First Trimester Guide: Pregnancy Weeks 1 to 12

The first trimester is the stretch from the first day of your last period to about week 12. Your body changes quickly and your baby's main organs begin to form, even though a bump may not show yet.

This guide covers what you may feel, how your baby develops, which checkups to expect and what to do and avoid. Use our due date calculator to find where you are.

How Weeks Are Counted

Pregnancy is counted from the first day of your last normal period, so in week 1 or 2 you are not yet pregnant in the usual sense. A full pregnancy lasts about 40 weeks. Sources differ slightly on where the first trimester ends. Cleveland Clinic says the end of week 13 and Womenshealth.gov says week 12, so guidelines vary. Your doctor will confirm your dates, often with an early scan.

What Your Body May Feel

Hormones change quickly and affect almost every system. Common experiences listed by Cleveland Clinic and Womenshealth.gov include:

• Tiredness, which can be extreme
• Nausea, with or without vomiting, at any time of day
• Tender, swollen breasts
• Needing to pass urine more often
• Mood swings, food cravings or dislikes
• Constipation, bloating and heartburn
• Headaches or mild breathlessness on light activity

Some women feel very little. That is also normal. For nausea tips, read our guide to morning sickness remedies.

How Your Baby Grows

According to Cleveland Clinic:

• **Weeks 1 to 4:** The structures that become the placenta and umbilical cord start to form, along with the brain, spinal cord and circulation. The embryo is about the size of a grain of rice.
• **Weeks 5 to 8:** The heart, lungs, ears, arms and legs form. By the end of week 8 the embryo is called a fetus and is about 1 inch long.
• **Weeks 9 to 12:** Fingers, toes and nails develop and the baby begins to move. By the end of week 12 the baby is about 3 to 4 inches long and weighs about 1 ounce.

The NHS adds that by week 12 the baby is about 5.4 cm from head to bottom, and the skeleton is hardening into bone. You will not feel movements yet.

Checkups and Tests

Cleveland Clinic says you can expect 2 or 3 visits in the first trimester. The NHS describes a booking appointment of about an hour between weeks 8 and 12. Typical steps include:

• Medical history, due date calculation, weight and blood pressure
• Urine tests and blood tests, such as blood group, Rh factor and iron levels
• Offers of screening tests for infections and for conditions such as Down's syndrome
• At least one ultrasound, often a dating scan between 8 and 14 weeks

Our guide to ultrasound scans trimester by trimester and our article on month-by-month checkups explain these in more detail. If your blood group is Rh negative, see Rh negative blood group in pregnancy.

A first visit can feel like a lot of information at once. Write down your last period date, any past pregnancies or surgeries, medicines you take and any family history of diabetes, high blood pressure or twins. Bring your partner or a family member if you wish, and ask for any advice to be written down so you can read it again at home.

Healthy Habits: Dos

• Take folic acid. The NHS recommends 400 micrograms daily until at least week 12. Read folic acid and prenatal vitamins.
• Eat a varied diet with fruit, vegetables, pulses, eggs, milk products and whole grains, as in foods to eat during pregnancy.
• Drink plenty of water and rest when you need to.
• Stay gently active. The NHS suggests starting with something small, such as 10 minutes of brisk walking daily.
• Attend every antenatal visit, and tell your doctor about any long-term condition or regular medicine. Do not stop a medicine without advice.

Tip: If nausea is bad, try small, frequent meals and going to bed earlier, as Womenshealth.gov suggests. Keep a dry snack by the bed.

Things to Avoid

• Alcohol, tobacco and recreational drugs. The NHS says it is safest not to drink any alcohol.
• Raw or undercooked meat and eggs, unpasteurised milk and juice, raw fish and high-mercury fish. See foods to avoid during pregnancy.
• Too much caffeine. The NHS sets a limit of 200 mg a day, and a cup of instant coffee has about 100 mg.
• Saunas, hot tubs and activities with a high risk of falls or blows to the tummy.
• Any medicine or herbal product without asking your doctor first.

Myths and Facts

• **Myth:** You must eat for two. **Fact:** The NHS says you do not.
• **Myth:** Everyone has morning sickness. **Fact:** Some have none, and that is fine.
• **Myth:** Light exercise harms the baby. **Fact:** Gentle activity is encouraged for most healthy women, but ask your doctor first.

When to be cautious: Heavy bleeding, severe one-sided tummy pain or shoulder-tip pain can signal a serious problem such as an ectopic pregnancy. Treat these as emergencies. Read ectopic pregnancy emergency signs.

When to See a Doctor

Call your doctor right away if you have any of the following, based on Cleveland Clinic's advice:

• Heavy bleeding or unusual vaginal discharge (see bleeding in early pregnancy)
• Severe cramping in the belly
• Persistent vomiting or diarrhea
• Fainting or dizziness
• Blurred vision

For emergencies, go to the nearest hospital or visit our emergency page.

Looking After Your Feelings

Early pregnancy can bring joy, worry and mood swings in the same day. The NHS suggests talking to your midwife or doctor if you feel anxious or low, and leaning on family and friends. The NHS also suggests thinking about when to tell your employer, with 12 weeks given as a point to consider. It also helps to visit the hospital where you plan to deliver and to ask about antenatal classes early, so that nothing feels rushed later.

Talk to a Doctor

Early care sets the foundation for a healthy pregnancy. You can book an appointment or call +91 944 103 0587. Learn about antenatal check-ups at Chaitanya Hospital, Kadapa.

This article is for general awareness and is not a substitute for a doctor's advice.