Baseline grid? How do you make type line up across facing pages?

Question

I'm laying out a book in Pages, and I have it set up as 12.5-point type on 15-point line spacing, exactly. The margin at the top and bottom of both pages is 0.9 inches. There is a header and a footer set on each page at 0.4 inches. But occasionally, one page will have 32 lines of body type on it, and the facing page will have 31 lines. No change in type size or leading on either page.
When I saw in the Pages user manual that you could specify the line spacing "exactly," I thought that was the solution. But still, occasionally, I will get two facing pages do not line up exactly, one still has 32 lines and the other 31.
I thought, hmm, what if I change the leading to 14.9-point on the 31-line page just to see what happens. Weirdly enough, the spacing does tighten up, way more than enough to fit that 32nd line onto the page, but the type does not flow back in from the next page. It just leaves a bigger space there than before, and still 31 lines. I'm stumped.
Is there any kind of baseline grid feature in Pages that might cure this? I didn't see anything like that in the user manual, but could there be some kind of equivalent, or a workaround? (Well, besides using Quark or InDesign?) It would look so much better if it didn't have the occasional blank line at the bottom of a page.
Thanks for any advice.

Answer 1

Thanks much, Walt and Peter, you were both right. I rethought my whole document layout, starting with the idea that I would put every line of 12-point body type on a 14-point slug. So I made the page length a multiple of 14-point lines. I also had some 16-point chapter titles that I formatted to be on 28-point slugs. I was not consistent enough in my chapter headline formatting before. And I tweaked my top and bottom margins so the length of the type area on the page would accommodate 37 lines of type. Once I had this setup, I was confident it would work. It did. For a while. Then I ran into a page that had only 36 lines, not 37. Hmmm. Yes, that's where unchecking the "prevent widow and orphan lines" box paid off. It allowed a line to flow back from the next page and fill in the 37th slug.
It doesn't have the elegance of setting up a baseline grid and locking the type to it, but it works. Thanks again for your assistance, guys.