The early weeks of pregnancy are fragile—and confusing. Here, the answers to your questions.
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Size>>About 1 millimeter long (slightly larger than a pinhead)
Looks like>>A cluster of cells
What’s going on>>The blastocyst is attached to uterine lining and starting to sort itself out into different layers.
Size>>Approximately 1.25 millimeters long (about the size of a small sesame seed) Looks like>>An even larger cluster of cells What’s going on>>Embryo’s heart, brain, spinal cord, muscles and skeleton are beginning to form.
Size>>2–4 millimeters long (about the size of a large sesame seed) Looks like>>A tadpole, complete with a head and tail What’s going on>>Brain and spinal cord develop; eyes and limbs begin to form; heart begins beating.
Size>>1/2 inch long (crown to rump; about the size of a raisin) Looks like>>A tadpole with thick arm and leg buds What’s going on>>Arms, legs, hands and feet continue to develop; heart divides into two chambers; air passages form in lungs; eyes are forming.
Size>>1/2–3/4 inch long (approximately the size of a pinto bean) Looks like>>a tadpole with longer arms and legs; eyes, nose and ears begin to show What’s going on>>Fingers and toes develop; embryo starts to move.
Size>>1–11/2 inches long (about the size of an olive) Looks like>>Eyes, nose, mouth, fingers, toes and ears are clearly visible. What’s going on>>Head, neck, fingers, toes and outer ears developing; movement can be seen on ultrasound.
Size>>11/4–13/4 inches long; weighs about 5 grams (about 1/5 oz.); about the size of a walnut Looks like>>Resembles a baby more, with a large head and recognizable features. What’s going on>>Most organ systems growing quickly; reproductive tract yet to form.
Size>>1 1/2–2 1/2 inches long; about 8 grams (roughly the size of a large lime)
Looks like>>Head still
disproportionately large, but limbs are catching up.
What’s going on>>Head stretches upward from chest; neck lengthens; fingernails
and external genitals begin
Size>>2 1/2 inches long;
about 8–14 grams (about the size of a small lemon)
Looks like>>Body size begins to catch up with head.
What’s going on>>Most
of the body is formed; hair starts to grow; genitals begin to look male or female; fetus can squint, open mouth, move fingers and toes.
Size>>2 1/2–3 inches long; weighs 13–20 grams (under 1 oz.; about the size of a tennis ball)
Looks like>>Face continues to look more humanlike; external genitals have distinct male or female form.