Читать книгу Genetic Disorders and the Fetus - Группа авторов - Страница 107

In early pregnancy, the creatinine level in the AF is similar to that found in maternal serum, rising to reach values twice those of maternal serumat term. In early gestation, it seems that creatinine moves from maternal to fetal serum and then to fetal urine and AF.³⁷⁰ In late pregnancy, AF creatinine may originate from fetal muscle as well.

Creatinine is one of many indices that was used to assess fetal maturity.³⁷¹ Many workers tried to improve maturity assessments by combining the results of creatinine estimations, the percentage of lipid‐positive cells,³⁷² and the L/S ratio. The simultaneous assessment of the three parameters correlates well with fetal maturity in normal pregnancy. However, in the very cases of abnormal pregnancy states (including diabetes, Rh isoimmunization, hypertensive disorders, intrauterine growth restriction, and hydramnios) in which guidance would be invaluable, these estimations, both singly and together, remain insufficient (see earlier).

As suggested by Muller et al.,³⁷³ prognosis on fetal outcome can rely only on sonography in cases of severe or mild uropathies, the most frequent being the obstructive anomalies. Serum creatinine cannot be used as a marker of glomerular filtration (GFR) because it crosses the placenta and is cleared by the mother. Cystatin C has been shown to be an accurate marker of GFR in adults and infants, and can be considered as a marker of fetal renal tubular damage rather than a marker of GFR.

Mussap et al.²⁴¹ compared the diagnostic accuracy of cystatin C with that of creatinine in discriminating renal function in fetuses without ultrasonographic evidence of renal malformations from those with obstructive uropathies, and concluded that cystatin C is a sensitive biomarker for early identification of obstructive uropathies.