Although it might sound strange, you are not actually pregnant in the first two weeks or so of your pregnancy.
Conception usually occurs about two weeks after your last period begins.
In third week fertilisation occurs. Soon after fertilisation, the fertilised egg travel down the fallopian tube towards the uterus; which is also known as the womb. This is where it stays for the next 9 months. At the same time, the fertilised egg rapidly starts dividing to form a cluster of cells, called an embryo. Once in the womb, the embryo attaches into the lining of the womb for nourishment. This is called implantation. Over time, this implantation site will develop into the placenta.
By fourth week of your pregnancy, the embryo will consists of two layers of cells, which will later develop into your baby’s vital organs and body parts. Amniotic sac and the yolk sac will also develop during this time.
Amniotic sac is filled with amniotic fluid - serves as a cushion; surrounds your growing baby; and protects it.
the yolk sac will provide nourishment to your baby until the placenta takes over that role.
By the end of the fourth month, your baby is about 6 inches in long and weighs about 100 grams.
Changes in your body -
You may not be aware of your pregnancy at this time but your baby has already started to grow and develop. During this time some of you might experience mild abdominal cramps and feel as if your period would start anytime soon. However, if you do not get your period on the specific date, you might be pregnant. You can be sure about your pregnancy by doing a home pregnancy test. If pregnancy is confirmed then it is the time to start on folic acid supplements which helps reduce the risk of neural tube defects in the baby which forms very early in pregnancy. If you have been taking folic acid supplement before pregnancy, your doctor will ask you to continue taking them. Apart from taking supplements you can also eat foods that contain folate such as green leafy vegetables, nuts, brown rice, etc. As your baby grows very rapidly, you need to ensure that your diet consists includes lots of protein and calcium rich foods .