Title: Fetal development: MedlinePlus Medical Encyclopedia
Headings: Fetal development
Fetal development
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Content: Fetal development: MedlinePlus Medical Encyclopedia
Fetal development
Learn how your baby is conceived and how your baby develops inside the mother's womb. Information
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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
The first week of pregnancy starts with the first day of a woman's menstrual period. She is not yet pregnant.