You are now well into your second trimester and your developing baby is gaining in size, skills, and coordination. By your fifth month of pregnancy, your developing baby's cognitive development is established to the point where he can not only detect sounds inside and outside the womb, but can also react to them. Refer to this month-by-month pregnancy calendar to learn about important milestones in your developing baby's development as well as helpful tips and advice for a safe, healthy pregnancy.