Study setting
This study was a component of the Rajarata Pregnancy Cohort (RaPCo)16. The study was performed in Anuradhapura, the largest district (geographically) in Sri Lanka. All pregnant women newly registered from July to September 2019 and residing in Anuradhapura were invited to participate in RaPCo and it recruited more than 90% of newly registered pregnant women in the district.
Out of the total of 3,407 pregnant women recruited for the RaPCo study, all pregnant women more than 18 years of age with a period of gestation (PoG) less than 12 weeks at recruitment were included in the present study. PoG was confirmed retrospectively after the dating ultrasound scan. The exclusion criteria included pregnant women with uncertain dates; a history of physician-diagnosed renal diseases, hypertension, diabetes mellitus, ischaemic heart diseases, hyperlipidaemia, autoimmune diseases, and thyroid dysfunctions; pregnant women with any renal disorders, hypertensive disorders and hyperglycaemic conditions in previous pregnancies and multiple pregnancies. At the baseline assessment, a 75 g OGTT was performed, and all pregnant women with fasting plasma glucose greater than 126 mg/dL and 2-hr plasma glucose greater than 200 mg/dL were excluded. Pregnant women with systolic blood pressure greater than 140 mmHg and/or diastolic blood pressure greater than 90 mmHg at the first visit (screened using Omron OMRON HEM-7320) were also excluded. A follow-up assessment was performed towards the end of the second trimester. Study participants were invited to participate in the follow-up clinic at approximately 24-28 weeks of gestation. Only those who attended the clinics at 24-30 weeks were included in the follow-up analysis.
A sample of venous blood was collected in a plain tube by a qualified nursing officer. All collected samples were stored at -80°C for further analysis. Serum creatinine was assessed using a creatinine-sarcosine oxidase method (CREA-S) assay kit in a fully automated Mindray BS-240 clinical chemistry analyser. For the estimation of eGFR, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula was used.
A sample of healthy non-pregnant females of reproductive age participating in a large community-based chronic kidney disease (CKD) screening programme in Anuradhapura in 2015-16 were recruited as the comparison group17. To define the age groups (nonpregnant women) and PoG groups (pregnant women) for the analysis, a homogenous subset identification table of ANOVA was used. A one-way, two-way or repeated-measures ANOVA was used as appropriate for the analysis. The proposed threshold for ‘abnormal’ sCr was based on the 97.5th percentile.