The Endowment for Human Development has produced a DVD showing prenatal development, with short clips showing relative size of the growing baby, using CGI, ultrasound, and endoscopic cameras. I can't embed the videos, but I'll provide the brief snippets of description with links to allow you to go and see for yourself. I'll add emphasis to make major milestones easier to find. I also recommend checking out the interactive timeline with quizzes.
The third trimester involves rapid brain growth and refinement. The combined Roe vs. Wade and Doe vs. Bolton decisions forbade states to entirely ban third trimester abortions. There must be some sort of "health" exception. The original Doe vs. Bolton decision (companion to Roe) defined "health" so broadly that the need for an expensive car repair would suffice. (This is not an exaggeration; Doe specifically said that financial matters were related to "health" and therefore must be taken into consideration.) The idea of aborting a third-trimester baby for the mother's real, actual health is nonsensical on its face. Induced labor or an emergency c-section can quickly end any pregnancy that threatens the mother's well-being. An abortion merely adds a step prior to induction or surgery in order to make sure that the fetus emerges dead.
So let's look at some neurological development in the third trimester:
"Fetal exposure to various substances appears to affect flavor preferences after birth. For instance, fetuses whose mothers consumed anise, a substance which gives licorice its taste, showed a preference for anise after birth. Newborns without fetal exposure disliked anise."The period of 22 - 26 weeks, as the second trimester ends and the third trimester begins, shows a range of state abortion laws. Some place limits on elective abortions after 22 weeks, others at 26 weeks, and others at some point in between. A total of ten states place no limits whatsoever on how late an abortion may be done; it's entirely up to abortion doctors to decide how large and developed a baby they're willing to kill, and for what reason.
"During the last 4 months of pregnancy, the fetus displays periods of coordinated activity punctuated by periods of rest. These behavioral states reflect the ever-increasing complexity of the central nervous system."
"By 28 weeks the fetus can distinguish between high- and low-pitched sounds."
"The pupils respond to light as early as 27 weeks. This response regulates the amount of light reaching the retina throughout life.""All components required for a functioning sense of smell are operational. Studies of premature babies reveal the ability to detect odors as early as 26 weeks after fertilization.Placing a sweet substance in the amniotic fluid increases the rate of fetal swallowing. In contrast, decreased fetal swallowing follows the introduction of a bitter substance. Altered facial expressions often follow.""During the third trimester of pregnancy, rapid brain growth consumes more than 50% of the energy used by the fetus. Brain weight increases between 400 and 500%.""Several investigators report exposure to loud noise may adversely affect fetal health. Immediate consequences include prolonged increased heart rate, excessive fetal swallowing, and abrupt behavioral changes."
Now let's look at second trimester neurological milestones:
"By 24 weeks the eyelids reopen and the fetus exhibits a blink-startle response. This reaction to sudden, loud noises typically develops earlier in the female fetus"Let that one sink in a bit. Between 16 and 20 weeks, abortions are typically performed by dismembering the live baby, a baby that exhibits a stress response if jabbed with a needle. Abortions past 20 weeks or so often involve injecting poison into the baby's heart, abdomen, or brain to cause fetal death, either to make later dismemberment easier or to prevent the dreaded live birth.
"By 16 weeks, procedures involving the insertion of a needle into the abdomen of the fetus trigger a hormonal stress response releasing noradrenaline, or norepinephrine, into the bloodstream."
The paucity of neurological milestones in the second trimester might seem to indicate that very little happens neurologically before the third trimester, but that's not actually the case. The bulk of neurological milestones take place during the first trimester.
Now let's look at the end of the first trimester: 10 to 12 weeks.
"With the exception of the back and the top of the head, the body of the entire fetus now responds to light touch."These are babies that respond to touch, and they're aborted by reaching in with forceps and dismembering them alive.
"In contrast to the withdrawal response seen earlier, stimulation near the mouth now evokes a turning toward the stimulus and an opening of the mouth. This response is called the 'rooting reflex' and it persists after birth, helping the newborn find his or her mother's nipple during breastfeeding."
8 - 10 weeks:
"By 10 weeks, stimulation of the upper eyelid causes a downward rolling of the eye. The fetus yawns and often opens and closes the mouth."
"By 9 weeks, thumb sucking begins and the fetus can swallow amniotic fluid."
"The fetus can also grasp an object, move the head forward and back, open and close the jaw, move the tongue, sigh, and stretch. Nerve receptors in the face, the palms of the hands, and the soles of the feet can sense light touch. In response to a light touch on the sole of the foot, the fetus will bend the hip and knee and may curl the toes."
Their tiny bodies are fragile enough to be torn apart by the suction machine alone.
From 6 - 8 weeks we see a lot of neurological progress as the embryo begins to move and respond to touch:
"The embryo is becoming more physically active during this time.Motions may be slow or rapid, single or repetitive, spontaneous or reflexive.Head rotation, neck extension, and hand-to-face contact occur more often.""By 8 weeks, 75% of embryos exhibit right-hand dominance. The remainder is equally divided between left-handed dominance and no preference. This is the earliest evidence of right- or left-handed behavior. ""At 8 weeks the brain is highly complex and constitutes almost half of the embryo's total body weight.""Hiccups have been observed by 7 weeks. Leg movements can now be seen, along with a startle response.""By 6 1/2 weeks, the elbows are distinct, the fingers are beginning to separate, and hand movement can be seen.""By 6 weeks the cerebral hemispheres are growing disproportionately faster than other sections of the brain.The embryo begins to make spontaneous and reflexive movements. Such movement is necessary to promote normal neuromuscular development."
During this period, there's a split between the suction method -- which pulls the embryo apart -- and a chemical abortion that kills it by cutting off its supply of oxygen and nutrition.
4 - 6 weeks, or between 28 and 42 days after conception:
"Between 4 and 5 weeks, the brain continues its rapid growth and divides into 5 distinct sections. The head comprises about 1/3 of the embryo's total size. The cerebral hemispheres appear, gradually becoming the largest parts of the brain.Functions eventually controlled by the cerebral hemispheres include thought, learning, memory, speech, vision, hearing, voluntary movement, and problem-solving."
Abortions at this stage or earlier, if the pregnancy is even detected that early, are usually done with chemicals.
3 - 4 weeks, or between 21 and 28 days after conception:
The first 2 1/2 weeks, or 18 days:
"By 1 week, cells of the inner cell mass form two layers called the hypoblast and epiblast. .... By approximately 2 1/2 weeks, the epiblast has formed 3 specialized tissues, or germ layers, called ectoderm, endoderm, and mesoderm. Ectoderm gives rise to numerous structures including the brain, spinal cord, nerves, skin, nails, and hair."
Clearly the unborn human becomes fairly sophisticated very quickly. Contrary to the way abortion-rights activists like to imagine neurological development, the unborn baby is not like a computer system, with components being manufactured then set aside to be "connected" just before delivery. The various bodily systems could not develop at all if they were not in use. This includes the nervous system, which is complex and needs a lot of practice to prepare the baby for life outside the womb.
The idea that the unborn are non-responsive and unsophisticated globs of protoplasm is wishful thinking on the part of those who wish to protect abortion as a right but don't wish to see themselves as condoning cruelty to tiny, helpless creatures.
Wish it or not, however, reality is what it is. What abortion-rights activists condone is cruelty to tiny, helpless creatures, human beings.