First Trimester

During the first trimester, your baby will evolve from a cluster of cells into a recognizable fetus measuring about 80mm (3in). All the major organs, muscles and bones will be formed. Until the placenta becomes mature enough to take over, your pregnancy is supported by maternal hormones, which also contribute to early symptoms such as nausea and tiredness. Although you may not look pregnant in the first trimester, you will certainly feel pregnant.