Any time you are facing criminal charges, legal representation is always a wise thing. I am not licensed to practice in Pennsylvania, so I'm offering general advice. Considering you are pregnant, the age of the charge and the apparently relative benign nature of it, coupled with your voluntary submission, I doubt they are going to hold you.
I'd talk with an attorney locally.
I recommend you get a lawyer involved who is licensed in the State of Maryland, to do the following. Have the lawyer call the Court and inform the Court you just became aware of the warrant, and are willing to turn yourself in and appear before the Court, but that being 9-months pregnant this could cause several medical issues requiring them to provoide you with medical care since you are near to full term. The lawyer should be able to work out an arrangement where the charge is either pled-to via an affidavit, or the enforcement of the warrant is restricted so long as you appear within a specified number of days after the delivery to answer the charge. As an alternative, the Court may want a bail posted, but this also will lift the warrant; and, the bail can be used later to satisfy the charge. Good luck to you and the baby.
Disclaimer: The above answer does not constitute legal advice, attorney advertising, or establish an attorney-client privilege; and, is offered for the limited purpose of educating the requester as to the potential legal issues they need to discuss with a lawyer in their State. I strongly recommend you discuss this situation with an experienced criminal defense lawyer admitted to practice law in your State before you make any decisions as to how to proceed. Do not presume that any legal analysis that may apply in NJ where I practice would apply in your State or under the facts and circumstances of your case, unless an attorney admitted in your State advises you that it applies to you and your case.