Is it common to have two placentas developing during pregnancy one empty and with a live fetus What will happen the sac as progresses?

The occurrence of two placentas during pregnancy, one empty and the other with a live fetus, is not a common phenomenon. This condition is known as "monochorionic diamniotic twin pregnancy" or "two-placenta twin pregnancy." It occurs when a single fertilized egg divides into two embryos, resulting in identical (monozygotic) twins. In such cases, the twins share a single outer chorion layer but have separate amniotic sacs and placentas.

As the pregnancy progresses, the empty sac will typically degenerate and be absorbed into the mother's body. The live fetus will continue to develop within its respective amniotic sac and placenta, receiving necessary nutrients and oxygen from the mother's blood supply. The presence of an empty sac does not usually affect the health and development of the live fetus.

Here's a breakdown of what might happen to the sac as the pregnancy progresses:

1. Degeneration: In many cases, the empty sac gradually shrinks and degenerates over time. The fetal tissues and fluids within the empty sac are resorbed by the mother's body.

2. Absorption: The empty sac may eventually be absorbed into the remaining placenta or the uterine lining. This process might occur naturally without causing any complications.

3. Twin-to-twin transfusion syndrome (TTTS): In some rare cases, the presence of an empty sac can be associated with TTTS. TTTS is a condition where there is unequal sharing of blood and nutrients between the twins due to abnormal connections in the placentas. This condition can lead to health complications for both twins.

4. Monitoring: Typically, the presence of two placentas and an empty sac is carefully monitored by healthcare providers throughout the pregnancy. Regular ultrasounds and tests help assess the well-being of the live fetus and track the progression of the empty sac.

It is important for individuals experiencing a two-placenta twin pregnancy to receive regular prenatal care and follow their healthcare provider's guidance. They will closely monitor the pregnancy and address any potential concerns that may arise.