[header] How to create a maternity shirt [title] Go to a thrift store and buy a large cotton t-shirt. [step] It can be a long sleeved or short sleeved shirt. Try to find an extra large to 2 extra large size, so that there is room for your belly. 
[substeps] A very small woman may be able to use a large size rather than an extra large. However, most people will want an extra large or slightly bigger.