Month 9

Babies are surprisingly tuned into the world of smell and taste before and after they are born. Newborns can detect and respond to scents more acutely than adults, including recognizing their own amniotic fluid and their mother’s breastmilk within hours of birth.^{9 10} These smells don’t just guide babies toward food — they also bring comfort and even reduce pain. A familiar scent like vanilla or mom’s milk can soothe crying and lower stress during a blood draw.^{11 12}

The unborn baby hears every word his mother says, and therefore gets lots of exposure to her voice and language. Babies prefer their mother’s voice and familiar stories she read before birth.¹³ Newborns even cry with the same melodic patterns from their mother’s native language.¹⁴ So, a German baby cries differently from a Chinese or English baby!

But the most fascinating discovery? Nutrition in the womb follows well after birth.  The tastes and smells that a baby encounters while in his mother’s womb, as well as while drinking breastmilk or formula shapes what he’ll enjoy eating years later. Flavors from a mother’s diet pass into amniotic fluid and breastmilk, giving babies early exposure to family foods.¹⁹ As a result, kids who are exposed to fruits, vegetables, and even bold flavors like broccoli or sour apple juice inside the womb will enjoy similar foods after birth.^{20 21}

From familiar stories to sweet anise, early exposure helps shape preferences after birth, showing that learning begins long before the first snuggle.

At birth, the heart pumps about 2,000 quarts of blood per day, which would likely fill a large hot tub!³² For comparison, an adult heart pumps three times that amount: about 6,000 quarts of blood each day. After birth, heart cells stop multiplying and instead grow bigger. Just one month after birth, the baby has nearly all the heart muscle cells he will ever have.³³

By 38 weeks, mature alveoli start forming in the lungs. About 95% of alveoli develop after birth. Most of the gas exchange area is created by subdividing existing air space to create new alveoli. At birth, newborns have about 150 million alveoli, approximately half of the alveoli found in an adult. Many of these early alveoli are still immature. Children keep growing more alveoli until about age 8, reaching a total of about 300 million.³⁴ New research shows that a few new alveoli continue to grow up to 21 years old!³⁵

By 9 months gestation, the unborn baby’s small intestine measures about 9 feet—roughly the height of a basketball hoop—while the large intestine is about 2 feet long.⁴¹ Both are tightly coiled within the small abdomen. For comparison, an adult’s small intestine is about 22 feet long⁴² and the large intestine about 5 feet.⁴³

In adults, lots of healthy bacteria inhabit the intestines. These bacteria help digest food, synthesize vitamins, provide immune system support and influence mood. Researchers have found that the same bacteria that aid in digestion and immunity only enter the intestines of healthy babies during and after birth.⁴⁶