Women have a lower haemoglobin concentration than men, either because of hormonal influences or because they are marginally iron deficient. If there is iron deficiency, menstrual blood loss is likely to be largely responsible. The literature is reviewed and discussed. The evidence is inconclusive and little is known about menstrual blood loss apart from the very wide range that may occur in apparently normal women.
A population study of menstrual blood loss and haemoglobin concentration was carried out in a Northumbrian mining village. 94 per cent (348) of the non -pregnant women between 17 and 45 years of age co- operated. Menstrual blood losses were measured for two consecutive periods. Haemoglobin, haematocrit, serum iron, iron binding capacity and fibrin degradation products were estimated from venous blood samples. A medical history was taken in each case, and a gynaecological examination was performed on the married women. Endometrial biopsy was attempted, but was successful in only a small proportion of cases.
The results confirmed the wide range of blood loss and the positively skewed distribution curve previously reported by other workers. There was a significant decrease in menstrual loss in women taking an oral contraceptive and a significant increase in those with an intra uterine contraceptive device. There was a positive correlation between menstrual loss and parity, but not with age. Within broad parity groups the women who had had heavy babies had larger menstrual losses than those with lighter babies; and menstrual loss may be related to stature, tall women lose more than short women.
Blood loss of over 45 ml per period is associated with significant changes in all the haematological indices measured, and a marked rise in the prevalence of anaemia (Hb <12 g /100 ml). This implies that many women are unable to tolerate losing blood equivalent to more than 1.4 ml per day.
Rises in the concentration of serum fibrin degradation products (F.D.P.) indicate pathological fibrinolysis. In this population there was no correlation between menstrual loss and F.D.P. concentration. Endometrial biopsy in 45 subjects did not show any histological pattern associated with either heavy or scanty blood loss. The gynaecological signs and symptoms discovered in the population were discussed.
Menstrual blood loss was thought to be associated with uterine size and blood flow. Although contradictory features remain, iron balance in women appears to be precarious.