Twin to twin transfusion syndrome - diagnosis and mangement overview

Twin to twin transfusion syndrome is diagnosed with antenatal ultrasound scan. There are 2 criteria required to diagnose the condition: 1) the presence of monochorionic diamniotic pregnancy, and 2) the presence of amniotic fluid volume discordance, i.e polyhydramnios of the recipient, defined as MVP>8cm, while oligohydramnios of the donor, with MVP<2cm.

Once a pregnancy is diagnosed with the condition, the next step is to stage the disease. The most commonly used staging system for this condition is Quintero staging system, which is based on the sonographic findings. Although it may not determine the prognosis for perinatal survival, it appears to be a useful tool to diagnose the condition, describe severity, guide treatment and monitor progression of the condition and effectiveness of the treatment.

Quintero system divides the condition into 5 stages, ranging from the most mild disease (with only amniotic fluid volume discordance) to the most severe one (with demise of one or both fetuses). Amniotic fluid volume discordance, with MVP<2cm in donor sac and MVP>8cm in recipient sac, defines stage 1 of the disease. Once fetal bladder of the donor twin is not visualized, the disease has progress to stage 2. Abnormalities in the Doppler findings put the disease in stage 3. Presence of fetal hydrops and demise, of either one of the twins or both, means the disease is at stage 4 and 5 respectively.

Stage	Parameter	Criteria
1	MVP of amniotic fluid	MVP<2cm in donor and MVP>8cm in recipient
2	Fetal bladder	Fetal bladder in donor twin is not visualized over 60min observation
3	Doppler waveforms:	At least one of these 3 abnormalities:
	a-umbilical artery	Absent or reversed diastolic flow.
	b-ductus venosus	Reversed a-wave flow.
	c-umbilical vein	Pulsatile umbilical vein flow.
4	Fetal hydrops	Hydrops in one or both twins
5	Fetal cardiac activity	Absent cardiac activity – fetal demise in one or both twins.

  -Quintero staging system-

Decision of treatment option is done by considering the stage of the disease and the gestational age of the pregnancy. Stage 1 disease usually can be managed expectantly since most of the cases remain stable or regress without invasive intervention. Fetoscopic laser photocoagulation therapy is considered as the best option for stages 2, 3 and 4 at gestational age <26 weeks. The aim is to prolong the pregnancy as long as possible until the fetuses are mature enough to survive outside the womb and to reduce the risk of complication from prematurity. Steroids for fetal lung maturation should be considered at gestational age of 24 weeks to 33 weeks for stage 3 and above, and those undergoing invasive interventions as a preparation in case premature delivery is required.

Treatment options in managing twin to twin transfusion syndrome include: 1)expectant management 2)serial amnioreduction 3)intentional septostomy of the intervening membrane 4)fetoscopic laser photocoagulation of placental anastomoses 5)selective reduction.