Every green card applicant who is also applying to U.S. Citizenship and Immigration Services (USCIS) for a provisional waiver on Form I-601A is naturally eager for a quick decision. After all, the sooner the waiver of unlawful U.S. presence is granted, the sooner the National Visa Center can schedule the visa interview at the U.S. consulate abroad, and then the sooner the immigrant can return to the United States as a lawful permanent resident. But the reality is that you could be facing a long wait, as discussed here.
Although USCIS has never released its standard processing times for this application, its goal is to make a decision within 90 days.
Unfortunately, there is no guarantee that you will receive a decision on your waiver application within 90 days, and it is not uncommon for USCIS to take longer than that. Moreover, unlike with some immigration applications, no arrangement exists by which you can pay a "premium processing" fee to guarantee speedy handling of an I-601A waiver application.
Your best hope if you really need a quick decision is to make a request to have your waiver request "expedited." USCIS doesn't grant such requests often, however. The agency requires a solid reason for making the expedite request, such as a medical, humanitarian, or similar emergency, or the possibility of severe financial loss to a business or a person. It also requires showing that the waiver applicant didn't cause the time-crunch, by being late to file the benefit request or to respond to agency requests for additional evidence.
To ask for an expedite, you can either submit a cover letter with your waiver application requesting the expedite, or send it later, via the USCIS Contact Center at 1-800-375-5283.
With your expedite request, you will need to provide documentary proof of any facts that you are claiming. For instance, if you were pregnant and worried about traveling later in your pregnancy, you would need to provide a letter or records from your doctor verifying the pregnancy and detailing any expected complications that could make it difficult for you to travel later. But in such a situation, if the normal wait for I-601A decisions is already long enough, USCIS could figure that your child will be plenty old enough to travel by the time you are scheduled for a visa interview.
Again, nothing is guaranteed. This is a "discretionary" decision, meaning USCIS is free to make its own judgment about who deserves what. (See 8 C.F.R. § 212.7(e).)
In the meantime, if you are in the U.S. and presumably with your U.S. spouse, that could make your waiver request less likely to gain approval than that of someone who is separated from close family.
For more about the waiver application process, see How to Apply for Provisional Waiver of Three- or Ten-Year Time Bar. You could also make your life easier by hiring an experienced immigration attorney to handle your family visa case. The attorney can analyze the facts of your case and spot any potential problems, prepare the paperwork, and monitor the progress toward approval.