There was a recent study into the changing size of women's feet during pregnancy. It explains a mechanism involved in making feet bigger, but it isn't reversible. It may be relevant as some taking HRT find that their feet inexplicably change size, but usually smaller. So if you already have big feet, you may want to avoid getting pregnant (or even simulating it)..
http://www.dailymail.co.uk/health/article-2287357/Being-pregnant-DOES-make-womens-feet-bigger-changes- (http://www.dailymail.co.uk/health/article-2287357/Being-pregnant-DOES-make-womens-feet-bigger-changes-)
permanent-say-researchers.html