Pregnancy at 5 Weeks
Your period is now overdue, so your pregnancy may just have been confirmed. You may not feel any different, but a tremendous amount of activity is going on inside your uterus. At first the hormone progesterone is produced by the discarded follicle to prevent womb lining from shedding. Later the placenta will produce progesterone in order to sustain the pregnancy.
For a small number of women (about 1 in 200 in the UK), the fertilized egg starts to develop outside the uterus, usually in a Fallopian tube. This is known as an ectopic pregnancy (see page 108). It is often detected around this stage but may still become apparent up until 10 weeks.
Development in 5th Week Pregnancy
The tiny embryo that will become your baby has a head end and a tail end. By this time all the building blocks for your baby's vital organs are in place. The central nervous system (brain and spinal cord) has already started to form. A basic circulation has begun to work, from you to your baby, and tiny blood vessels are now forming. The embryo is taking oxygen via the developing placenta, and the bag of membranes (the amniotic sac) is also developing. This will contain the water (amniotic fluid) in which your baby will be protected and continue to grow. Even at this early stage, the developing heart can be seen as a bulge, no bigger than a poppy seed, at the front of the embryo.
Appearance in 5th Week Pregnancy
Under a microscope, the embryo would look rather like a prawn in shape - but no bigger than a grain of rice. At this stage, the head can already be distinguished clearly from the body. The embryo has a curved back, like the letter C, with a stripe down it, which marks the beginning of the central nervous system. The embryo is attached by a stalk to the developing placenta.