All the vital organs such as the kidneys, liver and lungs, are now in place and begin to grow and develop rapidly. Up to this point, an additional sac inside the amniotic fluid has been providing red blood cells, but now the baby's liver is producing them for itself and the yolk disappears.
With your pregnancy at 10 weeks, your midwife will offer to take a blood sample. This is sent off to a laboratory when it is tested for serum markers, which are proteins that may be present in your blood. If you have these particular proteins, it can be an early indication of whether your baby is at risk of Down's syndrome. Your midwife might also recommend a test called chorionic villus sampling (CVS), if you're at particularly high risk of having a baby with a serious inherited condition such as cystic fibrosis. Week 10 is also when you're likely to have the highest levels of the pregnancy hormone HCG in your blood, so sickness and other symptoms may be particularly severe.
Despite the name, sickness in pregnancy doesn't just happen in the mornings. You can help prevent or reduce sickness by eating small but frequent low-fat meals, and trying to get plenty of rest and fluids. It might help to keep a plain biscuit or cracker by your bed, to nibble before getting out of bed or if you wake feeling sick in the night. If you have very severe sickness, talk to your doctor or midwife about treatment.