Drugs in pregnancy

Drugs used during pregnancy,can have temporary or permanent effects on the fetus. Any drug that acts during embryonic or fetal development to produce a permanent alteration of form or function is known as a teratogen.




Many physicians would prefer not to prescribe for pregnant women, the major concern being over teratogenicity of the drugs. The apprehension is not necessarily data driven and is mostly due to lack of clinical studies in pregnant women. This can result in inappropriate treatment of pregnant women and fetus. Use of drugs in pregnancy is not always wrong. For example, high fever is harmful for the fetus in the early months, thus the use of paracetamol (acetaminophen) is generally associated with lower risk than the fever itself. Similarly, diabetes mellitus during pregnancy may need intensive therapy with insulin to prevent complications to mother and baby.




Period of drug use


Pregnancy and development of fetus progresses through various changes. The period of one week from fertilisation to implantation of the fertilized egg is called preimplantation period. This is an 'all or none' period, .i.e an insult can either cause death or complete recovery. The period from the 8th day to the end of 8th week (2nd month) is the period of organogenesis during which the organs are formed in the fetus. This is the most crucial time with regard to 'structural malformations' and concern over teratogenicity of drugs. From the 3rd month week to the end of 9 months is the period of fetal maturation. Intake of drugs during this period may modify the 'function' of the fetal organs rather than causing gross structural malformations in the fetus, for example, aminoglycosides can affect the functioning of kidneys and also the hearing mechanism.






Categories of drugs


The Food and Drug Administration (FDA) has developed a rating system to provide therapeutic guidance based on potential benefits and fetal risks. Drugs have been classified into categories A, B, C, D and X based on this system of classification. Drugs like multivitamins that have demonstrated no fetal risks after controlled studies in humans are classified as Category A. On the other hand drugs like thalidomide with proven fetal risks that outweigh all benefits are classified as Category X.
Classification of a few important drugs/vaccines






Antibacterial agents


Category B : Penicillin, metronidazole, nitrofurantoin, cephalosporins, clindamycin, terbinafine, some macrolides e.g. azithromycin, erythromycin
Category C : Some aminoglycosides, chloroquine, quinolones, mebendazole, fluconazole
Category D : Tetracyclines, gentamicin, tobramycin
Cardiovascular drugs
Category B : Heparin (LMW)
Category C : Heparin (conventional), beta-blockers, (dihydropyridine) calcium antagonists, furosemide, digoxin, methyldopa
Category D : ACE inhibitors, ARBs, coumarins, thiazides, diltiazem
Central nervous system drugs
Category B : Acetaminophen, caffeine
Category C : Aspirin, clonidine, rofecoxib
Category D : Carbamezapine, valproic acid, diazepam, lithium
Vaccines
Category C : Tetanus toxoid, polio vaccine , BCG vaccine, hepatitis A vaccine, hepatitis B vaccine and rabies vaccine.



All about pregnancy:

• Pregnancy
• Complications of pregnancy
• Gestational hypertension
• Abortion
• Abortion law
• Health risks of unsafe abortion
• Immune tolerance in pregnancy
• Nutrition and pregnancy
• Prenatal care
• Maternal physiological changes in pregnancy
• Prenatal development
• Human embryogenesis
• Implantation (human embryo)
• Human fertilization
• Obstetrics
• Postnatal
• Sex during pregnancy
• Sex after pregnancy