an = 486. Data from Hallberg et al. (1966a), percentiles 10, 25, 50, 75, 90; Hallberg and Rossander-Hulthen (1991), percentile 95.
b The predicted values were estimated from a fitted log normal distribution with mean and standard deviation = -3.4312 ± 0.7783 (see text for methodology).
and the distribution is highly skewed. Although these high menstrual losses were found in apparently healthy women, it would be difficult to exclude unidentified hemostatic disorders (Edlund et al., 1996) or occult uterine disease as possible contributory factors. The investigators considered all the subjects they studied to be free of any condition that might affect menstruation. There are no criteria for identifying a subpopulation at risk for increased menstrual blood loss or for setting an upper limit for “normal” losses. Calculation of the EAR and RDA was therefore based on the complete set of observations.
Regression estimates of hemoglobin concentration and rates of change in hemoglobin concentration by age and gender have been derived by Beaton and coworkers (1989). Estimated hemoglobin concentration for females 14 to 20 years of age was 131 g/L + 0.28 × age (years).
The above data were used to compute median menstrual iron loss as follows:
(Blood loss [27.6 mL/28 days]) × (hemoglobin concentration [131 g/L] + [0.28 × age]) × iron content of hemoglobin (3.39 mg/g) ÷ 1,000.
Thus for adolescent girls, the median iron loss would be 0.45 mg/ day (Table 9-10). Discussion on menstrual iron losses prior to 14