Twin Anaemia-Polycythaemia Sequence is a rare complication that is specific to monochorionic pregnancies (babies who share a placenta) and occurs in 3-5 percent of these pregnancies.
Small blood vessels can form in the placenta between the babies, connecting their blood supplies, allowing a slow passage of blood from one baby to the other. This can cause the baby donating the blood (donor) to become anaemic (low blood levels), and the baby receiving the blood (recipient) to become polycythaemia (high blood levels), which can lead to overload and strain on the heart.
This can be more difficult to diagnose than TTTS, as there is no difference in the fluid volume around the babies. It can develop on its own, or after laser therapy for TTTS.
If your Obstetrician suspects your babies to have this condition, they will refer you to a specialist fetal medicine centre for further evaluation and treatment, and your babies will be monitored closely.
Treatments for severe cases such as laser therapy have been effective, but further research is still being done to determine the best treatment for this condition.