Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Folic acid, vitamin D and medication review
Obstetrics and gynaecology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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A medicine concern may need urgent specialist action
Pregnancy during treatment with valproate, methotrexate, an oral retinoid or another known high-risk medicine requires prompt expert assessment, but abrupt unsupervised withdrawal can also endanger the pregnant person and fetus.
Action: Confirm the medicine, formulation, dose, indication, last exposure and gestation; contact the relevant prescriber and obstetric or teratology service urgently; and tell the patient not to stop an essential medicine unless a clinician has made a safe replacement plan.
Role and principles
Use preconception and early-pregnancy contact to prevent avoidable fetal harm while preserving essential maternal treatment through individualised supplement and medicine decisions.
Preconception review works best before organogenesis, yet a first contact after conception remains valuable. Establish the first day of the last menstrual period, likely conception and current gestation, pregnancy intention and whether the pregnancy has been confirmed. Ask about previous pregnancies and congenital anomalies, diabetes, epilepsy, hypertension, renal or autoimmune disease, thrombosis, mental illness, bariatric surgery, anaemia and dietary restriction. The objective is not to make the medicine list shorter; it is to achieve effective maternal treatment with the lowest avoidable reproductive risk.
Standard folic acid is 400 micrograms once daily. It should begin ideally about 3 months before conception and continue through 12 completed weeks because neural-tube closure occurs early, often before the first antenatal appointment. If pregnancy was unplanned or supplementation was missed, start promptly without implying that late initiation can reverse an earlier exposure. Explore access, nausea, swallowing difficulty and misunderstanding when adherence is poor, and arrange a prescription when the indicated 5 mg strength is required.
Assessment and patient selection
Standard folate need
Most people planning pregnancy or within the first 12 weeks need 400 micrograms daily, even when a healthy diet contains natural folates.
High-dose folate indication
A relevant congenital-malformation history, diabetes, folate-requiring haemoglobinopathy or medicine affecting folate identifies the group offered 5 mg daily.
Vitamin D deficiency risk
Little outdoor exposure, extensively covered skin, dark skin, malabsorption or previous deficiency increases the need for year-round advice and sometimes testing.
High-risk medicine exposure
Valproate, methotrexate, systemic retinoids and other recognised teratogens trigger prompt specialist risk assessment while the underlying disease remains actively managed.
Duplicated supplementation
A pregnancy multivitamin combined with separate products can duplicate vitamin D, iron or other ingredients and may inadvertently contain vitamin A.
Red flags requiring action
New pregnancy while taking valproate requires urgent specialist contact and current Pregnancy Prevention Programme review; seizures or severe mental illness must not be destabilised by abrupt cessation.
Recent methotrexate, systemic retinoid, warfarin, ACE inhibitor or angiotensin-receptor blocker exposure needs prompt indication-specific assessment rather than reassurance or automatic advice about pregnancy outcome.
Baseline assessment
01Exact medication and supplement reconciliationFirst step
Why
Define actual exposure, indication and adherence before changing treatment or estimating fetal risk.
Interpretation and limitations
Brand, formulation, route, dose and dates matter; an incomplete list can miss long-acting preparations, recently discontinued medicines and duplicated vitamins.
02Gestational dating and exposure timeline
Why
Relate each medicine or infection exposure to conception and developmental stage.
Interpretation and limitations
Timing influences the type of potential effect, but dating uncertainty and long drug half-lives mean specialist interpretation may still be necessary.
03Full blood count and targeted haematinics
Why
Identify anaemia and investigate likely iron, folate or vitamin B12 deficiency when history or indices support it.
Interpretation and limitations
Microcytosis is not automatically iron deficiency and macrocytosis is not automatically folate deficiency; haemoglobinopathy and mixed deficiency can alter indices.
04Serum 25-hydroxyvitamin D
Why
Confirm suspected deficiency when symptoms, malabsorption, bone disease or specialist risk makes the result management changing.
Interpretation and limitations
Routine universal testing is unnecessary; a low result prompts a clinician-selected treatment course distinct from the 10-microgram prevention dose.
Interventions
01First contactStart prevention without waiting for bookingFirst stepPregnancy is planned, possible or newly confirmed and supplement status is unknown.+
1Start 400 micrograms folic acid daily immediately unless a 5 mg risk indication is identified, and set the 12-week stop point.
2Assess vitamin D intake and seasonal or year-round risk, while checking multivitamin labels for retinol and duplicated doses.
3Refer promptly for bariatric, malabsorption or complex nutritional needs and make antenatal referral early rather than deferring all decisions to booking.
02ReconciliationProtect maternal control while reducing exposure riskAny regular, intermittent or recently stopped medicine is reported around conception or in pregnancy.+
1Document exact products, doses, routes, timing, indication, prescriber and the patient's own changes, including non-prescription and herbal preparations.
Medicines and treatment safety
Reduces the population risk of fetal neural-tube defects when present during early embryonic development.
