Month 7 to 8

Sleep patterns and learning

Human Prenatal Age
  • PCW 26-29
    i
  • 7 Months Pregnant
  • Gestational Weeks 28-31
Highlights
  • Doctors observed varied sleep patterns in the unborn baby including rapid-eye movement (REM) and non-REM sleep.1

  • At 26 weeks after conception, the fetus has more neurons than she will ever have again.2

  • At 26 weeks after conception, the fetus starts smelling different odors within the amniotic fluid.3

  • By 29 weeks after conception, the fetal heart has beat more than 40 million times.4 At this point, the fetal heart pumps 750 quarts of blood each day!5

When a woman is 7 months pregnant, scientists have a variety of tools to study the growing child while still inside the womb. The fetus’s brain activity is now strong enough to detect outside the abdomen using neuroimaging techniques like functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG).6 These techniques use blood flow or electrical signals from neurons to measure brain activity.

Researchers have used these techniques to determine that at 26 weeks after conception, the fetal brain responds to different pitches and flashes of light much the way that the adult brain responds.7 Researchers who observed premature infants at these ages also could measure brain responses to touch and pain.8

Doctors can clearly distinguish the two major kinds of sleep: REM sleep and non-REM sleep, in fetuses starting 26 weeks after conception using ultrasound technology.9 During REM sleep, a person’s eyes move rapidly under their closed lids. This sleep is important for memory formation. Non-REM sleep is often considered deeper sleep. The older the fetus, the more time he spends in REM sleep.10

Modern ultrasounds allow parents to see their unborn child in marvelous detail. (Image Credit: Science Source)
Impressive brain growth

The brain creates an overabundance of neurons and an overabundance of synaptic connections in a process called blooming and pruning.

100
Billion Neurons
At 26 weeks after conception, the fetus has more neurons than he will ever have again. Some estimate that at this age, the fetus has over 100 billion neurons. Neurons that fail to integrate into meaningful brain circuits start to die off, leaving adults with 60-85 billion neurons.11

During the seventh month, 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 myelinate about 9 months after birth.12 Myelination does not end until age 25!13

Dive Deeper
Newborns remember sounds and tastes that they experienced in the womb...