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First trimester · roughly month 1 · about 39 weeks to go

1 week pregnant

Everything Hello Belly has for week 1 — how your baby is developing, what your body is doing, and the small things that are easier to know in advance.

Illustration of a pregnant woman at week 1

Your baby at 1 weeks

1–4 weeks

Yep, you once looked like that too! Your growing child now has a challenging but interesting journey ahead. During the 3rd and 4th weeks there is a metamorphosis and transformation.

In the beginning the egg was fertilized and became a zygote. When the zygote reached the uterus and attached to the wall of the uterus, it turned into a blastocyst. It is from this moment that pregnancy is considered to have happened. Imagine, a baby is growing inside you! In just a couple of weeks this tiny creature will increase tenfold. He will grow from 0.1 mm (0.004 in) to 1 mm (0.04 in).

The fetus actively develops and the rudiments of the muscular system and the bone and nervous systems are formed. By the end of the 4th week the embryo will already consist of 3 layers of cells, which later transform into specific parts of the baby's body. The inner layer, or endoderm, will develop into the digestive system, liver, and lungs. The middle layer, or mesoderm, will soon become your baby’s genitals, bones, kidneys, and muscles. The outer layer, ectoderm, will form the nervous system, hair, skin, and eyes.

This week's open tip

Read it in full right here — no account needed.

  • As my Granny said... — week 1 of pregnancy

    As my Granny said...

    Let’s talk about another angle to help you with conception: herbs. You might feel some prejudice one way or the other when you hear this term, but the connection between diet and women's health is an established fact.

    Read the full tip →

Also in the app this week

25 more tips for week 1 — a new one arrives each day inside Hello Belly.

Following week 1 in real time?

Pick your date and every page becomes yours — a new tip each day, for the week you're actually in.

Illustration of a pregnant woman at week 16Week 16 · Second trimester

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