A simple blood test might tell you the sex of your unborn baby. This is the conclusion of research published in the issue of the journal Obstetrics and Gynaecology. Between 2003 and 2009 the researchers tested women who were between eight and 10 weeks pregnant. They studied DNA from blood samples to predict the sex of the babies in 186 pregnancies. They predicted 105 boys and 81 girls. They were right every time.