Stem Cells - Brutes or Angels: Human Possibility in the Age of Biotechnology - page 55

Table 2.1. Continued

Development
time* Stage Remarks**

90 days End 1st

trimester

Fetus about the size of an apple; bones of the
cranial vault and face are developing.

130 days Fetus as long as a banana; nerves for sensing

pain are present.

180 days End 2nd

trimester

Fetus as large as a cauliflower head; viability
possible outside the uterus.

200 days Fetus weighs as much as four navel oranges;

first brain waves characteristic of consciousness.

270 days Neonate Birth; first breath.

2-4 years Postnatal Sense of a life narrative with past, present,

and future; “othermindedness” (empathy,
deception possible).

10 years Cerebral cortex (the “thinking brain”) fully

functional.

*Times in this chart begin with fusion of egg and sperm; physicians commonly mark devel-
opment beginning two weeks earlier, from the time of the woman's last menstruation.
**Size comparisons are taken from the Pregnancy Development Calendar at http://
www.babycenter.com/pregnancy-calendar (accessed December 14, 2011).

complete by 130 days; however, pain probably cannot be experienced until
after the second trimester at about 200 days, when brain waves character-
istic of human wakefulness first appear.
At six months, in utero connections between nerve cells and the cerebral
cortex, the part of the brain responsible for human consciousness, form at
an accelerated rate. At birth, a few seconds after the umbilical cord is tied
off, the infant takes its first breath. Awareness of a past, present, and fu-
ture (a life narrative) emerges at about two years after birth, ability to em-
pathize and deceive (“other mindedness”) at about four years, and a fully