"Born in the caul" is a phrase that's connected with a lot of cross-cultural myths and superstitions — babies born in the caul are supposed to be destined for lives of fame and fortune (or, possibly, misfortune and grisly death, depending on which legends you're listening to). Biologically, though, it refers to a baby that's born with part of the amniotic sac — the bubble of fluid a fetus grows in inside the uterus — still attached. Usually, a piece of the sac is draped over the baby's head or face. These are called caul births, and they're rare. But, about once in every 80,000 births, you'll get something truly extraordinary — "en-caul", a baby born inside a completely intact amniotic sac, fluid and all.
There's a photo of a recent en-caul birth making the rounds online. The photo is being attributed to Greek obstetrician Aris Tsigris. It's fascinating. But it's also pretty graphic, so fair warning on that. (If the sight of newborn infants and blood gives you the vapors, you might also want to avoid most of the links in this post, as well.)
My dad calls the first few months of a baby's life "the necessary larval stage". I've heard other people refer to it as "the fourth trimester". Basically, newborn human babies are pretty useless, as far as baby animals go. This is especially true in comparison to baby apes, who come out of the womb at a much higher level of development. Scientific American has an excerpt from an upcoming book by Chip Walter that talks about this fact and its connection to two key moments in human evolution — the development of bigger brains (and thus, bigger heads) and walking upright (which has the side effect of creating a narrower birth canal). — Maggie
There is definitely a seasonality to human births, writes Beth Skwarecki at Double X Science. The complicated bit is that human baby season isn't necessarily the same (or as strongly expressed) from place to place and culture to culture. In the United States, significantly more babies are born in July, August, and September. Meanwhile, in Europe, babies seem to make their way into the world in spring. So there's clearly a cultural component to this — but culture doesn't explain it, entirely. Skwarecki's piece explores a messy place where culture, genetics, and circadian rhythms intersect. — Maggie