When you're 16 weeks pregnant, the second trimester hums along and baby is developing rapidly. You may have another prenatal visit this week, where you can hear baby's heartbeat again. And more exciting still, you may start to feel baby kick. If you're a first-time mom, it might take some time to feel those tiny movements; they can be hard to distinguish from gas or muscle twitches at first.
As the pregnancy continues, your baby's eyes and ears are situated in their final positions, giving them a more distinctive appearance. Several more complicated body systems are also up and running, including the circulatory system, which can now pump about 25 quarts of blood per day. And that thumb-sucking habit that many newborns are born with may be starting.
During your 16-week ultrasound, the OB can usually determine your babe's sex, although this will depend on the positioning of the fetus. They can also look for signs of abnormality, like chromosomal abnormalities or anemia. If there are concerns, the OB can offer more invasive diagnostic tests like amniocentesis or chorionic villus sampling (CVS), but most women prefer to rely on noninvasive screening instead.