8 times as common as among women who got 5,000 IU or less¹².

The team estimated that about 1 in 57 of those babies had a malformation attributable to the vitamin¹. The paper ran in the New England Journal of Medicine in 1995, and it still shapes advice today²³.

That’s a vitamin, not an herb. Our article on herbs in pregnancy covers pennyroyal, blue cohosh, licorice and raspberry leaf. This one covers the rest of the shelf: vitamin A, cannabis and CBD, kratom, and the “natural induction” remedies people try at the end of pregnancy, from dates to castor oil.

Each gets a rating on our four-level evidence scale and a practical check you can bring to your next prenatal visit.

Preformed vitamin A: a 1995 study moved the safety line

Vitamin A comes in two main forms. Preformed vitamin A, the retinol kind, is the one tied to birth defects. Beta-carotene, the plant form, isn’t known to cause them, and it has no upper limit³.

The 1995 finding made biological sense. Synthetic retinoids, drugs related to vitamin A, were already known to cause defects in the same embryonic tissue, called the cranial neural crest¹. And the extra risk was concentrated among women with high intake before the seventh week of pregnancy¹. That’s why the question matters for anyone trying to conceive, not only for those already pregnant.

The study had critics. Some defects it counted may not have come from those tissues, and only a small number of women took high doses, a review in a professional newsletter noted². Several other studies found no link at about 10,000 IU a day². A 1999 European study of women who took 10,000 IU a day or more before the ninth week found no rise in birth defects among the 311 pregnancies it could evaluate².

Still, the advice shifted. Before 1995, the usual cap in pregnancy was 25,000 IU a day; afterward, it fell below 10,000 IU². The review’s author judged the evidence of harm below 10,000 IU weak, but found no reason for high-dose vitamin A pills in pregnancy².

Today the NIH Office of Dietary Supplements reports expert advice to keep vitamin A from supplements at or below 3,000 mcg RAE (10,000 IU) a day if you’re pregnant, might be pregnant or are breastfeeding³. The separate upper limit, which counts preformed vitamin A from food and supplements together, is 3,000 mcg RAE for adults and a bit lower, 2,800 mcg, for ages 14 to 18³.

Our article on upper limits explains how to add up a label, and our prenatal label check shows where beta-carotene appears. Our measles article describes children harmed in 2025 by vitamin A from daily cod liver oil, a reminder that “natural” sources count too.

Cannabis and CBD: no dose has been shown safe in pregnancy

The FDA strongly advises pregnant and breastfeeding people to avoid CBD, THC and marijuana in any form⁵. THC can reach the fetal brain through the mother’s bloodstream, the agency notes, citing the U.S. Surgeon General⁵.

The research has grown. In 2025, researchers at Oregon Health & Science University updated their earlier review, bringing it to 51 studies covering about 21 million people⁶. The studies had adjusted for other factors, including tobacco use alongside cannabis⁶.

Prenatal cannabis use was tied to these higher odds⁶:

• Low birth weight: 1.75 times the odds.
• Preterm birth: 1.52 times.
• Being small for gestational age: 1.57 times.
• Death around the time of birth: 1.29 times.

The eight newest studies added more than 1.7 million people, and the authors’ confidence in the results climbed from low to moderate⁶. The authors couldn’t sort out dose, frequency or route of use⁶. The work was funded by the Veterans Affairs Office of Rural Health, and the lead author had a grant from the National Institute on Drug Abuse⁶.

A separate 2023 review in Addiction pooled 57 studies of 12.9 million infants, 102,835 of them exposed⁷. It found more than 1.5 times the risk of preterm birth and more than twice the risk of low birth weight and of newborn intensive care. It found no rise in birth defects or in infant deaths in the first year⁷.

Those are relative figures. The reviews we opened didn’t report absolute rates, so we can’t tell you how many extra babies per 100 they mean. For scale, MotherToBaby, the expert service run by teratology specialists, puts the background chance of a birth defect in any pregnancy at about 3 in 100⁴. Its fact sheet adds that studies of cannabis and birth defects disagree, and that some exposed newborns had temporary jitteriness and irritability⁴.

