4 Weeks Pregnant

4 Weeks Pregnant

How is Your Baby Growing at 4 Weeks?

At four weeks, the newly formed embryo is developing in the lining of your womb. At this stage, the embryo has three layers of cells:

  • The outer layer (ectoderm) comes into contact with the blood vessels that supply the womb. These cells will eventually become your baby’s brain, nervous system, skin, nails, eye lenses, and tooth enamel.
  • The middle layer (mesoderm) eventually forms into your baby’s heart, blood vessels, bones, and muscles.
  • The inner layer (endoderm) will eventually become the lungs, digestive system, pancreas, and bladder.


At this stage, the embryo is supplied with nutrients by something known as yolk sac until the placenta is fully formed.

 4 week fetus

How Big is Your Baby at 4 Weeks?

At 4 weeks, the embryo is around 2 mm (around the size of a poppy seed) and weighs just 0.01 kg.


What Happens at 4 Weeks?

Your pregnancy may be confirmed by an at-home pregnancy testing kit that measures the amount of chorionic gonadotropin (hCG) in your urine. High levels of hCG indicate pregnancy. After this point, you should contact your GP to get referred to a midwife.


What Symptoms Will You Have at 4 Weeks?

You may not experience many symptoms within the first four weeks of your pregnancy aside from a missed period.


Some of the symptoms that you may experience during early pregnancy (1-4 weeks) include:

Missed period

  • Morning sickness
  • Sore breasts
  • Fatigue and lethargy
  • Unusual cravings or going off foods that you usually love
  • Metallic taste in your mouth
  • Needing to pee more often than usual
  • Reduce bowel movements or constipation