Drugs in pregnancy. Antihypertensives

Prevalence of Potential Drug-Drug Interactions Among Hypertensive Pregnant Women Admitted to a Tertiary Care Hospital

AIMS AND OBJECTIVES

The aim is to determine the frequency of potential drug-drug interactions (pDDIs) and to analyze the clinically relevant drug interactions among hypertensive pregnant women.

MATERIALS AND METHODS

This was an observational, cross-sectional study conducted at a tertiary care hospital. The prescriptions of the hypertensive pregnant women admitted to the hospital from June 2021 to December 2021 were analyzed for potential drug-drug interactions using the database from Lexicomp ® Solutions android mobile application version 7.5.4 (Wolters Kluwer, The Netherlands).

RESULTS

A total of 127 patients were evaluated during the study period of 6 months, of which 70 (55.12%) had pDDIs. The total number of pDDIs was 85, of which 70 (82.35 %) were clinically relevant interactions with the majority of them having moderate severity (81.17%) followed by minor severity (17.65%) and major severity (1.18%). The most frequently interacting pDDIs were between Labetalol and Lornoxicam (42.35%), followed by Labetalol and Diclofenac (22.35%).

CONCLUSION

This study highlights the high prevalence of potential drug interactions among hypertensive pregnant women and the need for rational drug use and strict vigilance in their monitoring.

Use of Prescribed Psychotropics during Pregnancy: A Systematic Review of Pregnancy, Neonatal, and Childhood Outcomes

This paper reviews the findings from preclinical animal and human clinical research investigating maternal/fetal, neonatal, and child neurodevelopmental outcomes following prenatal exposure to psychotropic drugs. Evidence for the risks associated with prenatal exposure was examined, including teratogenicity, neurodevelopmental effects, neonatal toxicity, and long-term neurobehavioral consequences (i.e., behavioral teratogenicity). We conducted a comprehensive review of the recent results and conclusions of original research and reviews, respectively, which have investigated the short- and long-term impact of drugs commonly prescribed to pregnant women for psychological disorders, including mood, anxiety, and sleep disorders. Because mental illness in the mother is not a benign event, and may itself pose significant risks to both mother and child, simply discontinuing or avoiding medication use during pregnancy may not be possible. Therefore, prenatal exposure to psychotropic drugs is a major public health concern. Decisions regarding drug choice, dose, and duration should be made carefully, by balancing severity, chronicity, and co-morbidity of the mental illness, disorder, or condition against the potential risk for adverse outcomes due to drug exposure. Globally, maternal mental health problems are considered as a major public health challenge, which requires a stronger focus on mental health services that will benefit both mother and child. More preclinical and clinical research is needed in order to make well-informed decisions, understanding the risks associated with the use of psychotropic medications during pregnancy.

Hypertensive Disorders of Pregnancy

Hypertensive disorders of pregnancy are common and contribute inordinately to maternal and fetal morbidity and mortality. Although not completely understood, recent clinical trials have provided important insights into pathogenesis of preeclampsia. Preeclampsia is considered a systemic disease with generalized endothelial dysfunction and risk of future cardiovascular disease. This review revisits the definitions and classifications of hypertensive disorders of pregnancy; discusses updates on pathophysiology, prevention, and early prediction of preeclampsia; reviews current management guidelines; and discusses potential risks and benefits associated with treatment. Improvement in management and outcomes of women with hypertensive disorders of pregnancy seems in sight in the near future.

Comparison of Efficacy and Safety of Intravenous Labetalol Versus Hydralazine for Management of Severe Hypertension in Pregnancy

Background

There is no consensus about the better intravenous drug between Hydralazine and Labetalol to control hypertension in cases of severe hypertension in pregnancy. Both drugs have their own advantages and disadvantages.

Methods

This is a prospective randomized controlled trial comparing the efficacy and safety of intravenous Labetalol versus Hydralazine for management of severe hypertension in pregnancy. A total of 152 eligible subjects were randomised in two groups consisting 76 subjects each by envelope method. Both the groups were comparable with respect to systolic, diastolic and mean arterial blood pressure at admission. One group received Labetalol and the other Hydralazine. The number of drug doses, the time taken to achieve target blood pressure and side-effects were noted.

Results

With a single dose, Labetalol (81.5%) was able to achieve target blood pressure in a significantly higher number of cases as compared to Hydralazine (69.5%). Labetalol could help in achieving the target blood pressure faster than Hydralazine. The incidence of maternal adverse effects was comparable between the groups. Fetal outcome was comparable in both groups.

