Month 6

Boys and girls move differently in the womb. For example, girls tend to develop the startle response before boys.⁵ Furthermore, if researchers use an electric toothbrush to stimulate a mother’s abdomen between 22 and 24 weeks, the unborn baby will start moving. Interestingly, girls seem to respond to this vibration-based stimuli about 2 weeks earlier than boys.⁶ At 21 weeks, boys spend more time making general movements than girls.⁷ The fetal movements recorded at these ages had little predictive value for a baby’s motor development and behavior for the first two years of life. However, when boys moved more in the womb at 36 weeks, they also moved more as one-year-olds. Interestingly, the opposite effect was observed for girls.⁸

At 25 weeks, the unborn baby may grasp objects that come near his hands, such as the umbilical cord.⁹ Furthermore, as early as 27 weeks, a premature infant can hold his own body weight momentarily.¹⁰ At six months, doctors have also studied premature infants to learn more about the capabilities of their counterparts in the womb. At 24 weeks, a premature infant sneezes when a doctor tickles his nostrils.¹¹

Newborns prefer looking at upright faces over upside-down faces or other images. But where does this preference come from? In a remarkable experiment, researchers used lasers to project three dots of light arranged like eyes and a mouth relative to the baby’s position in the womb. Fetuses as young as 26 weeks turn their eyes more often towards face-like patterns.¹⁷ At 34 weeks, unborn babies turned their whole heads toward the face-like pattern and away from the inverted one.¹⁸ This shows that by 6 months the fetus can see and respond to visual information from outside the womb and even prefers looking at face-like stimuli!

The human brain is wired early to recognize faces. In children and adults, faces are processed in a specialized brain region called the fusiform face area. While this region is difficult to directly study in the womb, scientists have observed strong face-selective brain responses there as early as two months after birth.¹⁹ Thus the foundations for recognizing faces are laid well before a baby ever opens his eyes to the outside world.

Around 22 to 24 weeks the lungs start creating surfactant, which is pivotal for survival.³⁰ Surfactant prevents the fragile air sacs from collapsing when the baby exhales. By 32 weeks, most babies produce enough surfactant to survive on their own outside the womb.³¹ However, for premature infants, breathing outside the womb can be difficult because the lungs are not yet fully developed. Fortunately, modern medicine offers remarkable support. Doctors can provide life-saving surfactant therapy or give mothers steroids before birth to accelerate lung maturation, helping fragile lungs function sooner and giving these tiny patients a far stronger chance to survive and thrive.^{32 33}

Early in pregnancy, the baby’s developing brain is mostly smooth. But by about 20 weeks, the major grooves that separate the brain’s lobes begin to appear. ⁴⁰ As the baby enters month 6 of pregnancy, the brain starts forming the ridges and valleys—called gyri and sulci—that give the human brain its familiar wrinkled appearance. ⁴¹ These folds form as billions of neurons grow, connect, and organize into an astonishing communication network. The outer layer of the brain grows faster than the layers beneath it, causing the surface to buckle into folds. ^{42 43} By birth, this beautifully folded brain contains about 100 billion neurons, including roughly 20 billion in the cerebral cortex alone. ⁴⁴ Those folds make it possible to fit an enormous amount of processing power inside a newborn’s tiny skull.

In the sixth month of pregnancy, the baby can now spontaneously smile⁵⁴ and many of those tiny smiles last over 3 seconds.⁵⁵ Smiling peaks between 24 and 32 weeks gestation.⁵⁶

At 25 weeks, the fetal heart pumps as much blood each day as three full bathtubs—about 375 quarts of blood!⁵⁷

The baby’s fingerprint patterns at 26 weeks are now set for life.⁵⁸