A Baby's First 25 Weeks of Life Day 1 - conception takes place. 7 days - tiny human implants in mother’s uterus. 10 days - mother’s menstruation cycle stops. 18 days - heart begins to beat. 21 days - pumps own blood through separate closed circulatory system with own blood type. 28 days - eye, ear and respiratory system begin to form. 42 days - brain waves recorded, skeleton complete, reflexes present. 7 weeks – can suck his/her thumb. Two thirds of abortions happen within the 1st trimester. This means the baby feels the pain! 8 weeks - all body systems present. 9 weeks - squints, swallows, moves tongue, makes fist. 11 weeks - spontaneous breathing movements, has fingernails, all body systems working. 12 weeks - weighs one ounce. 16 weeks - genital organs clearly differentiated, grasps with hands, swims, kicks, turns, somersaults, (still not felt by the mother.) 18 weeks - vocal cords work – can cry. 20 weeks - has hair on head, weighs one pound, 12 inches long. 23 weeks - 15% chance of viability outside of womb if birth premature.* 24 weeks - 56% of babies survive premature birth.* 25 weeks - 79% of babies survive premature birth.*
(*Source: M. Allen et. al., "The Limits of Viability." New England Journal of Medicine. 11/25/93: Vol. 329, No. 22, p. 1597.)