Pregnancy week 4 and baby development: The egg is fertilized in one of the fallopian tubes. After fertilization, cell division begins immediately and the fertilized egg moves towards the uterus. In the 4th week of pregnancy, the fertilized egg reaches the uterus and implants in the endometrium. Implantation may be accompanied by some bleeding, known as implantation bleeding. This can explain the bleeding and abdominal pain in the 4th week of pregnancy. After implantation, the fertilized egg continues to divide and is now called an embryo. In the 4th week of pregnancy, the cells divide into three layers. Each layer will develop into different parts of the baby’s body:
- The inner layer forms the respiratory and digestive systems, including the lungs, stomach, intestines and bladder.
- The middle layer forms the heart, blood vessels, muscles and bones.
- The outer layer forms the brain and nervous system, eye lenses, tooth enamel, skin and nails.
During pregnancy, the placenta also begins to develop at 4 weeks, but it takes several weeks for it to be fully formed. For this reason, a small yolk sac is formed during your pregnancy at week 4 to nourish the embryo during these early weeks of pregnancy. When the placenta is fully formed, it takes over the transfer of nutrients from the yolk sac to the embryo, and the yolk sac disappears. During your pregnancy in this 4th week, the development of the placenta also leads to the release of the pregnancy hormone hCG. This hormone can now be detected in your urine and will result in a positive pregnancy test. The hCG hormone can cause various pregnancy symptoms in pregnant women from the 4th week of pregnancy, including nausea.
Pregnancy symptoms at 4 weeks
At 4 weeks’ gestation, you won’t be able to tell from the outside that you’re pregnant. However, you may notice some pregnancy symptoms. Here are some of these symptoms:
Pregnancy week 4: Bleeding and pelvic pain
An important symptom is bleeding combined with abdominal pain. The fertilised egg is implanting in the womb lining, which can damage the lining, causing pain and possibly some bleeding.
Pregnancy 4 weeks: Nausea, tender breasts
Many women experience nausea in the early stages of pregnancy. Nausea may occur in the morning, later in the day or throughout the day. The amount of nausea varies from woman to woman. Nausea is caused by the hormone hCG. As described above, the development of the placenta begins in the 4th week of pregnancy. The placenta starts to secrete the hormone hCG at an early stage. This hormone signals to the body that you’re pregnant and causes processes such as ovulation and menstruation to stop. The hCG hormone can also be detected in the urine from the 4th week of pregnancy, resulting in a positive pregnancy test. Symptoms such as tiredness, headaches and mood swings are also common in the fourth week of pregnancy; these are also caused by the hCG hormone.
Pregnancy week 4: Bloating / Gas / Pelvic pain
Just had a positive pregnancy test and can’t stand tight trousers? Even though it’s only week 4 of your pregnancy, bloating (especially after eating) is caused by your bowels slowing down under the influence of the hCG hormone. Bloating with abdominal pain and flatulence is also a common symptom.
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