Not uncommon in some circles, but by '61 they'd have been extremely uncommon for the daughter of a banker and store manager.
Could you share those numbers, as fractions of total births, or just raw numbers with the total births, I can do division if I drag out one of my slide rules. :) Ditto for out of state births.
(As it happens one the cousins of my granddaughter, born a month after she was in 2005, was a non hospital birth. But it was attended. By an ambulance attendant, somewhere along the side of the road in New Jersey. :) Fortunately, while it was the first birth he attended, it was not her first birth.)
Look at the link below to the 1961 Natality Report:
http://www.cdc.gov/nchs/data/vsus/vsus_1961_1.pdf
Page 43 lists the states where births occurred distributed according to the state of residence. There were two births recorded in Washington state to Hawaiian residents. Then on this same table, there are 58 births to Hawaiian residents that took place in other states. These states include Washington, California, Colorado, Kentucky, Massachussetts (Harvard), Missouri, Montana, New Jersey, Oregon and South Carolina.
Page 49 gives a table that breaks down the number of births in each state by race. In the “other” category, there are a couple of footnotes that say 366 births occurred to Hawaiians or Part-Hawaiians living in other states. This is pretty good proof that Hawaii registered out of state births, else how they get these statistics??
Also, about all these tables say they don’t include foreign births. IOW, that seems to acknolwedge that states keep track of that information. I saw a table on a different page that lists numbers of births per month, which leads me to believe that by Aug. 4, there had to have been about 500 foreign or out-of-stae births that would have been registered in Hawaii, meaning Obama’s could have been one of those births.