3 weeks pregnant: your baby & body
Your baby this week
About 0.1 cm — around the size of a poppy seed. Every baby grows a little differently.
How your baby is developing
- Fertilization typically occurs this week; the resulting single cell begins dividing rapidly as it travels toward the uterus.UNSW Embryology (CC-BY)
- By the end of the week, a small ball of dividing cells (the blastocyst) typically reaches the uterus and prepares to implant.UNSW Embryology (CC-BY)
How you may feel
- It's typically too early for pregnancy symptoms; hCG hormone has usually not yet risen enough to detect.ACOG
Nutrition this week
- Folate (B9) — supports neural-tube closure — most critical in weeks 1–12 (Leafy greens)
- Iodine — fetal brain + thyroid development (Iodized salt)
- Vitamin B12 — with folate, for blood + nerves (Meat)
Part of the First trimester (weeks 1–13).
Educational reference only — not medical advice. Typical/average figures; every pregnancy differs. Always consult your doctor or midwife. Seek urgent care for any warning sign.