Your baby is the size of a sesame seed

📏 Length: 0.2 cm⚖️ Weight: < 1 g

The heart begins to beat this very week.

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 6: Little arm and leg buds are appearing. Baby will be about the size of a lentil.

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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.