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Weeks 1-12 • Foundation Stage

First Trimester of Pregnancy

The first 12 weeks of pregnancy are a time of incredible development and adjustment. Your baby's major organs form during this critical period while your body adapts to pregnancy changes.

Duration

12 weeks

Weeks 1-12 of pregnancy

Key Milestone

All Major Organs Form

Critical development period

Common Experience

Morning Sickness

Affects about 80% of women

👶Your Baby's Development in the First Trimester

Weeks 1-4: The Beginning

  • • Conception occurs around week 2
  • • Fertilized egg implants in uterus
  • • Basic cell layers form
  • • Neural tube begins developing
  • • Heart starts forming

Weeks 5-8: Rapid Growth

  • • Heart begins beating (around week 6)
  • • Limb buds appear
  • • Brain and spinal cord develop
  • • Facial features start forming
  • • Major organs begin developing

Weeks 9-12: Organ Formation

  • • All major organs are present
  • • Fingers and toes form
  • • Baby can move and kick
  • • External genitalia develop
  • • Risk of miscarriage decreases significantly

Size Progression

  • • Week 4: Poppy seed (2mm)
  • • Week 6: Lentil (4mm)
  • • Week 8: Raspberry (16mm)
  • • Week 10: Strawberry (31mm)
  • • Week 12: Lime (54mm)

🤰Your Body Changes in the First Trimester

Physical Changes

  • Breast changes: Tenderness, enlargement, darkening areolas
  • Fatigue: Increased tiredness due to hormonal changes
  • Frequent urination: Pressure on bladder increases
  • Weight gain: 1-5 pounds total for trimester

Common Symptoms

  • Morning sickness: Nausea and vomiting (peaks around weeks 8-10)
  • Food aversions: Strong dislike for certain foods
  • Mood swings: Emotional changes due to hormones
  • Heightened smell: Increased sensitivity to odors

🩺Important Appointments & Tests

First Prenatal Visit (Weeks 6-8)

Confirm pregnancy and establish care

  • • Medical history and physical exam
  • • Blood tests (blood type, infections, genetic screening)
  • • Urine tests
  • • Discussion of prenatal vitamins and lifestyle

Nuchal Translucency Screening (Weeks 11-14)

Optional screening for chromosomal abnormalities

  • • Ultrasound measurement of neck area
  • • Blood test for hormone levels
  • • Risk assessment for Down syndrome and other conditions

Regular Monitoring

Monthly appointments throughout first trimester

  • • Weight and blood pressure checks
  • • Urine tests for protein and glucose
  • • Fetal heartbeat monitoring (after week 10)
  • • Address any concerns or symptoms

✓First Trimester To-Do Checklist

Health & Medical

Schedule first prenatal appointment
Start taking prenatal vitamins with folic acid
Quit smoking and avoid alcohol
Limit caffeine intake
Get flu vaccination if recommended
Discuss medications with your doctor

Lifestyle & Planning

Inform your partner and close family
Research health insurance coverage
Start thinking about work maternity leave
Avoid harmful chemicals and activities
Begin documenting your pregnancy journey
Join pregnancy support groups or classes

💡Managing First Trimester Symptoms

Morning Sickness

  • • Eat small, frequent meals throughout the day
  • • Keep crackers by your bedside for morning nausea
  • • Try ginger tea or ginger supplements
  • • Stay hydrated with small sips of water
  • • Avoid strong odors and trigger foods

Fatigue

  • • Get 7-9 hours of sleep per night
  • • Take short naps during the day if possible
  • • Maintain light exercise as approved by your doctor
  • • Ask for help with daily tasks
  • • Eat iron-rich foods to prevent anemia

Breast Tenderness

  • • Wear a supportive, well-fitting bra
  • • Consider a sleep bra for nighttime comfort
  • • Use warm or cold compresses as needed
  • • Avoid caffeine which can increase tenderness

First Trimester Week by Week

Click on any week to get detailed information about your baby's development and your body's changes.

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🚨When to Contact Your Healthcare Provider

Contact your doctor immediately if you experience any of these symptoms:

Emergency Symptoms

  • • Heavy bleeding or passing clots
  • • Severe abdominal or pelvic pain
  • • Severe, persistent vomiting
  • • High fever (over 100.4°F)
  • • Fainting or dizziness

Concerning Symptoms

  • • Persistent severe headaches
  • • Vision changes or blurriness
  • • Unable to keep food or fluids down
  • • Signs of dehydration
  • • Unusual vaginal discharge or odor

Next: Second Trimester

Weeks 13-26: The golden period

Energy returns, morning sickness fades

All Pregnancy Weeks

Complete week-by-week guide

Detailed information for each week

Medical Disclaimer

The information provided about the first trimester of pregnancy is for educational purposes only and should not replace professional medical advice. Every pregnancy is unique, and individual experiences may vary significantly. Always consult with your healthcare provider for personalized medical guidance and to address any concerns about your pregnancy.