25th week:169-175 days
The fetus can now inhale, exhale and even cry. Eyes have completely formed, and the tongue has developed taste buds. Under intensive medical care the fetus has over a 50% chance of surviving outside the womb. In the last trimester: the baby’s skin thickens as it prepares for its life outside the womb. The baby also forms a layer of fat for both insulation as well as food. Antibodies that give immunity from diseases are being built up. The baby absorbs a gallon of amniotic fluid each day and the fluid is being replaced every three hours. The heart pumps three hundred gallons of blood per day and the placenta begins to age.
26th week:176-182 days
The baby now weighs between 1.5 and 2 pounds/ 680 and 900 grams and is approximately 9 inches/ 23 centimeters long from crown to rump. He makes breathing movements but has no air in his lungs yet. At 26 weeks, fetal brain scans show response to touch. If you shine a light on the mother’s abdomen, the baby may turn his head, which according to researchers, means his optic nerve is working. At 26 to 28 weeks a fetus: is rapidly developing its brain, controls some body functions, has eyelids which open and close, has a rapidly developing respiratory system
27th week:183-189 days
The baby may now Measure 15 inches/ 38 centimeters from top to toe with his legs extended; from crown to rump he is about 10 inches/25.5 centimeters. He weighs a little more than 2 pounds/ 900 grams. The baby's eyes begin opening about this time. Response to sound grows more consistent toward the end of the seventh month, when the network of nerves to the ear is complete. He also continues to take small breaths and although he's only breathing in water and not air, it's still good practice for when he's born. From 27 weeks on the fetus finishes development and prepares for delivery
28th week:190-196 days
The baby now weighs about 2.5 to 3 pounds/ 1.1 to 1.3 kilograms and measures 10.5 inches/ 26 centimeters from crown to rump (15.5 inches/ 39 centimeters from top to toe). Her eyes open and close, she sleeps and wakes at regular intervals and she may suck a finger or thumb. By 28 weeks the eye is so sensitive to light that if a physician peers into the uterus with a telescope, the fetus will try to shield its eyes with its hands.
The baby weighs nearly 3 pounds/ 1.3 kilograms and may measure 16.5 inches/ 42 centimeters from top to toe. At about this time, the baby can open his eyes and turn his head in utero if he notices a continuous, bright light shining from the outside. His fat layers are forming and his fingernails appear.
30th week:204-210 days
For several months, the umbilical cord has been the baby's lifeline to the mother. Nourishment is transferred from the mother's blood, through the placenta, and into the umbilical cord to the fetus. If the mother ingests any toxic substances, such as drugs or alcohol, the baby receives these as well. This is generally the time the baby stops growing and drops. Usually head down, into the pelvic cavity awaiting its birth. The fetus is usually capable of living outside the womb and would be considered premature at birth
31st week:211-217 days
The baby’s lungs and digestive tract are almost fully developed. The baby may soon slow up growing in length, (he measures about 17.25 inches/ 45 centimeters from crown to toe by now), he will continue to gain weight until he's born. The baby continues to open and shut his eyes. He can probably see what's going on in utero, distinguish light from dark and even track a light source. If the mother shines a light on her stomach, the baby may move his head to follow the light or even reach out to touch the moving glow. Some researchers think baring the mother’s stomach to light stimulates visual development. A pint and a half/around a liter of amniotic fluid now surrounds the baby but that volume decreases as he gets bigger and has less room in the uterus.
32nd week:218-224 days
The baby's arms, legs and body continue to fill out — and they are finally proportional in size to her head. She weighs about 4 pounds/1.8 kilograms and looks more like a newborn. She measures about 18 inches/ 45 centimeters from crown to toe. This is the most rapid period of body growth. Hair follicles develop. If born, baby has excellent chance of survival. He/She begins to move down into the pelvis in preparation for birth. The fetus sleeps 90-95% of the day, and sometimes experiences REM sleep, an indication of dreaming.
33rd week:225-231 days
The baby now weighs approximately 4.5 pounds/ 2 kilograms and is about 18.5 inches / 46 centimeters long from head to toe. Although his lungs won't be fully developed until just before birth, the baby is inhaling amniotic fluid to exercise his lungs and practice breathing. Also by week 33, the pupils of the eye can now detect light and constrict and dilate, allowing your baby to see dim shapes. Studies shining a bright light on the belly of a woman at 37 weeks have shown a baby's heart rate speeding up in response, or the baby turning toward the light. (Note: Exposing a fetus or premature infant to bright light before it's ready can damage its eyes.)
34th week:232-238 days
At about 34 weeks the baby's head will move down into the mother’s pelvis as the baby gets into the right position for birth. The baby now weighs about 5 pounds / 2.2 kilograms and measures approximately 19 inches/ 48 centimeters from head to toe. The baby's skull is still quite pliable and not completely joined, in part so he can ease out of the relatively narrow birth canal. But the bones in the rest of his body are hardening. The baby's skin is also gradually becoming less red and wrinkled.
35th week:239-245 days
36th week:246-252 days
By week 37, the baby has developed enough coordination so that he or she can grasp with the fingers. Along with these common movements, babies perform some odder activities, including licking the uterine wall and "walking" around the womb by pushing off with its feet. The baby is still gaining weight — about an ounce/ 28 grams a day. She weighs about 6.5 pounds/ 2.9 kilograms and is 20.5 inches/ 51 centimeters long from head to toe.
This marks the end of the normal gestational period. The baby, now approximately seven and a half pounds, is ready for life outside its mother's womb. At birth the placenta will detach from the side of the uterus and the umbilical cord will cease working as the child takes his first breaths of air. The child's breathing will trigger changes in the structure of the heart and bypass arteries, which will force all blood to now travel through the lungs. Many babies now have a full head of hair, with locks maybe around one inch / 2.5 centimeters long
Sources: When you were formed in Secret, By Gary Bergel , The First days of human life , CCC Publications Service, Conclusions determined from the testimony of Dr. Bruce Carlson, a leader in human embryology, Report of South Dakota Task Force to study abortion: December 2005/ The New England Journal of Medicine, Volume 317, Number 21: Pages 1321-1329,19 November 1987. Pain and its effects in the human neonate and fetus, By: K.J.S. Anand , M.B.B.S., D. PhilL., and P.R. Hickey , M.D / Conclusions determined from the testimony of Dr. Bruce Carlson, a leader in human embryology, Report of South Dakota Task Force to study abortion: December 2005/ South Dakota Task Force to study abortion: December 2005/ South Dakota Task Force to study abortion: December 2005/ Life Magazine August 1990: The first pictures: How life begins/ Westside Pregnancy Resource Center Website/ Expectant Mother’s Guid: Fetal Growth & Development How Your Baby Grows, Editorial provided by Dr. Charles Ingardia, Director, Fetal-Maternal Medicine Obstetrics and Gynecology at Hartford Hospital./Baby Centre: Fetal development/ Sources: The Nemours Foundation; Association for Pre- & Perinatal Psychology and Health; Janet L. Hopson, "Fetal Psychology," Psychology Today, September-October 1998-Discovery Health: Alertness in the womb