Women's Health

Pregnancy Week by Week: Your Complete Development Guide

A comprehensive guide to pregnancy development, symptoms, and important milestones throughout your 40-week journey. Track your baby's growth and understand the changes in your body.

Dr. Emily Watson
Dr. Emily Watson, MD Obstetrician & Gynecologist
January 10, 2024 15 min read
Pregnancy Guide

Understanding Pregnancy Trimesters

Pregnancy is divided into three trimesters, each lasting approximately 13-14 weeks. Each trimester brings unique developments, symptoms, and milestones for both you and your baby.

First Trimester (Weeks 1-12)

Key Focus: Organ formation and early development

  • Major organs begin to form
  • Morning sickness may occur
  • Fatigue and breast tenderness
  • First prenatal appointments

Second Trimester (Weeks 13-27)

Key Focus: Rapid growth and movement

  • Energy levels typically improve
  • Baby's movements become noticeable
  • Anatomy scan around week 20
  • Gender may be determined

Third Trimester (Weeks 28-40)

Key Focus: Final development and preparation for birth

  • Rapid weight gain for baby
  • Increased discomfort and fatigue
  • Braxton Hicks contractions
  • Birth preparation classes

Key Developmental Milestones

Here are the major milestones throughout pregnancy:

Week 4

Implantation Complete

Baby is about the size of a poppy seed. Neural tube begins to form.

Week 8

All Major Organs Present

Baby is about the size of a raspberry. Heart is beating regularly.

Week 12

End of First Trimester

Baby is about the size of a lime. Risk of miscarriage decreases significantly.

Week 16

Gender May Be Visible

Baby is about the size of an avocado. You may feel first movements.

Week 20

Anatomy Scan

Baby is about the size of a banana. Detailed ultrasound checks development.

Week 24

Viability Milestone

Baby is about the size of an ear of corn. Survival rate increases significantly.

Week 28

Third Trimester Begins

Baby is about the size of an eggplant. Eyes can open and close.

Week 36

Considered Full-Term Soon

Baby is about the size of a cantaloupe. Lungs are nearly mature.

Week 40

Due Date

Baby is about the size of a watermelon. Ready for birth!

Common Pregnancy Symptoms by Trimester

First Trimester Symptoms

Morning sickness
Fatigue
Breast tenderness
Frequent urination

Second Trimester Symptoms

Increased energy
Baby movements
Growing belly
Better sleep

Third Trimester Symptoms

Weight gain
Shortness of breath
Sleep difficulties
Braxton Hicks contractions

Important Prenatal Care

Regular prenatal care is essential for a healthy pregnancy:

Regular Check-ups

Monthly visits in first two trimesters, then more frequent as due date approaches.

Prenatal Vitamins

Folic acid, iron, and other essential nutrients for baby's development.

Healthy Nutrition

Balanced diet with adequate calories and nutrients for two.

Safe Exercise

Regular, moderate exercise as approved by your healthcare provider.

When to Contact Your Doctor

Call Immediately:

  • Severe abdominal pain
  • Heavy bleeding
  • Severe headaches
  • Vision changes
  • Signs of preterm labor

Discuss at Next Appointment:

  • Mild cramping
  • Light spotting
  • Unusual discharge
  • Persistent nausea
  • Sleep problems

Track Your Pregnancy Journey

Use our pregnancy calculator to track your due date, current week, and baby's development milestones.

Calculate Due Date