No one is talking! However thinking back to the one baby picture of Jr which has now been released I would date him as 9 months old. Babies today are much more developmently advanced than they were in the 60’s. In the photo Jr is holding his head up which was common in a 9 month old. There are no reports of an infant until Ann appears on Mercer Island. There is no testimony from anyone who was in the “Russian” language class with Sr and Ann. Her pregnancy and birth are complete blanks! Another thing is that hospitalization for birth in 1961 averaged 5.3 days, meaning that the registration happened even before Ann’s discharge from the hospital!
Obama was born 8/4/1961. My bet is that his mother was off from school in August since it would be summer vacation and she went to Kenya to have the baby when school ended, probably around June of 1961. She may not have even looked pregnant at the time she left.