Event Schedule Hall: First Trimester

Between weeks 9 and 13 of pregnancy, your baby grows and changes quickly. By the end of this stage, your baby is "fully formed." This means all major organs, muscles, limbs, and bones are in place. There is still a lot of growing and maturing ahead, but the basic structures are ready. Your baby grows from a tiny embryo into a small fetus about 6 cm long and weighs around 18 grams-the size of a plum! These weeks are very important for development, as the baby goes from basic shapes to a more recognizable human form.

It’s possible to start noticing some early signs of pregnancy at four weeks, though many women don’t experience any symptoms this soon. The hormonal changes happening in your body now can sometimes bring on noticeable changes. By week four, your body is starting a series of important changes as the tiny embryo (formerly called a blastocyst) implants in your uterus and starts to grow. Even though you might not look or feel different yet, a lot is going on inside. Knowing what’s happening in your body can help make sense of this exciting and sometimes confusing stage.

It might come as a surprise, but your baby’s sex is determined right when conception takes place. Even though you won’t know the answer for months, whether you’re having a boy or a girl is decided from the moment the egg and sperm join. All the genetic material needed, including the information that sets your baby's sex, is in that very first cell.