CBD. It isn’t a gentler loophole. High-dose CBD caused reproductive problems in developing male fetuses in animal tests, and there’s no comprehensive human research⁵.

CBD products may also contain THC, pesticides, heavy metals, bacteria or fungus⁵. MotherToBaby warns that products labeled “THC free” may still hold measurable THC⁴. Our sleep-aid article covers a 2017 test of CBD labels.

If you use cannabis for morning sickness, sleep or anxiety, telling your prenatal team what you use, and why, lets them help with the problem it was solving. Our companion article on pregnancy nausea covers dispensary advice and cannabis-linked vomiting.

Kratom: a newborn in withdrawal, and a drug screen that missed it

In 2018, a neonatologist in Florida, Whitney Eldridge of BayCare Health System, described a baby in the journal Pediatrics⁸. The newborn was jittery and screaming, and doctors diagnosed neonatal abstinence syndrome, the withdrawal some babies go through after opioid exposure in the womb⁸.

The mother had used oxycodone for almost a decade and reported two years of sobriety⁸. She denied using substances, but her husband said she drank kratom tea every day for withdrawal symptoms and sleep⁸.

Mother and baby both passed urine screens for oxycodone and other opioids. Those screens never looked for kratom⁸. The baby needed morphine and went home on day 8⁸.

Kratom acts on the body’s opioid receptors⁸. At the time, FDA Commissioner Scott Gottlieb said the agency knew of four other cases of newborns exposed to kratom in the womb⁸.

The report had limits. Edward Boyer of Harvard pointed out that the kratom use came from the husband’s account and wasn’t confirmed⁸. Even the chair of the American Kratom Association, an advocacy group, supported warning labels about pregnancy⁸.

If kratom helps you manage pain, cravings or withdrawal, tell your prenatal clinician and your baby’s care team. This isn’t about blame. Because routine screens can miss kratom, the people caring for your newborn need to know what to watch for⁸. Our article on hidden drugs in herbal products covers concentrated kratom compounds and the federal response.

Natural induction: dates have the best data

Near a due date, many people look for gentle ways to get labor going. Among the options we reviewed, dates have the largest body of research.

A 2024 review in BMC Pregnancy and Childbirth pooled 48 studies, 15 of them randomized trials⁹. Most came from Indonesia and Iran, with groups of 10 to 105 women⁹. A typical amount was about 6 or 7 dates a day, roughly 60 to 80 grams, in the last month of pregnancy⁹.

Women who ate dates were about half as likely to need an induction (risk ratio 0.48) and more likely to go into labor on their own⁹. The first stage of labor ran about 55 minutes shorter, and the early, latent phase about 214 minutes shorter⁹. The drop in cesareans wasn’t statistically clear⁹. The review gave relative risks, not absolute rates, for induction.

Before you stock up, note the limits. The certainty of most findings was low or moderate, and only four trials were at low risk of bias in every area checked⁹. Only four studies looked for side effects at all, and none reported any⁹.

Dates are also high in sugar, which the authors flagged as a concern with diabetes or gestational diabetes, and the review reported no blood sugar data from its studies⁹. If you have either, ask your clinician or dietitian first. Our article on insulin resistance in pregnancy explains why.

Rating: Promising but early. It’s a food, and the early signal is real, but better trials are needed.

Castor oil and evening primrose oil: thin evidence, real side effects

Castor oil is a traditional way to start labor, taken by mouth or as an enema¹⁰. A Cochrane review found only three trials, with 233 women, each using a single dose¹⁰.

In those trials, nausea struck every woman who swallowed the oil¹⁰. Two trials reported cesareans and found no clear difference¹⁰. The trials were too small and too weak to show other benefits or harms, and none reported data on illness or death in mothers or babies¹⁰. The review dates from 2013, and Cochrane lists no newer version¹⁰.

Evening primrose oil is taken by mouth or placed in the vagina to soften the cervix. Two reviews read the same small literature differently.

