The advancement of the imaging techniques and the diagnostic possibilities of the last 30 years enabled the scientific community to understand to a great extend the physiology of the fetus and its diseases. In some of them there is the possibility of intra-uterine intervention that enhances the chance of the birth of a healthy child.

The oldest intra-uterine therapy is the intra-uterine transfusion practiced in cases of severe fetal anaemia. The technique is similar to the fetal blood sampling with the difference that blood is given to the fetus by transfusing it into the umbilical vein. Depending on the cause of the problem one or more transfusions may be needed. Usually the symptoms regress within a few weeks and the pregnancy advances to the third trimester.

Another useful intervention is the removal of fluid accumulating in the chest of the fetus. The presence of fluid around the lungs is rare, it usually occurs in the third trimester and can cause heart failure to the fetus. Under ultrasound guidance we can either remove the fluid or insert a catheter to ensure continuous shunting of the fluid into the amniotic cavity.

One special group of intra-uterine procedures are the ones performed in the twins that share the same placenta (mono-chorionic twins). In mono-chorionic twins every fetus has its own sac, umbilical cord and placental circulation but there is only one placenta. The two fetal circulations communicate through the common placenta and usually the exchange of blood is balanced. However, occasionally (about 10% of cases) the exchange becomes unequal and one fetus is getting more blood than its twin (twin-to-twin transfusion syndrome) with the consequence that both fetuses are suffering. The condition manifests through abnormalities in the growth patterns, amniotic fluid and Doppler flows of the twins. It is because of this condition that the mono-chorionic twins need close surveillance by fetal medicine experts. Once the condition is present in its severe form, it can be treated with intra-uterine coagulation of the communicating vessels by laser ablation. The procedure reverses the cause of the problem and has been found to increase the chances of survival of healthy children.