Brunswick hills fits that bill. They have an office in Hillsborough and deliver at St Peter's which is the best hospital in the area for high risk deliveries. They have a great NICU that can handle very premature babies plus they have an affiliation with Children's Hospital of Philadelphia. BH definitely does bloodwork and they have an ultrasound machine right in the office. In fact, you can get bloodwork done there any time during your pregnancy; just call and talk to the nurse who will tell you when to come in. The biggest "con" about the practice is that they have a lot of doctors that attend deliveries. I thought most of the doctors were pretty nice. I had 2 surgeries with them and found them to be good and competent. I did leave them though but that's because I wanted to have an ultra-crunchy drug free birth the second time.
The other hospital in the area is Somerset Medical Center. Their NICU can handle preemies beyond 32 weeks but I don't know if that's what you are looking for. Actually, Hunterdon Medical Center isn't far either. They are in Flemington so it depends on what part of Somerset County you are. They are a hike from North Plainfield but not far from Branchburg. Like Somerset Medical, they can handle preemies at 32 weeks and beyond. I have a friend who had all kinds of complications with her pregnancies (though she carried full term). She used All Women's Health Care (I think one of their doctors was voted a NJ Top Doc). She had very good care with frequent ultra-sounds. The rooms at Hunterdon are amazing! It's like being in a hotel.