Serial Amniofusion Via Subcutaneous Amnioport—Offered Only at Cincinnati Children’s Fetal Care Center—May Help Increase Survivability of Fetal Renal Failure

Fetal renal failure has historically been considered ultimately fatal for infants. Kidneys cannot be transplanted until age 2, and survival to transplant—or even to discharge from neonatal intensive care—has been discouragingly low. One contributing factor is the fact that lungs do not develop properly without consistent levels of amniotic fluid (fetal urine) produced by the kidneys. However, prenatal interventions to save the lungs may be considered futile care when the kidneys have failed.

Now, research at Cincinnati Children’s is showing that prenatal intervention to save the lungs during fetal renal failure can be effective and worthwhile—and that it may be more effective when fluid is infused through a subcutaneous amnioport rather than through commonly used percutaneous needle amniofusion. Cincinnati Children’s is the first to offer the new approach.

“The port is surgically placed into the uterus so we don't have to put a needle in and out of the uterus every time we want to put fluid in,” says Stefanie Riddle, MD, neonatal director of the Cincinnati Children’s Fetal Care Center. “Every time you put a needle in, it increases the risk of infection and breaking the water for the pregnancy. So, by surgically placing the port, we have one procedure at the beginning to avoid many smaller ones.”

The procedure to perform needle amnioinfusion is similar to amniocentesis, which is commonly performed and has a long record of safety.

“We’re just doing it for the opposite reason,” says Riddle. “Instead of taking fluid out, we’re putting it in.”

Comparing Results

To get a snapshot comparing the two methods of amnioinfusion, the team conducted a retrospective study from 2011-2020 on all patients with fetal renal failure who received amnioinfusion either by percutaneous needle (PN) or subcutaneous amnioport (SA). The results, presented by Mounira Habli, MD, Maternal-Fetal Medicine Specialist at Cincinnati Children’s Fetal Care Center, at the Society for Maternal-Fetal Medicine’s annual meeting in January 2022, are encouraging.

Out of 86 patients who met inclusion criteria, 65 were treated with PN and 21 were treated by SA (n=21). Baseline characteristics and complication rates were similar, and there were no maternal complications. Fetuses in the SA group all survived to delivery, compared to 91% for the PN group. The SA group also had significantly higher neonatal survival at 24 hours (90% compared to 61%) and at seven days (75% compared to 46%), as well as much higher rates of dialysis (60% versus 33%).

Why the difference? Compared to PN, SA had:

• Significantly higher number of amnioinfusions per pregnancy (15 compared to six)
• Higher total volume of amnioinfusion per pregnancy (4,210 ml compared to 2,840 ml)
• Smaller volume per amnioinfusion (233.7 ml compared to 453.2 ml)
• Longer duration of latency from first infusion procedure to last (8.9 weeks versus 6.2 weeks)

Some women are not candidates for serial amnioinfusions.

“It’s only offered to patients that have a singleton pregnancy because we don’t want to present a risk to other fetuses who are not in renal failure,” Riddle says. “Or, if the family cannot relocate to Cincinnati for treatment, we would not want to place an amnioport. Also, if there are other issues with the fetus, such as a severe heart defect or a significant genetic problem that would make it unlikely for the infant to do well, we would not offer fetal intervention.”

The Bigger Picture

While the results are promising for the future of prenatal intervention for fetal renal failure, Riddle is careful not to overstate the findings’ significance for families, who still face many challenges and difficult decisions.

“It’s still a really long road that ultimately ends in kidney transplant for most families,” Riddle says. “So, it’s a lot to take on, both during the pregnancy and after delivery.”

Cincinnati Children’s is working to change the prognosis for fetal renal failure, and progress is ongoing. In another “first,” in November 2020, our pediatric intensive care unit became the first in the nation to use the CArdio-Renal PEdiatric DIalysis Emergency Machine (Carpediem™), a specially designed machine for providing continuous kidney replacement therapy (CKRT) for infants. Its success has led to wider use and collaboration to help more infants bridge the gap to transplant.

“It’s exciting to see the progress being made here and to be a part of it,” Riddle says.

(Published February 2023)

Read More from the Perinatal Institute