The general advice is that if you are already exercising you can continue to keep up your exercise routine for as long as you feel comfortable. If you are new to exercise you should start gradually with 15 minutes three times a week working up to 30 minutes daily. If you can, start with pregnancy specific exercise classes, low impact cardiovascular exercise or supervised resistance training. Tell your exercise instructor you are pregnant if the class is not pregnancy specific. Avoid anything high impact or high intensity if you are not used to it.