Unexpected risks for surrogates

Can a woman really fall pregnant, when she is already carrying a surrogacy pregnant?  This is not an issue I generally include for discussion in my pre-surrogacy implications counselling for women contemplating becoming a gestational surrogate, but the truth is, strange things really do happen!  The process is known as superfetation, and involves the simultaneous occurrence of more than one stage of developing offspring in the same animal. In mammals, it manifests as the formation of an embryo from a different estrous cycle while another embryo or fetus is already present in the uterus.  There are a very small number of confirmed cases in the medical literature, but it really does happen.  In this case a US surrogate fell pregnant to her partner after she was ALREADY pregnant with a surrogate embryo.  The parentage implications were rather complex, but a great case demonstrating we really can’t anticipate all the possible outcomes of surrogacy! http://abcnews.go.com/Lifestyle/surrogate-mom-pregnant-child-carrying-couples-baby/story?id=50801029