Tried very sincerely,as if it was my dissertation topic to find out the answer.Remember........don't wish to misguide you as I know you have shown a lot of faith and belief in the R and Ds which I Post on this blog.
Here ,I didn't get any scientific study/paper on this topic............not even a study conducted on any possible animal.
Some not so reliable sites ,mentioned of bromelain,a chemical being present in the Pineapple,which can ripen the cervix and induce labour if taken in such a great dose as to induce diarrhoea......phew!!Confusing!!
My advice would be,have pineapple in moderation.