Amnioinfusion Benefits and Risks

Jun 30 2009

Amnioinfusion is a technique introduced relatively recently into obstetrical care. In this technique, a physiologic fluid, usually saline(salt water) is infused into the uterus. It may be infused as a one-time dose, or continually throughout labor. Amnioinfusion is beneficial in three situations:

When fetal heart rate decelerations indicate cord compression.
raman amplifierWhen there is reduced amniotic fluid(oligohydramnios).
When there is thick meconium.

In the first two instances, the purpose of the amnioinfusion is to provide cushioning for the umbilical cord for optimal blood flow through it. Reduced fluid may occur when the membranes have been ruptured for a long time before labor and sometimes in pregnancies that are 2 weeks or more past the due date. In the third situation, the purpose of the infusion is to dilute the meconium(the often thick and sticky contents of the fetal bowel). This is an attempt to prevent meconium aspiration syndrome, in which the fetus breathes in some of this thick substance and subsequently develops pneumonia and breathing difficulties.

The research on amnioinfusion has shown conflicting results. Although researchers have documented fewer variable decelerations after amnioinfusion, studies have not always shown that this has reduced the need for cesarean delivery or improved the condition of the newborn. The same can be said for research on the effect of amnioinfusion on meconium aspiration syndrome. Studies have shown beneficial effects and no effects.

Amnioinfusion is not without risks. It can cause an increase in pressure inside the uterus, leading to abnormalities in fetal heart rate patterns. It also has been associated rarely with infection, rupture of the uterus, heart or respiratory problems in the mother, placenta abruptio(the tearing away of the placenta from the uterine wall), and, most rarely, a fatal problem called amniotic fluid embolism in the mother.

Amniotic fluid embolism(or clot) is an extremely rare occurrence, usually believed to be unavoidable in obstetrics-a true “act of God.” It occurs in 1 out of 8,000 to 1 out of 30,000 pregnancies. Although only two case reports have appeared of this fatal complication with amnioinfusion, this is a relatively large number of women having an amniotic fluid embolism for the number of amnioinfusions that are performed. Amniotic fluid embolism has been considered to be the result of solid material in the fluid, such as fetal cells, somehow getting into the maternal pulmonary(lung) circulation. Today, an alternative explanation is that the embolism is a result of a type of maternal allergic reaction to the fluid. Although it is thought that the maternal and fetal tissues are separate, it is possible for fluid to get into the mother’s circulation during procedures, in this case amnioinfusion, and even during normal labor and delivery as tiny tears occur in the lower part of the uterus or the cervix.