Pregnancy: Signs, Stages and Prenatal Care

Early signs of pregnancy

• missed period: often the first sign
• breast tenderness and swelling
• nausea with or without vomiting ("morning sickness," which can happen any time of day), usually starting around weeks 4 to 6
• tiredness
• needing to pee more often
• light spotting around the time of implantation in some women
• food cravings or aversions, a metallic taste, bloating and mood swings

These signs can also have other causes, so a test is needed to confirm pregnancy.

Confirming pregnancy

Home urine tests detect the hormone hCG and are reliable from the first day of a missed period. A clinician may confirm with a blood test and an early ultrasound, which also checks the pregnancy is in the uterus and estimates the due date.

How pregnancy is dated

Pregnancy is counted from the first day of the last menstrual period, about 2 weeks before conception. The due date is 40 weeks from that day. An ultrasound in the first trimester gives the most accurate dating.

The three trimesters

First trimester (weeks 1 to 13)

The baby's major organs form. Common experiences include nausea, tiredness, breast changes and frequent urination. Most miscarriages occur in this period. Screening for chromosome conditions is offered, including cell-free DNA blood tests.

Second trimester (weeks 14 to 27)

Nausea usually eases and energy returns. The belly grows, and movements are first felt around 18 to 22 weeks (earlier in later pregnancies). An anatomy ultrasound at about 18 to 22 weeks checks the baby's development. Glucose screening for gestational diabetes is done at 24 to 28 weeks.

Third trimester (weeks 28 to 40)

The baby gains weight rapidly. Back pain, heartburn, swelling, breathlessness, poor sleep and practice contractions (Braxton Hicks) are common. Visits become more frequent, and group B strep screening is done at 36 to 37 weeks.

Prenatal care

A typical schedule for an uncomplicated pregnancy:

• every 4 weeks until about 28 weeks
• every 2 weeks from 28 to 36 weeks
• weekly from 36 weeks until birth

Visits include blood pressure, weight, urine checks, measuring the uterus, listening to the baby's heartbeat, and blood tests for blood type, anemia, infections and immunity.

Recommended vaccines

• flu vaccine in any trimester during flu season
• Tdap (whooping cough) at 27 to 36 weeks in every pregnancy
• RSV vaccine at 32 to 36 weeks during RSV season, or an antibody shot for the baby after birth
• COVID-19 vaccination as recommended

Nutrition and healthy habits

• Folic acid: at least 400 micrograms a day, ideally starting 1 month before conception, to reduce neural tube defects. A prenatal vitamin usually contains it plus iron and iodine.
• Eat a variety of vegetables, fruit, whole grains, protein and dairy or calcium-rich alternatives.
• Fish: 2 to 3 servings a week of low-mercury fish; avoid shark, swordfish, king mackerel, tilefish and bigeye tuna.
• Food safety: avoid unpasteurized dairy and juice, raw or undercooked meat, fish and eggs, and deli meats unless heated until steaming, to prevent listeria and other infections.
• Caffeine: less than 200 mg a day (about one 12-oz cup of coffee).
• No alcohol at any stage; no smoking, vaping or recreational drugs, including cannabis.
• Exercise: about 150 minutes a week of moderate activity is safe for most.
• Medicines: check every medicine and supplement with your clinician or pharmacist.

Weight gain

Recommended total weight gain depends on pre-pregnancy BMI:

Common pregnancy discomforts

• nausea: eat small, frequent bland meals; ginger may help; vitamin B6 is a common first step after discussion with your clinician
• heartburn: smaller meals, avoid lying down after eating
• constipation: fluids, fiber and activity
• back pain: good posture, supportive shoes, exercise
• leg cramps and swelling: stretching, raising the legs
• tiredness and poor sleep: sleeping on your side with pillows

Complications to know about

• miscarriage and ectopic pregnancy
• hyperemesis gravidarum: severe vomiting
• gestational diabetes
• high blood pressure and preeclampsia
• placenta previa and placental abruption
• preterm labor
• anemia, urinary infections and blood clots
• postpartum depression after birth

Frequently asked questions

What are the first signs of pregnancy?

The earliest signs are usually a missed period, tender or swollen breasts, nausea, tiredness and needing to pee more often. Some people notice light spotting, bloating or mood changes. A home pregnancy test confirms it from the day the period is due.

How soon can a pregnancy test detect pregnancy?

Most home tests are reliable from the first day of a missed period. Some sensitive tests can detect pregnancy a few days earlier, but false negatives are more likely. If negative and your period still has not come, test again in a few days.

How much weight should I gain during pregnancy?

It depends on your weight before pregnancy. Someone with a healthy BMI is generally advised to gain 25 to 35 lb (11.5 to 16 kg). Recommended gain is higher for underweight people and lower for those with overweight or obesity.

What should I avoid during pregnancy?

Avoid alcohol, smoking, vaping and recreational drugs, high-mercury fish, unpasteurized dairy, raw or undercooked meat, fish and eggs, and cold deli meats. Limit caffeine to under 200 mg a day, and check all medicines with your clinician.

What are the warning signs during pregnancy?

Get urgent help for heavy bleeding, severe belly pain, severe headache, vision changes, sudden swelling of the face or hands, fever, leaking fluid, regular contractions before 37 weeks, decreased baby movements, chest pain or trouble breathing.