If you are in the U.S. and your employer filed an H-1B petition that includes a request for a change of status, then on the start date of the H-1B petition, your status will automatically change from H-4 to H-1B. Typically, H-1B workers who are on medical leave (including maternity leave) do not fall out of status, as long as they do not sever their employment from the H-1B employer. This depends on the applicability of the FMLA in your specific situation, and also possibly the companion law of the state in which you reside.
The questions you are asking should be directed to your employer's immigration lawyer, and your employer's HR, as they are familiar with your case and with the employer's policies on leave.
Answered on Feb 07th, 2014 at 1:30 PM