Pregnancy lasts about 40 weeks from the first day of your last period to delivery, divided into three trimesters that each bring distinct changes to your body and your developing baby. Whether you just found out you’re pregnant or you’re planning ahead, here’s a practical walkthrough of what to expect, what to eat, how to stay active, and what to watch for along the way.
How Your Baby Develops by Trimester
The first trimester spans conception through week 12. Development moves fast: by week 3, a fertilized egg has implanted in the uterus. By week 5, the brain and spinal cord are beginning to form. By week 8, all major organs and body systems are developing. Most of this happens before you even look pregnant.
The second trimester runs from week 13 through week 28. This is when many people start to feel more comfortable as early nausea fades. Your baby’s body is catching up to its head in proportion, a protective waxy coating covers the skin, and by week 27, the eyes can open and blink. You’ll typically start feeling movement somewhere between weeks 16 and 22.
The third trimester begins at week 29 and continues through week 40. The brain matures rapidly around week 30. Bones harden by week 33, except for the skull bones, which stay soft so the baby can fit through the birth canal. By week 39, the baby is considered full-term.
Prenatal Visits and Screening
For a low-risk pregnancy, expect 12 to 14 office visits total. The standard schedule is monthly visits until 28 weeks, then every two weeks until 36 weeks, then weekly until delivery. These visits include lab work, ultrasounds, blood pressure checks, and screenings that track both your health and the baby’s growth.
Early visits typically involve blood typing, infection screening, and a dating ultrasound to confirm how far along you are. A detailed anatomy scan usually happens around week 20. Later visits focus on the baby’s position, your blood pressure, and signs of complications like preeclampsia or gestational diabetes. If your pregnancy is higher risk, your provider will schedule more frequent monitoring.
Nutrients That Matter Most
Three nutrients deserve special attention during pregnancy: folate, iron, and omega-3 fatty acids.
Folate is critical for brain and spinal cord development in the earliest weeks, often before you know you’re pregnant. The recommended intake during pregnancy is 600 micrograms per day from food and supplements combined. If you’re of childbearing age and could become pregnant, experts recommend getting 400 to 800 micrograms daily from a supplement or fortified foods as a baseline.
Iron needs jump to 27 milligrams per day during pregnancy because your blood volume increases significantly. Many prenatal vitamins cover this, but some people need additional supplementation, especially if they become anemic. Taking iron with vitamin C (like a glass of orange juice) helps your body absorb it.
DHA, an omega-3 fat found in fatty fish and algae supplements, supports the baby’s brain development. There’s no official government recommendation, but clinical guidelines suggest at least 250 milligrams per day of DHA plus EPA, with an extra 100 to 200 milligrams of DHA during pregnancy. Two servings of low-mercury fish per week generally covers this.
Foods to Avoid
The biggest food safety concern during pregnancy is listeria, a bacteria that can cause serious complications including miscarriage. Your immune system is suppressed during pregnancy, making you about 10 times more susceptible to foodborne illness than the general population.
The foods to skip or handle carefully include:
- Deli meats, hot dogs, and luncheon meats unless reheated until steaming hot
- Unpasteurized milk and any products made from it
- Soft cheeses like queso fresco, queso blanco, and similar fresh-style cheeses, even when made with pasteurized milk
- Refrigerated smoked seafood (labeled as lox, nova-style, kippered, or smoked) unless cooked into a dish like a casserole
- Refrigerated pâtés or meat spreads
- High-mercury fish like swordfish, shark, king mackerel, and tilefish
Raw or undercooked meat, poultry, eggs, and unwashed produce also carry risk. Cooked fish that’s low in mercury (salmon, sardines, tilapia) is not only safe but encouraged for its omega-3 content.
Exercise During Pregnancy
Staying active during pregnancy is safe and beneficial for most people. The recommendation is at least 150 minutes of moderate-intensity aerobic activity per week, spread across multiple days rather than packed into one or two sessions. Walking, swimming, stationary cycling, and prenatal yoga all count.
