More from Yuval Levin:
Thanks for posting those caveats about amniocentesis. It’s always important to understand that every medical intervention carries risk, and these are especially important to keep in mind during pregnancy. But the rate of miscarriage you quoted (1 in 200 to 400) is a controversial statistic and the most recent research suggests it is not correct (see for instance this recent item). Studies in the past few years have found there is not a higher rate of miscarriage with the procedure. But whether the newer or older studies are right, there is no question that amniocentesis, like any medical procedure in pregnancy, carries risks that should not be taken lightly, including, as your emailer noted, risks of infection and other complications. The point about this recent stem cell study is just that amnio is done quite routinely and for the most part quite safely, and so a source of apparently embryonic-like stem cells derived from that procedure offers a way around techniques that would intentionally destroy human embryos for cells.