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  The phase when a mother releases an ovum.
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  The process of the sperm fertilizing the ovum
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  Size: The size of a pin head
 Weight: Not determined
 Development: Egg attaches lining of uterus. Internal organs and circulatory system begin to form. The heart begins to beat.
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  Size: About 1/4 inch (6 mm)
 Weight: Not determined
 Development: Face, eyes, ears, and limbs take shape. Bones begin to form
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  Size: About 1 inch (25 mm)
 Weight: Not determined
 Development: Nostrils, mouth, lips, and eyelids form. Buds for all 20 baby teeth appear. Fingers and toes almost complete. All organs present but still immature.
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  Size: 3 inches (7.6 cm) long
 Weighs: 1 ounce (28 g)
 Development: can suck thumb, swallow, hiccup, and move around. Facial features become clearer.
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  Size: 6 1/2 - 7 inches (7.6 cm) long
 Weight: about 4-5 ounces (113-142 g)
 Development: Hair, eyelashes, and eyebrows appear. Teeth continue to develop. Organs are maturing. Becomes more active.
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  Size: About 8-10 inches (21-25 cm) long
 Weight: About 8-12 ounces (227-340 g)
 Development: Fat deposits under skin, but fetus appears wrinkled. Breathing movements begin.
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  Size: About 10-12 inches (25-31 cm) long
 Weight: about 1 1/2 - 2 pounds (680-907 g)
 Development: Has periods of activity followed by periods of rest and quiet
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  Size: about 14-16 inches (36-41 cm) long
 Weight: About 2 1/2 - 3 pounds (1.0-1.4 kg)
 Development: Rapid weight gain continues. May react to loud noises with a reflex jerking action. Moves into a head-down position.
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  Size: About 17-18 inches (43-46 cm) long
 Weight: About 5-6 pounds (2.3- 2.7 kg)
 Development: Weight gain continues. Skin becomes smooth as fat deposits continue. Movements decrease as the fetus has less room to move around. Acquires disease-fighting antibodies from the mother's blood. Descends into pelvis, ready for birth