A tiny cluster of cells embeds into the uterine lining
Baby this week: about 0.1 cm — smaller than a grain of rice · under 1 g
≈ 0.1 cm — about the size of a poppy seed
Illustration enlarged for clarity — the amber marker shows true relative size
Your baby this week
- The fertilized egg, now called a blastocyst, burrows into the uterine wall
- Cells are already sorting into two groups — one that will become the embryo, one that will become the placenta
- The placenta and early umbilical cord begin forming
- Levels of the pregnancy hormone hCG start climbing, which is what a home test detects
Your body this week
- A missed period is often the first sign something has changed
- Some notice light spotting or cramping as implantation happens, though many feel nothing at all
This week's tip: If a home test comes back positive, book an appointment with a doctor or midwife to confirm the pregnancy and talk through early prenatal care.
When to get help now
Call emergency services now or go to an emergency department now if you have sudden, severe tummy pain, pain in the tip of your shoulder, feel very weak, faint or dizzy, or have heavy bleeding that soaks a pad soon after putting it on. For lighter bleeding or spotting, or pain low down on one side, contact your doctor, maternity unit or an early pregnancy unit today.
Sizes and milestones are typical ranges — every pregnancy runs on its own clock. Educational content; your prenatal care team's guidance always comes first.