Which supplement side effects in pregnant women in Switzerland?

Which food supplements are recommended or contraindicated for a pregnant woman in Switzerland?

Which supplements can a pregnant woman take safely in Switzerland?

Only three supplementations are validated by the Swiss health authorities for a normal pregnancy in the mother-to-be: folic acid, vitamin D and iodine^[3]. Folic acid, sold as a tablet or capsule, is taken at 400 µg/day in synthetic form, ideally during the preconception period (3 months before conception) and until the 12th week of pregnancy. This recommended dosage supports the baby’s development and plays a key role in preventing neural-tube anomalies in early pregnancy. The Swiss Folic Acid Foundation points out that a healthy, varied and balanced diet only delivers 200 to 250 µg/day of natural folates — only half of the doubled needs during pregnancy^[2]. Vitamin D is recommended at 600 IU/day by the Federal Nutrition Commission to ensure a sufficient intake. At this dose, more than 97% of the population reaches the target blood level of 50 nmol/L, including pregnant women^[4]. Iodine mainly comes through Swiss iodised cooking salt (enriched to 25 mg/kg since January 2014). The FSVO observes in its 2019 Swiss Nutrition Bulletin that pregnant women do not consume enough of it. A targeted intake of 200 to 250 µg/day is therefore recommended (WHO, taken up by the federal authorities)^[1].

Which food supplements are contraindicated during pregnancy?

Supplements containing preformed vitamin A (retinol, retinyl palmitate), berberine, or oestrogen-mimicking plant extracts are formally contraindicated in the mother-to-be, both during pregnancy and during breastfeeding^[8]. Vitamin A becomes toxic to the foetus (teratogenic effect) above 3,000 µg RE/day, i.e. about 10,000 IU. This limit must not be exceeded in women who are pregnant or who might be^[9]. Iron without a biological work-up is not part of routine supplementations, contrary to what is suggested by certain pregnancy vitamin brands such as Elevit, Burgerstein or Natalben Plus, widely present on the Swiss market. The Watt et al. meta-analysis published in February 2025 in Family Practice found no clinical benefit in pregnant women who are not deficient^[5], and the Cochrane Finkelstein 2024 review concludes that systematic supplementation reduces maternal anaemia but does not bring long-term clinical benefit in women who are not deficient^[6].

What are the risks of vitamin or mineral overdose during pregnancy?

Why is high-dose vitamin A teratogenic for the foetus?

Preformed vitamin A induces, above the teratogenic threshold, a specific malformation syndrome affecting the central nervous system, the heart and the face^[9]. Excess vitamin A acts directly on the genes that drive embryonic development from the very first weeks, which disrupts the formation of organs. The Zamil et al. study published in 2021 in Dermatology Practical & Conceptual analysed 49 “skin health” and acne supplements sold online. 26 of them (53%) contain vitamin A. Three are judged probably teratogenic, and four exceed daily nutritional needs^[9]. Retinol-based skincare products and “anti-ageing” supplements aimed at the face or skin beauty rest on the same mechanism and should be set aside. The CHUV recommends, as a precaution, avoiding eating animal liver — a food naturally rich in retinol — during the first trimester: 100 g of veal liver contains on average 10,000 to 15,000 µg RE of vitamin A according to the ANSES Ciqual table, i.e. 3 to 5 times the teratogenic threshold in a single serving^[3].

Why is stacking several sources of vitamin D or iodine dangerous?

The stacking of “pregnancy-special” supplements is responsible for documented cases. These cases combine excess calcium in the blood (hypercalcaemia) and thyroid disorders in newborns (congenital hypothyroidism), reported to the Anses nutrivigilance scheme^[8]. Multiplying the boxes and packs of supplements purchased in parallel exposes mothers-to-be to a silent threshold breach — each product taken in isolation seems safe, the stack is no longer so. A genetic sensitivity to vitamin D — rarely investigated — combined with too high an intake can cause an excess of calcium in the blood in the baby. If this excess persists, it leads to growth retardation, narrowing of an artery of the heart (aortic stenosis), damage to the retina and a disruption of normal cell division^[12]. For iodine, stacking sources (supplements, iodine-based medicines, iodised salt) saturates the baby’s thyroid and increases the risk of goitre at birth, with an impact on the first weeks of life^[8]. The Cochrane Finkelstein 2024 review confirms on iron that systematic supplementation reduces maternal anaemia, but does not bring long-term benefit in women who are not deficient — hence the value of starting from a blood test^[6].

Which plants and active substances should be banned from supplements during pregnancy?

