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First trimester

Weeks 1–13: conception and early development, when the major organs form. Common early symptoms include fatigue, nausea, and tender breasts.

Weeks 1–13. Choose a week for a sourced overview of typical development, common symptoms, and when to contact your provider.

Week 1—Week 2—Week 3about 0.006 inch (Week 4about the size of Week 5about the size of Week 6about the size of Week 7about the size of Week 8about the size of Week 9about the size of Week 10about the size of Week 11about the size of Week 12about the size of Week 13about the size of

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Every week from 1 to 40, with a quick-facts table.

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Informational only — not medical advice. Pregnancy Week to Week is a general educational reference. It is not a substitute for professional medical care, diagnosis, or treatment. Every pregnancy is different: always consult your doctor, midwife, or other qualified healthcare provider about your own pregnancy, and never disregard or delay professional advice because of something you read here. In an emergency, contact your maternity unit or local emergency number immediately.

First trimester

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