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Abstract
Pregnancy loss is one of the most common medical problems in reproductive age. About 25% of all attending pregnancy will experience at least one spontaneous abortion. Abortion is the expulsion of the products of conception before the age of medicolegal viability which is 28th week of gestation in Egypt or 20weeks or fetal weight <500 gm according to WHO definition.(1)
Abortion classified into two main groups, either spontaneous or induced abortion. Spontaneous abortion sub classified into five subgroups; threatened, inevitable, incomplete, complete, and missed abortion. (6) Missed abortion is that uterus retains dead products of conception behind a closed os for days or even weeks. (11)
The causes of abortion are maternal, fetal and paternal. Environmental pollutants play a definite role in the etiology of abortion. Lead is now considered to be one of the major environmental pollutants which pose a serious potential threat to the health of general population in both developed and developing countries. Exposure to lead usually occurs from a number of sources: Occupational, (31) lead based paint, (33) air, (34) water, (35) soil, (35) and food. (36)
Lead is absorbed mainly from gastrointestinal tract and lungs (ingestion and inhalation). Lead is excreted via the bile into the small intestine and hence eliminated in the feces. Lead readily crosses the placenta. Fetal blood lead levels are 80-100% of maternal values. The kinetic distribution of lead follows a three compartments model. from blood, lead diffuses into soft tissue (liver, kidney, bone marrow and brain) then into bone.(37)
There is no clearly recognized biological requirement for lead, and there is no definite manifestation of lead deficiency. Most of lead in blood is present in erythrocytes. The value of plasma is found not exceed 0.07 microgram per millimeter even in lead intoxication. (38)
Acute exposure to lead generally means: exposure for a short time, but a high levels.(39) Chronic lead poisoning means: exposure for a long time, for low lead level. Chronic lead poisoning characterized by neurological defects, renal tubular dysfunction and anemia. (40)
The male reproductive toxicity of lead has been known for a long time. There is a link between exposure to lead and reduced sperm count and affect semen characteristic. (46)
The effect of lead on female reproductive system is profound and multiple. Effects on menstrual status and pregnancy outcome manifested mainly as higher prevalence of menstrual disturbance, dysmenorrhea, anemia, emesis, toxaemia, threatened and spontaneous abortion in exposed females. (47)
During pregnancy, stores of lead deposited in bone over the lifetime may be mobilized in women who smoke or in women whose calcium intake is low. (51) During the preconception period, it interacts with the gamete (sperm or ova), either impair their fertilization or causes severe alterations in the resulting zygote that an early unrecognized abortion. In the early post conception period, the lead has definite embryotoxic effects .