The outcomes for fetuses diagnosed with congenital complete heart block depend on several factors, but especially significant is whether structural heart disease is also present. The prognosis for these fetuses is guarded, particularly if there are complex malformations. Hydrops, or swelling of the fetus, is an unfavorable sign and is usually associated with a very poor prognosis. Fetuses with complete heart block and very low heart rates are at increased risk for development of hydrops.
The prognosis is better for fetuses diagnosed with congenital complete heart block without other structural defects of the heart. Treating hydrops in utero with steroids and other drugs may allow the pregnancy to continue and avoid premature delivery, which increases the newborn’s risk of sickness and death.
If the fetus is close to term and the complete heart block is considered to be in stable condition, a normal vaginal delivery may be done, but with close monitoring. If repeated measurements indicate that the fetal heart is deteriorating and that the fetus can no longer survive in utero, the baby will be delivered prematurely by caesarean section. In these cases, the newborn usually requires ventilation, a surfactant (a mixture that coats the air sacs in the lungs to prevent lung collapse), and a drug to increase the baby’s heart rate.
In some cases, a temporary pacemaker is connected to the newborn’s heart. A permanent pacemaker is implanted once the baby is stable, with no signs of infection, and weighs approximately 1.5 to 2 kg (3.3 to 4.4 lbs).
Some studies indicate that using steroids that cross the placenta may possibly prevent or reverse the degree of complete heart block in fetuses of women who previously had a child affected by complete heart block, but these studies need to be verified.