In utero
This temporary organ, unique to pregnancy, produces hormones, transfers oxygen and nutrients, and filters waste. It is delivered after the baby.
The placenta
It grows from the same fertilized egg as the baby. Some cultures have deep historical practices of burying, planting over, or eating it.
This hormone surges during labor to drive contractions and peaks at birth.
Oxytocin
It is also released during skin-to-skin contact.
Newborns have around 300 of these while adults have 94.
Bones
Babies are born with mostly cartilage that gradually ossifies. The extra 'bones' are actually separate cartilaginous segments that will fuse over the first two decades of life.
The first milk produced, rich in antibodies and nutrients. It is a thick yellow substance sometimes called 'liquid gold.'
Colostrum
It's produced in small volumes but is incredibly concentrated. It also acts as a laxative, helping clear the baby's first stool from their gut.
Ancient Egyptians recorded the earliest known pregnancy test: A woman would urinate on what?
Barley and wheat seeds
If they sprouted, she was pregnant. Researchers tested it in 1963 and found it worked 70% of the time! Likely because elevated estrogen in pregnant urine promotes germination.
By week 28, fetuses have developed these sensory organs.
Eyelids / Eyes
Before this, the eyelids are fused shut. Fetuses have been observed responding to light shone through the uterine wall.
This seals the cervix throughout pregnancy to protect the fetus against infection. Its release can precede labor by hours or weeks.
Mucus Plug
Newborns can see, but only clearly at about this distance.
8–12 inches
Which happens to be the distance from a nursing baby's face to the parent's face.
This reflex, triggered by a baby's cry or even just thinking about a baby, causes milk to release from the breast, sometimes unexpectedly.
The let-down reflex or milk ejection reflex
It's driven by oxytocin. Some people experience it with other people's babies crying, or even from watching videos of their own baby.
The baby shower as a celebration gift-giving event emerged in the US after this era, when consumer goods like cribs and layettes became widely available to the middle class.
Post-WWII (1950s)
Before that, gifts were given after a safe birth, not before. Infant mortality was high enough that celebrating early felt risky at the time.
The fetus can taste what the mother eats: Flavor molecules from her diet pass into this fluid that the baby swallows throughout pregnancy.
Amniotic fluid
Research shows babies exposed to garlic or carrot in utero show preference for those flavors after birth.
A baby born 'in the caul' was historically considered incredibly lucky or destined for greatness. What does it mean to be born 'in the caul'?
The amniotic sac
Caul births happen in roughly 1 in 80,000 deliveries. Sailors once paid fortunes for cauls, believing they protected against drowning.
Newborns are born with this reflex: When something touches the corner of their mouth, they turn toward it and open their mouth wide.
The rooting reflex
It disappears around 4 months as voluntary feeding behaviors replace automatic ones.
The World Health Org. recommends exclusive breastfeeding for this long before introducing solid foods.
6 months
After 6 months, complementary foods are introduced while breastfeeding continues. The WHO also recommends breastfeeding up to 2 years or even longer.
This country has one of the world's lowest infant mortality rates, partly due to universal home visiting by nurses after birth.
Denmark
The Nordic model includes universal paid parental leave, free healthcare, and postpartum home nurse visits. These factors strongly linked to infant outcomes.
Fetal kicks are felt as early as 16 to 25 weeks, but they also include this rhythmic, hiccup-like movement that can be felt as a regular pulse.
Fetal hiccups
Hiccups are thought to be practice breathing. The diaphragm contracts as the fetus 'inhales' amniotic fluid.
This score, given at 1 and 5 minutes after birth, assesses a newborn on five criteria: color, heart rate, reflexes, muscle tone, and breathing.
The Apgar score
Named for Dr. Virginia Apgar, who created it in 1952. It's one of the most widely used medical assessment tools in the world.
This dark, tar-like first stool is made up of everything the baby ingested in the womb: amniotic fluid, mucus, skin cells, and bile.
Meconium
It's nearly odorless and sterile. The baby passing it in the womb before birth can be a sign of fetal distress.
The glass bottle with a rubber nipple was invented in 1845, but for most of human history, babies whose mothers couldn't breastfeed were fed by these two means.
Wet nurses or animal milk from clay vessels
Wet nursing was common in ancient Egypt, Rome, and throughout the Middle Ages. Clay feeding vessels shaped like animals date back to 2000 BCE.
In Japan, a tradition called 'satogaeri bunben' involves the pregnant person doing this in the final weeks before birth.
Returning to their parents' home
The tradition provides community support and rest. The mother and baby may stay for weeks or months after birth as well.
This fine, downy hair covers the fetus starting around week 16 and is usually shed before birth. Some babies arrive still wearing it.
Lanugo
It's thought to help regulate temperature and anchor the newborn's biofilm to the skin.
Before the epidural's widespread adoption in the 1970s, this medicine was the main pain relief option for laboring people.
Nitrous oxide (laughing gas)
It's inhaled through a mask and works in seconds. Unlike epidurals, it doesn't affect mobility and wears off almost instantly.
A newborn's skull is not one solid bone. It has these soft spots that allow the skull to compress during birth and the brain to grow rapidly afterward.
Fontanelles
The front fontanelle doesn't fully close until 18 months. You can sometimes see it pulsing with the baby's heartbeat.
Breast milk actually changes its composition throughout a single feeding session. The first milk is thirst-quenching, and this richer milk comes later.
Hindmilk
Foremilk is higher in water and lactose. Hindmilk is higher in fat and calories. The distinction isn't a sharp switch but a gradual change.
The 'fourth trimester' concept describes the first three months of life as an extension of the womb and explains why babies are calmed by these five things.
Swaddling, shushing, swinging, side/stomach position, and sucking (the 5 Ss)
Popularized by pediatrician Harvey Karp. The idea is that human babies are born earlier than other primates relative to brain development, because our heads are too big for longer gestation.