At around 14 weeks, your baby may be starting to suck his or her little thumb. At around 20 weeks, an ultrasound may be able to determine if you're having a boy or girl. You should start to feel baby moving and kicking inside you soon — an unforgettable moment for most moms. By 20 weeks, your baby has grown: it now weighs about 1 pound and measures about 7.5 inches from head to toe about the size of a banana. By 27 weeks, it should measure around 10.5 inches long.