Yes, in the United States, IVF doctors perform a maximum two-embryo transfer. However, it is not recommended by ASRM and doctors. The two-embryo transfer will raise the success rate of implantation. However, it will bring double risks for pregnancy. The majority risk for carrying twins is preterm labor. The baby may suffer serious complications with early-birth and may not be surviving if they come out too early. The international intended parents may have to pay costly medical bills for NICU or medical treatments for the newborn baby if the newborn insurance is not applicable for non-resident intended parents.
ACRC being a professional agency, we educate our intended parents and remind them of the risks. But yes, you could choose a two-embryo transfer at will and with your surrogate's consent.