Your First Trimester of Pregnancy

What to expect and how to prepare

 The first trimester marks the beginning of your pregnancy journey. During these first weeks, your body goes through many changes as your baby starts to grow and develop. Knowing what to expect can help you feel more prepared and confident as you move through early pregnancy. 

How long is the first trimester?

The first trimester starts on the first day of your last menstrual period and lasts through week 12. During this time, your baby develops rapidly and you may start to notice new physical and emotional changes. 

What to expect in the first trimester 

Even though you may not look pregnant yet, your body is already working hard. Hormones rise quickly, supporting early development and causing many of the symptoms people associate with early pregnancy. These changes can feel exciting and overwhelming at the same time. 

Common changes in early pregnancy 

Hormonal shifts can affect almost every system in your body. You may notice: 

• Frequent urination 
• Fatigue 
• Constipation 
• Bloating 
• Heartburn 
• Nausea or morning sickness 
• Mood changes 
• Breast tenderness 
• Food aversions or smell sensitivity 

Many people also experience emotional changes. It’s normal to feel happy, anxious or unsure as you think about your growing family, your health and your plans. Talk with your support system and let your doctor know if emotions feel hard to manage. 

When to call your doctor 

Contact your provider right away if you have: 

• Heavy bleeding 
• Severe abdominal pain 
• Fever 
• Dizziness or fainting 
• Signs of dehydration from vomiting 

Your Banner Health team is always here if something doesn’t feel right. 

How your baby develops in the first trimester 

Your baby grows quickly during these first weeks. By the end of the trimester: 

• The brain, spinal cord and organs begin to form 
• The heart starts beating 
• Limbs, fingers and toes develop 
• Facial features start to take shape 
• Sex organs form 
• Your baby measures about 3 inches long and weighs around 1 ounce 

These early steps lay the foundation for your baby’s growth in the months ahead. 

First trimester prenatal care 

If you think you are pregnant, contact your doctor so you can start prenatal care as early as possible. Taking a daily prenatal vitamin with folic acid is recommended for everyone who may be pregnant. 

Your first prenatal visit 

Your provider will: 

• Confirm the pregnancy 
• Review your medical and family history 
• Check your weight and blood pressure 
• Collect blood and urine samples 
• Determine your due date 
• Provide guidance about nutrition, lifestyle and symptoms 

You will typically have prenatal appointments every four weeks during the first trimester. 

First trimester testing 

Many people have a nuchal translucency (NT) ultrasound around 11–14 weeks, which measures the thickness at the back of the baby’s neck. Your provider may also recommend genetic screening to check the chances of specific chromosomal conditions. 

Questions to ask your provider 

• What symptoms are normal at this stage 
• What medications or supplements are safe 
• What lifestyle changes are recommended 
• How to contact the care team with questions 
• What prenatal tests are available 

First trimester checklist 

Use this list to stay organized during early pregnancy: 

• Start a prenatal vitamin 
• Schedule your first prenatal appointment 
• Review your medications for pregnancy safety 
• Drink plenty of water 
• Eat balanced meals 
• Limit caffeine 
• Avoid alcohol and smoking 
• Learn which foods to avoid during pregnancy 
• Get enough sleep 
• Exercise as recommended by your provider 
• Understand your health insurance 
• Plan how and when you want to share your news 
• Discuss parenting expectations with your partner 
• Create or update your household budget 
• Avoid changing cat litter to reduce toxoplasmosis risk 

What’s next? Learn what to expect in your second trimester.