Human toxic effects not predicted from animal experiments are often reversible, but even the most optimistic enthusiasts for drugs must shrink from the thought that their hands wrote prescriptions resulting in deformed, surviving babies.
Clinical data are, at present, inevitably open to doubt, and any list of suspected drugs must become obsolete and misleading very quickly. This topic must, therefore, be followed in the periodical press and manufacturers' up-to-date information.
The medical profession clearly has a grave duty to refrain from all unessential prescribing of drugs with, say, less than 10-15 years widespread use behind them, for all women of childbearing potential. It is not sufficient safeguard merely to ask a woman if she is or may be pregnant, for it is also necessary to consider the possibility of a woman, who is not pregnant at the time of prescribing, may become so whilst taking the drug.
Since morning sickness of pregnancy occurs during the time when the fetus is vulnerable, it is specially important to restrict drug therapy of this symptom to a minimum; but severe vomiting with its accompanying biochemical changes may itself harm the fetus.
Thus, before a drug is condemned as a cause of fetal damage, it is necessary to consider whether the disease for which it was given, or other intercurrent disease, might perhaps be responsible. Since the only way to be certain that a drug causes fetal damage in humans is to test it in humans, it is necessary that doctors should (a) suspect a drug-induced abnormality when it occurs and (b) report it to a central organisation (e.g. UK Committee on Safety of Medicines) or to a national register of all birth defects (such a register ideally should be kept plus a full drug history of the mother from prior to conception). Unfortunately, none of these requirements is easily satisfied. Minor congenital abnor malities are common in the absence of drug therapy and some may be virtually undetectable, e.g. reduced intelligence or learning ability. In addition, the more cautiously a new drug is introduced, the more difficult it is going to be to detect, by epidemiological methods, a capacity to cause fetal abnormality. This is especially so if the abnormality produced is already fairly common. Human frailty also causes any reporting system based on voluntary cooperation to be less than perfect.
The possibility of fetal abnormalities resulting from drugs taken by the father exists but has only begun to be explored.
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