Conclusion

Hydralazine and Labetalol both were found to be equally efficacious in reducing blood pressure in cases of severe hypertension in pregnancy. Labetalol achieved the target blood pressure faster than Hydralazine. The adverse effects of both the drugs were comparable.

Drug treatment of hypertension in pregnancy

Hypertensive disorders represent major causes of pregnancy-related maternal mortality worldwide. Similar to the non-pregnant population, hypertension is the most common medical disorder encountered during pregnancy and is estimated to occur in about 6-8 % of pregnancies. A recent report highlighted hypertensive disorders as one of the major causes of pregnancy-related maternal deaths in the USA, accounting for 579 (12.3 %) of the 4,693 maternal deaths that occurred between 1998 and 2005. In low-income and middle-income countries, preeclampsia and its convulsive form, eclampsia, are associated with 10-15 % of direct maternal deaths. The optimal timing and choice of therapy for hypertensive pregnancy disorders involves carefully weighing the risk-versus-benefit ratio for each individual patient, with an overall goal of improving maternal and fetal outcomes. In this review, we have compared and contrasted the recommendations from different treatment guidelines and outlined some newer perspectives on management. We aim to provide a clinically oriented guide to the drug treatment of hypertension in pregnancy.

Hypertension and antihypertensive drugs in pregnancy and perinatal outcomes

OBJECTIVE

Despite high rates of hypertension in pregnancy, the effects of hypertension have not been separated appropriately from the effects of the medications that are used. We evaluated the safety of exposure to antihypertensive medications during pregnancy, while accounting for disease effects.

STUDY DESIGN

A population-based retrospective cohort study was performed that compared all pregnancies of women with hypertension who were either exposed or unexposed to antihypertensive medications. A computerized database of the medications that were dispensed to pregnant women from 1998-2008 was linked with computerized databases that contained maternal and infant hospitalization records from the district hospital during the same period.

RESULTS

During the study period, 100,029 deliveries occurred; of those, 1964 pregnant women experienced chronic hypertension, and 620 neonates (0.6%) were exposed to at least 1 antihypertensive medication (methyldopa or atenolol) during pregnancy. A higher rate of intrauterine growth restriction (7.2% vs 2.1%, respectively; adjusted odds ratio [OR], 4.37; 95% confidence interval [CI], 3.00-6.36; P < .001), small for gestational age (3% vs 1.7%, respectively; adjusted OR, 2.23; 95% CI, 1.27-3.92; P = .005), and preterm deliveries (<37 weeks, 22.9% vs 8.0%, respectively; adjusted OR, 3.69; 95% CI, 2.90-4.69; P < .001) were noted among the pregnancies of women who were exposed to antihypertensive medications during the third trimester. Importantly, a similar association was detected when we compared women with chronic hypertension who were not treated during pregnancy (n = 1074) to women who had no chronic hypertension and who were unexposed to antihypertensive medications (n = 97,820).

CONCLUSION

Chronic hypertension with or without treatment during pregnancy is an independent and significant risk factor for adverse perinatal outcomes such as intrauterine growth restriction, small for gestational age, and preterm delivery.

Potentially increasing rates of hypertension in women of childbearing age and during pregnancy--be prepared!

Abstract

The incidence of hypertension in young women is likely to increase in the near future because of the rising rates of the metabolic syndrome, obesity and dyslipidaemia worldwide. Consequently, more women will be on antihypertensive agents, which have the potential for teratogenecity. It is also likely that the increasing number of young women with essential hypertension who become pregnant will develop pregnancy-specific disorders such as pre-eclampsia. Health professionals should be aware of the effects of hypertension in women during the childbearing years, as well as the impact of pre-eclampsia on cardiovascular disease in later life. Pre-conception counselling skills, and knowledge on the use of antihypertensives and the changes that occur during pregnancy should be added to the clinical armamentarium of all health professionals.

