Objective To monitor changes in the maternal renin–angiotensin–aldosterone system following laser therapy and amnioreduction in severe twin‐to‐twin transfusion syndrome (TTTS).
Design Observational prospective study.
Setting Single university hospital in Poissy, France.
Population Sixty cases of TTTS at 16–26 weeks of gestation.
Method Maternal blood sampling before, 6 and 24 hours following the procedure.
Main outcome measures Plasma levels of aldosterone, renin, angiotensin II (AII), atrial natriuretic peptide (ANP), vasopressin, sodium, potassium and plasma proteins together with full blood count were measured before, 6 and 24 hours following the procedure.
Results TTTS is associated with maternal hyperaldosteronism dissociated from renin–angiotensin changes. Correcting TTTS by placental surgery and amnioreduction triggers incomplete correction of hyperaldosteronism, as early as 6 hours following the procedure, without changes in AII but an increase in the levels of ANP in plasma. Electrolyte concentrations remained stable despite haemodilution, while vasoactive hormone levels such as that of vasopressin remained unchanged.
Conclusion Mechanisms involved in marked fluid retention in TTTS are rapidly corrected by laser therapy followed by amnioreduction while maintaining electrolyte homeostasis.