Spontaneous heterotopic triplet pregnancy with intrauterine monochorionic-monoamnionic twins

Heterotopic pregnancies are an unusual phenomenon, which have recently become more prevalent with assisted reproductive technologies (ART). Triplets that are part of a heterotopic pregnancy are exceedingly rare. Here, we describe a case of a woman who presented at 15+1 weeks of gestational age with a known monochorionic-monoamniotic intrauterine pregnancy with several days of abdominal pain with an otherwise unremarkable gastrointestinal (GI) assessment. Salpingectomy was performed, and pathology revealed chorionic villi within the fallopian tube consistent with a heterotopic triplet pregnancy. This pregnancy was conceived spontaneously. Even without the prior use of ART, physicians need to be aware of the risk of heterotopic pregnancy in a patient with a known twin gestation. In addition, this case highlights how heterotopic triplets can present even within the second trimester.