Obstet Gynecol Sci.  2020 Mar;63(2):117-125. 10.5468/ogs.2020.63.2.117.

Determination of maternal risk factors of preterm delivery: adjusted for sparse data bias; results from a population-based case-control study in Iran

  • 1Department of Epidemiology, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
  • 2Department of Communicable Disease Control and Prevention, Deputy of Health, Lorestan University of Medical Sciences, Khorramabad, Iran.
  • 3Department of Community Medicine, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran.
  • 4Department of Epidemiology, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
  • 5Lorestan University of Medical Sciences, Khorramabad, Iran.
  • 6South Tehran Branch, Islamic Azad University, Tehran, Iran.
  • 7Department of Nursing and Midwifery, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran.
  • 8Department of Biostatistics and Epidemiology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran. kamyarmansori@yahoo.com


To determine the maternal risk factors associated with preterm delivery in Iran.
A population-based case-control study was conducted including 48 women having preterm delivery (case group) and 100 women having term delivery (control group) between March 2007 and March 2012 in the maternity hospitals of the Selseleh County, Lorestan province, Iran. Information regarding maternal risk factors was collected by structured interview and reviewing the medical records. The maternal risk factors associated with preterm delivery were identified using univariate and multivariable logistic regression analysis after adjusting the sparse data bias. The area under the receiver operating characteristic (ROC) curves was estimated to evaluate the discrimination power of the statistical models.
Multivariable analysis demonstrated that multiparty (odds ratio [OR], 14.23; 95% confidence interval [CI], 1.60-127.05), history of gestational diabetes (OR, 0.10; 95% CI, 0.01-0.99), thyroid dysfunction (OR, 97.32; 95% CI, 5.78-1,637.80), urinary tract infection (OR, 16.60; 95% CI, 3.20-85.92), and taking care during pregnancy (OR, 0.12; 95% CI, 0.03-0.50) had significant impact on preterm delivery after adjusting the potential confounders. The area under the ROC curve for the aforementioned maternal risk factors was 0.86 (95% CI, 0.80-0.92).
Our study provides evidence for the associations between multiparty, history of gestational diabetes, thyroid dysfunction, urinary tract infection, as well as taking care during pregnancy, and preterm delivery.


Pregnancy; Risk factors; Premature delivery; Case-control studies; Iran

MeSH Terms

Bias (Epidemiology)*
Case-Control Studies*
Diabetes, Gestational
Discrimination (Psychology)
Hospitals, Maternity
Logistic Models
Medical Records
Models, Statistical
Risk Factors*
ROC Curve
Thyroid Gland
Urinary Tract Infections


  • Fig. 1 Receiver operating characteristic (ROC) curves of model 1 (all variables in the multivariable analysis) and model 2 (significant variables in the multivariable analysis).CI, confidence interval.


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