Try unplugging it and plugging it back in.

Nah, in all seriousness try demolishing and replacing, it worked for me when my medbay time kept going up for seemingly no reason.

Meh~ As long as you have multiple pregnancies going on at once an upgraded radio room helps quite a bit. Isn't it like 8 or is game hours for a child to be born? V.s the time it takes for the radio to get out. Every little bit helps I guess.

Found a good explanation and tip online:

http://www.gamersheroes.com/game-guides/how-to-have-a-baby-in-fallout-shelter/

"The baby will take about 4 hours(real hours) to come out. The pregnant woman can still work but she cannot deal with disasters. If Raiders or Rad Roaches attack they can’t help. They also cannot put out fires. Once the kid is finally born you can watch them progress to an advlt by looking at the SPECIAL menu. This also takes a couple of hours but the kid will count towards your population for new rooms. Eventually, the Dwellers form the outside will slow down. Having a baby will help you get a bigger population.

Eventually...