Pregnancy week 4
This week your baby is about the size of a poppy seed — around 0.1 cm and 0 g.
Your baby this week
Your baby is now too small to see, about the size of a poppy seed, and is called a blastocyst that has just implanted into the uterine lining. Cells are organizing into layers that will become the nervous system, heart, skin, and other organs. At the same time, the placenta and umbilical cord begin forming to nourish your baby throughout pregnancy. It is a tiny but foundational stage of development.
Your body this week
Your period may be late, which is often the very first sign of pregnancy. Some women feel light cramping, bloating, or tender breasts, and a little spotting from implantation can appear. Symptoms vary widely, and you may feel nothing noticeable just yet.
Tips for this week
You can now take a home pregnancy test, ideally with your first morning urine for the most accurate result. Keep taking your daily folic acid, as it is crucial for your baby's developing nervous system. Book an appointment with your doctor to confirm the pregnancy and begin your care.
Frequently asked questions
How big is the baby at week 4?+
At week 4, your baby is about the size of a poppy seed — roughly 0.1 cm and 0 g, though every baby grows at its own pace.
Which trimester is week 4?+
Week 4 falls in the First trimester.
How many weeks are left at week 4?+
At week 4, you have about 36 weeks to go until the typical 40-week due date.
Is week 4 normal?+
Every pregnancy is different. If you feel well and your check-ups are on track, week 4 is usually a normal part of the journey — but always reach out to your doctor or midwife with any concern.
This guide is for general information and reassurance — it isn't medical advice. Always follow your doctor or midwife for your own pregnancy.