4 weeks pregnant


4 weeks pregnant

This implantation of the blastocyst is probably completed, which means you’re likely to get a positive pregnancy test 😉

Your Child’s development
Your Child is now as big as a poppy seed and medically known as a blastocyst. This structure of growing cells has now completed its journey from your fallopian tube to your uterus.

The great divide: As soon as the blastocyst is settled in your uterus, it will undergo the great divide, splitting into two groups. The cells in the middle will become the embryo. The outer cells start to differentiate and reach out to form links  with your blood supply — later, this will become the placenta. Only these outer cells produce the hormone hCG, which indicates pregnancy on a pregnancy test. 

Three layers: By the end of this week, the embryo has started to differentiate into three layers of cells. The top layer is where Your Child’s brain, backbone, spinal cord, and nerves will develop from. Skin, hair, and nails will also develop from this layer. The middle layer is where the skeleton and muscles grow from, and it is also where the heart and blood circulation system will form. The inner layer houses the beginnings of what will become the lungs, the intestines, and the urinary system. 

Since the placenta is not fully formed yet, Your Child is still receiving nutrients from the yolk sac of your egg.

Your development
Even though you may not be aware of your pregnancy at this point, a lot of changes are occurring in your body.

Effects of hormones: If you are sensitive, you may already feel early symptoms of pregnancy like bloating, cramping, and mood swings. These symptoms occur because your body is releasing more estrogen and progesterone.

Cramps: You may also experience cramping and spotting. This happens because Your Child is implanting into your uterine wall. As the walls of the uterus thicken, you may have white vaginal discharge. 

What you can do now
This is the week where you may want to do a pregnancy test. Your hCG levels should now be high enough to test positive if you are pregnant. But if you get a negative result, wait. It may take up to a week after missing your period to get a positive pregnancy test.  

Your first doctor’s appointment: If you do test positive, you may want to do your first doctor’s appointment. Although some obstetricians (OBs) and gynecologists (GYNs) may ask that you wait until you’re at least 6 to 8 weeks pregnant before a visit.

Please acknowledge
We are trying to be as accurate as possible, but, especially during the first 4 weeks of your child’s life, the medical and scientific community is not quite sure what exactly happens. So, despite great progress in the last 100 years, there are still many unknowns and many mysteries to be discovered. 

We, therefore, want to remind you to be mindful of the fact that the information presented might not be accurate or apply to your individual pregnancy or child.


Dr. Wanwadee Sapmee Panyakat (OB-GYN) (20 October 2021)


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