First Trimester Safety Guide (Weeks 1–13): Evidence-Based Checklist

Creator: SafeMama Editorial Team
Published: 2026-05-21

Published May 21, 2026 | By SafeMama Editorial Team

Weeks 1–13 are the period during which your baby's major organs form. Small choices have outsized effects, which is why establishing a safety routine early is important. This checklist draws on guidance from ACOG, the NHS, the CDC and the WHO.

1. Supplements

Folic acid 400–800 µg per day, ideally starting pre-conception. The CDC reports that adequate folic acid intake reduces the risk of neural tube defects (such as spina bifida) by up to 70%.
Prenatal vitamin with iron, iodine, choline, DHA and vitamin D.
Vitamin D 600 IU per day — most prenatals already include this.
Avoid stand-alone vitamin A (retinol) supplements and high-dose fish liver oils due to the risk of teratogenic vitamin A excess.

2. Foods to Avoid

See our full Foods to Avoid During Pregnancy guide. First-trimester priorities:

Cold deli meats, patés, soft cheeses made with unpasteurised milk (listeria risk)
Raw or undercooked seafood, meat and eggs (salmonella, toxoplasmosis)
High-mercury fish such as swordfish, shark and king mackerel
Alcohol — no amount is known to be safe per ACOG, CDC, NHS and WHO
Caffeine — keep under 200 mg per day per ACOG
Liver (vitamin A excess)

3. Medications

Avoid (unless specifically prescribed by your obstetrician):

NSAIDs such as ibuprofen and naproxen
Isotretinoin (Accutane) — confirmed teratogen
Methotrexate, ACE inhibitors, warfarin, certain antibiotics such as tetracyclines

Generally acceptable (always confirm with your provider):

Acetaminophen / paracetamol at the lowest effective dose
Prenatal vitamins
Doxylamine/B6 for nausea (per ACOG)
Levothyroxine for hypothyroidism

Always tell every clinician (dentist, urgent care, pharmacist) that you are pregnant before they prescribe anything. The NHS maintains a useful general overview of medicines in pregnancy.

4. Skincare

Switch out:

All retinoids (retinol, tretinoin, adapalene, isotretinoin, retinyl palmitate)
High-percentage salicylic acid > 2%
Hydroquinone
Permanent and semi-permanent hair dye in the first trimester — consider highlights or balayage that do not touch the scalp

Switch in: bakuchiol, azelaic acid, vitamin C, niacinamide, mineral SPF. Full list in our Ingredients to Avoid During Pregnancy and Safe Skincare Routine guides.

5. Environmental Hazards

Cat litter — let someone else change it during pregnancy. The CDC notes that cat faeces can contain Toxoplasma gondii.
Gardening soil — wear gloves and wash hands afterwards (toxoplasmosis).
Hot tubs and saunas above 101°F / 38.3°C — the ACOG notes elevated body temperature in early pregnancy may increase neural tube defect risk.
X-rays — avoid unless medically necessary; always tell the clinician you are pregnant.
Second-hand smoke and vaping — avoid completely.
Household chemicals — open windows, wear gloves, and avoid pesticide sprays.

6. Exercise

The ACOG recommends 150 minutes per week of moderate-intensity activity (about 30 minutes most days) unless contraindicated by your provider. Safe options include:

Walking
Swimming
Prenatal yoga
Stationary cycling
Strength training with light-to-moderate weights

Avoid: contact sports, scuba diving, hot yoga, high-altitude exercise above 6,000 feet without acclimatisation, and any activity with a high fall risk.

7. Travel

Most flying is safe before 36 weeks (28 weeks for multiples). Walk every 1–2 hours on long flights to reduce DVT risk and stay well hydrated. Airline policies vary after week 28 — check the rules before booking, and carry a letter from your obstetrician if asked.

8. Red-Flag Symptoms — Call Your Provider

Per ACOG and NHS guidance, contact your provider promptly for:

Heavy bleeding (more than light spotting)
Severe abdominal or pelvic pain
Severe or persistent headache, vision changes, swelling of hands and face
Fever above 100.4°F / 38°C
Persistent vomiting (unable to keep fluids down for 24+ hours)
Painful urination or blood in urine
Sudden, severe shortness of breath or chest pain

Quick Reference Summary

Category	Action
Folic acid	400–800 µg/day from pre-conception
Caffeine	Under 200 mg/day
Alcohol	None
NSAIDs	Avoid; use acetaminophen if needed
Retinoids	Stop all topical and oral
Hot tubs/saunas	Avoid > 101°F
Cat litter	Delegate to someone else
Exercise	150 min/week moderate intensity

The Bottom Line

The first trimester is the most critical for foetal development, but most safety guidance is straightforward: take folic acid early, avoid known teratogens (alcohol, retinoids, isotretinoin), keep caffeine moderate, eat safely-prepared foods, exercise gently, and call your provider promptly about red-flag symptoms. Lean on tools like SafeMama for the everyday product decisions so you can save your energy for the things that matter.

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