Hands holding a pregnancy test.

As a new life begins, yours forever changes. And so does your body. That’s why we’ve put together this pregnancy primer—we’ve got the scoop on what tests to anticipate, what’s normal (and what’s not) and some tricks of the trade.

“Pregnancy is going to be a great time in your life,” says Dr. Carlos Perez-Cosio, MD, FACOG, an obstetrician and gynecologist at Memorial Hermann Medical Group The Woodlands OB/GYN. “And the better prepared you are, the better the experience.”

His trimester guide to pregnancy has five stages, starting with the decision to have a baby.

Pre-Pregnancy: Before You Get Pregnant

Meds and Tests: What Do You Need?

WHAT: Ideally, you should start taking prenatal vitamins three months before you conceive, Dr. Perez-Cosio says.

WHY: You need enough folic acid, iron, calcium and other nutrients to spur along a baby’s healthy development.

WHAT: Review your current medications with your doctor.

WHY: You need enough folic acid, iron, calcium and other nutrients to spur along a baby’s healthy development.

Great Expectations: How Your Body Will Change

WHAT: Keep—or adopt—healthy habits, including diet and exercise.

WHY: “Pregnancy is a big challenge for the body, physically and mentally, Dr. Perez-Cosio says. “It could be as rough as a marathon. The healthier you are, the more likely you are to have a healthier and easier pregnancy.”

Surprise! Unexpected Events

WHAT: Be prepared: You may get pregnant the first time you try or it may take months—even years.

WHY: Each body and pregnancy is unique, he says.

Cause for concern: If you haven’t gotten pregnant within a year of trying, consult your OB/GYN. The older the mother, the lower the number and quality of her eggs—and the higher the chance of genetic defects.

On the Menu: What Should You Eat and Avoid?

WHAT: Start weaning yourself of that morning Joe and evening wine. Once you’re pregnant, most doctors will limit coffee to one cup daily. Booze usually is off the table.

WHY: Studies show caffeine may affect fertility, while alcohol can hike the likelihood of learning disabilities in children.

First Trimester (1-14 Weeks)

Meds and Tests: What Do You Need?

WHAT: Early on your doctor will confirm your pregnancy, order blood tests and perform an ultrasound at your first appointment. Ten weeks in, your OB/GYN usually takes your baby’s first selfie and draws blood. By the end of your first trimester, your OB/GYN will offer genetic testing.

WHY: These tests can rule out hepatitis, HIV and other sexually transmitted infections or alert you to conditions that should be treated promptly to curb complications for mother or child. The 10-week ultrasound shows you whether you’re having a boy or a girl.

Great Expectations: How Your Body Will Change

WHAT: You’ll be exhausted even before your bump shows.

WHY: “Your body is building a baby–that’s work,” Dr. Perez-Cosio says. “Also hormonal shifts, your expectations of yourself and your future baby can be overwhelming.”

Surprise! Unexpected Events

WHAT: Some women experience nausea or vomiting. Symptoms may cease by the 13th week of pregnancy or last longer.

WHY: Your hormones and the baby’s development are working overtime.

WHAT: Constipation.

WHY: Your body pumps out progesterone, hormones that create space for your baby, but also slows down your digestion. That’s yet another reason to add fiber-rich fruits and vegetables to your diet.

Cause for concern: “If you have cramping or bleeding, go to your doctor or the closest emergency room,” Dr. Perez-Cosio says. “The highest chance of miscarriage is in the first trimester.”

On the Menu: What Should You Eat and Avoid?

WHAT: Avoid alcohol, tobacco and recreational drugs. Stay well hydrated. Skip unpasteurized dairy, raw sushi and raw meat. Start snacking on fruit, almonds and cashews. Keep working out, but don’t go from zero to triathlete.

WHY: Raw foods (other than fruits, vegetables and salads) boost likelihood of infections before your baby is developed enough to survive them. Extreme exercises expose you to possible complications: cycling or skiing (falls), karate (with possible blows to the belly) and hot yoga (which might cause dehydration). Working out helps you maintain a healthy weight gain and pays off later in less rigorous labor.

Second Trimester (14-28 Weeks)

Meds and Tests: What Do You Need?

WHAT: Your doc will run blood tests and blood pressure checks at each appointment. He or she will also monitor your baby’s growth via ultrasounds.

WHY: Even if you’ve never had diabetes, it might develop as the placenta—your baby’s lifeline—churns out hormones that interfere with your insulin levels. Just as too much sugar can make you gain weight, it can super-size your baby.

Great Expectations: How Your Body Will Change

WHAT: “You’ll see your biggest changes physically, with weight gain, and you’ll feel your baby moving,” he says. Pay attention to your baby’s kicks, which should start as soon as 20 weeks, at first a flutter. “In the early stages the kicks are subtle, but then they kick hard.”

