Pregnancy Timeline: Week-by-Week Guide to Baby Development

Pregnancy is an exciting journey, full of changes for both you and your baby. Understanding the typical pregnancy timeline can help you track your baby's development and prepare for each stage. Pregnancy is divided into three trimesters, each bringing new milestones for your growing baby.

Although pregnancy is often thought of as lasting nine months, a full-term pregnancy is actually 40 weeks (280 days) from the first day of your last period. Depending on when you deliver, you may be pregnant for nine or ten months, and both are completely normal!

Let’s explore what happens during each trimester and month of pregnancy, from conception to birth.

First Trimester (Weeks 1-12)

The first trimester marks the earliest stages of fetal development, starting from conception. While you may not show any physical signs of pregnancy yet, your body is already going through major changes.

Month 1 (Weeks 1-4)

• Fertilization occurs, and the fertilized egg implants in the uterus.
• The amniotic sac begins forming around the embryo for protection.
• The placenta starts developing, supplying oxygen and nutrients.
• Early pregnancy symptoms like nausea and fatigue may appear.

Month 2 (Weeks 5-8)

• The baby’s facial features begin forming, and tiny buds grow into arms and legs.
• The brain, spinal cord, and nervous system are developing rapidly.
• The heart starts beating and can be detected on an ultrasound.
• You may experience morning sickness, food cravings, and mood swings.

Month 3 (Weeks 9-12)

• The baby starts moving, though it may be too early for you to feel it.
• Fingernails, toenails, and external ears begin forming.
• Reproductive organs start developing, but the gender is still difficult to determine.
• The risk of miscarriage drops significantly after this month.

Second Trimester (Weeks 13-26)

The second trimester is often the most comfortable period of pregnancy. Many early symptoms like nausea start to fade, and you may begin to feel the baby move.

Month 4 (Weeks 13-16)

• The baby’s heartbeat can be heard using a Doppler.
• Eyebrows, eyelashes, and hair start growing.
• The baby can yawn, stretch, and make facial expressions.
• You may begin to show a small baby bump.

Month 5 (Weeks 17-20)

• The baby becomes more active, and you may feel the first kicks (quickening).
• A fine layer of hair (lanugo) covers the baby’s skin for protection.
• The baby develops a sleep cycle and starts responding to sounds.
• Your doctor may schedule an anatomy scan to check for development.

Month 6 (Weeks 21-24)

• The baby’s skin appears red and wrinkled but will smooth out later.
• Fingerprints and footprints form.
• The baby’s eyes start opening, and they begin to practice breathing.
• You may experience Braxton Hicks contractions (practice contractions).

Third Trimester (Weeks 27-40)

You are now in the final stretch of pregnancy! Your baby is growing quickly, preparing for birth.

Month 7 (Weeks 25-28)

• The baby recognizes voices and reacts to sounds, light, and touch.
• Fat storage increases, making the baby plumper.
• The baby moves frequently, but space is getting tighter.

Month 8 (Weeks 29-32)

• The baby’s brain is rapidly developing, and they can see and hear.
• Movements become more pronounced and stronger.
• You may experience shortness of breath and trouble sleeping.

Month 9 (Weeks 33-36)

• The baby’s lungs are almost fully developed.
• The baby is practicing blinking, grasping, and turning their head.
• Your body prepares for labor, and the baby drops lower into the pelvis.

Month 10 (Weeks 37-40)

• The baby is full-term and ready for delivery.
• You may experience less movement due to limited space.
• Labor can begin at any time! Look out for contractions, water breaking, and other signs.

What to Expect at BASS Medical Group

Whether you’re planning for pregnancy, currently expecting, or approaching labor, BASS Medical Group provides expert prenatal care. Our OB-GYNs and pregnancy specialists offer:

• Routine prenatal checkups
• Ultrasounds and diagnostic screenings
• High-risk pregnancy care
• Labor and delivery guidance

Schedule an appointment today with one of our trusted OB-GYNs to ensure a healthy pregnancy.