While every woman's pregnancy journey is different, a typical pregnancy lasts 40 weeks and is divided into stages known as trimesters. As your baby continues to develop in utero -- and as your belly swells to make room for his growth -- you'll experience a host of positive and not-so-fun physical changes with each stage.
For many women, the first trimester, which lasts up to week 12 of a pregnancy, is the most difficult, because the levels of the pregnancy hormone hCG are doubling every 72 hours. While some lucky women escape this stage without ever suffering from a single bout of morning sickness, others find themselves nauseous all day long. Either way, you'll likely be exhausted and moody, with tender breasts, strange cravings and heartburn. Once your hCG levels peak and level off, some of these discomforts will subside. In the meantime, your baby's brain, spinal cord, heart, major organs, arms, legs and external genitalia have begun to form, and by the 12th week of pregnancy, your baby's muscles will begin to work together, allowing him to make a fist.
Stage Two: Flutters and Kicks
In the second trimester, which lasts from week 13 to 28 of pregnancy, morning sickness and extreme exhaustion typically start to dissipate. You'll also experience "quickening" -- the first detectable movements of your baby. According to the American Pregnancy Association, quickening can occur as early as 13 weeks or as late as 25 weeks; first-time mothers typically experience these flutters later than moms who've already given birth. By the end of this stage, baby will have formed taste buds, fingerprints and immature lungs and grown some hair. He's now about 12 inches long and weighs about 1 pound. As baby continues to grow, you may experience stretch marks, itchy skin and swelling of the hands and feet.
Stage Three: In the Home Stretch
In this stage, which lasts from the 29th to 40th week of pregnancy, you'll grow more uncomfortable. As your baby continues to grow and press on your organs, you may have trouble breathing or sleeping, and hemorrhoids may develop. Once you near your due date, your doctor will begin internal examinations to see if your cervix is starting to efface, or thin out, and dilate in preparation for delivery. Baby, in the meantime, is growing rapidly; his lungs mature and he begins to store vital nutrients and body fat. By the time your due date arrives, he'll be about 19 to 21 inches long and weigh between 6 and 9 pounds.
Somewhere around your 37th to 40th week of pregnancy, the big day will arrive. Baby's organs are ready to function on their own, and he may shift into a head-down position to prepare for delivery. There are typically three stages of labor, according to the APA: the first stage, in which your cervix will dilate to 10 cm; the second stage, in which you deliver the baby; and the third stage, in which you deliver the placenta. Labor is divided into stages: early labor, active labor, and a transition phase. Early labor typically is the longest stage and lasts until you're 3 cm dilated. When you reach active labor -- when your contractions become longer, stronger and closer together -- it's time to head to the hospital.