All About Your First Trimester: Week-By-Week

For most women, the first trimester of pregnancy is the most consuming! Everything is all so new, so exciting, and overwhelming. To satisfy the little voice inside your head that keeps asking questions, here’s a guide. Keep it handy.

Week 1

First Trimester: Week-By-Week

Week 1: You’re actually not pregnant yet—the clock starts ticking from the first day of your last period. So even though pregnancies are said to be 40 weeks long, you only carry your baby for 38 weeks.

What to do now:
• Start taking a daily prenatal vitamin with at least 400 micrograms of folic acid; this B vitamin has been shown to help prevent neural-tube defects, such as spina bifida.
• Quit any unhealthy habits, such as smoking or drinking. There’s no time like the present.

Week 2

First Trimester: Week-By-Week

Week 2: Ovulation occurs. For the best chances of getting pregnant, have sex one to two

days before your expected ovulation date.

What to do now:
• Keep (or start) moving. Experts recommend that you exercise for at least 30 minutes on most, if not all, days throughout pregnancy.
• Begin looking for an obstetrician or midwife … just in case. Many will already be booked up.

Week 3

First Trimester: Week-By-Week

Week 3: You may be pregnant but probably won’t have any symptoms.

What to do now:
• Don’t take any medications, prescription or over-the-counter without checking with your doctor. Particularly avoid all products containing vitamin A or its derivatives, such as Retin-A or Accutane. However, many conditions, such as asthma and diabetes, require ongoing treatment, so talk to your doctor before discontinuing any necessary medications.
• Get a flu shot if you haven’t already; they’re safe.

Week 4

First Trimester: Week-By-Week

Week 4: Positive test: You’re pregnant! You may be starting to feel bloated, crampy, tired

and moody, and experiencing sore breasts, nausea/vomiting and a frequent need to pee. But don’t worry if you’re not, that’s normal.

What to do now:
• Invest in an extra supportive bra, especially if your breasts are expanding. Many women grow a full cup size in the first few weeks.
• Avoid chemicals and secondhand smoke. Ask your partner to take over the litterbox duties (cat feces may harbor parasites that cause toxoplasmosis, an infection that can harm the fetus) and to pump the gas in your car.

Week 5

First Trimester: Week-By-Week

Week 5: Though the embryo is only about the size of a grain of sand, the heart is pumping blood, most other organs have begun to develop, and arm and leg buds appear. You may be starting to experience “pregnancy brain”.

What to do now:
• If it helps, make lists at work and at home to help your fuzzy brain function.
• Make an appointment with your OB or midwife. Most caregivers want

to see you for the first time between six and 10 weeks.

Week 6


Week 6: Now that the pregnancy is feeling more real, you might be worrying about miscarriage.

What to do now:
• Reassure yourself that aside from extreme behaviors, such as using drugs, there’s nothing you can do to cause a miscarriage. Yet, some research links early pregnancy losses to consuming more than 300 milligrams of caffeine daily, so to be safe, limit your intake.
• Think about when you want to tell family, friends and your boss you’re pregnant. Some women wait until after the first trimester, when miscarriage risk drops.

Week 7


Week 7: The embryo doubles in size but is still less than a half-inch long. As your pregnancy hormones increase, morning sickness may be worsening. Or, you may be ravenous 24/7.

What to do now:
• If you’re nauseated, try eating several small

meals throughout the day, especially ones with ginger and citrus; avoid strong odors; and wear acupressure wristbands.
• Try not to overdo it on the chow: Weight gain should be minimal in the first trimester. But don’t feel guilty if you give in to an occasional craving.

Week 8


Week 8: Your doctor may look or listen for the baby’s heartbeat with an ultrasound. Once you see or hear it, your miscarriage risk drops to about 2 percent. He’ll also give you an official due date—though very few women actually deliver on that day.

What to do now:
• Though your due date sounds very far away, start reading up on baby care now. You won’t have time after your newborn arrives.

Week 9


Week 9: The pressure of your growing uterus on your bladder may cause you to leak small amounts of urine.

What to do now:
• Start

doing Kegels: Squeeze the muscles around your vagina as if you’re stopping the flow of urine; do several at a time, a few times a day throughout pregnancy. They strengthen your pelvic-floor muscles, helping with incontinence while preparing your body for delivery.

Week 10

Biomedical illustration of week 10 in fetal development. Series.

Week 10: Your inch-long baby is now called a fetus. While the icky side effects of pregnancy may be starting to abate, your anxiety about having a healthy baby might be increasing.

What to do now:
• If you will be 35 or older when you deliver, make an appointment to discuss genetic screening or diagnostic tests, such as chorionic villus sampling (CVS). They look for certain birth defects and are usually done between 10 and 12 weeks. Your doctor’s office may provide counseling; if not, ask for a referral to a genetic counselor.

Week 11



11: Your cravings may run the gamut from cheeseburgers to chalk (really!). Weird nonfood cravings are known as pica and can reflect a deficiency in your diet. This week, nearly all of the fetus’s organs are beginning to function, and genitals begin to take on male or female form.

What to do now:
• Call your doctor if you’re experiencing pica.
• Make an appointment if you’re having the nuchal translucency test, which screens for Down syndrome and other chromosomal abnormalities. The test must be done between 11 and 14 weeks.

Week 12


Week 12: Your uterus has begun to expand outside the protective pelvic bones. It will increase in size by almost 1,000 times by the end of your pregnancy! You may really be starting to show now, especially if it’s not your first baby.

What to do now:
• From now on, steer clear of any activities that pose the risk of a fall or abdominal trauma, such as horseback riding. Also avoid exercises

that require you to lie flat on your back—your growing fetus can place too much weight on a major vein, causing reduced blood flow to the uterus.

Week 13


Week 13: Now that you’ve finished your first trimester, you can start eating for two—a little. Plan on gaining about 12 pounds during the next 14 or so weeks.

What to do now:
• To support your baby’s growth without gaining too much weight, aim to get 300 extra calories a day from healthy foods.
• Start shopping for maternity clothes. Many shops have belly bumps to mimic your girth in later pregnancy.