I thought of this connection because of the philosopher Daniel Dennett's writing about the Sphex wasp.
The Sphex wasp behaviour is common to most wasps. They are fierce mothers. I have seen it first hand with tarantula wasps in my farm where the female wasp will paralyze tarantula with a neurotoxin. Then she lays the eggs in the still alive tarantula’s belly. It’s insides liquify and after the baby wasps come along, they are nourished by the fortifying soup of the ..wait for it..still-living tarantula’s innards.
http://www.bbc.com/earth/story/20150109-the-wasp-that-scares...
A more dramatic telling here on video: https://www.newsweek.com/horrifying-video-shows-giant-wasp-p...
Having said that, symbiosis only occurs with two distinctly different species.
With pregnancy and the human fetus, it’s is a kind of quasi-parasitic relationship because the host survives the parasite. Even though it’s changed. (Pregnancy changes body chemistry and functionally not just physical change)
all babies are born premature because we evolved quickly and the human female's pelvic bones didnt grow as wide and as quickly as the baby's head to come through the birth canal. even after birth, the human baby needs the mother/father for a much longer time for survival.
progestrone, semen, testosterone, pregnancy etc hijacks not just the blood stream, hormones but also the brain because the fetus basically converts the mother's body into a fortress and a machine to keep itself alive. after birth, the immature baby/fetus also hijacks the father's brain and instincts.
it's best to remember that all biological organisms are mere vehicles for DNA and it's survival instinct. this isnt just for humans. my favourites are insects. at the farm..watch the praying mantis and the tarantula wasp and the drone bees play out their lives changes your perspective on life forever.