Doctor Guide: Pregnancy
Doctor Guide: Pregnancy
Written by BePurer's medical advisory team. For educational purposes only — always consult your midwife or GP for personalised advice.
Preconception: The 3 months before trying to conceive
The preconception period is one of the most nutritionally important windows in a woman's life. Egg quality, hormonal balance, and uterine health are all influenced by nutritional status before pregnancy begins. Ideally, preconception preparation begins 3–6 months before trying to conceive.
Preconception checklist
- ✅ Start methylfolate (400–800mcg daily)
- ✅ Test and optimise vitamin D (aim for 75–150 nmol/L)
- ✅ Begin omega-3 supplementation (200–300mg DHA daily)
- ✅ Check iron and ferritin levels
- ✅ Consider CoQ10 (200–600mg) if over 35 or with known egg quality concerns
- ✅ Reduce alcohol, caffeine (under 200mg daily), and ultra-processed foods
- ✅ Stop retinol use and use clean skincare products and household cleaning products
- ✅ Achieve a healthy weight if possible (BMI 18.5–24.9)
- ✅ Review any medications with your GP for pregnancy safety
First Trimester (Weeks 1–12): Foundation
The first trimester is critical for organ formation. Neural tube closure occurs by week 6 — before most women know they are pregnant. This is why preconception supplementation is so important.
Clinical priorities
- Methylfolate: Continue 400–800mcg daily. Women with MTHFR variants or previous neural tube defect pregnancies may need 5mg (prescription dose).
- Vitamin D: 1,000–2,000 IU daily. Test if possible.
- Choline 450-550mg daily for neural tube defects.
- DHA: 200–300mg daily. Critical from the earliest weeks.
- Iodine: 150–220mcg daily. Often missing from standard prenatal supplements.
- B6: 10–25mg up to three times daily if experiencing nausea.
- Iron: Test ferritin. Supplement if below 30 mcg/L.
Foods to avoid in pregnancy
- Raw or undercooked meat, fish, and eggs (listeria, salmonella risk)
- High-mercury fish (shark, swordfish, marlin, raw tuna)
- Unpasteurised dairy and soft cheeses (listeria risk)
- Liver and liver products (excess vitamin A)
- Raw sprouts
- Alcohol (no safe level in pregnancy)
Second Trimester (Weeks 13–26): Growth
Nausea typically eases and appetite returns. This is the time to focus on building nutritional stores for the rapid growth phase ahead.
Clinical priorities
- Iron: Blood volume expansion accelerates. Retest ferritin at 28 weeks.
- Calcium: 1,000mg daily from food and supplements. Dairy, fortified plant milks, leafy greens, almonds.
- Magnesium: 300–400mg daily. Supports muscle function, sleep, and may reduce risk of preterm labour.
- Vitamin C: Enhances iron absorption. Take with iron-rich meals.
- Omega-3 DHA: Continue 200–300mg daily.
Third Trimester (Weeks 27–40): Maturation
The third trimester is dominated by fetal growth and brain development. DHA requirements are at their highest. Iron needs peak. The body begins preparing for labour and breastfeeding.
Clinical priorities
- DHA: Consider increasing to 300–500mg daily in the third trimester.
- Iron: Highest requirements. Retest at 36 weeks if anaemic.
- Vitamin K2: Supports fetal bone mineralisation.
- Magnesium: Leg cramps, sleep, and Braxton Hicks management.
- Vitamin D: Continue throughout. Newborns need vitamin D drops from birth.
Preparing for birth
From around 36 weeks, some women choose to take raspberry leaf tea or capsules to tone the uterus in preparation for labour. Evidence is limited but it is generally considered safe from 36 weeks. Perineal massage from 34–36 weeks has good evidence for reducing the risk of tearing.