Week 18: Your pregnancy

Your baby's growth: She can hear!

By now the bones of your baby's inner ear and the nerve endings from the brain have developed enough so that your baby can probably detect sounds clearly. Experts believe that one of the most comforting sounds she hears is Mom's heartbeat. She may also hear your voice, your stomach rumbling and the sound of blood moving through the umbilical cord to and from the placenta, which is now almost as big as she is.

Here's what else is happening to your baby this week:

• Starts to swallow. Some experts think thirst may trigger your baby to swallow. Since amniotic fluid is constantly being produced, your baby's swallowing of excess fluid helps keeps it at a constant level.
• Mimics breathing. Your baby's chest will continue to move up and down to mimic breathing, but she's not breathing air—just swallowing and inhaling amniotic fluid. This is a normal part of your baby's development. This intake of amniotic fluid will not harm her.
• Female reproductive parts. If your baby is a girl, the vagina, uterus, and fallopian tubes will be in place by the end of the week.

What's happening with you

• Weight gain. On average, pregnant moms have gained about 10 or 11 pounds by now. It's a good idea to gain weight gradually. By not putting on a lot of weight all at once, your body won't be as stressed, and you may have an easier time delivering the baby.
• Trouble sleeping. If you're having difficulty getting a good night's sleep because of this added weight and the resulting discomfort, try urinating before going to bed, propping yourself up with pillows in bed and resting on your left side.
• Ultrasound. This week your doctor may prescribe a mid-pregnancy ultrasound, which is often recommended sometime during the second trimester, usually between 18 and 22 weeks. This test can help your doctor assess fetal growth and development, screen for certain birth defects, check the placenta and umbilical cord and determine whether the projected due date is accurate.