WHY: Your baby grows at its fastest rate during the second and third trimesters, plus you’ll retain fluids that cocoon your baby. Less nausea, bigger belly and greater cravings and energy can lead to you to overeat.

Your baby should move at least six times an hour, every hour. If not, let your doctor know so you can be sure your little one is healthy and growing stronger and larger.

Surprise! Unexpected Events

WHAT: Early contractions can scare you.

WHY:You’re parched. Be sure to hydrate with water, milk or juice.

CAUSE FOR CONCERN: Any bleeding or sustained or severe cramps may signal fetal distress, so seek medical attention.

On the Menu: What Should You Eat and Avoid?

WHAT: Your doctor may allow you to return to some prescription medications.

WHY: Your baby’s development is far enough along that your little one is stronger and better able to handle your medication.

Third Trimester (28 Weeks and Beyond)

Meds and Tests: What Do You Need?

WHAT: Take a tour of your hospital’s labor and delivery unit and nail down a birthing plan, including labor anesthesia and post-delivery contraception. Consider signing up for classes in labor or CPR (cardiopulmonary resuscitation).

WHY: Babies are full of surprises, so be flexible on your delivery date and method. Your health and your baby’s are the final arbiter. The skills you learn will help you in your delivery and protect your baby in the unlikely event of an emergency.

WHAT: Your doctor will check your baby’s growth with an ultrasound, and at 35 to 37 weeks you’ll receive a GBS, Group B Strep test, which is a genital culture done with a swab.

WHY: This screens for bacteria that should be battled with antibiotics during labor.

WHAT: Your blood pressure will be checked at each doctor visit. You’ll also be asked to report any headaches.

WHY: Soaring blood pressure, known as preeclampsia, threatens you and your baby. A rise in blood pressure may hamper the placenta’s ability to feed your baby, and uncontrolled hypertension can cause a stroke.

Great Expectations: How Your Body Will Change

WHAT: Big baby means big belly which throws you off-kilter. Your swelling tummy puts pressure on your pelvis, causing an urge to urinate as well as back pain.

WHY: Resist the impulse to curb fluids: “Drink tons of water, especially when it’s hot out,” Dr. Perez-Cosio says. “Dehydration can lead to a premature contractions and delivery.”

WHAT: Your feet and lower limbs swell.

WHY: Take a hint from fluid retention in your lower limbs. Put up your feet and avoid high heels. It’s hard enough balancing an ever-changing body.

Surprise! Unexpected Events

WHAT: You may develop forgetfulness and or some depression.

WHY:Shifting hormones, sleepless nights and anxiety about labor and motherhood may be the culprit. If your emotions bounce between glee and fear, it’s normal.

WHAT: Pimple-like milk and sweat glands may sprout around nipples.

WHY:Montgomery glands. They lubricate nipples while secreting a scent the baby is drawn to.

WHAT: Your joints may ache and you may feel pelvic pressure.

WHY:The hormones (relaxin and progesterone) that relax joints in the pelvis to create space for your growing baby and ease delivery.

CAUSE FOR CONCERN: Phone your doctor’s office and head to the emergency room if you’re bleeding, having six or more contractions an hour or your water breaks. Also seek care if you fall and hit your abdomen hard: You may rupture the placenta – your baby’s life support system — start bleeding or go into preterm labor. “You should not wait. Get checked.”

On the Menu: What Should You Eat and Avoid?

WHAT: Stick with what’s worked for you throughout your pregnancy and continue to avoid pregnancy no-nos like raw animal proteins.

WHY: The end is in sight—keep nourishing your body and baby to the best of your ability.

Postpartum: After Your Baby is Born

Meds and Tests: What Do You Need?

WHAT: Enjoy your baby.

WHY: This is an amazing moment. You’ll hear advice from so many sources, but “everybody is different,” Dr. Perez-Cosio says. “What works for somebody might no work for you.”

Great Expectations: How Your Body Will Change

WHAT: Sleepless nights thanks to your new boss, who communicates through crying.

WHY: Giving birth is hard work, as is taking care of an infant. “Ask for help with your baby if you need to,” Dr. Perez-Cosio says. “That does not make you weaker. It actually makes you stronger.”

Surprise! Unexpected Events

WHAT: You may have lingering weight gain and still look pregnant, despite what celebrities’ photos suggest.

WHY: Your postpartum pooch takes six to eight weeks—at least—to shrink to its normal size.

CAUSE FOR CONCERN: If post-delivery blues persist or you’re having trouble nursing, seek care. Your doctor may prescribe drugs that will help you without harming your new arrival, and lactation nurses can help you with nursing.

On the Menu: What Should You Eat and Avoid?

WHAT: Avoid alcohol and coffee if you’re breastfeeding.

WHY: They may curb growth or development of your baby.

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