Pregnancy-induced hypertension is associated with altered anatomical patterns of Hyrtl's anastomosis

Umbilical arteries carry the blood from the fetus to the placenta and are typically connected by Hyrtl's anastomosis, a connection that is located near where the umbilical cord meets the placenta. The investigation of the anastomosis in pathological conditions, including pregnancy-induced hypertension is limited. Hence, 200 placenta and umbilical cords, 100 from normotensive and 100 from pregnancy-induced hypertensive subjects, were dissected and measurements were recorded. A single anastomosis between the umbilical arteries was observed in 167 specimens. In 16 cases, the two umbilical arteries were fused, in 15 cases there was no anastomosis, and in two cases there was a single umbilical artery. In one specimen from a normotensive case, a double anastomosis was observed. To our knowledge this is only the second report of this rare anatomical variant. When an anastomosis is present, the connecting vessel can be transverse to or form an oblique angle with the umbilical arteries. We observed a striking increase in the number of artery pairs connected by a transverse vessel in specimens from hypertensive subjects relative to those from normotensive subjects. Moreover, placentas from hypertensive donors were small if the umbilical arteries were connected by an oblique anastomosis. In addition, the length of the anastomosis and its distance from the cord insertion was shorter in specimens from hypertensive compared to normotensive subjects. We conclude that pregnancy-induced hypertension alters the anatomy of Hyrtl's anastomosis, and in some circumstances, the placenta.