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Background & Aim: Randomized clinical trials (RCTs) are studies which are able to provide the most valid evidence to compare various interventions in health research. Biases can affect the quality of research and ultimately make the results of a study invalid. One of the most important biases is selection bias. The best way to reduce selection bias is the use of random allocation. The aim of this study is to provide comprehensive, practical and simple information regarding proper implementation of the random allocation process in randomized clinical trials.

Methods & Materials: A review study was performed using available resources and comprehensive analysis. For this purpose, we searched the relevant books & articles in databases including Medline, Scopus, Science Direct, Google Scholar and Magiran. Key words were randomization, random sequence, allocation concealment, randomized controlled trial, randomized clinical trial, and bias.

Results: From the literature review, we obtained 39 articles and one relevant book that their findings were presented in a simple language with practical examples in three parts including random sequences generation, random allocation concealment and implementation.

Conclusion: Selection bias in clinical trials has an adverse effect on the accuracy of results. In order to avoid it, researchers should employ proper methods in randomization and random allocation concealment, and report it in their articles properly. Therefore, researchers can obtain valid results through a better understanding of randomization and its proper implementation.

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Background & Aim: Pregnancy is one of the enjoyable and evolutionary aspects of women’s life, which is often associated with many stresses and concerns. Counseling is one of the most appropriate interventions to reduce concerns and increase the decision-making power of pregnant women. This study aimed to determine the effect of solution-focused group counseling on pregnant women’s worries.
Methods & Materials: A randomized clinical trial was conducted on 108 pregnant women with gestational age of 6 to 19 weeks and a score of worry ≥55, from May to September 2017 in health centers of Sabzevar University of Medical. The intervention group received a solution-focused counseling and the control group received routine prenatal care. Concerns of pregnant women were evaluated before, after, and two months after the intervention using the Farsi version of Cambridge Worry Scale. The data were analyzed using t-test, chi-square, and repeated measure analysis of variance through the SPSS software version 22. A P value less than 0.05 was considered statistically significant.
Results: The mean score of worry before the study was 58.9±5.9 for the intervention group and 58.8±4.37 for the control group, and no significant difference was observed. After the intervention, these values for the intervention group and the control group were 34.6±13.3 and 57.7±8.78, respectively. Two months after the study, these values were 31.1±10.1 and 54.6±10.9, respectively. The analysis of variance with repeated measurements showed that pregnant women’s concerns about childbirth, fetal health, maternal health, and family relationships were significantly reduced after the intervention and two months later (P<0.001). Women’s worries about socioeconomic issues were not significantly reduced after the intervention and two months later in comparison with the control group (P=0.563).
Conclusion: The solution-focused counseling is an effective way to reduce pregnant women’s concerns about maternal and fetal health, family relationships and childbirth. It can be used in conjunction with pregnancy care.
Clinical trial registry: IRCT20180123038485N1