4 Weeks Pregnant: Your Tiny Baby Starts to Grow

(10 minute read)

4 Weeks Pregnant: Your Tiny Baby Starts to Grow

At week 4, the embryo has now reached your uterus, where it can start developing into your baby.

Even at week 4, many women may not even realise that they're pregnant. This period, continuing the implantation process started in week 3, is crucial for your baby's development. Understanding the changes occurring in your body and the development of your baby is essential for a healthy pregnancy journey.

How Big is Baby at 4 Weeks?

At week 4, your baby is at the beginning stages of development. The embryo is tiny, roughly the size of a poppy seed, measuring about 0.04 inches (1 mm) in length. Despite its minuscule size, the foundation for its major organs and systems is being laid down.

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The Baby's Development at Week 4

While the baby is only the size of a poppy seed, your body is already adjusting to pregnancy.

  1. Hormonal Changes: The increase in pregnancy hormones like human chorionic gonadotropin (hCG) and progesterone starts to affect your body.
  2. Uterine Changes: Your uterus is preparing to support the growth of your baby for the next nine months.
  3. Blood Volume Increase: There's a slight increase in blood volume to support the developing embryo.

Pregnancy Symptoms at Week 4

At four weeks, some women may not experience any symptoms, while others may start noticing changes. Common symptoms include:

  1. Missed Period: This is often the first sign of pregnancy.
  2. Breast Changes: Your breasts may feel tender or swollen due to hormonal changes.
  3. Mild Cramping and Spotting: Light spotting and cramping can occur due to implantation.
  4. Fatigue: Increased progesterone levels can make you feel unusually tired.
  5. Nausea: Some women may start experiencing morning sickness, though it's more common in later weeks.
  6. Heightened Sense of Smell: Many women report a heightened sense of smell, which can lead to food aversions or cravings.
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Tips for a Healthy Pregnancy at Week 4

  1. Prenatal Care: Schedule your first prenatal appointment. Regular check-ups are crucial for monitoring your and your baby's health.
  2. Healthy Diet: Focus on a balanced diet rich in folate, iron, calcium, and protein.
  3. Stay Hydrated: Drink plenty of water to stay hydrated.
  4. Avoid Harmful Substances: Refrain from alcohol, tobacco, and drugs. Limit caffeine intake.
  5. Rest: Get plenty of rest and sleep to support your body's increased demands.


Week 4 is a period of significant but invisible changes. Your baby, though just the size of a poppy seed, is rapidly developing, and your body is preparing to nurture this new life for the months to come. Paying attention to your health and well-being during this time is vital for a healthy pregnancy.


Click here to read all about week 5 of pregnancy.

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