Things are really getting crowded now that your baby might weigh more than 6 pounds and stretch beyond 20 inches. Your baby is so big that her knees and elbows have to be constantly flexed or even folded. However, she'll still wiggle and bump you, so you should be aware of her movements. Her heart rate will be between 120 and 160 beats per minute during labor and delivery. You'll probably also be very aware of her hiccups now. They're the result of your baby inhaling amniotic fluid as she practices her breathing, and they can be vigorous enough for your partner to see your clothes move. Her lungs are most likely fully mature.
Not all contractions mean that you're going to deliver soon. Just like your unborn baby's body takes time to develop and mature before he's ready for his birth, your body readies itself for labor by "practicing." You might have felt a tightening of your uterus that comes and goes, and it might be slightly painful. The next time your abdomen feels tight, place your hand at the top of your baby bump -- it will appear hard and then soft within a few seconds. Think of it like your flexing bicep: As you bring your clenched fist toward your shoulder, the muscle in your arm balls up and hardens. Your uterus is a large muscle, too, and as it contracts, or flexes, it will then harden. When you relax your arm the bicep softens, just as when the contraction ends the uterus becomes more elastic once again. These beginner contractions are called Braxton Hicks. Although they do not lead to active labor, they do prepare your body (and your psyche!) for when the time comes. On an ultrasound, a sonographer can observe contractions -- the uterine wall thickens slightly. Most likely your facial grimaces would also signal that you're having a contraction!
With Braxton Hicks contractions, if you take time to sit down, put your feet up, and drink a glass of water or two, the contractions will subside. Labor-inducing contractions don't stop even if you relax for an hour or two. Instead, these contractions become longer and stronger, and come more regularly. As the contractions begin to come more frequently and with greater intensity, you might find that you're unable to speak as you're experiencing them. Once your contractions start coming at regular intervals -- for instance, lasting one minute every five minutes -- it's probably time to call your health care provider.
If your provider has any questions about whether you're in labor or not, she may have you come into her office to evaluate your condition or she may tell you to pack your bags for the hospital.
Braxton Hicks contractions: A tightening and softening of the uterus, usually sporadic but sometimes at regular intervals. An expectant mother may experience these contractions throughout pregnancy; they do not lead to active labor.
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Images courtesy of the American Institute of Ultrasound in Medicine (AIUM.org).