Not sure what to expect now that you're expecting? We've got the inside scoop on your changing body -- and your baby's development -- trimester by trimester.

By Julie Knapp
October 05, 2005

First Trimester: Weeks 1 through 13

Congratulations! You're going to be a mom. Once you get over the initial shock, be prepared for some pretty crazy changes to your body. To start, your surging hormones can cause everything from morning sickness to acne. You may also notice that your breasts feel tender, and bluish veins may appear across your chest. You'll also feel more tired than usual--so go to bed earlier to give your body the rest it needs. Despite all this, you'll be overjoyed that your baby is growing inside you.

First-Trimester Checklist

  • Start a journal. Use a pregnancy diary to track your feelings and the changes in your body. It's also a handy place to jot down questions for your doctor. Wish there was an easy, interactive way to record your thoughts? Now there is! Visit our free interactive pregnancy journal.
  • Get tested. At your first prenatal visit, your doctor will test your blood for everything from anemia to hepatitis B and check your immunity to diseases like rubella.
  • Take your vitamins. If you aren't already taking a prenatal vitamin containing at least 400 micrograms of folic acid, ask your doctor for a prescription. This will help prevent neural-tube defects like spina bifida.
  • Hold off on the hair dye. Though studies have shown that it's safe to color your hair during pregnancy, many doctors recommend waiting until the second trimester.
  • Stock up on saltines. Experts believe morning sickness occurs when the placenta releases high levels of the hormone human chorionic gonadotropin (hCG). Eating several small meals a day and snacking on bread, crackers, and other carbs can help keep nausea to a minimum. Many moms-to-be also swear by ginger tea or vitamin B6.
  • Use more sunscreen. Pregnancy hormones cause pigment cells to go into overdrive, making you extra sensitive to UV rays.

Your Focus This Trimester: Eating Right

You know that alcohol is off-limits. Here's what else you should avoid.

  • Sushi and smoked raw seafood. Uncooked fish may contain parasites that could make you sick. In addition, steer clear of shark, swordfish, tilefish, and king mackerel (and limit yourself to an average of six to 12 ounces of canned tuna a week) since they contain high levels of mercury.
  • Caffeine. While studies have shown that a little caffeine (a cup of coffee or a can of soda a day) is perfectly safe, drinking more than 300 milligrams (about three 8-ounce cups of coffee) may increase your risk of miscarriage.
  • Soft cheeses. Raw-milk or unpasteurized cheeses may contain listeria, a bacterium that can cause premature delivery. But Brie, feta, and other soft cheeses are perfectly safe if they've been pasteurized.
  • Caesar salad dressing. Eating anything made with raw or undercooked eggs increases your risk of food poisoning.
  • Artificial sweeteners. Since experts don't know whether sugar substitutes affect a fetus, your best bet is to limit yourself to one or two servings a day.

The Inside Story

Your baby's very busy in the first three months. What started as an embryo has developed into a fetus with organs such as a heart, a brain, and lungs. At less than four inches long and weighing only one ounce, she may be tiny—but she's already got all her fingers and toes!

Second Trimester: Weeks 14 through 27

Welcome to the feel-good trimester. You'll notice that you have lots more energy and a lot less nausea. In addition, many moms-to-be find that their skin glows and their hair is shinier and thicker, thanks to surging hormones. Around week 20 your ligaments will start to soften in preparation for childbirth, and owing to extra pressure on your bladder from your expanding uterus, you'll need to hit the bathroom often. Still, this is the time to be good to yourself. Manicures and prenatal massages are totally safe, and remember, you won't have time for pampering after the baby comes!

Second-Trimester Checklist

  • Go to the dentist. Left untreated, periodontal disease can increase your risk of preeclampsia and preterm labor. If you canceled your appointment during the first trimester because of morning sickness, reschedule it now.
  • Load up on fruits and vegetables. You need an additional 300 calories a day when you're expecting. Give your body—and your baby—extra vitamins, minerals, and nutrients by eating foods like apples, spinach, blueberries, and broccoli.
  • Get a peek at your baby. Many women have their first ultrasound between 18 and 22 weeks. Your doctor will check the baby's size and can tell you whether it's a boy or a girl. You may also have several prenatal screenings during this trimester, including alpha-fetoprotein (AFP), gestational diabetes, and in some cases, amniocentesis.
  • Register for baby gear. Now's the perfect time to hit the baby stores to test strollers, carriers, and all the other stuff you'll need.
  • Have sex. Many women find that they have a higher libido during pregnancy. Not only is sex safe during pregnancy (unless your doctor says to avoid intercourse), it can be particularly hot as a result of increased blood flow to your pelvic region.
  • Take a trip. Want to enjoy one last getaway with your husband before the baby comes? Go now while your energy's up and your belly is still small. If you fly, be sure to walk around the cabin every hour or so to prevent fluid from accumulating in your legs; most experts recommend that you stop traveling by air at the 36-week mark.

