Information sources and examine individuals
This nationwide examine was based mostly on the Korean Nationwide Well being Insurance coverage (NHI) claims database. The Korean NHI system is a nationwide insurance coverage system operated by the Korean authorities and covers as much as 98% of the Korean inhabitants. The Korean NHI claims database incorporates sufferers’ sociodemographic data, their use of inpatient and outpatient companies, analysis, and medical therapy. The Worldwide Classification of Illnesses tenth Revision (ICD-10) code was used to document diagnoses on this database. It has been proven that the database gives dependable estimates of the prevalence of sure ailments in Korea20,21,22.
This examine included ladies aged > 19 years outdated who had no less than one supply between 2007 and 2018 (ICD-10: R4351, R4335, R4356, R4358, R3131, R3138, R3141, R3143, R3146, R3148, R4361, R4362, R4370, R4376, R4376, R4376, R4379, R7380, R4514, R4516, R4507, R4508, R4509. R4510, R4514, R4516, R4517, R4518, R1519, R4520, R5001, R5002). Amongst them, we excluded ladies who had diagnostic codes for hypertension or diabetes mellitus through the earlier 5 years. We recognized donors who donated a kidney between 2007 and 2016 by looking the standardized code for donor nephrectomy (R3272) and wholesome kidney donor (Z52.4). We excluded donors with multi-fetal gestation (a couple of fetus at a time) or a historical past of organ transplant (ICD-10: O30, O31, O632, O661, O663 and O692 for multi-fetal gestation; R3280, Q8040-Q8050, Q8140-Q8150, Q8061, Q8062, Q8080, Q8101, Q8102, Q8103, Q8121, Q8122, Q8123 for historical past of organ transplant). Every donor’s nephrectomy date served as her cohort-entry date.
The management group was chosen amongst pregnant ladies who had no historical past of hypertension, diabetes mellitus, or organ donation throughout the identical interval. We additionally excluded ladies who had multi-fetal gestation or a historical past of organ transplant. We randomly assigned a cohort-entry date to all ladies in accordance with the distribution of cohort-entry dates of donors (January 1, 2007, to December 31, 2017). We then matched six controls per donor on the premise of age at entry, yr of cohort entry, residency, earnings, variety of pregnancies, and the time to the primary being pregnant after cohort entry.
This examine was accredited by the Institutional Evaluate Board of Nationwide Well being Insurance coverage Service Ilsan Hospital (2021-04-009). The necessity for written knowledgeable consent was waived by the board owing to the retrospective nature of the examine. All strategies had been carried out in accordance with the related tips and rules.
Definition and examine endpoints
The first examine endpoint was gestational hypertension or preeclampsia. Secondary endpoints had been extreme gestational hypertension or preeclampsia, parity, low start weight (< 2500 g), stillbirth, ectopic being pregnant, and maternal dying. Ladies had been adopted till dying, immigration from Republic of Korea, or the tip of the examine interval (December 31, 2019).
We investigated being pregnant outcomes utilizing ICD-10 code and prescription information from the Korean NHI claims database (ICD-10: O10, O13, and O16 for gestational hypertension; O11 and O14 for preeclampsia; O15 for eclampsia; O365 for low start weight (< 2500 g); O364 for stillbirth; O00 for ectopic being pregnant; O03, O04, O05, O06, O07 for maternal dying). Gestational hypertension was outlined as new onset hypertension (blood strain ≥ 140/90) after 20 weeks of gestation within the absence of proteinuria. Preeclampsia was outlined as gestational hypertension with proteinuria (≥ 0.3 g per day or ≥ + 1 on a normal urine take a look at strip). The operational definition of extreme gestational hypertension or preeclampsia is outlined as a diagnostic code with a historical past of prescription of antihypertensive medicines. If there have been a number of prescriptions through the goal interval (from 10 months earlier than the supply day to the supply day), it was thought-about that the treatment was used.
Confounding variables
We investigated age at entry, time from entry to supply, variety of deliveries, residence, and earnings. The earnings quintiles of every insured individual signify the financial standing of the individuals and are based mostly on the quantity of medical health insurance funds. Comorbid situations of the sufferers had been evaluated on the premise of declare codes inside 5 years earlier than the cohort entry utilizing the Charlson comorbidity index23.
Statistical evaluation
To match being pregnant outcomes between residing kidney donors and non-donors, we carried out propensity rating matching to regulate for variations in affected person traits. Propensity scores had been estimated utilizing a number of logistic regression evaluation. Regression evaluation predicted the chance that every affected person could be handled based mostly on age at entry, complete variety of pregnancies, residency, and earnings. The discrimination and calibration skills of the propensity rating fashions had been assessed with the C-statistic and Hosmer–Lemeshow statistic. After the propensity score-matched pattern was shaped, we assessed the baseline variable steadiness between the 2 propensity-matched cohort teams.
Steady variables had been in contrast utilizing the paired t-test or the Wilcoxon signed rank take a look at, as applicable, and categorical variables had been in contrast with the McNemar’s or marginal homogeneity take a look at, as applicable24. The Mann–Whitney U and Wilcoxon signed rank checks had been used to match steady variables between topic teams, and the chi-square take a look at was used to match categorical variables. Cox proportional hazards evaluation was used to match being pregnant outcomes and danger components for gestational hypertension or preeclampsia between donors and non-donors. We adjusted the comorbid situations of the sufferers utilizing the Charlson comorbidity index. All statistical analyses had been carried out with SAS 9.2 (SAS Institute Inc., Cary, NC, USA) and RStudio v1.1.463 (RStudio Inc., Boston, MA, USA), and P values of lower than 0.05 had been thought-about statistically important.
