Second week is a turning point in the development of your baby. So, as a pregnant mother, you should now begin to focus on changing your lifestyle and dietary habits. At the beginning of second week, you may ovulate. If your menstrual cycle is of 28 days, then 15th day will be the beginning of this week. When this happens an egg erupts from its follicle and it is swept from your ovary into fallopian tube. During the next 24 hours, that egg will be fertilized if one (or more) sperm manages to penetrate it.
Baby’s Development during second week of pregnancy-
Out of the 46 chromosomes, X and Y chromosomes are two most important ones. These two are responsible for determining sex of the baby. Every egg has an X chromosome and every sperm has either an X or a Y chromosome. You’ll have a girl, if the sperm fertilizes egg with an X chromosome. On the other hand, if it’s a Y chromosome, then you’ll have a baby boy. The gender is decided at moment of fertilization.
After fertilisations, egg will start dividing into multiple cells over the next several days. During this period, egg travels down the fallopian tube, enters your uterus, and starts to burrow into uterine lining.
The baby at this stage is called an embryo. It consists of 150 cells that will begin to divide into three separate layers.
First Layer: The internal layer is known as endoderm or endoblast. This layer becomes the baby’s digestive system and respiratory tract, which includes glands like pancreas, thyroid, liver and thymus.
Second Layer: The middle layer is known as mesoderm. This layer becomes the bones, inner skin layer, muscles, cartilage, circulatory system, genitalia, excretory system, and outer covering.
Third Layer: The outer layer is known as ectoderm or ectoblast. It becomes the nervous system, brain, and epidermis, which includes skin, nails, and hair of baby.
During this time of transformation, the embryo floats within uterus and it is protected by secretions of uterus lining. Your baby is very small and appears as tiny as a microscopic chicken egg. The amniotic fluid is somewhat similar to yolk sac (also known as egg white) and embryo to egg yolk. The main function of amniotic fluid is to provide nourishment to developing fetus until placenta is fully formed.
This is a study on ‘Neglected symptoms of heart failure presented as peripartum cardiomyopathy: a case of maternal near-miss’. https://goo.gl/7b4E5H