Which plants are contraindicated for uterotonic or hormonal effects?

Three families of plants are formally to be avoided during pregnancy: those that mimic female hormones, those that contract the uterus, and those that are laxative by intestinal irritation^[13]. The “organic” or “natural” label on a supplement or a plant oil does not remove these risks. Plants that mimic female hormones (sage, ginseng, hops, fennel, aniseed, liquorice) contain phytoestrogens that stimulate the uterus and can cause a miscarriage. Plants that contract the uterus (fenugreek, raspberry leaf before the 3rd trimester, bearberry, pennyroyal, feverfew) trigger documented uterine contractions^[13]. Stimulating laxatives (senna, buckthorn, cascara, aloe, Chinese rhubarb) irritate the intestine and can reflexively trigger uterine contractions. Traditional herbal medicine also includes bitter plants and fruits or barks considered toxic during pregnancy: mugwort, wormwood, génépi (Artemisia spp.), tansy, celandine, goldenseal, rue, yellow gentian^[13].

Which stimulants and active substances should be avoided during pregnancy?

Supplements containing guarana, ginseng, mate, kola, ephedra or concentrated theine should be avoided throughout pregnancy because of their load of caffeine and stimulating alkaloids^[13]. Guarana delivers 4 to 7 times more caffeine than coffee per equal weight, and caffeine crosses the placenta. Yet the baby takes much longer to eliminate it than the mother does, because their liver does not yet have the necessary enzyme. Essential oils, internally as well as on the skin or as a fragrance, are contraindicated as a precaution throughout pregnancy, whether presented as a cosmetic active or as a wellness accessory. Their concentration of active principles is far above that of a simple infusion^[13]. Berberine, found in certain “blood-sugar balance” or “immunity” supplements, is explicitly advised against in pregnant and breastfeeding women: it crosses the placenta, can stimulate uterine contractions and induce kernicterus in the newborn^[8]. Slimming, draining, detox, anti-water-retention or “hair-growth” products based on plants combine several risks: oestrogenic plants, digestive irritation, toxic mobilisation of placental fats.

How do you choose a food supplement suited to pregnancy in Switzerland?

Which criteria should you check on the label in Switzerland?

A supplement intended for a pregnant woman in Switzerland must display four verifiable elements, and the label must be written in French (or in the other official languages depending on the region), whatever the form — box, capsule, tablet or sachet. First, the exact form of each active; then the dose in standardised units. Next, the absence of contraindicated ingredients, and finally compliance with Swiss food legislation on food supplements (reference SR 817.022.14). For vitamin A, the label must distinguish retinol (the form at risk for the foetus) from beta-carotene (the form without documented risk). The amount must be indicated in µg RE (retinol equivalents), not just in IU^[9]. For folic acid, check the dose of 400 µg and the form. Synthetic folic acid remains the standard. 5-MTHF (methylfolate, the already active form, also known as active folate) is better suited to women carrying a frequent variation of the MTHFR gene, which slows the use of classic folic acid^[10]. The possible presence of animal-derived gelatin in the capsule should be checked by women on a vegan or vegetarian diet; gelatin-free prenatal vitamins are available in Swiss pharmacies. The absence of added iodine should also be checked if the diet already uses iodised salt^[1]. The “pregnancy-special” claim on the box brings no particular guarantee in Switzerland. Swiss food legislation only requires a declaration to the cantonal chemist, not a marketing authorisation as for medicines controlled by Swissmedic.

Which health professional should you ask for advice before supplementing?

Before any supplementation, consulting a healthcare professional remains the rule: the gynaecologist, the midwife and the Swiss pharmacist are the three qualified contacts to give personalised advice on pregnancy in Switzerland, in line with a healthy lifestyle. The gynaecologist prescribes after the routine blood test of the 1st trimester. This blood test measures iron stores (ferritin), the vitamin D level and the proper functioning of the thyroid (TSH). They are also the only professional authorised to prescribe 4 mg/day of folic acid in case of a history of neural-tube anomaly or antiepileptic treatment^[10]. The midwife provides routine nutritional follow-up and adjusts intakes in case of first-trimester nausea, a vegan diet or a multiple pregnancy^[3]. The Swiss pharmacist, trained in dispensing food supplements, checks interactions and the coherence of combined doses. This contact in the pharmacy is valuable for spotting a stacking of iodine or vitamin D between several products, and their advice service remains free of charge. Self-supplementation by purchase on the internet or in supermarkets concentrates the cases reported to the nutrivigilance scheme^[8].

Frequently asked questions