What does implantation bleeding look like?

Implantation bleeding is typically light pink or brown spotting that lasts 1-2 days. It is much lighter than a normal period and occurs 6-12 days after conception. Not all women experience it.

Can I test positive at 3 weeks pregnant?

Some sensitive pregnancy tests can detect hCG as early as 10 days after conception, but for the most reliable results, it is best to wait until after your missed period (around week 4-5).

First Trimester 3 weeks pregnant

Pregnancy Week 3 - Implantation & Early Cell Division

Week 3 is when conception actually occurs. The sperm fertilizes the egg, creating a single cell called a zygote. This cell begins dividing rapidly as it travels down the fallopian tube toward the uterus, where it will implant into the uterine lining.

Smaller than a poppy seed

Baby Size

0.1 mm

Length

Less than 1 mg

Weight

Week 3

of 42

Baby Development This Week

After fertilization, the zygote begins a journey of rapid cell division. Within 24 hours, it becomes a two-cell embryo, then four cells, then eight. By day 5-6, it forms a blastocyst, a hollow ball of cells. The blastocyst will implant into the uterine lining around day 6-10 after ovulation. The inner cell mass will become the baby, while the outer layer becomes the placenta and membranes.

Changes in Your Body

You may not notice many changes yet, but some women experience implantation bleeding, which appears as light spotting 6-12 days after conception. You might also feel mild cramping as the embryo implants. Your body begins producing hCG (human chorionic gonadotropin), the hormone detected by pregnancy tests.

Common Symptoms at Week 3

Implantation bleeding (light spotting)Mild crampingBreast tendernessFatigueFrequent urination

Tips for Week 3

Avoid alcohol, recreational drugs, and unnecessary medications.
Continue taking prenatal vitamins with folic acid daily.
Stay hydrated and eat a balanced, nutrient-rich diet.
Avoid hot tubs and saunas, as excessive heat can affect early development.

When to Call Your Doctor

If you experience heavy bleeding or severe abdominal pain, contact your healthcare provider immediately as this could indicate an ectopic pregnancy.

Frequently Asked Questions — Week 3

Explore Our Pregnancy Tools

Due Date Calculator

Conception Calculator

Ovulation Calculator

Week Calculator

Week 2 All Weeks Week 4