A comprehensive review of hypertension in pregnancy

Hypertension is the most common medical disorder encountered during pregnancy. Hypertensive disorders are one of the major causes of pregnancy-related maternal deaths in the United States. We will present a comprehensive update of the literature pertinent to hypertension in pregnancy. The paper begins by defining and classifying hypertensive disorders in pregnancy. The normal vascular and renal physiological changes which occur during pregnancy are detailed. We will summarize the intriguing aspects of pathophysiology of preeclampsia, emphasizing on recent advances in this field. The existing diagnostic tools and the tests which have been proposed for screening preeclampsia are comprehensively described. We also highlight the short- and long-term implications of preeclampsia. Finally, we review the current management guidelines, goals of treatment and describe the potential risks and benefits associated with various antihypertensive drug classes. Preeclampsia still remains an enigma, and the present management focuses on monitoring and treatment of its manifestations. We are hopeful that this in depth critique will stimulate the blossoming research in the field and assist practitioners to identify women at risk and more effectively treat affected individuals.

Older blood pressure medications-do they still have a place?

Hypertension is a major risk factor for cardiovascular disease, but control of hypertension remains inadequate, often because of poor patient adherence to prescribed medical regimens that are viewed as poorly tolerated and expensive. Physicians have largely stopped using some older blood pressure medications in favor of newer agents, mostly because of a presumed more favorable side effect profile. The investigators reviewed the pharmacologic properties and the evidence supporting the effectiveness and tolerability of several older blood pressure drugs: sympatholytic agents such as reserpine, methyldopa, and clonidine; diuretics such as chlorthalidone, ethacrynic acid and spironolactone; the vasodilators hydralazine and minoxidil; and others. In conclusion, some of these drugs are well studied and represent alternatives for patients who cannot afford or tolerate newer medications.

Tight control of mild-moderate pre-existing or non-proteinuric gestational hypertension

BACKGROUND

The question of the target blood pressure in pregnant women with mild-moderate hypertension continues to be an area of debate.

OBJECTIVES

To compare tight versus very tight control of mild-moderate pre-existing or non-proteinuric gestational hypertension for improving outcomes

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 March 2011), CENTRAL (The Cochrane Library 2011, Issue 3), MEDLINE (January 1966 to March 2011), and the metaRegister of Controlled Trials (31 March 2011). We handsearched citation lists of relevant publications, review articles, and included studies.

SELECTION CRITERIA

Randomized controlled trials of tight versus very tight control in pregnant women with mild or moderate pre-existing or non-proteinuric gestational hypertension.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. We expressed results as risk ratio (RR) or mean differences, together with their 95% confidence intervals (CI).

MAIN RESULTS

We included two studies (256 participants) with mild-moderate pre-existing or non-proteinuric gestational hypertension. There was no evidence of a difference between tight and very tight control groups regarding severe pre-eclampsia (risk ratio (RR) 1.28, 95% CI 0.97 to 1.70; two trials, 256 participants). More women in the tight group were hospitalized during their pregnancy (RR 2.53, 95% CI 1.14 to 5.63; one trial, 125 participants). There was no evidence of a difference in other outcome measures including fetal distress, IUGR, neonatal admission to a NICU, perinatal deaths, induction of labor and cesarean delivery between the tight and the very tight control groups. Gestational age at delivery had a non-significant mean difference (MD) of -0.15 weeks between the tight and very tight control groups (MD -0.15, 95% CI -1.52 to 1.21, random-effects, T² = 0.75, I² = 77%; two trials, 256 participants). The MD in birthweight between the tight and the very tight control group was not significant (MD -100.00 grams, 95% CI -363.69 to 163.69; one trial, 125 participants).

AUTHORS' CONCLUSIONS

For pregnant women with non-severe pre-existing or non-proteinuric gestational hypertension, there is insufficient evidence to determine how tight control of hypertension should be achieved to improve maternal and fetal-neonatal outcomes.

Antihypertensive drugs in pregnancy

Blood pressure targets and medications that are safe differ in pregnant women compared with nonpregnant individuals. The principles of treatment for mild, moderate, and severe hypertension in pregnancy, chronic versus gestational versus preeclampsia, and women hypertensive at term versus remote from term are reviewed. The choice of antihypertensive drugs also is discussed; methyldopa, labetalol, and nifedipine, among others, appear safe for use in pregnancy, whereas angiotensin converting enzyme inhibitors and angiotensin receptor blockers should be avoided. The management of increased blood pressure in the postpartum period, and agents to use in lactation, are also discussed.

