How the Baby Grows: Week by Week

A fetus is a developing human being with its own separate, distinct set of DNA that manages its own development. Nourishment is the only thing it will need to grow – from conception until the end of its natural life.

Week 1
Last Menstrual Period
Week 2
Conception
Week 3
Baby attaches to the uterus
Week 4
Nerves, brain and spinal cord begin to develop
Week 5
Baby’s heart begins to beat
Week 6
Eyes, arms, legs, lungs, and stomach begin to form
Week 7
Hands and feet are forming
Week 8
Upper lip, teeth, fingers and ears begin to form
Week 9
Toes and genitals are forming
Week 10
Baby has permanent fingerprints
Week 11
Baby starts to produce urine
Week 12
Fingernails are forming
Week 13
Baby flexes and kicks
Week 14
Hormones gear up
Week 15
Skin begins to form
Week 16
Facial expressions are possible
Week 17
Fat accumulates
Week 18
Baby begins to hear
Week 19
  Lanugo covers baby’s skin
Week 20
The halfway point
Week 21
Nourishment evolves
Week 22
Taste buds develop
Week 23
Lungs prepare for life outside the womb
Week 24
Sense of balance develops
Week 25
Exploration continues
Week 26
Eyes remain closed
Week 27
  Second trimester ends
Week 28
Baby’s eyes open
Week 29
  Movement is more forceful
Week 30
Baby packs on pounds
Week 31
Reproductive development continues
Week 32
Downy hair falls off
Week 33
Baby detects light
Week 34
Protective coating gets thicker
Week 35
Rapid growth continues
Week 36
Baby can suck
Week 37
Baby is full-term
Week 38
Organ function continues to improve
Week 39
Placenta provides antibodies
Week 40
Your due date arrives

Videos: The Endowment for Human Development. (2011). Retrieved from https://www.ehd.org/get-free-videos.php
Facts: Mayo Clinic (2011). Fetal Development – The first trimester.  Retrieved from: https://www.mayoclinic.com/health/prenatal-care/PR00112

Medically Reviewed By:

CINDY L. PIPER, BSN, RN

STAFF NURSE, ROCHESTER