When a labor and delivery nurse in a Spanish hospital captured a recent birth on video, she didn’t realize that she was about to film a relatively rare event. The baby whose birth she recorded was born inside a fully intact amniotic sac. Fewer than one out of every 80,000 babies is born with a piece of the amniotic sac attached to their bodies. Fewer still are born encased in the entire amniotic sac. Such deliveries are known as “en caul” births, and the amniotic sac or the piece of it that survives delivery is called a “caul.”
What Is an Amniotic Sac?
The amniotic sac is the pair of membranes within which the unborn baby grows inside a mother’s womb. The amniotic sac contains the placenta and the umbilical cord through which oxygen and nutrients from the mother’s blood flow to the baby. Amniotic fluid within the sac cushions the baby from sudden jolts and impacts. Amniotic fluid also provides some protection against bacteria and other microorganisms.
The amniotic sac begins developing shortly after conception. The fluid in the sac is mostly composed of water, but once the baby’s kidneys are mature enough begin functioning after the 10th week of gestation, a small amount of urine will pass into the fluid as well.
By week 38, the amount of fluid in the amniotic sac will measure approximately one quart in normal gestations. After that, the amount of fluid begins to decrease gradually in preparation for the birth process.
In approximately 80 percent of all births, labor begins before the rupture of the amniotic sac. For some women, however, a few hours may pass before the rupture of the membranes and the onset of labor. If labor doesn’t commence within 24 hours of the time a woman’s water breaks, her physician is likely to induce labor and to administer antibiotics prophylactically because of the increased risk of infection.
In the Middle Ages, a baby born with a caul was believed to be someone who was destined for greatness. Cauls were thought to protect the children who’d been born with them from the spells of witches and sorcerers. Cauls were also believed to protect against drowning but only so long as the caul was kept in a safe place. Many Victorian families sold their babies’ birth cauls to sailors.
En caul births almost never happen with vaginal deliveries, and they’re exceedingly rare with Caesarian sections as well because the scalpel the obstetrician uses to make an incision in the mother’s uterus typically pierces the amniotic sac.
En caul births are no more dangerous than regular births so long as the umbilical cord has not yet been cut and the mother has not yet delivered the placenta. The baby inside the amniotic sac is still receiving oxygen through the umbilical cord. The obstetrician, however, will quickly cut the sac and sever the cord in order to make sure the newly born infant is able to breathe properly.
Premature infants or infants born with a low gestational weight are more likely to be born en caul than full-term infants. Since twins often weigh less than singleton births, one might expect twins to be born more often with cauls. In the case of the en caul baby whose birth was recorded on video by the Spanish labor and delivery nurse, the infant was a twin. Though we’re much more knowledgeable about the physiology of birth now than we were in medieval times, a baby born with a caul is still an awe-inspiring sight. Watch the full video here!