Cobas 701

At Wave 1, a venous blood sample (25 mL) was collected from each participant who provided consent. Samples were transported to a central laboratory in temperature-controlled shipping boxes where they were centrifuged, aliquoted into cryovials and stored at −80°C. Cystatin C and creatinine were measured simultaneously from frozen plasma. Cystatin C was measured using a second-generation particle-enhanced immunoturbidimetric assay (Roche Tina-quant) on a Roche Cobas 701 analyser. The assay has a measuring range of 0.40–6.80 mg/L and is traceable to the European reference standard material (ERM-DA471/IFCC) for cystatin C. Creatinine was measured on the same analyser using an enzymatic method traceable to isotope-dilution mass spectrometry. GFR was estimated using the Chronic Kidney Disease Epidemiology Collaboration equations for cystatin C [18 (link)] or creatinine [19 (link)].

The basic characteristics of all pregnant women, including age, height, pre-pregnancy weight, number of births, annual family income and alcohol consumption during pregnancy were obtained using a questionnaire. At 24–28 week of obstetric examinations, blood samples were refrigerated and centrifuged at 4 °C by a laboratory physician. Plasma and serum samples were stored at −70 °C until assayed. The OGTT test was performed as in previous studies [19 (link)]. Plasma glucose was measured at fasting and 1 h and 2 h after the 75 g glucose load. The plasma glucose, serum iron and calcium concentration were measured by an automatic biochemical analyzer (Cobas 701, Roche), serum ferritin was measured by Abbott i2000 automated immune analyzer. Adverse pregnancy outcomes included caesarean section, postpartum hemorrhage [20 (link)] (≥500 mL for vaginal deliveries and ≥1000 mL for deliveries by caesarean section), hydramnios[21 (link)] (≥2000 mL of amniotic fluid on ultrasound during pregnancy), premature rupture of membranes [22 (link)], preeclampsia [23 (link)] (SBP≥140 mmHg and/or DBP≥90 mmHg with urinary protein ≥0.3 g/24 h or random urine protein), preterm (gestational age <37 weeks), macrosomia [24 (link)] (birth weight ≥4000 g), neonatal hypoglycemia (blood glucose <2.2 mmol/L) and neonatal respiratory distress [25 (link)].