The Royal Foetus

Here is a modular poem.  below, I have appended various options for the third and fourth lines, which you can select according to taste (or lack thereof)

The Royal pair have feasted on sprout.
It's had an effect, without doubt.
[See below
                                                  ]
Because she's got one up the spout.*

* this line might need slight tweaking depending on which of the following  missing lines you opt for.

Options for third and fourth lines
A: The result of their f***ing
     Is that Kate is up-chucking

B: This royal fornication
     has delighted the nation

C: Because those sprouts from Brussels
     Sustained William's muscles

D: Pippa's next book, in future
      Is the royal Karma Sutra

E: Because the Royal Willy
     Has covered the filly