First trimester

Pregnancy Week 1

A practical week 1 guide covering fetal development, symptoms, nutrition, prenatal tests, baby size comparison, and warning signs to discuss with your care team.

Week 1 ยท poppy seed

Fetal development

Implantation and early cell division are the main story this week.

Baby size comparison

Around week 1, baby is roughly comparable to a poppy seed. Estimated size: about 0.08 inches and 0.03 ounces, with natural variation.

Common symptoms

  • Energy, appetite, sleep, and digestion may change.
  • Some people notice cramps, bloating, skin changes, or back discomfort.
  • Symptoms vary widely, and absence of a symptom does not always mean a problem.

Tests and appointments

  • Continue regular prenatal care; no major routine screening window is highlighted for this exact week.

Nutrition focus

  • Include protein, fiber-rich carbohydrates, colorful produce, and healthy fats.
  • Ask about iron, folic acid, iodine, vitamin D, choline, and omega-3 needs.
  • Follow local food-safety advice for fish, caffeine, unpasteurized foods, and supplements.

Warning signs

  • Call your care team for heavy bleeding, severe pain, fever, fainting, severe headache, vision changes, fluid leakage, or decreased fetal movement later in pregnancy.
  • Emergency symptoms should be handled urgently according to local medical guidance.

Medical disclaimer

This week-by-week pregnancy content is educational and does not replace care from a qualified healthcare professional.