Major Teratogenic Effects on Pregnancy

Major Teratogenic Effects on Pregnancy

Drugs which should not be used in pregnancy except in except in exceptional circumstances can be regarded as falling in this class. They are few in number. Thalidomide is not longer available. Its mode of actins was probably a combination of impairment of folic acid, riboflavin and glutamic acid metabolism, together with effects on the primordial neurons, particularly those related to the affected limbs.

 Cytotoxic Drugs –in Pregnancy

These are all potentially teratogenic in the first trimester, with their specific action on rapidly dividing cells. Some of them have proved less dangerous than was at first thought. Of the alkyl ting agents, cyclophosphamide and chlorambucil have been reported to cause major abnormalities, though successful pregnancies have also been recorded. With busulphan the abnormality rate is about 10%. Of the antimetabolities, the antifolate agents’ aminopterin and methotraxate cause abortion in 50% of women and a proportion of the surviving fetuses are grossly abnormal. In contrast, many women have had normal babies after taking 6- mercaptopurine throughout pregnancy and azathioprine seems to be benign in humans. There are some grounds for avoiding cytarabine, which affects the developing brain in animal experiments, and the antimitotic alkaloids such as actnomcin with their widespread toxic effects on mucleic acid synthesis, but there is no clear evidence of these effects in humans. Whilst data are limited, none of the cytotoxic agents has been demonstrated to be teratogenic in humans when given in the second and third trimesters.

Teracycline Drugs –in Pregnancy

 The teracyclines pass through to the fetus, chelate with calcium ortho-phosphate in the developing deciduous teeth and cause hypoplasia and brown Staining due to an oxidation product. In the third trimester, developing secondary dentition can also be affected.

Radioactive isotopes –in Pregnancy

Radioactive ¹³¹ I can pass through to the fetus and cause neonatal goiter and bypothroidism. Technetium can be used for radioactive scans –its radioactivity is minimal and its half-life short. ³² P may localize in the fetal bones and perhaps affect fetal bone marrow activity deleteriously.