Pulmonary hypoplasia correlates with the length of anhydramnios in patients with early pregnancy renal anhydramnios (EPRA)

Abstract

Background: Early pregnancy renal anhydramanios (EPRA) occurs when the fetus is anuric before 22 weeks gestational age (GA) and is considered universally lethal. Serial amnioinfusions have successfully ameliorated the lethal pulmonary hypoplasia associated with EPRA and have resulted in cases of neonatal survival, peritoneal dialysis, and renal transplant.

Objective: We sought to evaluate the lung pathology of untreated fetuses and neonates that had EPRA.

Study design: This is a retrospective case series of all fetuses and neonates diagnosed with isolated EPRA that underwent autopsy at a single tertiary care center between 1987 and 2018. Autopsy data were correlated with ultrasound findings and GA at delivery. Fetal weights, lung weights, and lung developmental stage were recorded.

Results: Nineteen cases met criteria for analysis and ranged from 16 to 38 weeks GA at termination or birth. The observed-to-expected (O/E) lung-to-body-weight ratio was significantly associated with GA (r = -0.51, p = 0.03), such that as GA increased the O/E ratio decreased. When limited to patients >22 weeks, this relationship strengthened (r = -0.75, p = 0.01). Importantly, overall O/E body weight had no relationship with GA.

Conclusion: This study shows that the degree of pulmonary hypoplasia in EPRA increases with the length of anhydramnios. This suggests that amnioinfusions are likely to be of most benefit the soonest they can feasibly be initiated.

Fig. 1. Normal Lung Weight and EPRA Lung weight by Gestational Age (Overlay).

Scatter plot of lung-weight deviations from normal and duration of anhydramnios suggest a strong positive correlation, which is confirmed by a Pearson correlation coefficient (r) of 0.90812 (p < 0.0001).

Fig. 2. O/E Lung: Fetal Weight Ratio by Gestational Age.

Plot of observed/expected lung-to-body-weight ratio by gestational age suggests a negative linear relationship between these variables, which is confirmed by an r of 0.50570 (p = 0.03).

Fig. 3. Plot of observed/expected lung-to-body-weight ratio split by GA groups (≤22 vs. >22 weeks) suggests a negative linear relationship among both GA groups.

Pearson correlation coefficients indicate a strong negative correlation between observed/expected lung-to-body-weight ratio and gestational age among those >22 weeks (r = −0.74927, p = 0.01). However, among those ≤22 weeks r = −0.08292 with p = 0.86, indicating no linear relationship between these variables in this age group.

Fig. 4. Plot of observed and expected fetal weights by GA.

The one extreme outlier was a fetus of a diabetic mother with macrosomia. There were no significant differences in this case series compared to normal pregnancies.