Title: Fetal Period | The final stage of fetal development
Headings: Fetal Period
Fetal Period
The final stage of fetal development
Weeks 10 to 12
Weeks 13 to 16
Weeks 17 to 20
Weeks 21 to 25
Weeks 26 to 28
Weeks 29 to 36
Weeks 37 to 40

Content: Weeks 21 to 25
Between weeks 21and 25, the fetus becomes covered in lanugo. Eyelashes and fingernails begin to develop. Around this time, doctors are first able to hear the fetal heartbeat using a stethoscope. Movement continues to increase and the fetus develops a startle reflex. Weeks 26 to 28
From week 26 to 28, the lungs are rapidly developing as the fetus readies for its first breath of air. By week 28, gas exchange is possible and the fetus may survive outside of the womb. The brain is also developing at a fast pace and the fetus' nervous system begins to control some of its bodily functions. Around week 28, the eyelids open for the first time since early in the embryonic period of development. Weeks 29 to 36
Between weeks 29 and 35, the lungs continue to develop and the fetus puts on weight (much of it in the form of body fat). The fetus develops its first immunities, increasing the likelihood of survival should a premature birth take place (by week 36, an infant has a high probability of survival, provided it receives sufficient medical care).