The definition of the term ‘substance abuse’ is difficult, since the use of non-medically indicated substances ranges from socially acceptable activities such as smoking and moderate alcohol intake, to abuse of intravenous drugs. Many types of abuse coexist.
Drug abuse is an increasing problem in inner-city maternity units. Most experience is from the USA, where up to 20% of pregnant women are thought to have abused illicit substances (usually marijuana or cannabis) at some point during their pregnancy.
Problems and special considerations
Problems may be related to the maternal effects of drug use, including acute intoxication, chronic organ impairment and the risk of infection with blood-borne viruses and endocarditis for intravenous drug users; the control of drug use and withdrawal during pregnancy, labour and the postnatal period; and the effects of drug abuse on the fetus and neonate.
Because delivery is seen as a ‘normal’ process and the mothers may not consider themselves as unwell, they may continue taking the drug(s) up to and through the peripartum period, thus presenting with the acute effects of intoxication, including altered mental state. This may make communication, and especially consent, difficult or impossible. Many addicts present for the first time in labour, with poor antenatal care. There is a greater incidence of sexually transmitted disease in addicts.
Alcohol
Alcohol abuse is a more widespread problem than abuse of many recreational drugs, with well-known manifestations including malnutrition, hepatic disease and cardiac impairment. Acutely intoxicated mothers may have concurrently taken other drugs and may display aggressive behaviour, making regional anaesthesia more challenging. If the stomach is full there may be increased risk of aspiration. Acute withdrawal typically reaches its worst about 24-36 hours after cessation of intake.
A particular feature of alcohol abuse in pregnancy is the fetal alcohol syndrome, which comprises craniofacial, neurological, cardiac, urological and musculoskeletal abnormalities. The upper safe limit of alcohol consumption in pregnancy has not been determined, but recent evidence suggests that even minimal intake may be associated with behavioural difficulties in the child.
Tobacco
Smoking is a common problem worldwide; in the UK its prevalence is about 20% in women of childbearing age. Maternal effects include premature rupture of membranes, placenta praevia, placental abruption and stillbirth. Impaired mucociliary function may increase the incidence of respiratory morbidity associated with general anaesthesia. In the neonate it has long been associated with low birth weight, although the precise mechanism is unclear.
Cocaine
Cocaine, or its water-insoluble derivative crack, causes central and peripheral dopaminergic and adrenergic stimulation resulting in euphoria, increased alertness, vasoconstriction and hypertension. Myocardial ischaemia, malignant arrhythmias or aortic dissection may occur. Cardiotoxicity associated with cocaine use is exaggerated in pregnancy, possibly secondary to increased production of its active metabolite or increased sensitivity of a-adrenergic receptors. Convulsions, intracranial haemorrhages and renal, hepatic and haematological impairment (including thrombocytopenia) have been reported. Cocaine abuse has been associated with increased incidence of spontaneous abortion, placental abruption, premature labour and fetal morbidity and mortality. Prolonged action of suxamethonium has also been reported.
Diagnosis may be difficult since its use is often denied, and the presentation may resemble that of pre-eclampsia and phaeochromocytoma. Urine remains positive for cocaine metabolites up to 3 days after use, and testing has been suggested in all at-risk groups (e.g. known users of other drugs, unbooked pregnancies).
Opioids
Opioid abuse is associated with hepatic, renal, pulmonary and cardiovascular impairment. Gastric emptying is delayed. The incidence of pre-eclampsia is reportedly increased. Addicts may require central venous cannulation because of their poor peripheral veins. Apart from these considerations, opioid withdrawal may complicate labour and delivery, and postoperative analgesia maybe difficult to provide. Withdrawal typically occurs 8-16 hours after cessation of intake and may present with tachycardia, hypertension, myalgia and agitation that worsen over 1-3 days. Opioid antagonists may precipitate acute withdrawal (including neonatal). Neonatal withdrawal may occur several days postpartum. Other neonatal effects of opioid addiction include increased fetal loss and fetal growth restriction.
Cannabis (marijuana)
Cannabis is a potent psychoactive drug that has been associated with increased incidence of arrest of labour and fetal morbidity. Cardiac arrhythmias including tachycardia or bradycardia, hypotension and myocardial depression have also been reported, especially if large doses are taken.
Amphetamines
Although less commonly abused than the above drugs, amphetamines acutely cause similar effects to cocaine including hypertension, arrhythmias, agitation, fever and confusion. Fetal effects include fetal growth restriction, premature labour and placental abruption. Acute ingestion may increase the requirement for anaesthetic drugs, whereas chronic abuse may result in central depression and depletion of catecholamine stores. Both regional and general anaesthesia may be accompanied by severe hypotension in chronically abusing patients.
Others
Experience with methylenedioxymethylamphetamine (MDMA; ‘ecstasy’) and solvent abuse in obstetrics is limited, but the same maternal manifestations may occur as are seen in nonpregnant subjects. Barbiturate abuse is less common now; its main problems are acute intoxication and chronic addiction/withdrawal.
Management options
Substance abuse may be difficult to identify in pregnant women but should always be considered in the differential diagnosis of any atypical case, for example when a woman presents with unexplained collapse or acute confusion. The timing of the most recent intake in relation to labour and delivery should be established. General management is directed at any specific organ impairment (including central nervous system depression) and providing appropriate nutrition, psychological support and counselling.
Management of acute alcohol withdrawal includes oral chlormethiazole or benzodiazepines. Alcohol infusion may also be used (10-150 ml/h of a 5-10% solution) although it may suppress uterine contractions.
If abusers of cocaine require general anaesthesia, pre-treatment with antihypertensive drugs should be considered, since severe hypertension and arrhythmias may follow tracheal intubation. Labetalol has been suggested as the drug of choice, as pure ^-blockade may precipitate severe hypertension and coronary vasoconstriction via unopposed а-stimulation. Glyceryl trinitrate has also been used. Benzodiazepines have been recommended to reduce sympathetic activity. Drugs causing sympathetic stimulation (e.g. ketamine) should be avoided. During regional anaesthesia, haemodynamic instability may be greater than normal and resistance to ephedrine has been reported, possibly related to noradrenaline depletion (directly acting vasopressors such as phenylephrine may be preferable). Increased requirement for analgesic supplementation during caesarean section has also been described.
Management of opioid addicts is often simplified if opioids are avoided altogether and local anaesthetic alone is used for regional analgesia and anaesthesia.
Key points
• Problems of substance abuse in pregnancy/labour include the maternal effects of chronic abuse, acute effects on presentation and fetal/neonatal effects.
• A high index of suspicion is required in all atypical cases on the labour ward.
Further reading
Jones HE, Deppen K, Hudak ML, et al. Clinical care for opioid-using pregnant and postpartum women: the role of obstetric providers. Am J Obstet Gynecol 2014; 210: 302-10.
Louw KA. Substance use in pregnancy: the medical challenge. Obstet Med 2018; 11: 54-66.
Scott K, Lust K. Illicit substance use in pregnancy. Obstet Med 2010; 3: 94-100.
Wong S, Ordean A, Kahan M; Society of Obstetricians and Gynecologists of Canada. SOGC clinical practice guidelines: Substance use in pregnancy, no. 256. Int J Gynaecol Obstet 2011; 114: 190-202.
Young JL, Lockhart EM, Baysinger CL. Anesthetic and obstetric management of the opioid-dependent parturient. Int Anesthesiol Clin 2014; 52: 67-85.