Folic acid standard prevention
Take 400 micrograms orally once daily from ideally 3 months before conception through 12 completed weeks of pregnancy.
Do not assume diet replaces supplementation, and do not continue delaying initiation while trying to establish an exact conception date.
Provides the current UK high dose for defined congenital-malformation, diabetes, haematological or medicine-related risk.
Folic acid high-risk prevention
Take 5 mg orally once daily before conception and through the first 12 weeks when a NICE increased-risk criterion applies.
BMI of 25 kg/m² or more alone is not an indication under NG247; bariatric surgery requires individual specialist advice.
Supports maternal vitamin D status when dietary intake and sunlight synthesis may not meet recommended population requirements.
Colecalciferol routine supplementation
Consider vitamin D 10 micrograms orally once daily during October to March, and year round when deficiency risk is increased.
A confirmed deficiency may need a different supervised regimen; check combined products to prevent unrecognised cumulative dosing.
Reduces pre-eclampsia risk in the defined higher-risk antenatal population and should be prescribed with a documented indication.
Targets, monitoring and follow-up
At booking, confirm whether folic acid started before conception, which strength is being taken and the date on which it should stop.
Reconcile the medication list again after every specialist appointment, hospital admission and new prescription because pregnancy plans can become fragmented across services.
Track the maternal condition being treated, not only fetal exposure: document seizures, glycaemia, blood pressure, mood, renal function or other relevant control measures.
Check that an urgent teratology or fetal-medicine referral was received and that the patient understands the proposed scan or diagnostic pathway and its limitations.
Review adherence and affordability sensitively and offer Healthy Start access or prescription support where eligible rather than recording non-adherence without intervention.
Special situations
BMI guidance changed
The 2025 NICE update removed weight category alone as a reason for 5 mg folic acid, so older local habits can now generate overprescribing.
Exposure is not diagnosis
Taking a potentially harmful medicine does not prove fetal injury; risk depends on agent, dose, timing and maternal disease and needs evidence-based counselling.
The untreated illness matters
Seizures, severe mood relapse, uncontrolled diabetes or thrombosis can threaten both patient and fetus, making abrupt medicine withdrawal a preventable hazard.
Natural folate is insufficient
A balanced diet is valuable but cannot reliably supply the recommended synthetic folic acid exposure during the narrow neural-tube closure window.
One label can hide duplication
Pregnancy vitamins, fortified drinks and separate tablets may overlap, so ingredient and unit review is more reliable than counting containers.
Common pitfalls
01
Prescribing 5 mg folic acid solely because BMI is above 25 kg/m² despite the current NICE recommendation.
02
Waiting for the booking appointment before starting standard folic acid in a newly recognised pregnancy.
03
Telling a patient to stop valproate, insulin, anticoagulation or psychiatric treatment immediately without specialist coordination.
04
Equating a teratogenic exposure with certain fetal abnormality or offering false reassurance before timing and dose have been reviewed.
05
Recommending cod-liver oil or a multivitamin containing retinol because it is marketed as a natural supplement.
06
Using routine vitamin D prevention doses as treatment for confirmed severe deficiency without an individualised regimen.
Practice
Two practice questions
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Question 1 of 2
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Obstetrics and gynaecologyOriginal SBA
Selecting folic acid by risk
A 29-year-old planning pregnancy has a BMI of 33 kg/m², no diabetes, no relevant family or pregnancy history and takes no folate-interacting medicine. What folic acid regimen is indicated?
Sources and review status6 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
NICE changed an important examination trap in 2025. A BMI of 25 kg/m² or above, including obesity, is no longer by itself an indication for high-dose folic acid. Use 5 mg daily for increased neural-tube-defect or congenital-malformation risk: either parent or a family member has a relevant history, a previous pregnancy was affected, the pregnant person has type 1 or type 2 diabetes, sickle cell disease or thalassaemia needing folate, or takes a medicine that alters folate absorption or metabolism such as an antiseizure or HIV medicine. Previous bariatric surgery requires individual advice from the bariatric and maternity teams.
Vitamin D advice combines a population dose with risk assessment. A 10-microgram daily supplement is considered during October to March; year-round supplementation is appropriate when skin is rarely exposed to sunlight, the person usually covers most skin outdoors, has dark skin, or otherwise has a high likelihood of low vitamin D. Pregnancy multivitamins and Healthy Start products may already provide this amount. Deficiency treatment uses a separate, clinician-directed regimen based on clinical context and should not be improvised by multiplying routine supplements.
Medication reconciliation includes prescriptions, recent courses, depot and injectable preparations, pharmacy sales, vitamins, traditional remedies, protein or gym products, cannabis and other substances. Record exact names, strengths, routes and timing rather than writing only a drug class. Determine why each treatment is used and the harm caused if it is stopped. Check current BNF, SmPC, UKTIS or BUMPS information and involve the relevant specialist for high-risk or unfamiliar exposure; absence of a patient leaflet is not evidence of safety or harm.
