Your body has likely expanded enough for others to realize you're pregnant and not just gaining a few extra pounds. Your uterus is similar to the size of a small melon and can be felt just below your belly button. Don't be surprised if your "inny" becomes an "outy" soon! You are probably gaining weight quite steadily at this point; possibly up 10- 13 pounds by now. You're looking pregnant, but it's still probably pretty easy to get your shoes and socks on without too much trouble, although your pre-pregnancy pants are too tight to zip and your shirts may be starting to become snug this week. If you haven't already; it's time for maternity clothes shopping. There are so many stylish maternity clothes options out there, you should have fun shopping for your new wardrobe! Also, don't be surprised if some of your girlfriends who have children offer to give you (or let you borrow) some of their maternity clothes. This is a great way to get a maternity wardrobe without spending a lot of money.
You may be scheduled for an ultrasound exam this week or within the next couple of weeks. Ultrasounds are routinely performed sometime between 18 and 20 weeks along as part of your prenatal care. You may be asked to drink a certain amount of water prior to your ultrasound, which will help produce a better picture, because a full bladder helps lift the uterus up so it can be seen more easily. Your ultrasound will probably last anywhere from 15- 25 minutes on average.
An ultrasound done at this time can detect many birth defects and structural abnormalities, determine the position of your baby and the placenta, check amniotic fluid level and calculate gestational age. Body measurements are taken to estimate your baby's age and also to ensure your baby is growing properly. Estimates on age or weight aren't all that accurate during this time and into the third trimester. The overall skill of the technician and also your baby's position helps, but the earlier in pregnancy the ultrasound is done, the more accurate it is for estimating the age. Right after conception (during the first trimester), babies grow about the same speed, but as time goes on, babies tend to start growing at different rates. During the first trimester, estimates using ultrasound are usually within a week of the correct age. By the time the second trimester rolls around, they can be off by two weeks or more.
Some measurements which will likely be taken include the distance around your little one's abdomen (abdominal circumference), the distance across your baby's head, the distance around the outside of your baby's head (head circumference) and the length of your baby's upper leg bones (femur length). Body parts will be examined including your baby's brain, spine, kidneys, stomach, bladder and the four chambers of your baby's heart. The umbilical cord will be examined as well. If any birth defects or problems are suspected, you'll be scheduled to have a more detailed ultrasound done (often called a "level II ultrasound")