Effects of guided imagery on blood pressure in pregnant women with hypertension: a pilot randomized controlled trial

BACKGROUND

Hypertension occurs in nearly 10 percent of pregnancies, and is associated with higher risk of infant and maternal morbidity and mortality than in normal pregnancies. Previous studies have suggested that relaxation therapies reduce blood pressure in nonpregnant adults. The objectives of this pilot randomized trial were to provide preliminary evidence of whether relaxation by means of guided imagery would reduce blood pressure in hypertensive pregnant women, and to assess the feasibility of a larger trial.

METHODS

A total of 69 pregnant women with hypertension were randomized to periods of guided imagery or of quiet rest, twice daily for 4 weeks or until delivery, whichever came first. Daytime ambulatory mean arterial pressure, systolic and diastolic blood pressure, and anxiety were measured weekly for up to 4 weeks.

RESULTS

Women allocated to guided imagery had lower mean arterial pressure elevations over time than those allocated to quiet rest (guided imagery: M = 1.58 mmHg, SD = 7.63; quiet rest: M = 5.93 mmHg, SD = 6.55; t = 2.36, p = 0.02). However, when adjusted for baseline mean arterial pressure and gestation, the effect was not significant (p = 0.14). Numbers of women prescribed antihypertensive medication postrandomization were similar (guided imagery: n = 16; quiet rest: n = 13, χ(2) = 0.74, p = 0.46). There was also no evidence of an effect on women's anxiety. Nearly 90 percent (n = 26) of the guided imagery group indicated that they would use it again.

CONCLUSIONS

Further rigorous study is warranted to determine effects of guided imagery on maternal blood pressure and perinatal health outcomes.

Antihypertensive treatment during pregnancy and functional development at primary school age in a historical cohort study

OBJECTIVE

To determine the functional development of children born after treatment of mild-to-moderate gestational hypertension with labetalol versus methyldopa, and no antihypertensive treatment.

DESIGN

Historical cohort study.

SETTING

Twelve Dutch hospital departments of obstetrics.

POPULATION

Live-born children born in these hospitals and prenatally exposed to labetalol, methyldopa, or bed rest because of mild-to-moderate gestational hypertension.

METHODS

Central nervous system development was measured with standard tests at 4-10 years of age. Linear regression techniques and Pearson's chi-square tests were used to compare the groups with regard to the outcome measures.

MAIN OUTCOME MEASURES

Intelligence quotient (IQ), concentration, motor development, and behaviour at primary school age.

RESULTS

A total of 202 children were included in the analyses. More children exposed to labetalol had attention deficit hyperactivity disorder (ADHD) than those exposed to methyldopa (OR 2.3; 95% CI 0.7-7.3), or those born to women who had been admitted for bed rest (OR 4.1; 95% CI 1.2-13.9). Sleeping problems seemed to be reported more frequently after prenatal methyldopa exposure than after exposure to labetalol (OR 3.2; 95% CI 0.6-16.7) or bed rest (OR 4.5; 95% CI 0.9-23.2), although the differences were not statistically significant. Test scores on other aspects of functional development did not differ between the three groups.

CONCLUSIONS

In this hypothesis-generating study, labetalol exposure in utero seemed to increase the risk of ADHD among children of primary school age, whereas prenatal methyldopa exposure might influence sleep. Further studies with appropriate sample sizes are warranted to determine the long-term effects of antihypertensive medications.

Use of traditional Chinese medicine among pregnant women in Taiwan

OBJECTIVE

To investigate the patterns of traditional Chinese medicine (TCM) use among pregnant women in the National Health Insurance program in Taiwan.

METHODS

Women who gave birth in Taiwan in 2006 were identified from the National Health Insurance Research Database. Claims for reimbursement following TCM ambulatory visits by these women were analyzed.

RESULTS

In total, 20.9% of women in the study who gave birth in 2006 used TCM during pregnancy, with older women more likely to utilize this form of care (23.9% of women >35 years of age vs 16.2% of women <20 years of age). There was an increase in the use of TCM for pregnancy-related problems such as hypertension (194 women before pregnancy vs 2163 during) and nausea/vomiting (220 women before vs 1648 during). The predominant modality (88.4%) of TCM treatment during pregnancy was herbal preparation.

CONCLUSION

Traditional Chinese medicine, with the exception of acupuncture, is popular among pregnant women in Taiwan. In addition to its efficacy, the safety of TCM during pregnancy requires future investigation.

A randomized trial of tight vs. less tight control of mild essential and gestational hypertension in pregnancy

OBJECTIVES

To assess the effects of applying a tight vs. a less tight control of mild chronic essential or gestational non-proteinuric hypertension in pregnancy.

