Introduction: Most lysosomal-storage disorders (LSDs) are diverse groups of autosomal-recessive inherited inborn errors of metabolism that encompass about 14 disorders linked with nonimmune hydrops fetalis (NIHF) and are responsible for 1–15% of NIHF cases, sialic acid-storage disease (SASD) is one of the most recurrent LSDs and pose a 25% estimated clinical risk of recurrence. Diagnosing or excluding SASD as an underlying cause for NIHF via quantifying sialic acid in amniotic fluid is crucial, since their recognition permits for prenatal diagnosis at an earlier stage in future gestations and enhances postnatal management. Aim: Quantification of free sialic acid (FSA) in amniotic fluid to evaluate the association between SASD and NIHF. Patients and Methods: The study has been conducted over 3 years and included two equally divided groups of 50 pregnant women: case group is composed of 25 pregnant females affected by NIHF and control group composed of 25 pregnant females not affected by NIHF. FSA was measured in amniotic fluid by tandem mass spectrometry. Results: SASD was diagnosed in six out of 25 cases, which represented 24% of case group, FSA was nonsignificantly higher among hydrops fetalis cases. The receiver-operating characteristic curve analysis has found that a cutoff value 11 μmol/l of sialic acid is the best threshold to expect SASD, with a sensitivity 24% and specificity 96%, hence, sialic acid had significant low diagnostic performance in differentiating case group from control group, where area under the curve is 0.322. Conclusion: SASD could lead to NIHF as prognosis, however, it is still a nondominant cause, meanwhile, as increased FSA helps directing DNA sequencing to the Sialin/SLC17A5 gene for biallelic mutations, which is a reliable diagnosis of SASD, we recommend including quantification of FSA in amniotic fluid using tandem mass spectrometry as a possible biochemical screen for LSD causes of NIHF.