A 2023 review in Heliyon pooled 7 trials with 920 women and found better scores on the Bishop scale, a tool clinicians use to judge how ready the cervix is for labor¹¹. Its authors called the oil clinically effective¹¹.

A 2026 review in the Evidence Based Care Journal, funded by Iran’s Mashhad University of Medical Sciences, pooled 16 trials with 1,662 women¹². Most trials were from Iran, with others from Egypt, the Philippines and the U.S.¹². Oil taken by mouth didn’t improve cervical scores¹². Vaginal use beat a placebo but did no better than misoprostol, a drug used to ripen the cervix¹².

That review rated 13 of its 16 trials at high risk of bias, reported its cesarean findings inconsistently and didn’t track side effects systematically¹². It also cited a 1999 U.S. study that tied oral evening primrose oil to more prolonged rupture of the membranes, slower labor and more vacuum-assisted births¹².

Cohosh and raspberry leaf. Our herbs-in-pregnancy article covers blue and black cohosh, whose newborn case reports are the most worrying of the labor herbs, and the raspberry leaf trial.

Natural induction: what’s been tested

Method	What was tested	What it showed	Rating	Main cautions
Dates, about 60–80 g a day in the last month	48 studies, 15 randomized9	About half the need for induction; shorter early labor9	Promising but early	Sugar with diabetes; few safety checks9
Castor oil, single dose	3 trials, 233 women10	No clear benefit shown10	Not enough evidence	Nausea in every woman who swallowed it10
Evening primrose oil, by mouth	Several small trials1112	Reviews disagree; no cervical gain in the newer one1112	Not enough evidence	Linked in one study to more interventions12
Evening primrose oil, vaginal	A few small trials12	Beat placebo, not misoprostol12	Not enough evidence	High risk of bias; side effects untracked12

The pregnancy shelf check

Use this table with your bottles in hand. It’s our own summary of the sources above, not a substitute for your clinician.

Product	The concern	Rating	What to do
Vitamin A as retinol (preformed)	Birth defects at high intake, especially early13	Evidence says no, or unsafe above 10,000 IU a day	Add up every supplement, and ask whether your total stays within the 10,000 IU limit3
THC: marijuana, edibles, vapes	Lower birth weight, preterm birth, smaller babies67	Evidence says no, or unsafe	The FDA advises avoiding all forms5; tell your team what you use and why
CBD oils, gummies, drinks	Little human safety research; possible THC and contaminants45	Not enough evidence of safety	The FDA advises avoiding it; “THC free” may not be45
Kratom: tea, powder, capsules	Newborn opioid-type withdrawal8	Evidence says no, or unsafe (case reports)	Tell your prenatal and newborn teams; screens can miss it8
Any other herb or supplement	Pregnancy data vary by product	Varies	Ask MotherToBaby before assuming natural means tested13

Other common products. Our melatonin article notes how little pregnancy research exists. Our magnesium article covers upper limits and kidney cautions, and our essential-oil article covers safety around newborns. Our herbal tea and contamination articles cover what can hide in a cup or capsule.

How to check anything on your shelf

MotherToBaby, run by the Organization of Teratology Information Specialists, offers free help by phone, text, chat or email to people in the U.S. and its territories¹³. Call 866-626-6847 or text 855-999-3525¹³. It also has more than 300 fact sheets in English and Spanish¹³.

For breastfeeding questions, the National Library of Medicine’s free LactMed database covers medicines, herbs and supplements.

At each prenatal visit, bring every bottle or a photo of each label, with how much you take. Include teas, tinctures, gummies, powders and anything a friend recommended. If a child or adult swallows too much of a product, call Poison Control at 1-800-222-1222.

Natural-health values point in a useful direction here. The best-supported induction option, dates, is a food. But vitamin A is a vitamin, and cannabis and kratom are plants, and each has documented risks in pregnancy.

Asking how a product was tested isn’t distrust of nature. It’s the same care you’d want anyone else to take with your baby.

