CLI Comment on NIH Proposal to Fund Human-Animal Chimeras

In the fourth week, the embryonic heart starts beating. The neural tube, which becomes the brain and spinal cord, forms. At this point, a woman has likely only been aware of her pregnancy for one week.

In the seventh week after conception, networks of neurons produce brain waves that have been recorded as early as 6 ½ weeks after conception. The embryo spontaneously moves his arms, hands, and legs, and may even hiccup. The embryo’s heart now has all four chambers.

By the seventeenth and eighteenth week after gestation, the fetus shows a clear response to pain in multiple studies, and at least one brain pathway is mature enough to create a perception of pain. The fetus also practices breathing, crying, and breastfeeding in the womb. The fetal heart has beat over 20 million times and circulates about 55 quarts of blood per day.

In the eighth month of pregnancy the fetal brain is ready to learn! At 32 weeks after conception, neurons are creating 40,000 new connections, called synapses, every second! With repeated exposures, the fetus can learn flavors, nursery rhymes, songs, and even words that she will recognize after birth!