Exposure to toxic chemicals during pregnancy may affect the mother and induce changes in the physiology and development of the embryo, fetus, neonate or infant.
The Environment Health Criteria document number 30 on "Principles for Evaluating Health Risks to Progeny Associated with Exposure to Chemicals During Pregnancy" (1984) was prepared by the IPCS as an aid in the design and assessment of studies on the association between exposure to chemicals during pregnancy and defective development. This document is being updated.
The effects on the health of mother and child will depend on the type of chemical, dose and length of exposure, and period of pregnancy during which the toxic exposure occurred (first, second or third trimester). For example, labor may be affected by pharmaceuticals if absorbed near the time of delivery, as in the case of aspirin overdose, which may induce postmaturity and increase the duration of labor, as well as the incidence of antepartum and postpartum hemorrhage.
Circumstances of exposure to chemicals during pregnancy may be accidental, environment, occupational or intentional.
The incidence of accidental poisoning in pregnant women follows the usual trends of accidental exposure to chemicals in the population. However, the consequences of anoxic injury to the mother and fetus may have severe consequences. For example, acute accidental exposure to carbon monoxide and pyrolysis products during fires or incomplete combustion in non-ventilated areas may affect the mother and produce ferotoxic effects (Elkharrart et al, 1991; Ellenhorn, 1982). Over-the-counter drugs and other pharmaceuticals are used during pregnancy to avoid vomiting, stress, insomnia, headaches and hypotension, and no drug is considered 100% safe to the developing fetus (including topical preparations). In fact, the effect of a drug on the fetus may not necessarily be the same as the intended therapeutic effect on the mother.
The exposure of the pregnant women to environmental pollutants such as methylmercury, lead, polyhalogenated biphenyls (dioxines) and pesticides has produced adverse effects on the mother and especially on the offspring. Some of the incidents were tragic due to the large population groups affected and the severity of the effects (e.g. Minamata Bay). One of the most significant occupational and public health concerns is excessive lead exposure form lead-based paint, drinking water, household dust, contaminated soil and air near membrane rupture, pre-eclampsia, pregnancy hypertension and premature delivery (Winder, 1993; Davis et al 1993, Mushak, 1993).
Occupational exposure of pregnant women occurs more frequently in countries where labor regulations are loose, or where the potentially adverse effects of industrial and agricultural chemicals on human health are ignored. It is estimated that approximately 42% of pregnant women are also working women (Brix, 1982). If pregnant women work in the chemical industry, in areas where pesticides are heavily used, or in cottage industries where safety measures are poor, the risk of exposure to toxic chemicals is high. Women who work in rural areas may also be exposed to envenoming due to poisonous or venomous animals. For example, the bite of Bothrops snakes has been reported to cause disseminated intravascular coagulation, acute renal failure and abruptio placenta with stillbirth (Zugaib et al, 1985)
However, one of the main areas of concern ( expressed mainly by developing countries) relates to exposure to agrochemicals during reproductive years and pregnancy.
Intentional poisonings tend to be rare during pregnancy. It is generally accepted that pregnant women seldom attempt suicide. However, pregnancy (especially if unwanted) can be an associate factor in about 5% of all female suicides (Whitlock and Edwards, 1968). Abortion attempts through the ingestion of highly toxic products or plants concoctions are common in some countries, where abortion is illegal and unacceptable by the family, the local community or society. Abortion with high doses of synthetic prostaglandins use intravaginally has been implicated in complications such as bleeding, sepsis and uterine rupture (Austin et al 1997; Costa and Vessey, 1993).
Drug abuse may lead to acute overdoses and adverse health effects on the mother and the child. Cocaine overdose may cause headache, blurred vision, abdominal pain and seizures in the third trimester of pregnancy symptoms associated with pre-eclampsia and eclampsia (towers et al, 1993; Weddington, 1993). In countries whgre the incidence of drug abuse is high, special attention is need to diagnose and manage the course of overdosed in pregnant women.
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