Questions readers ask

The bottom line

The riskiest items on a pregnancy shelf aren’t always herbs. High doses of preformed vitamin A, cannabis in any form and kratom all have documented risks, while beta-carotene doesn’t carry the vitamin A warning. CBD has too little human research to call safe.

At the end of pregnancy, dates are the one natural induction method with a meaningful, if imperfect, evidence base. Castor oil and evening primrose oil haven’t proved themselves. Bring every bottle to your prenatal visits, and use MotherToBaby when you want an expert second look.

Related reading

• A few herbs are known pregnancy risks, and most were never tested
• A Vitamin’s Upper Limit Is a Safety Margin, Not a Target or a Cliff
• Cod liver oil didn’t stop measles, and some illnesses can’t wait for natural care
• Some herbal pills hide prescription drugs, and others swap out the herb
• Severe pregnancy vomiting was once blamed on the mind, but a fetal hormone is key

Sources

1. Rothman KJ, Moore LL, Singer MR, Nguyen USDT, Mannino S, Milunsky A. “Teratogenicity of High Vitamin A Intake.” New England Journal of Medicine, 1995;333(21):1369–1373 (abstract via RTI International). rti.org
2. Scialli AR. “Does Vitamin A Cause Birth Defects?” Relias Media professional newsletter review, undated (references through 2001). reliasmedia.com
3. NIH Office of Dietary Supplements. “Vitamin A and Carotenoids: Fact Sheet for Health Professionals.” Updated March 10, 2025. ods.od.nih.gov
4. MotherToBaby, Organization of Teratology Information Specialists. “Marijuana (Cannabis)” fact sheet. May 1, 2025 (page modified December 2, 2025). mothertobaby.org
5. U.S. Food and Drug Administration. “What You Should Know About Using Cannabis, Including CBD, When Pregnant or Breastfeeding.” Consumer Update, content current as of October 16, 2019 (page republished January 6, 2026). fda.gov
6. Lo JO, et al. “Prenatal Cannabis Use and Neonatal Outcomes: A Systematic Review and Meta-Analysis.” JAMA Pediatrics, 2025 (news release via Scimex, May 6, 2025; summary via JournalFeed). scimex.org and journalfeed.org
7. Society for the Study of Addiction. News release on Sorkhou M, et al., Addiction, 2023, reprinted by Neuroscience News, November 16, 2023. neurosciencenews.com
8. FOX 13 (Scripps national news). “She drank kratom tea while pregnant. Then her newborn went into withdrawal.” November 7, 2018, on a case report by Eldridge W, et al., Pediatrics, November 2018 (journal page linked from the story; not opened). fox13now.com
9. “Is oral consumption of dates (Phoenix dactylifera L. fruit) in the peripartum period effective and safe integrative care to facilitate childbirth and improve perinatal outcomes: a comprehensive revised systematic review and dose-response meta-analysis.” BMC Pregnancy and Childbirth, January 2024. link.springer.com
10. Kelly AJ, Kavanagh J, Thomas J. “Castor oil, bath and/or enema for cervical priming and induction of labour.” Cochrane Database of Systematic Reviews, 2013, Issue 7, CD003099 (plain-language summary and version history). cochrane.org and cochranelibrary.com
11. Shahinfar S, Abedi P, Jahanfar S, Khajehpoor M, Chashmyazdan M. “The effect of evening primrose oil on cervical ripening and birth outcomes: A systematic review and meta-analysis.” Heliyon, 2023;9(2):e13414 (abstract via DOAJ). pubmed.ncbi.nlm.nih.gov
12. Niazi A, Ghavami V, Beiranvandi F, et al. “The Effects of Oral and Vaginal Administration of Evening Primrose Oil on Cervical Ripening and Birth Outcomes: A Systematic Review and Meta-Analysis.” Evidence Based Care Journal, 2026;16(1):72–86. ebcj.mums.ac.ir
13. MotherToBaby, Organization of Teratology Information Specialists. “Pregnancy and Breastfeeding Exposures.” Accessed October 2026. mothertobaby.org