Amnioinfusion: why it helps variable decelerations and what the nurse monitors

The reasoning behind amnioinfusion

Variable decelerations are generally attributed to umbilical cord compression, which is more likely when amniotic fluid is reduced. Adding fluid back into the uterus aims to float and cushion the cord so contractions squeeze it less. The goal is to relieve a mechanical cause of the decelerations, not to treat fetal hypoxia from other causes.

Amnioinfusion usually follows first-line intrauterine resuscitation. Repositioning the mother, giving an intravenous fluid bolus and reducing or stopping oxytocin come first, because they are quick and non-invasive. When recurrent variable decelerations persist despite these measures, the provider may decide amnioinfusion is appropriate. Documenting these first steps also shows the team which measures have already been tried.

Requirements and the steps nurses support

The fluid is infused through an intrauterine pressure catheter, so membranes must be ruptured and the catheter placed by a qualified provider, away from the placental site. Placental location should be known beforehand. Isotonic fluid is infused, with the type, volume and rate set by the prescriber and the unit protocol.

The nurse prepares the fluid and pump, labels the line clearly so it cannot be confused with an intravenous infusion, and confirms the catheter is working by checking the pressure waveform. Continuous fetal heart rate monitoring continues throughout, and the response is judged by whether the depth and frequency of decelerations improve. Keep the patient informed and comfortable, and change underpads regularly so returning fluid can be estimated and the skin kept dry.

Monitoring for overdistension and other complications

Infused fluid is expected to leak out vaginally over time, and protocols ask the nurse to compare fluid in with fluid out. If little or no fluid returns, the uterus may be overdistending, which can raise resting tone, make contractions more frequent and compromise placental blood flow. Track pad or underpad saturation, watch the resting pressure on the catheter and palpate the uterus between contractions. A sudden increase in resting pressure or a uterus that feels firm between contractions is a reason to pause and reassess rather than continue at the same rate.

The catheter itself can cause complications. Persistent uterine hypertonicity, new vaginal bleeding or sudden fetal bradycardia after insertion may signal placental abruption or perforation, and an absent pressure tracing despite palpable contractions can indicate misplacement. Infection is also possible, so monitor maternal temperature. Report these findings immediately.

Apply it to a hypothetical labour question

Consider a hypothetical patient receiving amnioinfusion for recurrent variable decelerations. Over the past hour the underpads have stayed dry, the resting tone on the catheter has risen and contractions are closer together. Options include increasing the infusion rate to improve cord cushioning, applying oxygen and documenting, continuing to monitor, or stopping the infusion and notifying the provider.

Stopping the infusion and notifying the provider is the best response because dry pads with rising tone suggest fluid is accumulating and the uterus is overdistending. Increasing the rate would worsen the problem. Continuing to monitor sounds safe but delays action when a clear warning trend is already present. Oxygen and documentation alone do not address the cause. Once the infusion is stopped, the nurse continues fetal monitoring, repositions the patient and stays with her while the provider reassesses.

Documentation and communication

Document the indication, the intrauterine resuscitation measures already tried, the start time, the fluid type and the volumes infused, along with estimated fluid return, resting tone, contraction pattern and fetal heart rate response. Comparing the amount infused with the amount returned is the practical check for overdistension.

Handover should state why amnioinfusion started and how the tracing has responded. If decelerations continue or the pattern deteriorates despite amnioinfusion, the team needs to reassess the plan for birth, so the nurse's trend description is an essential part of that decision. Clear communication also prevents the amnioinfusion line being mistaken for an intravenous line at a shift change.

Sources and further reading

Cochrane Database of Systematic Reviews: Amnioinfusion for potential or suspected umbilical cord compression in labour. Rationale of preventing or relieving cord compression by infusing fluid into the uterus, and trial evidence of fewer fetal heart rate decelerations and caesarean births with transcervical amnioinfusion.

Case Reports in Obstetrics and Gynecology: Complications associated with insertion of intrauterine pressure catheters. Placement away from the placenta, abruption and perforation presenting with bleeding, hypertonicity or bradycardia, absent waveform as a clue, and infection.

MSD Manual Professional: Fetal monitoring during labor and delivery. Internal catheters require ruptured membranes, and lateral positioning and rapid IV fluid as first responses to concerning heart rate patterns.