I am an English lady living here and i have had one child here and will be having my next in a couple of months.
I would suggest getting yourself a good medical insurance that includes Maternity, you have to have this at least 3 months before actually becoming pregnant to qualify for the coverage. I pay 10,000 pesos approx USD300 every three months which covers my daughter, myself, pregnancy and prescriptions with Medical Insurance company Humano. This covers 100% of EVERYTHING! Even c-section surgery and hospital stay at Hospiten and Centro Medico(Tourist hospital's in Punta Cana).
You can get alot more here now than you could 4 years ago when i had my first, allthough it is pricey! If you family are helpful they can maybe send you some things when you are expecting. Other mums will understand, but finding cotton blankets and clothing for baby is very difficult, many things are Polyester and in this heat that is a nightmare. I buy all of my baby clothes online from the UK.
Most of the other bigger pieces you can find but again at price, but i bought alot of my bigger pieces on ebay and had it sent to a mail forwarding service in Florida and still saved alot.
However talk to other mums and you will no doubt find out what you really need and what is a waste of time and money. Also keep posting on DR1 as you may be lucky enough to find someone like me who will have finished with all the bigger pieces and will want it to go to a good home.