Drugs and drugs of abuse in pregnancy

Published on 09/03/2015 by admin

Filed under Obstetrics & Gynecology

Last modified 09/03/2015

Print this page
rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 0 (0 votes)

This article have been viewed 950 times

Chapter 29 Drugs and drugs of abuse in pregnancy

The decision on whether to prescribe a drug to pregnant women must take into account the risk of the therapy and the risk of withholding the treatment. This requires a thorough up-to-date understanding of the drug and its risk/benefit ratio in pregnancy, as well as knowledge about the pharmacokinetics of the drug in pregnancy and the accurate assessment of the gestational age at the time of possible in utero exposure.

During the period from fertilisation to implantation, the pregnancy is relatively immune from teratogenic effects from medications, as the fetomaternal circulation has not developed. The period of organogenesis (17–70 days postconception) is when the embryo is most susceptible to teratogens. After this period, the risk of structural defects abates, but the fetus may be affected by anomalies in the functional development of organs and systems.

Teratogens

A teratogen is an agent that acts to irreversibly alter the growth, structure or function of a developing embryo or fetus. Recognised teratogens include:

Information on the teratogenic effect of specific medications is not always readily available, as few therapies have been specifically tested for safety and efficacy in human pregnancies. Current methods to assess teratogenic risk rely on pregnancy registries and case-control surveillance studies which have inherent shortcomings in design.

Information about the potential teratogenic risk of medications can be sourced from the Australian Government Therapeutic Goods Administration (see Box 29.1) and online databases (see Box 29.2).

Box 29.1 Australian categorisation of drugs in pregnancy