[USNBandit]

For births abroad for one alien and one USC parent. For birth between December 24, 1952 and November 13, 1986, a period of ten years, five after the age of fourteen are required for physical presence in the U.S. to transmit U.S. citizenship to the child.

Secton 301(g)INA, assuming the parents were married. If they weren't then the requirements are even less. I don't know what happens if the Mother isn't 19 by the time she gives birth.

[USNBandit]

An interesting legal question would be if Mom couldn’t transmit citizenship, could Obama move to have a deceased mother’s marriage annulled based on bigamy. Being born out of wedlock reduces the mother’s residency requirements quite a bit.