METHODS

A randomized trial was conducted in 2006-2007 in the University of Ain Shams, Egypt. Eligible participants (n=125) were randomly assigned to either tight or less tight control of mild chronic (essential) or gestational (non-proteinuric) hypertension. The primary outcome measure was the development of severe hypertension during follow-up. Analysis was by intention-to-treat.

RESULTS

In the tight target group, adjustment of the dose with an increment of 191 mg yielded a mean dose of methyldopa of 1267+/-406 mg. Both systolic and diastolic BP levels were significantly less than in the tight target group. More women in the less tight group had severe hypertension during follow up (RR 3.167 and 95% CI 1.36-7.37). The rate of antenatal hospitalization was significantly higher in the less tight target group with a relative risk of 2.57 and 95% CI 1.16-5.70. The gestational age at delivery was significantly better in the tight target group. Preterm delivery and birth weight were not significantly different between the study groups.

CONCLUSION

Tight control of blood pressure reduces the rate of antenatal hospitalization and does not adversely affect perinatal outcomes in women with mild essential or gestational hypertension.

Identification of Photoproducts of Hexahydroquinoline Derivatives by GC-EI-MS and HPLC-ESI-MS

Photoproducts of hexahydroquinoline derivatives have been analyzed with gas chromatography electro ionization-mass spectrometry (GC-EI-MS) and high performance chromatography electrospray ionization-mass spectrometry (HPLC-ESI-MS). The study was performed on four HHQ derivatives: 2,6,6-trimethyl-3-carbomethoxy-5-oxo-4-(R-phenyl)-1,4,5,6,7,8-hexahydroquinoline; R=2'-Me, 3'-Me, 2'-MeO, and 3'-MeO. The photochemical degradation of each of the HHQ derivatives led to the appearance of one product. The photoproducts were identified as the corresponding tetrahydroquinoline analogues, which were formed by dehydrogenation of dihydropyridine moiety. In GC-mass spectra, the most frequent way of fragmentation was elimination of CH3* or CH3O* radical of the ester group. In the photoproducts substituted at 2'-position of the phenyl ring, elimination of isobutene (C4H8) was observed. In the photoproducts with 3'-position substituents, elimination of COOCH3* radical was noted.

Hypertension in pregnancy

Hypertensive disorders of pregnancy are the most common medical disorders of pregnancy and are associated with increased maternal and perinatal risks. The pathophysiology, diagnosis, and treatment are herein reviewed for chronic hypertension, preeclampsia, gestational hypertension, and severe hypertension. The benefits and risks of treating mild, moderate, and severe hypertension are discussed. A variety of oral and parenteral therapies are approved for the treatment of hypertension in pregnancy; methyldopa, labetalol, and nifedipine have been used safely in pregnancy, as has hydrochlorothiazide in those already taking this medication before conception. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are contraindicated in pregnancy because of adverse fetal effects, and atenolol should be avoided due to concerns with fetal growth. Severe hypertension >160/110 mmHg may require parenteral therapy, and treatment with intravenous labetalol now supplants the use of hydralazine. Women may remain hypertensive for a period postpartum and require treatment for a short interval. Early or severe preeclampsia warrants workup postpartum for secondary causes. Pregnancy induced hypertension or preeclampsia are emerging as risk factors for future cardiovascular risk.

The Team Approach to Pregnancy and Congenital Heart Disease

The successful pediatric management of congenital heart disease has resulted in increasing numbers of these patients in the reproductive age group and increasing clinical challenges for their physicians. These challenges can be met successfully, with improved results for mother and child, through a concerted comprehensive team approach that relies on a thorough understanding of the patient's underlying cardiac pathology and its anticipated interaction with the pregnancy, and ongoing close evaluation and communication with a team of trained and experienced specialist, including (but not limited to) cardiologist, obstetricians, anesthetists, pediatricians, clinical nurse specialists, and clinical geneticists. Such teams are not always available locally and it will be necessary to refer medium- and high-risk patients to a specialized tertiary care center.

Goodpasture Syndrome in a Pregnant Woman

BACKGROUND

Goodpasture syndrome, an immunologic disorder characterized by glomerulonephritis and pulmonary hemorrhage, rarely presents in pregnancy.

