I had faced this issue last year when I received my medicals last year in Mar 2012 . My wife was 3 months pregnant . We consulted a DMP . He gave us 2 options
1) Do the x-ray with a metal plate on the stomach area ( not guaranteed it will not effect the baby)
2) avoid the x-ray , do the rest of the medicals and send it to the VO. Later after the delivery do the x-ray and update your medicals
We went for the 2nd option bcos we didn't want to take a chance on the baby and also we could include the new baby into the application .
So we did our medicals on June 5th 2012 and updated the medicals with the x-ray on Sept 2012 and included the baby by Oct 2012 .
And also as you mentioned you have 60 days validity for your medicals , better to make maximum use of the 60 days and do your medicals 1 week before the validity expires . So you will get 1 year from the date of medicals to land and the mother and the child will able to travel comfortably ..
My medicals were getting over by June 15th 2012 and I did my medicals on june 5th 2012 and landed on april 29th 2013 . all went fine....by God's grace...