What supplements should a woman planning pregnancy take?

Preconception Supplementation for Women Planning Pregnancy

All women planning pregnancy should take a daily supplement containing 400-800 μg (0.4-0.8 mg) of folic acid starting at least 2-3 months before conception, combined with vitamin D at 1,000 IU daily, and a comprehensive multivitamin containing iron, calcium, and other essential micronutrients. 1, 2, 3

Folic Acid: The Critical Foundation

Standard-risk women require 400-800 μg (0.4-0.8 mg) of folic acid daily, beginning at least 1 month before conception and continuing through the first 12 weeks of pregnancy. 1, 4 This dosing reduces neural tube defect risk by approximately 50-72% based on randomized controlled trials. 4

High-Risk Women Require Higher Doses

Women with specific risk factors need substantially more folic acid—4-5 mg daily starting 3-6 months before conception. 1, 4, 5 High-risk categories include: 1, 5

• Previous pregnancy affected by neural tube defects
• Personal or family history of neural tube defects in either partner
• Type 1 diabetes mellitus
• Taking antiepileptic medications (particularly valproate or carbamazepine)
• BMI >30 kg/m² 1

After 12 weeks gestation, high-risk women should reduce to the standard 400-800 μg daily dose. 3, 5

Critical Safety Consideration

Before initiating high-dose folic acid (>1 mg), screen for vitamin B12 deficiency to avoid masking pernicious anemia while neurologic damage progresses. 4 However, for standard doses (400-800 μg), no pre-supplementation screening is required. 5 Taking folic acid within a multivitamin containing 2.6 μg/day of vitamin B12 mitigates even theoretical concerns. 5

Vitamin D: Essential for Maternal and Fetal Health

Women planning pregnancy should supplement with at least 1,000 IU (40 mcg) vitamin D daily, targeting serum 25-hydroxyvitamin D levels ≥50 nmol/L (20 ng/mL). 2 Supplementation should begin 2-3 months before planned conception to optimize stores. 2

Monitoring Strategy

• Check serum 25-hydroxyvitamin D, calcium, phosphate, magnesium, and parathyroid hormone (PTH) every 6 months during the preconception period 2
• Recheck 3-6 months after any dosage adjustment 2
• Add calcium supplementation (1,200-1,500 mg daily in divided doses) if needed to maintain PTH within normal limits 2

Use vitamin D₃ (cholecalciferol) rather than D₂ (ergocalciferol), as D₃ is more effective at raising serum levels. 2

Comprehensive Multivitamin Requirements

A daily multivitamin should contain the following minimum amounts: 1

• Iron: 45-60 mg elemental iron (or >18 mg for women with gastric banding) 1
• Calcium: 1,200-1,500 mg total daily (from food and supplements combined) 1
• Zinc: 15 mg 1
• Copper: 2 mg (maintain 8-15 mg zinc per 1 mg copper ratio) 1
• Selenium: 50 μg 1
• Thiamine: >12 mg 1
• Vitamin E: 15 mg 1
• Beta-carotene (vitamin A): 5,000 IU 1

Vitamin A: Form Matters

Avoid retinol-form vitamin A during pregnancy planning due to teratogenicity risk; use beta-carotene form instead. 1 The recommended upper limit for retinol supplements is 3,000 IU/day. 6

Special Populations Requiring Intensified Monitoring

Women with BMI >30 kg/m²

These women require the same vitamin D dose but must take 4-5 mg folic acid daily (not 400-800 μg) throughout the preconception period and first trimester. 1, 2

Women with History of Bariatric Surgery

These women require more intensive monitoring every 3-6 months and should check: 1

• Serum folate or red blood cell folate (every 3 months)
• Vitamin B12 or transcobalamin (every 3 months)
• Ferritin, iron studies, full blood count (every 3 months)
• Vitamin A levels (every 3 months)
• 25-hydroxyvitamin D with calcium, phosphate, magnesium, PTH (every 6 months)
• Zinc, copper, selenium (every 6 months)

Pregnancy should be avoided for 12-18 months following bariatric surgery to allow weight stabilization. 1

Critical Timing and Common Pitfalls

Start Early—Don't Wait for Pregnancy Confirmation

Since 50% of pregnancies in the United States are unplanned, all women of reproductive age (12-45 years) who are capable of pregnancy should take folic acid supplements, regardless of whether pregnancy is actively planned. 4, 5 Early pregnancy is a critical period for vitamin D-dependent processes, so delaying supplementation until pregnancy confirmation is too late. 2

Avoid Overdosing

Women taking high-dose folic acid (>1 mg) should not take multiple multivitamin tablets. 5 Instead, take one multivitamin and add separate folic acid-only tablets to reach the desired dose. 5 Keep total daily folate consumption below 1 mg per day for standard-risk women to avoid masking vitamin B12 deficiency. 3

Calcium and Iron Separation

Single calcium doses should not exceed 600 mg and must be separated by 2-hour intervals from iron supplements or multivitamins containing iron to optimize absorption. 1

Avoid Mineral Oil

Mineral oil interferes with absorption of fat-soluble vitamins, including vitamin D. 7

Practical Implementation Algorithm

For standard-risk women:

1. Start 400-800 μg folic acid + 1,000 IU vitamin D + comprehensive multivitamin 2-3 months before conception 1, 2
2. Continue through first trimester 1
3. No pre-supplementation screening required 5

For high-risk women:

1. Check baseline vitamin B12 if prescribing >1 mg folic acid 4
2. Start 4-5 mg folic acid + 1,000 IU vitamin D + comprehensive multivitamin 3-6 months before conception 1, 4
3. Continue high-dose folic acid through 12 weeks gestation, then reduce to 400-800 μg 3, 5
4. Monitor vitamin D and other micronutrients every 3-6 months 2

For women with BMI >30 kg/m²:

1. Treat as high-risk: 4-5 mg folic acid (not standard dose) 1
2. Same vitamin D and multivitamin as standard-risk 2

For women with bariatric surgery history:

1. Delay pregnancy 12-18 months post-surgery 1
2. Intensive monitoring every 3-6 months 1
3. Adjust supplementation based on serum levels 1