Month 7

Cutting-edge 3D ultrasound recordings have also revealed that at 31 weeks the fetus responds with different facial expressions to painful versus startling stimuli.¹¹ Researchers examined different facial gestures before and after a fetus received an injection of anesthetic in their thigh prior to an in utero surgical procedure. The researchers compared these facial movements to those that a fetus made before and after hearing a startlingly loud noise. They found that the fetuses who received a painful injection made more horizontal and vertical mouth stretches, as a baby might make while crying, and were more likely to lower their brows and squeeze their eyes shut than the fetuses who merely got startled.¹² These facial features are also associated with a conscious pain experience in newborn babies, who also cannot communicate their pain experience with words.

Watch the movie to see the fetus’s reaction to the painful injection.

The brain creates an overabundance of neurons and an overabundance of synaptic connections in a process called blooming and pruning. Just as a tree needs trimming to clear away the excess branches, synaptic pruning removes unneeded connections in the brain. At 28 weeks, the fetus has the most neurons she will ever have. For the rest of fetal development, childhood and adulthood, neurons that do not become part of useful circuits undergo programmed cell death, called apoptosis. Neurons are energy-intensive cells, so removing unhelpful neurons makes the brain more efficient. The remaining neurons also undergo periods of explosive synaptic growth, where they make thousands of connections with other neurons. Advantageous connections get stronger and useless connections deteriorate, leaving the brain with useful and efficient circuits.¹³

At seven months, myelination also begins. Myelination is the process of wrapping neurons in a fatty sheath to speed up their signaling. While neural circuits still function before each neuron is myelinated, myelination makes each connection in a circuit more efficient. First, the sensory systems myelinate, then the motor systems, and finally the association areas start to myelinate about 9 months after birth.¹⁵ Myelination does not end until age 25!¹⁶

If a woman delivers her baby when she is 7 months pregnant, most of the time that baby will survive without any major disabilities. At 28 weeks gestation, at least 92% of all premature babies survive the first year. By 31 weeks, that number has risen to over 96%.¹⁷ Premature children born before 30 weeks still have significantly higher risks of vision and hearing problems, as well as lower IQs than their full-term counterparts.¹⁸