What will you be doing next tests you on future structures.
English has a wide and subtle range of Future verb structures: here's your chance to grapple with them once again and to distinguish their formation and purpose. 'What will you be doing next?' Wait and see, from Question to Question!
Although the baby belongs to both of 'them', we usually speak of a woman 'having A baby' ~ come to think of it, that indefinite article does seem a bit surprising, when she has been making that baby her own for 3/4 of a year ~ rather than 'her' or 'their' baby or even just 'the' baby (grammatically Definite since we all know it's on the way, because we can see and/or have already been told about it).
One way and another, Answer 2 is the best here. Meanwhile the 'thin chances' in the Question are perhaps a slip of the speaker's tongue (or mind) ~ since Megan herself will, presumably, be growing larger over the months to come!