Drugs in pregnancy

Drug use 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. Drugs may refer to both pharmaceutical drug and recreational drugs.

Prescription drugs
Many physicians prefer not to prescribe drugs for pregnant women due to concerns over teratogenicity. The apprehension is not necessarily data driven and is a cautionary response to the lack of clinical studies in pregnant women. The indication is a trade-off between the adverse effects of the drug, the risks associated with intercurrent diseases and pregnancy complications, and the efficacy of the drug to prevent or ameliorate such risks. In some cases, the use of drugs in pregnancy carries benefits that outweigh the risks. 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.

Pregnancy categories
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, and some multivitamins, that have demonstrated no fetal risks after controlled studies in humans are classified as Category A, while drugs like thalidomide with proven fetal risks that outweigh all benefits are classified as Category X.

Examples
Antibacterial agents


 * Category B : Penicillin, nitrofurantoin, 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 : Low molecular weight heparin


 * Category C : Unfractionated heparin, beta blockers, (dihydropyridine) calcium antagonists, furosemide, digoxin, methyldopa


 * Category D : ACE inhibitors, angiotensin II receptor blockers (ARBs), coumarins, thiazides, diltiazem

Central nervous system drugs


 * Category B : Acetaminophen,


 * Category C : Acetylsalicylic acid (ASA or Aspirin), clonidine, rofecoxib, risperidone, caffeine


 * Category D : Carbamazepine, valproic acid, diazepam, lithium

Others


 * Category C : Vaccines such as tetanus toxoid, polio vaccine, BCG vaccine, hepatitis A vaccine, hepatitis B vaccine and rabies vaccine.
 * Category '''X": Alcohol is one of the most dangerous drugs for a pregnant woman, especially in the early weeks of pregnancy.

Alcohol
Ethanol (alcohol) during pregnancy can cause fetal alcohol syndrome and fetal alcohol spectrum disorder.

Recreational drugs
Recreational drug use during pregnancy can cause various pregnancy complications.

Cannabis
Cannabis in pregnancy is the subject of various scientific studies, usually regarding whether it has effects on the child later in life.

Smoking
A number of studies have shown that tobacco use is a significant factor in miscarriages among pregnant smokers, and that it contributes to a number of other threats to the health of the fetus. Smoking and pregnancy, combined, cause twice the risk of premature rupture of membranes, placental abruption and placenta previa. Also, it causes 30% higher odds of the baby being born prematurely.

Others

 * Prenatal cocaine exposure is associated with, for example, premature birth, birth defects and attention deficit disorder.


 * Prenatal methamphetamine exposure can cause premature birth and congenital abnormalities. Other investigations have revealed short-term neonatal outcomes to include small deficits in infant neurobehavioral function and growth restriction when compared to control infants. Also, prenatal methamphetamine use is believed to have long-term effects in terms of brain development, which may last for many years.

By pregnancy stage
Pregnancy and fetal development progress through various changes. The period of one week from fertilisation to implantation of the fertilized egg is called the preimplantation period. This is an 'all or none' period, .i.e. an insult can either cause death or complete recovery can occur. The period from the eighth day to the end of eighth week is the period of organogenesis during which the organs are formed in the fetus. This is the most crucial time with regards to 'structural malformations' and concern over teratogenicity of drugs. From the third month to the end of nine 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 the kidneys as well as the hearing mechanism.