Plotted A Good Waste: Carlos is 5 years old, and in one episode, Alice claims to be 21. This was originally an oversight on the part of the writers (who didn't calculate the difference between the two characters' ages), but they decide to make it canon.
Deconstructed: This is going to cause a lot of problems for Alice. She is not educated enough to qualify for a job that will allow her to support herself and the baby, and all her dreams for the future will have to be put on hold. And Bob may not stay with her. Or, if she decides not to keep the baby, she'll probably suffer some Angst, and might endure scorn from others. On the subject of "scorn from others," she'll have to endure people whispering as she starts to show, because of My Girl Is Not a Slut. And let's not even mention Morning Sickness and other "joys" of pregnancy, and how that might affect her at school, or what her parents might do.
Reconstructed: Alice has people who love and support her, no matter what. They make sure her pregnancy is a safe and healthy one, and help her either care for the baby, or find an adoption agency to give it to at birth. If she decides to keep the baby, Alice manages to balance completing high school (or at least getting a GED), holding a job, and taking care of the baby. And, of course, either Bob marries her, or Alice's parents raise the baby as her brother rather than her son.