Your baby is about the size of poppy seed – 2mm...
The newly formed embryo which will eventually become your baby now has three layers, the inner layer (endoderm) will become the lungs, liver, digestive system and pancreas, the middle layer (mesoderm) the skeleton, muscles, kidneys, blood vessels and heart; and the outer layer (ectoderm) will form the nervous system, teeth and skin.
Your baby's nervous system and heart are already beginning to develop. Blood vessels are forming and blood is starting to circulate. Some of these blood vessels will become the umbilical cord, which will connect you to your baby.
Your pregnancy can be confirmed by using a home pregnancy test. This measures the amount of human chorionic gondatrophin (hCG), the pregnancy hormone, in your urine.
You may start to experience some pregnancy symptoms. One of those most common early symptoms is morning sickness. Although it more usually occurs in the morning and resolves itself by midday, morning sickness can come at any time, day or night.
Other early pregnancy symptoms include; sore breasts, tiredness, going off certain foods/tea or coffee, a metallic taste, peeing more and constipation.
Things for you to consider during week 4 of your pregnancy:
What to expect at week 5 of your pregnancy...