It is totally safe, as long as you have already been doing it. Pregnancy is not the time to start a new exercise routine. As long as you are comfortable with it, and don't overdue it, it will be fine. Make sure that your heartrate doesn't get over 140 beats/min. If it does, slow down some.
Running after the baby is born is an excellent way to get back into shape. Using a stroller is a great way to add some resistance, but still have baby with you and most babies really enjoy it. They will probably sleep right through it, but they love it.
mom of 2, OB/Gyn CNP