Revisiting the MOMS criteria for prenatal repair of spina bifida: should upper limit of gestational age and anatomical level be maintained?

ABSTRACT Objectives To determine if the lower extremity motor function of a fetus with open spina bifida deteriorates within a four‐week interval between their first prenatal motor assessment at 22 weeks of gestation and second presurgical evaluation in cases operated at later gestational age (26‐27 weeks of gestation), and to compare prenatal and postnatal motor function to the anatomical level of the lesion. Methods Multicenter cohort study involving cases from two centers that perform percutaneous fetoscopic repair of open spina bifida (SAFER technique). 94 fetuses with open spina bifida underwent two prenatal ultrasound evaluations before fetal surgery in approximately a four‐week interval, and one postnatal evaluation within two months of birth. Motor function classification was performed according to key muscle function from L1 to S1. Prenatal assessments were performed systematically by ultrasound at the first visit and the second evaluation occurring before fetoscopic repair. Postnatal evaluation was done via physical examination within the first two months of life. Each leg was analyzed individually; in case of discrepancy between the two legs, the worst level was considered for analysis. All motor level evaluations were compared to the anatomical level. Independent factors to a postnatal motor function reduction were assessed using a logistic regression model. Results Prenatal motor level was assessed at 22.5 (20.7‐24.3) and at 26.9 (25.4‐27.3) weeks’ gestation, with a median interval of 4 (2.4‐6.0) weeks. Median gestational age at surgery was 27 (25.6‐27.6) weeks. No significant difference in motor function was found between both prenatal evaluations (p=0.861). All prenatal and postnatal motor function evaluations were significantly different from the anatomical level (1st preoperative assessment, p=0.0023; 2nd preoperative assessment, p=0.0015; postnatal assessment, p=0.0333). Comparing prenatal versus postnatal motor function, we found almost 90% of babies maintained or improved motor function as compared to pre‐surgery level. In the logistic regression, lower anatomical level and higher difference between anatomical and motor level were found as independent factors for postnatal motor function (OR 0.237, p=0.002; and OR 3.44, p<0.001, respectively). Conclusions The 4‐week interval between the first evaluation and the “late” fetal surgical repair does not significantly change motor function, suggesting that later repair > 26 weeks does not have a negative impact on motor outcome. The preoperative neuromotor functional assessment via ultrasound was better predictive of postnatal motor function as compared to the anatomical level of the lesion in cases undergoing prenatal repair of open spina bifida and should be included in preoperative counseling. This article is protected by copyright. All rights reserved.