Synopsis
Use preconception and early-pregnancy contact to prevent avoidable fetal harm while preserving essential maternal treatment through individualised supplement and medicine decisions.
- 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.
Key red flags
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.
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.
Investigation priorities
Define actual exposure, indication and adherence before changing treatment or estimating fetal risk.
Management branches
Pregnancy is planned, possible or newly confirmed and supplement status is unknown.
- Start 400 micrograms folic acid daily immediately unless a 5 mg risk indication is identified, and set the 12-week stop point.
- Assess vitamin D intake and seasonal or year-round risk, while checking multivitamin labels for retinol and duplicated doses.
- Refer promptly for bariatric, malabsorption or complex nutritional needs and make antenatal referral early rather than deferring all decisions to booking.