CASE

We describe a patient who was diagnosed with Goodpasture syndrome in her second trimester. She required daily hemodialysis, intermittent plasmapheresis, and immunosuppressive therapy. Her pregnancy was complicated by hypertension, and she delivered a low birth weight neonate prematurely at 26 4/7 weeks of gestation by cesarean due to nonreassuring fetal status. Deterioration in the fetal status may have been secondary to complications of hypertension, in addition to prematurity.

CONCLUSION

Goodpasture syndrome in pregnancy may be associated with significant maternal and fetal morbidity.

Diabetes and pregnancy

Diabetes in pregnant women is associated with an increased risk for maternal and neonatal morbidities and remains a significant medical challenge. Fortunately, the prognosis has changed dramatically, related to an increased clinical awareness of the potential risks for the mother and the infant, better health care and intensive treatment strategies to maintain the closest to normal metabolic milieu. Diabetes and pregnancy may be divided into pregestational diabetes (women previously diagnosed with type 1 or type 2 diabetes) and gestational diabetes defined as any glucose intolerance detected during pregnancy that has evolved from a diagnosis associated with the metabolic risk of type 2 diabetes to a clinical condition associated with higher risks for maternal and perinatal morbidity. Early diagnosis of gestational diabetes is an important step to improve outcomes and systematic or selective screening with the OGTT should be established. Associated with the global epidemic in diabetes, pregnancy associated with diabetes is saturating high-risk obstetric clinics and neonatal intensive care units, becoming a heavy burden to the health care systems around the world.

Antioxidant activity and inhibitory effects of hydralazine on inducible NOS/COX-2 gene and protein expression in rat peritoneal macrophages

This study investigated the effects of the peripheral vasodilator hydralazine on in vitro generation of reactive species of oxygen (ROS), nitrogen (RNS) and prostaglandin (PG) biosynthesis in elicited murine peritoneal macrophages, and on the gene expression and protein synthesis of two key enzymes in the inflammatory process, inducible NO(*) synthase (NOS-2) and inducible cyclooxygenase 2 (COX-2). Hydralazine at 0.1-10 mM inhibited both extracellular and intracellular ROS production by inflammatory macrophages, by a ROS-scavenging mechanism probably affecting superoxide radical (O(2)(*-))-generation by xanthine oxidase (XO) and nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) oxidase. Hydralazine at 0.1-10 mM significantly reduced NO(*) generation, and this effect was attributable to an inhibition of NOS-2 gene expression and protein synthesis. At 1-10 mM, hydralazine also effectively blocked COX-2 gene expression which perfectly correlated with a reduction of protein levels and PGE(2) synthesis. These data suggest that hydralazine, at the concentrations tested, show antioxidant properties and strongly attenuates the macrophage activation.

Prescription drugs and pregnancy

Prescribing drugs in pregnancy is an unusual risk-benefit situation. Drugs that may be of benefit or even life-saving to the mother can deform or kill the fetus. However, the risk to the fetus should not be exaggerated. There are only approximately 20 drugs or groups of drugs which are known to cause birth defects in humans. For one of these drugs to cause birth defects, a number of criteria must be fulfilled. The drug exposure must take place at a critical stage of pregnancy and the dose must be high enough to cause a threshold of exposure for an appropriate duration of time. For most of the known human teratogens, > 90% of pregnancies exposed during the first trimester result in normal offspring. Although only a few drugs are known to cause birth defects in humans, uncertainty about the safety of the majority may lead to underprescribing for pregnant women and women of childbearing age. Epidemiological studies of pregnancy outcome after specific drug exposures are often superficially reassuring, but most are severely limited in their power to detect adverse outcomes. Safety in animal studies may also be reassuring but species differences demand caution in this interpretation. Concerns about prescription drugs in the first trimester, when they can cause birth defects, are mostly quite different to concerns about use in the second and third trimesters. As the fetal organ systems mature, the fetus can be affected by the pharmacological activity of the drug in the same way as the mother. Many drugs have pharmacological effects on the fetus in the second and third trimesters but in most cases, they are well recognised and can be managed or avoided. The material presented in this paper is mostly concerned with the 'risks' associated with drugs in pregnancy. No attempt has been made to quantitate the possible benefits to the mother or fetus. Communicating the risk-benefit situation to the patient is always a challenge for physicians with limited time and sometimes limited knowledge. Fear of litigation is an unfortunate and an unwanted parameter in the assessment. Better knowledge of the parameters that determine teratogenicity may allow physicians to feel more confident in assessing the risks and benefits associated with prescribing in pregnancy.