Background: The World Health Organization has suggested that the health professional use the breastfeed observation aid for breastfeeding support. But there has not been any previous studies about the validity and reliability of the breastfeed observation aid in exclusive breastfeeding prediction.

Objective: To find the validity and reliability of the breastfeed observation aid and the cut-off point to predict exclusive breastfeeding at six weeks postpartum.

Materials and Methods: The breastfeed observation aid was translated to Thai. The validity was assessed by ten breastfeeding specialists. The reliability was tested by 130 singleton pregnant women who had delivered, without complications, at the HRH Princess Maha Chakri Sririndhorn Medical Center in the Nakhon Nayok province during the period of July 2014 to June 2015. The breastfeeding data at six-weeks postpartum were collected by follow-up done by telephone. The cut-off point of the breastfeed observation aid for the six-week breastfeeding prediction was calculated by the ROC curve.

Results: The exclusive breastfeeding rate at six weeks postpartum was 59.0%. The validity of the breastfeed observation aid was 93.2%. The intraclass correlation coefficient was 0.91 (95% CI 0.88 - 0.94). The inter-rater reliability was 73.7%. The cut-off point to predict breastfeeding at six week was 15 points. The sensitivity and specificity of tests for six-week exclusive breastfeeding predictions were 90.3 and 74.0, respectively. The area below the curve was 0.61.

Conclusion: The breastfeed observation aid in the Thai version had good validity and reliability. It could be used to predict the exclusive breastfeeding rates at six weeks postpartum.

Keywords: Breastfeed observation aid, Validity, Reliability