During this trimester, the weight of your growing baby will multiply more than seven times—and you will start showing more.
Screening is usually performed by taking a sample of the mother's blood between the 15th and 20th weeks of pregnancy (16th to 18th is ideal).
You will begin to feel your baby moving sometime between the 18th and 25th weeks of pregnancy. Those first movements feel like a fluttering, but as the weeks progress, you'll notice a pattern of sleeping and waking cycles, the American Pregnancy Association says. It's a good idea to spend some time each day counting the movements so you'll notice if there are any significant changes.