Month 8

In month 8, the unborn baby responds differently to pleasant and unpleasant flavors. Flavors from the mother’s diet peak in the amniotic fluid about 45 minutes after she eats.⁸ When researchers asked mothers to swallow a capsule with sweet carrot flavor, their unborn babies at 34 weeks gestation made more “laughter-faces.” In contrast, when mothers swallowed a capsule with bitter kale flavor, their unborn babies made more “cry-faces.”⁹ Similarly, after 34 weeks gestation the fetus will swallow less amniotic fluid if it contains a bitter dye,¹⁰ and swallow more if it is sweet.¹¹ By 8 months, babies don’t merely detect flavors—they show clear preferences.

Premature infants show different brain responses to pleasant versus unpleasant smells. Researchers studied the relationship between sensory stimulation and blood flow in the brains of premature infants from 30 to 37 weeks gestation in response to different odors.  They found that pleasant smells like vanilla or breastmilk increased blood flow in the parts of the baby’s brain that process smell¹² while disinfectant or detergent decreased blood flow in the same locations.¹³

Newborn babies prefer the same flavors tasted and sounds heard inside their mother’s womb. For example:

• Five and six-month old infants made fewer negative faces for carrot flavored cereal if their mothers drank carrot juice four times a week for 3 weeks when she was 8 months pregnant.²³
• One-month-old infants had a stronger calming response to a simple melody they had heard their mother play twice a day from 35 to 37 weeks gestation even though they had not heard the melody again for many weeks.²⁴
• Newborns less than 3 days old preferred a story that their mother had read aloud in the last 6 weeks of pregnancy.²⁵
• Newborns less than a week old preferred a lullaby that their mothers sang for 2 months while they were pregnant, compared to an unfamiliar lullaby.²⁶
• Newborns less than 5 days old preferred classical music that they heard in the last 6 weeks before birth.²⁷

Skin pigmentation begins early but matures gradually over time. By about 9 weeks of pregnancy, melanocytes—the cells that produce pigment—can be found in the developing skin.³⁵ Strikingly, individuals of different skin tones have roughly the same number of these cells;³⁶ what differs is how much melanin they produce and how it is distributed within the epidermis.³⁷ Melanin production starts during the second trimester, with darker-skinned babies showing visible pigment before birth, while lighter-skinned infants produce less melanin prenatally.³⁸ Even so, skin color differences are subtle until around 32 weeks,³⁹ and pigmentation continues to deepen after birth as melanocytes become more active after light exposure.⁴⁰

About 8 in 100 babies are born at 8 months gestation.⁴² Thanks to advances in neonatal care, more than 98% of these babies survive in high-income countries. ^{43 44 45 46} Most also go on to develop normally, with fewer than 1 in 20 experiencing any long-term disabilities.⁴⁷

At 34 weeks, the fetal heart pumps about 247 gallons of blood each day. For comparison, an adult heart pumps about six times more, or 1,500 gallons of blood each day.⁴⁸

At 32 weeks, the unborn baby practices breathing almost 40% of the time.⁴⁹

The baby gains a little less than half a pound per week on average this month.⁵⁰ By about 19 weeks, the fetus begins making brown fat, which helps produce heat. White fat, which stores energy, develops later. By 28 weeks, white fat makes up about 3.5% of body weight. By month 8, it rises to 8%. At full term, it reaches nearly 16% of the baby’s weight, and starts making the baby’s cheeks chubby.^{51 52}