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First Trimester 4 weeks pregnant

Pregnancy Week 4 - Positive Test & Embryonic Development

Week 4 is often when you discover you are pregnant. Your missed period prompts a pregnancy test, and the result is positive. The embryo is now implanted in the uterus and has divided into two layers: the epiblast (future baby) and the hypoblast (future yolk sac).

Poppy seed
Baby Size
0.2 cm
Length
Less than 1 gram
Weight
Week 4
of 42
Baby Development This Week

The embryo is now a tiny disc made of two layers of cells. The amniotic sac and cavity are forming, providing a protective environment for your baby. The yolk sac is producing red blood cells and nutrients before the placenta takes over. The placenta is beginning to form and will soon produce hormones to sustain the pregnancy. Neural plate development is starting, which will eventually become the brain and spinal cord.

Changes in Your Body

Your missed period is the most obvious sign of pregnancy. You may begin experiencing early pregnancy symptoms such as breast tenderness, fatigue, and frequent urination as hCG levels rise. Your body is producing more progesterone, which helps maintain the uterine lining but can also cause bloating and mild nausea.

Common Symptoms at Week 4
Missed periodBreast tendernessFatigueFrequent urinationMild nauseaBloating
Tips for Week 4
  • Confirm your pregnancy with a healthcare provider by scheduling your first prenatal visit.
  • Start a pregnancy journal to track your symptoms and milestones.
  • Avoid raw fish, unpasteurized cheese, deli meats, and excess caffeine.
  • Begin researching healthcare providers and birth options if you have not already.
When to Call Your Doctor

Schedule an appointment with your healthcare provider to confirm the pregnancy. Seek immediate care if you experience heavy bleeding or severe pain.

Frequently Asked Questions — Week 4

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