Some conditions become more dangerous when treatment is withdrawn. Abrupt antiseizure-drug cessation can precipitate convulsive seizures; stopping corticosteroids, insulin, anticoagulation or psychiatric treatment without a plan can destabilise maternal health. Conversely, certain medicines need preconception substitution or urgent pregnancy review. Valproate has strict regulatory controls and substantial reproductive risk, methotrexate and oral retinoids are contraindicated exposures, and renin-angiotensin-system medicines or warfarin require indication-specific alternatives. A patient who has already taken a medicine deserves a quantified expert assessment, not blame or a deterministic prediction.
Supplement review extends beyond folate and vitamin D. Avoid multivitamins containing preformed vitamin A described as retinol, and avoid cod-liver oil and liver products. Do not prescribe iron solely because pregnancy exists: check haemoglobin and treat identified deficiency with an appropriate preparation and follow-up. Vegan diets, malabsorption and previous bariatric surgery may require assessment of vitamin B12, iron, calcium, iodine or other nutrients through a dietetic or specialist pathway rather than a generic high-dose bundle.
Low-dose aspirin belongs to pre-eclampsia prevention rather than routine vitamin advice. NICE recommends 75 to 150 mg daily from 12 weeks until birth for one high-risk factor, including previous hypertensive pregnancy disease, chronic kidney disease, autoimmune disease, type 1 or type 2 diabetes or chronic hypertension, or for more than one moderate-risk factor. Confirm allergy, bleeding history and interacting treatment, prescribe rather than suggesting self-purchase, and document the reason and stop point.
Key points
Advise folic acid 400 micrograms orally once daily from ideally 3 months before conception, or as soon as pregnancy is recognised, through the first 12 weeks.
Use folic acid 5 mg orally once daily through 12 weeks when neural-tube-defect or congenital-malformation risk is increased by personal, partner or family history, a previous affected pregnancy, type 1 or type 2 diabetes, a folate-requiring haematological disorder, or a medicine that disrupts folate.
Under NICE NG247, BMI of 25 kg/m² or more alone does not justify 5 mg folic acid; prescribe the high dose only when another listed risk factor is present.
Consider vitamin D 10 micrograms daily during October to March, and throughout the year when sun exposure is limited or deficiency risk is increased; avoid unplanned pharmacological loading doses.
Check every prescribed, over-the-counter, online and herbal product, including allergies, adherence, indication, contraception history and what has already been stopped or substituted.
Do not tell a pregnant person to stop long-term treatment before comparing fetal exposure risk with the maternal and fetal consequences of uncontrolled disease.
Avoid supplements containing retinol and avoid liver, liver products and cod-liver oil; pregnancy-specific multivitamins should be checked for dose duplication.
Assess pre-eclampsia risk separately: prescribe aspirin 75 to 150 mg daily from 12 weeks until birth for one high-risk factor or more than one moderate-risk factor, unless contraindicated.
Severe vomiting, inability to retain medicines, recurrent seizures, hyperglycaemia with ketones or deterioration of a chronic disorder requires same-day maternal assessment.
A supplement labelled as vitamin A, retinol or cod-liver oil should be stopped and its contents checked because excessive preformed vitamin A can impair fetal development.
Bariatric surgery, malabsorption, renal disease or a complex restrictive diet warrants specialist micronutrient review instead of routine-dose escalation without testing.
05Condition-specific baseline review
Why
Assess control of diabetes, epilepsy, hypertension, thyroid, renal, autoimmune or psychiatric disease before medicine adjustment.
Interpretation and limitations
Poor maternal control often carries substantial fetal risk, so laboratory and clinical status guide whether to continue, switch or intensify therapy.
2
AlternativeUse current pregnancy evidence and specialist input to compare continued exposure, dose optimisation and a planned alternative against the harm of untreated disease.
3Give a written plan stating what continues, what changes, who owns follow-up and which new symptoms or pregnancy events require urgent review.
03High-risk findingCoordinate urgent expert assessmentA potentially teratogenic medicine, uncontrolled chronic disease or clinically important deficiency is identified.+
1Contact the relevant specialty, obstetric medicine or fetal medicine service and provide the exposure timeline and current maternal status.
2Do not abruptly stop essential treatment unless the immediate toxic risk clearly requires it and an appropriate prescriber directs the change.
3Arrange indicated maternal monitoring and fetal screening, explain uncertainty honestly, and document shared decisions without predicting an outcome from exposure alone.
Low-dose aspirin for pre-eclampsia risk
Take 75 to 150 mg orally once daily from 12 weeks until birth when NICE high-risk or multiple moderate-risk criteria are met.
Check hypersensitivity, active bleeding and relevant interactions; it is not a universal pregnancy supplement or a reason for high-dose folic acid.