Pregnancy Week 4

Written by Lone Parenting Advisor

Pregnancy week 4 is when most women discover that they are pregnant and start to accept their unborn foetus. The foetus at 4 weeks of pregnancy is still just a ball of cells dividing within the uterus to become the embryo. The placenta and umbilical cord are in early stages of development and are already starting to feed the embryo with nutrition and oxygen.

You are now 4 weeks pregnant and at this time you should be due to have your menstrual period which is late! This is where most women discover their pregnancy.

Foetal Development

The balstocyst is from now on referred to as the embryo and measures less than 2mm. On the 18th day post conception the baby within you has already began to form the spinal cord and brain which is also referred to as the Neural Tube.

The ectoderm (which is the top layer of the divided cells of the blastocyst) starts to form the rear of the embryo. This is done when the two flat sheet of cells crease in the centre and begin to wrap around themselves to make a tube which will become the spinal cord. The spinal cord stretches and at one end starts to expand into what will become the brain of the embryo although these are very early stages and will take at least the rest of week 4 of pregnancy to complete the process and finish at the end of the week where the two sheets of cells eventually meet and bond together to become the Neural Tube.

The endoderm (which is the bottom layer of the divided cells of the blastocyst) start to protrude at the frontal chest area of the embryo and form a sac containing yolk for vital nutrition and fluids that will feed the embryo initially until the umbilical cord is formed. The body of the embryo forms a type of stalk that extends from the waistline of the embryo.

This stalk will eventually form into the umbilical cord within the body of the embryo and will start to accept nutrition when the placenta is developed and fully functional, meanwhile until this process is complete the sac containing the yolk will feed the embryo enough to allow the liver, lungs, bowel and bladder of the embryo to form.

A blood supply for the embryo will also form through the nutrition provided from the sac containing yolk.

Ultrasound

Detection of the pregnancy at week 4 through ultrasound is possible now, but visible images are of a tiny sac and can often be missed due to the minute size of the sac.