Your baby is the size of a poppy seed

📏 Length: 0.1 cm⚖️ Weight: < 1 g

A tiny spark of life — the neural tube is just forming.

You're in the first trimester — the foundation weeks. Your baby's major organs, brain, and heart are all taking shape, and your body is working harder than it ever has (which is why you're so tired). Every week brings a big developmental leap.

Coming up in week 5: The heart begins to beat this very week. Baby will be about the size of a sesame seed.

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Lengths and weights are averages (crown-to-rump until week 19, head-to-toe after) — every baby grows at their own pace. This page is for general information and isn't medical advice; always consult your healthcare provider.