Pregnant in week 4
In week 4 the fertilised egg has just implanted in the lining of your uterus, and your body has started producing the pregnancy hormone hCG. Your baby is the size of a poppy seed – less than a millimetre – but the very first foundations of the brain, spine and heart are already being laid.
Your baby in week 4
The fertilised egg has divided many times on its way down the fallopian tube and has now burrowed into the soft lining of the uterus. From this tiny cluster of cells things split in two: one part becomes your baby, the other the placenta and membranes.
This week the beginnings of your baby consist of three cell layers, each of which becomes different parts of the body – nervous system and skin, skeleton and muscles, and internal organs. The neural tube, which later becomes the brain and spinal cord, is already beginning to take shape.
The yolk sac supplies your baby with nourishment at first, until the placenta is ready to take over the task over the coming weeks.
Your body and symptoms in week 4
On the outside there is usually nothing to see yet, and many don't actually know they are pregnant in week 4. Your period is just about to be missed, and it is often only now that a pregnancy test can begin to show a faintly positive result.
Some experience light spotting as the egg implants – known as implantation bleeding. It is typically lighter and shorter than a period. You may also feel mild cramping in the lower abdomen, tender breasts and a creeping tiredness, which many mistake for their period being on the way.
Your body is now busy adjusting, even though you can't feel very much. The most important thing you can do yourself is about giving the developing nervous system the best possible conditions.
Good advice for week 4
Take folic acid now
The Danish Health Authority recommends 400 micrograms of folic acid daily from when you are planning pregnancy until week 12. It lowers the risk of neural tube defects while the neural tube is forming right now.
Stop alcohol and smoking
There is no known safe amount of alcohol in pregnancy, and smoking increases the risk of complications. The sooner you stop, the better for your baby.
Remember vitamin D too
10 micrograms of vitamin D daily is recommended throughout pregnancy. A standard pregnancy multivitamin typically covers both folic acid and vitamin D.
Contact your doctor
When the test is positive, call your own GP, who starts your pregnancy care and refers you on to the public services.
Frequently asked questions in week 4
When does a pregnancy test show positive?
Most tests are reliable from the day your period was due – that is, around week 4. If you take it too early, the result can be falsely negative because the hCG level is still low.
Can you scan in week 4?
It is still very early. A scan can rarely show anything definite before weeks 5-6, when the pregnancy starts to be visible. We therefore recommend waiting a little for the first scan.
Are mild lower-abdominal pains dangerous?
Mild cramping and pulling are completely normal as the uterus begins to change. With strong one-sided pain or bleeding like a period, contact your doctor or out-of-hours service.
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Read on in week 4
Early pregnancy scan in Copenhagen – everything you need to know (2026)
Guide to your first pregnancy
