The aim of this study was to evaluate the length of time required to achieve full iodination using potassium tri-iodide as a contrast agent, prior to human fetal postmortem microfocus computed tomography (micro-CT) imaging. Prospective assessment of optimal contrast iodination was conducted across 157 human fetuses (postmortem weight range 2-298 g; gestational age range 12-37 weeks), following micro-CT imaging. Simple linear regression was conducted to analyse which fetal demographic factors could produce the most accurate estimate for optimal iodination time. Postmortem body weight ( = 0.6435) was better correlated with iodination time than gestational age ( = 0.1384), producing a line of best fit, = 0.0304 × body weight (g) - 2.2103. This can be simplified for clinical use whereby immersion time (days) = 0.03 × body weight (g) - 2.2. Using this formula, for example, a 100-g fetus would take 5.2 days to reach optimal contrast enhancement. The simplified equation can now be used to provide estimation times for fetal contrast preparation time prior to micro-CT imaging and can be used to manage service throughput and parental expectation for return of their fetus. A simple equation from empirical data can now be used to estimate preparation time for human fetal postmortem micro-CT imaging.