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.