In brief — the direct answer
Amnio-infusion is a specialized fetal medicine procedure where a small volume of sterile, warm saline is injected into the amniotic sac. This is typically done when there is a severe lack of natural amniotic fluid (**Oligohydramnios**). By 'filling up' the womb, we create a clear window for advanced ultrasound imaging, provide a cushion for the baby, or create the necessary space to perform life-saving fetal surgeries like FETO or shunting.
What is Amnio-infusion?
The procedure involves passing a thin needle through the mother's abdomen under ultrasound guidance. We then slowly infuse saline that has been warmed to the mother's body temperature.
Because ultrasound waves cannot travel well through air or compressed tissues, adding fluid allows us to see the baby's anatomy—such as the kidneys or the heart—with much higher clarity. It effectively acts like a 'contrast medium' that unlocks a better diagnosis in difficult cases.
Who is at risk?
Amnio-infusion is primarily used in two scenarios:
- Diagnostic (Amnio-infusion for diagnosis): When fluid is so low (e.g., from a slow leak or kidney issue) that we cannot see the baby's organs clearly enough to make a diagnosis.
- Therapeutic/Operative: Before procedures like FETO (for CDH) or Vesico-amniotic Shunting (for LUTO), we must create a pocket of fluid so the surgical instruments can move safely without touching the baby.
How we diagnose it
Before infusing, we assess the safety and targets:
- Pocket Search: Finding even the smallest space of fluid to guide the needle entry.
- Infection Screen: Ensuring there are no signs of maternal infection, as entering the sac when fluid is low requires extreme sterile technique.
- Volume Planning: Usually, we add between 200ml and 500ml of saline, depending on the stage of pregnancy.
What does management involve?
The procedure is carried out with precision:
- Local Anesthesia: The skin is numbed to ensure maternal comfort.
- Needle Placement: A fine needle is guided into the uterus.
- Warming: The saline is carefully warmed in a specialized medical heater to match 37°C, ensuring the baby is not shocked by a change in temperature.
- Observation: We watch the baby's heart rate continuously. As the fluid fills the sac, the baby often becomes more active and easier to visualize.
What are the outcomes?
Adding fluid may improve imaging or access for a selected procedure, but it does not correct the underlying cause of low fluid or guarantee a diagnosis or successful surgery. The fluid can be lost or absorbed. Risks include membrane rupture, infection, bleeding, contractions and fetal loss. Serial antepartum infusion to improve lung development is a distinct, selected or investigational pathway and must not be presented as routine treatment for every low-fluid pregnancy.
When to see a subspecialist
If you have been told that 'the fluid is too low to see the baby clearly' or that 'surgery is needed but cannot be done because there is no fluid,' you should seek a second opinion at a tertiary fetal therapy center.
Led by Dr. Gareth Waring, the MFM Unit utilizes amnio-infusion as a critical tool in our diagnostic and surgical arsenal. We provide the specialized equipment and expertise needed to safely manage pregnancies with low fluid levels, giving families the answers and treatments they need.