How harmful are heels for women? is it true that it can cause pregnancy issues later?

Very harmful; No: Heels are very harmful and often cause permanent harm including arthritis, bunions and chronic pain. I recommend women wear high heels on rare occasions if ever. However, i know of no evidence they can cause any pregnancy issues. See http://saludify.Com/high-heels-health-risks/ and http://well.Blogs.Nytimes.Com/2012/01/25/scientists-look-at-the-dangers-of-high-heels/.

Depends: It depends on the type of high heels, genetics, and amount of wear on your feet. Standard advice is to always bring a pair of supportive shoes to change into later. Pregnancy adds a lot of weight in a short period of time so your feet may swell or widen, but wearing heels before is not directly related.