2. 8-12 WEEK FETUS

Between 8 and 12 weeks, the embryo becomes a fetus, growing from the size of a raspberry to a lime (approx. 2.5 inches and 0.5 oz). All major organs and body systems form, webbed fingers/toes separate, and nails begin to develop. By week 12, the fetus has a distinct human profile and active movement. 

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Key Developmental Milestones (Weeks 8–12):

• Transition: The embryo officially becomes a fetus at the end of the 8th week.
• Physical Growth: The head makes up roughly 50% of the total length. By week 12, the fetus is about 2.5 inches (61 mm) long and weighs about 1/2 ounce (14 grams).
• Physical Features: Facial features become more distinct, including eyelids, ears, and a nose. Webbed hands and feet become distinct fingers and toes, and nails begin to develop.
• Movement & Senses: Muscles develop, allowing for movement, although the mother cannot feel it yet.
• Organ Development: The heart is fully developed, and its heartbeat can often be heard via Doppler by week 10. The liver begins producing blood cells.

• Vital Systems: The intestines, which previously grew in the umbilical cord, move into the abdomen. The sex is determined, though it may not be visible on ultrasound until later. 

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Key Health & Screening Information:

• First Trimester Screening: Combined screening tests (ultrasound and blood work) are often performed around week 12 to check for chromosomal conditions like Down syndrome.
• Vulnerability: The fetus is particularly vulnerable to external factors (substances, toxins) during this period of rapid organ development.
• Prenatal Care: It is recommended to continue taking folic acid and prenatal vitamins