Obstetrics & Gynaecology/Preconception & pregnancy supplements

Folic acid & pregnancy supplements

also: folic acid NTD · iron pregnancy · vitamin D · preconception

Overview

The supplements every pregnancy needs — folic acid (neural tube defect prevention) is the highest-yield, with the high-dose criteria a common exam point.

Mechanism

Folic acid supports neural tube closure (complete by ~28 days) → reduces neural tube defects; needed pre-conception because the tube closes before many know they are pregnant. Iron corrects the increased demand; vitamin D supports fetal bone.

Indications

Preconception & first-trimester (folic acid)
Throughout pregnancy (vitamin D)
Iron-deficiency anaemia in pregnancy

The agents

Folic acid 400 mcgstandard

preconception → 12 weeks

All women trying to conceive.

Folic acid 5 mgHIGH-dose

Previous NTD, diabetes, BMI>30, antiepileptics, sickle/thalassaemia, coeliac.

Vitamin D 10 mcgall pregnancy

Throughout.

Iron (ferrous salt)if anaemic

Treat iron-deficiency anaemia (not routine).

Adverse effects

Iron: constipation, black stools, GI upsetcommon

Avoid vitamin A / retinol / liver in pregnancyserious

Teratogenic.

Cautions & contraindications

High-dose vitamin A / retinoids in pregnancypregnancy

Teratogen.

Interactions

Iron absorption ↓ by calcium/tea; ↑ by vitamin C

Monitoring & kinetics

FBC for anaemia; folic acid started ideally before conception

Oral. Folic acid is preventive — must start pre-pregnancy.

Source: NICE — Antenatal care (NG201) · BNF — Folic acid