What to avoid: contact sports and high-impact activities with a risk of falls or blunt force to the abdomen, like downhill skiing, horseback riding, and kickboxing. Overheating is also a concern, so stay hydrated and avoid exercising in extreme heat. If you were active before pregnancy, you can generally continue your routine with modifications. If you weren’t, starting with short walks and gradually building up is a safe approach.
Weight Gain by Pre-Pregnancy BMI
How much weight you should gain depends on where you started. The CDC’s current guidelines for a single pregnancy are:
- Underweight (BMI under 18.5): 28 to 40 pounds
- Normal weight (BMI 18.5 to 24.9): 25 to 35 pounds
- Overweight (BMI 25 to 29.9): 15 to 25 pounds
- Obese (BMI 30 to 39.9): 11 to 20 pounds
For twins, these ranges roughly double. Most weight gain happens in the second and third trimesters. In the first trimester, gaining 1 to 4 pounds total is typical. The weight isn’t just baby. It includes the placenta, amniotic fluid, increased blood volume, breast tissue, and fat stores your body builds for breastfeeding.
Managing Nausea and Heartburn
Nausea affects up to 80% of pregnant people, most commonly in the first trimester. Eating smaller, more frequent meals instead of three large ones helps keep blood sugar stable and reduces the queasy feeling. Bland carbohydrates like crackers, toast, or rice are easier to tolerate. Ginger (in tea, candies, or capsules) has good evidence behind it as a nausea remedy.
Heartburn often picks up in the second and third trimesters as the growing uterus pushes stomach acid upward. Lifestyle changes are the first line of defense: eat smaller meals, avoid lying down right after eating, and elevate the head of your bed. If that’s not enough, antacids containing aluminum, calcium, or magnesium are safe during pregnancy. Stronger acid-reducing medications are also considered safe when needed. Avoid antacids containing bicarbonate or high doses of magnesium trisilicate, which can cause complications.
Mental Health During Pregnancy
Mood and anxiety disorders are the most common complication of pregnancy, affecting an estimated 15 to 21% of pregnant and postpartum people. About 1 in 7 experience perinatal depression, and 13 to 21% deal with perinatal anxiety. These aren’t just “baby blues” that resolve on their own in a couple of weeks.
If you had anxiety or depression before pregnancy, your risk is higher. About 60% of people diagnosed with depression during the perinatal period had a preexisting mental health condition, and 80% of those were anxiety disorders. Black women face disproportionately high rates, with more than 40% experiencing postpartum depression, over double the rate of the general population.
Symptoms to pay attention to include persistent sadness, loss of interest in things you used to enjoy, excessive worry that interferes with daily life, difficulty bonding with the pregnancy or baby, trouble sleeping beyond normal pregnancy discomfort, and intrusive or frightening thoughts. These are treatable conditions, and both therapy and certain medications can be used safely during pregnancy.
Warning Signs That Need Immediate Attention
Most pregnancies progress without emergencies, but knowing the red flags can be lifesaving. Seek medical care right away if you experience any of these:
- Vision changes: flashes of light, bright spots, blind spots, blurry or double vision, or temporary loss of sight
- Vaginal bleeding: anything heavier than light spotting, or fluid leaking from the vagina
- Decreased fetal movement: the baby stops moving or moves noticeably less than usual
- Severe headache that doesn’t respond to rest or hydration
- Swelling in the face or hands that comes on suddenly
- Difficulty breathing
Vision changes, sudden swelling, and severe headaches can signal preeclampsia, a blood pressure condition that develops after 20 weeks and can escalate quickly. Vaginal bleeding can have causes ranging from minor to urgent, but it always warrants a call to your provider. For fetal movement, if you’re past 28 weeks and notice a change, try drinking cold water, lying on your side, and counting kicks. If you don’t feel 10 movements within two hours, contact your provider.