Table 4 Effects of various risk factors on hyperkalemia occurrence in 3,732 infants who were born at 32–36 gestational weeks.

Risk factors^a	Univariate analysis			Multivariable analysis^b
Risk factors^a	Crude odds ratio (95% CI)		P-value	Adjusted odds ratio (95% CI)		P-value
Combination of MgSO₄ and ritodrine
MgSO₄ alone vs. no usage	0.87	(0.47–1.61)	0.654	0.63	(0.33–1.20)	0.155
Ritodrine alone vs. no usage	1.19	(0.90–1.59)	0.224	1.20	(0.89–1.62)	0.231
Both MgSO₄ and ritodrine vs. no usage	1.78	(1.29–2.45)	<0.001	1.53	(1.09–2.15)	0.015
Obstetrical complications
pPROM	0.78	(0.58–1.04)	0.085	0.78	(0.57–1.07)	0.118
GH/PE/eclampsia/HELLP/AFLP	1.21	(0.89–1.65)	0.232	1.37	(0.96–1.96)	0.085
Placental abruption	0.60	(0.26–1.38)	0.233	0.46	(0.19–1.09)	0.076
Placenta previa/Low lying placenta	1.33	(0.85–2.09)	0.210	1.24	(0.76–2.02)	0.389
DM	0.64	(0.15–2.65)	0.535	0.85	(0.20–3.56)	0.818
GDM	1.53	(0.94–2.47)	0.085	1.63	(0.998–2.67)	0.051
Cesarean section	1.13	(0.87–1.47)	0.354	0.96	(0.71–1.31)	0.798
Delivery at <35 wk	1.45	(1.14–1.85)	0.003	1.46	(1.13–1.88)	0.004
Twins/triplets	1.15	(0.88–1.49)	0.303	1.11	(0.82–1.50)	0.501
Sex: male	0.91	(0.71–1.16)	0.994	0.92	(0.72–1.18)	0.511
SGA infants	0.88	(0.61–1.27)	0.496	0.87	(0.59–1.28)	0.477
Large-for-gestational-age infants	0.37	(0.05–2.68)	0.323	0.35	(0.05–2.61)	0.306
Apgar score at 1 min < 3	2.01	(1.21–3.36)	0.008	2.21	(1.29–3.81)	0.004

Abbreviations: CI, confidence interval; MgSO₄, magnesium sulfate; pPROM, preterm premature rupture of the membranes; GH, gestational hypertension; PE, preeclampsia; HELLP, hemolysis, elevated liver enzymes, and low platelets; AFLP, acute fatty liver of pregnancy; DM, diabetes mellitus; GDM, gestational diabetes mellitus; wk, gestational weeks; SGA, small-for-gestational-age; min, minute.
This analysis was performed using “Hyperkalemia set”.
^aRisk factors were determined based on both clinical relevance and univariate analysis as follows: combination of MgSO₄ and ritodrine, obstetrical complications, cesarean section, delivery at <35 wk, twins/triplets, infantile sex, SGA infants, large-for-gestational-age infants, and Apgar score at 1 min <3.
^bMultivariable analyses were performed using all the risk factors using the univariate analyses. However, birthweight was not used as a risk factor due to the close relationship with gestational weeks. In addition, the obstetric complication of TPL/shortened CL/CI was not used as a risk factor because either ritodrine or MgSO₄ was commonly used under these conditions. Excluding 40 patients with missing data for 14 variables, a total of 3,692 patients underwent multivariable analysis. abbreviations: TPL, threatened preterm labor; CL, cervical length; CI, cervical incompetency.

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