The amniotic sac -- which contains the amniotic fluid necessary to support your baby's growth and development during pregnancy -- is your baby's home for the first nine months, and it can even be your baby's home during the first few moments after birth. It is indeed possible for a baby to be born in the amniotic sac, although it is extremely rare.
The amniotic sac, which is also sometimes called the caul or membranes, is filled with amniotic fluid. This fluid is very important for the health of your baby. It helps your baby's lungs develop, provides lubrication so that your baby can move around and works as a shock absorber. It even helps your baby develop his digestion system, because he swallows the fluid and then expels it through urination.
Rupture of the Membranes
Usually, the membranes rupture during or shortly before labor begins. Once ruptured, the fluid leaks out, which is what is happening when a woman's water breaks. This triggers contractions. In some cases, doctors will manually rupture the amniotic sac in an attempt to start or speed up labor. Because of this, births within an entirely intact sac are very rare.
Rare & Harmless
It is not dangerous for a baby to be born in the amniotic sac. In fact, one baby lived for over 25 minutes inside the amniotic sac after being born, according to an article in JAMA Pediatrics. It is most commonly seen in premature births because there is more fluid present in the sac. Full-term babies are usually quite crowded in the sac, and the membranes are stretched thin, making them much more inclined to break easily. Babies born in the amniotic sac account for one out of every 80,000 births, and the births usually happen by cesarean section.
Superstitions about "caul births" date back to medieval times. It was thought that a baby born with part of the membranes over his or her face would bring good luck to his family. Such babies were believed to be destined for great things. Babies born within an entirely intact caul were considered to be even more fortunate and lucky. Sometimes in these cases, the cauls were preserved. Such cauls were believed to be able to protect the owner from drowning.