Congenital malformations (second of two parts).

Abstract

As the 1st part of this discussion of congenital malformations indicated there has been only limited success in identifying environmental chemicals that may be responsible for human congenital malformations. Attention in this discussion is directed to major environmental causes (occupational hazards chemicals of predilection or habituation pharmaceutical drugs anticonvulsant drugs cytotoxic drugs vaginal spermicides and nutrition); and prevention of congenital malformations. Of all substances and situations persons are exposed to at work only anesthetics have aroused more than a mere suspicion of prenatal harmfulness. An analysis of a large number of reports alleging that increased rates of congenital malformation and spontaneous abortion were induced by exposure of pregnant women to anesthetic gases concluded only that some evidence indicated an increased rate of spontaneous abortion. Recent findings emphasize that spontaneous abortion is a soft sign. Personal habits and preferences involving a variety of substances have been suspected of causing prenatal maldevelopment. They are coffee tea and alcohol drinking; cigarette smoking; tobacco chewing; toluene and gasoline sniffing; and drug addiction. Addictive drugs and agents have not been convincingly associated with congenital malformations although increased stillbirth rates reduced birth weight and neonatal withdrawal symptoms have consistently been found in studies of the most commonly used drugs--heroin and methadone. Recent studies would seem to have laid to rest the accusation of teratogenesis that had been charged against coffee and by inference other products containing caffeine. Only reduced birth weight has been found to be associated with heavy coffee drinking. Like coffee drinking and cigarette smoking the drinking of alcoholic beverages during pregnancy has been reported to have a great variety of effects on the unborn--abortion growth retardation defects of the central nervous system mental retardation and congenital structural anomalies. None of the drugs most frequently prescribed or self administered has been clearly or consistenly implicated as being teratogenic including aspirin which has come under suspicion. Many such medications have been either called into question or accused outright. Those for which such charges are considered by current medical opinion to be dubious or unproved are listed in a table. 2 studies indicate a possible role of a deficiency of folate in the development of neural tube defects but acceptance of this association should be reserved until expanded trials are completed. The causes of the majority of congenital defects are still unknown. In time some of these defects and some of those now included in the multifactorial group may be controllable. It is to the understanding and control of such conditions that efforts and resources should be turned.