Although the fetus used to move away when something touched his face, the fetus now rotates his head towards things that touch his face while simultaneously closing his mouth.7 These movements mark the start of the rooting reflex, which helps a newborn find his mother’s nipple during breastfeeding.
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Weeks 17 & 18
Breathing, crying, and the rooting reflex
- PCW 17&18iPost-Conception Weeks
- 5 Months Pregnant
- Gestational Weeks 19&20
Multiple research studies have shown that the fetus responds to painful stimuli with a stress response that includes recoiling and increased circulating stress hormones separate from stress hormones in the mother’s bloodstream.1
The skin has developed sweat glands.2
By 17 weeks after conception, the fetal heart has beat over 20 million times.3
The fetal heart pumps about 55 quarts of blood each day.4
Although the eyelids are fused shut between 7 and 24 weeks gestation, the eyes keep developing. The back of the eye, called the retina, which converts light into neural signals, now has discrete layers, each with a different main type of cell.11
In animals, waves of spontaneous electrical activity cross the retinas. This allows the retinal cells to properly connect to the visual cortex in the brain, and to organize inputs from the right and left eyes.12 Although these spontaneous retinal waves have never been directly measured from the human fetus, they likely begin around this age.