Your Focus This Trimester: Exercising

Haven't been hitting the gym since you learned you were pregnant? Now's the time to put fitness first. Try these bump-friendly workouts.

  • Walking. Take a 30-minute stroll most days of the week to boost your circulatory system, ease constipation, and relieve stress. Carry a water bottle to stay hydrated, and don't push yourself too hard. If you're walking so fast that you can't talk in complete sentences, slow down.
  • Swimming. As your belly gets bigger, you'll find that this no-impact exercise is the most comfortable. Hate to swim? Consider signing up for a water aerobics class.
  • Prenatal yoga: In addition to teaching you breathing techniques, yoga poses can relieve tight muscles and work out the kinks in your lower back and hips. It's best to take classes with a certified instructor who can modify the poses for you.
  • Weight training: Lifting light weights will help you maintain muscle tone in your arms and shoulders. Avoid any move that requires you to lie on your back, since this can hinder blood flow to the uterus.

The Inside Story

During the second trimester, your baby's senses develop. His retinas and taste buds form, and he can even recognize your voice! He becomes more active during this phase too: You may be able to feel him kicking and turning in your belly at around 18 weeks. By the end of the 27th week, your baby will be nearly nine and a half inches long and weigh about two pounds.

Third Trimester: Weeks 28 through 40

You're in the home stretch now! The skin on your bulging belly is beginning to feel tight and itchy, and you may notice a linea nigra—a dark line that runs from your pubic bone up to your navel—starting to appear. Don't be surprised if overeager friends or even strangers clamor to touch your belly. You may also be shocked when you jump on a scale: A woman of healthy weight gains about 30 pounds during her pregnancy. Even more amazing, your uterus will expand to 1,000 times its original volume. Finally, you can feel Braxton Hicks contractions at any time during the third trimester. Unlike real contractions, these irregular, mild tightenings of the uterus may go away if you simply walk around. Still, if you aren't sure what you're experiencing, call your doctor.

Third-Trimester Checklist

  • Take a prenatal class. Ease your delivery-day fears by learning about relaxation techniques for labor. While you're at it, sign up for an infant CPR class.
  • Find a pediatrician. Check with your insurance company, get advice from friends, or ask your hospital for a referral.
  • Get a group B strep culture. While this bacterium is normally harmless, it may cause infection in a newborn. Your doctor will give you this test at around 36 weeks to see whether you're one of the approximately 10 to 30 percent of women who carry strep B. If you test positive, you'll be given antibiotics during labor.
  • Buy -- and install -- a car seat. The hospital won't let you go home without one. Can't completely finish your nursery? Just make sure the crib or bassinet is assembled.
  • Prepare to breastfeed. If you plan to nurse, buy a breast pump and make sure you know how to use it.
  • Pack your bag. You could go into labor anytime after the 36-week mark, so gather anything you'll want in the hospital.

Your Focus This Trimester: Staying Comfortable

Your rapidly expanding middle may leave you with aches and pains. Here are some common complaints.

  • Hemorrhoids. Soaking in a warm bath or sitting on an ice pack can soothe these swollen veins around the rectum. Or ask your doctor about over-the-counter creams to ease the burning and itching.
  • Fat feet. Fluid shifts from blood vessels into the tissues in your hands and feet, causing them to swell. Try to elevate your legs as often as possible.
  • Heartburn. Eating small meals, and not lying down for 30 minutes after you eat can help. Your doctor may also recommend an over-the-counter antacid.
  • Shortness of breath. As your due date nears, your baby nestles right under your rib cage. Luckily, this gets much better after your baby drops, at around 36 weeks.

The Inside Story

Your baby is getting ready for life outside the uterus: Her organs are formed, her central nervous system's working, and her brain continues to grow. During this final trimester she'll continue to get bigger, putting on at least four pounds and growing six more inches.

Sources: Nancy Jasper, M.D., assistant clinical professor of obstetrics and gynecology at Columbia University Medical Center; Bruce Flamm, M.D., Parents adviser and clinical professor of obstetrics and gynecology at the University of California in Irvine; Joanne Stone, M.D., coauthor of Pregnancy for Dummies.

All content here, including advice from doctors and other health professionals, should be considered as opinion only. Always seek the direct advice of your own doctor in connection with any questions or issues you may have regarding your own health or the health of others.

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