Fetal Development

Diagram  represents a pregnancy timeline, detailing the stages of gestation in terms of weeks, months, and key developmental milestones. 

Sections Explained:

1. Weeks and Months of Gestation:

The timeline is divided into weeks (0–46) and corresponding months (0–10) of gestational age, starting from the last menstrual period (LMP).

2. Key Milestones:

Last Menstrual Period (LMP): Marks the beginning of the pregnancy timeline.

Fertilization: Occurs around week 2.

Embryogenesis (Weeks 3–8): The formation of the embryo, including organ development.

Fetal Development (Weeks 9–40): Growth and development of the fetus.

3. Trimesters:

First Trimester (Weeks 1–12): Early development and organ formation.

Second Trimester (Weeks 13–26): Growth and detailed development.

Third Trimester (Weeks 27–40): Final maturation and preparation for birth.

4. Viability and Survival:

A 50% survival chance on birth appears around week 24, marking the lower limit of viability outside the womb.

5. Maturity and Term:

Preterm: Babies born before week 37.

Early Term: Week 37 to 38.

Full Term: Week 39 to 40.

Late Term: Week 41.

Postmature: Beyond week 42.

6. Perinatal and Neonatal Period:

The perinatal period overlaps with late pregnancy and early neonatal life.

Key Insights:The diagram is a visual guide for understanding the timeline of pregnancy, developmental milestones, and the classification of gestational periods.

Important medical insights, such as survival chances and maturity stages, are highlighted to assess fetal viability and outcomes.


Breakdown of Each Trimester: Click to expand 


1.First Trimester (Weeks 1–12)

     - Weeks 1–4 : Conception occurs, and the fertilized egg implants in the uterus. Early cell division happens, forming the blastocyst.

     - Weeks 5–6: The embryo’s heart starts beating, and the beginnings of the brain, spinal cord, and other organs start to form.

     - Weeks 7–8 : Limb buds (arms and legs) appear, and facial features begin to take shape.

     - Weeks 9–12: The fetus looks human-like. Major organs are formed, and fingers and toes are distinct.  

        The fetus begins to move, although it's too small to feel.


2. Second Trimester (Weeks 13–26)

     - Weeks 13–16: The fetus develops more distinct features, and bones begin to harden. The sex of the    

        baby can often be determined through ultrasound.

     - Weeks 17–20: By now, the mother can feel fetal movement. Hair (lanugo) starts to grow on the baby’s  

        head and body.

     - Weeks 21–24 : The baby’s lungs develop and become more functional. The baby can hear sounds from 

         the outside world and might respond to music or voices.

     - Weeks 25–26 : The baby’s skin becomes less translucent, and the baby begins to practice breathing 

       movements in the womb, although the lungs are not fully mature yet.


3. Third Trimester (Weeks 27–40)

     - Weeks 27–30: The baby’s brain and lungs continue developing, and bones are fully formed, though still 

        soft. The baby is gaining fat to regulate body temperature.

     - Weeks 31–34: The baby’s brain continues maturing, and the baby’s eyes can open and close. The baby is 

        gaining weight quickly during this time.

     - Weeks 35–37: The baby’s organs are almost fully developed, and the body is preparing for birth. The 

        baby is in a head-down position for most births.

     - Weeks 38–40: The baby is considered full-term. The lungs are fully developed, and the baby is ready to 

           be born.


Important Milestones:

- First Trimester: Major organ formation, and the fetus begins to take on a more recognizable human form.

- Second Trimester: Growth and development of external features and organs, baby’s movements become more noticeable.

- Third Trimester: Final maturation and preparation for birth, with the baby gaining weight and developing skills for life outside the womb.

This breakdown helps to highlight how the baby’s development accelerates in the second and third trimesters, with significant growth and preparation for birth in the final stages.