4 Weeks
4 Weeks size comparison
Baby is the size of a
poppy seed
Baby at 4 weeks in womb

Baby this Week

  • The embryo is formed.
  • These three primitive cell layers will generate every organ and tissue in your baby's body.
  • Around the end of this week, primitive blood vessels and circulatory system are formed.

How Big is Baby?

Baby is 0.04 inches long (0.1 cm)
(Very hard to estimate weight at this stage)
Baby weighs 0oz (0 grams)
*Metrics above are estimates of baby at 4 weeks
Layout Belly
4 Weeks pregnant illustration

Your Developments

  • Missing your period this week may be your first real sign of pregnancy.
  • Time for a pregnancy test as results are more likely to be reliable now. Make sure to follow the manufacturer's instructions to avoid an incorrect result.

Pregnancy To Do's

  • Find a practitioner to assist you during pregnancy. A obstetrician-gynecologist or OB-GYN is the preferred option for many pregnant women. A family physician, midwife or doula make great additions also.
4 Week old baby in womb