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Fetal development

Zygote; Blastocyst; Embryo; Fetus

Learn how your baby is conceived and how your baby develops inside the mother's womb.

Images

Fetus at 3.5 weeks
Fetus at 7.5 weeks
Fetus at 8.5 weeks
Fetus at 10 weeks
Fetus at 12 weeks
Fetus at 16 weeks
Fetus at 24 weeks
Fetus at 26 to 30 weeks
Fetus at 30 to 32 weeks

Animation

Cell division

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Information

WEEK BY WEEK CHANGES

Gestation is the period of time between conception and birth when a baby grows and develops inside the mother's womb. Because it's impossible to know exactly when conception occurs, gestational age is measured from the first day of the mother's last menstrual cycle to the current date. It is measured in weeks.

This means that during weeks 1 and 2 of pregnancy, a woman is not yet pregnant. This is when her body is preparing for a baby. A normal gestation lasts anywhere from 37 to 42 weeks.

Week 1 to 2

Week 3

Week 4

Week 5

Weeks 6 to 7

Week 8

Week 9

Week 10

Weeks 11 to 14

Weeks 15 to 18

Weeks 19 to 21

Week 22

Weeks 23 to 25

Week 26

Weeks 27 to 30

Weeks 31 to 34

Weeks 35 to 37

Week 38 to 40

References

Feigelman S, Finkelstein LH.  Assessment of fetal growth and development. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 20.

Ross MG, Ervin MG. Fetal development and physiology. In: Gabbe SG, Niebyl JR, Simpson JL, et al, eds. Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 2.

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Review Date: 6/30/2019  

Reviewed By: John D. Jacobson, MD, Professor of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda Center for Fertility, Loma Linda, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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