18 weeks already!

By week 18 of your pregnancy, your baby's crown-to-rump length is 5 to 5.5 inches long. Your baby continues to develop fat layers and weighs about 5.25 ounces. Your baby will continue to grow and develop, but the rapid growth will slow down for a little while. Around this time, your baby becomes more sensitive to the outside world and shows her presence through powerful kicks and prods. The bones through which sound is passed to the inner ear have hardened and the parts of the brain that receives and processes nerve signals from the ears are developing. This means that your baby can hear now. Your baby will get used to familiar sounds, such as your heart beating, familiar voices, blood rushing through the umbilical cord and other daily routine sounds. Your baby will become startled if he hears a loud sound.
Info from www.i-am-pregnant.com