Transcript for Mom Gives Birth to 13th Child After Having 12 Boys
Finally tonight here, 12 boys in a row. And now, baby 13. Did science stack the deck? One, two, three -- Reporter: The Schwandt family. Can you imagine, 12 boys? The boys from 22 down to 1 1/2. And they've done the math. Yes, definitely outnumbered at times. Reporter: When the due date arrived -- Baby coming tonight? No baby. Reporter: And then Tuesday night. It's go time. Reporter: Mom does not look amused. But she was ready. Congratulations. Reporter: And 9:00 A.M. Yesterday morning at nearly nine pounds -- number 13. Hi, David! Reporter: And mom here tonight with the answer. You know, it's still a little bit of a surprise but it is a boy. What is it? Reporter: And dad let the other 12 boys know -- Baby brother number 13. Yay! Are you serious? Reporter: Our medical team telling us tonight, for most couples, it really is a 50/50 chance. But for some, the father is genetically predisposed to having boys. But get this, kateri and jay might try again. Long answer to your question is -- we don't know. Not giving up. I love the one son who said, are you serious? Thanks for watching tonight. I'm David Muir. And we hope to see you right back here tomorrow.
This transcript has been automatically generated and may not be 100% accurate.