As far as anybody knew, she hadn't even married her fiance Josh yet and we saw her working so hard to get on birth control on a recent episode of Teen Mom 3, things just didn't seem to line up.
When people found out about the second pregnancy, Mackenzie revealed that she apparently already was married to Josh, even though they hadn't had their "wedding" yet, and she also revealed a sad reason about why she wanted to have another baby ASAP.
In response to the criticism and fans telling her she was "stupid," Mackenzie fired back with a tweet that read "If a doctor told you your body would no longer be able to have babies after the age 21. And your married and 19. What would you do?"
Although Mackenzie didn't reveal why she can't have a child after age 21, she does suffer from diabetes, which has caused her many health problems in the past, so it could be related to that?
Either way, that would definitely explain why they wanted to have a baby so quickly, especially if they want to try for a third, which will be cutting it pretty close.
In a recent Instagram post, Mackenzie revealed that she and Josh are expecting a girl. They already have one son together, Gannon.