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12. Drugs in pregnancy


Drug use in pregnancy should be reduced to a minimum. This is because the embryo and foetus are more sensitive to the effects of all drugs. Rapidly developing tissues are particularly vulnerable. The placenta is not a barrier to the passage of most drugs, so it should be assumed that drugs taken during pregnancy will reach the foetus in at least small amounts. Pregnant women who are identified as using drugs should be referred for specialist management.




It has been known for centuries that alcohol taken in excess during pregnancy may damage the foetus.

The risks of prematurity, small for gestational age and miscarriage as well as a wide variety of congenital abnormalities are all trebled in drinkers, and these should be regarded as non-specific risks of alcohol consumption.

The effects of alcohol on the foetal brain, however, are fairly specific and the following clinical points are important:

  1. The time of greatest sensitivity of the foetal brain is the third trimester, so that if the patient can achieve abstinence by then, the baby's brain may escape damage.
  2. The foetal brain is exquisitely sensitive to alcohol during the third trimester and the first twelve months after birth. Epidemiological studies have failed to demonstrate a threshold dose for risk. Therefore total abstinence is the only responsible advice to give.
  3. Foetal Alcohol Syndrome should only be diagnosed if the criteria are met (see below). Other foetal effects seen in association with alcohol should be called Foetal Alcohol Effects (FAE).

    Risk factors for Foetal Alcohol Syndrome (FAS)

Characteristics of Foetal Alcohol Syndrome (FAS)

A diagnosis of Foetal Alcohol Syndrome requires: (9)

  1. growth retardation
  2. CNS abnormalities
  3. facial abnormalities

    Other abnormalities include:


    Smoking during and after pregnancy can have many adverse effects on the child.

    The most important toxin in tobacco smoke is nicotine which has been shown to impair placental function by:

    • reduced placental vascularisation
    • constriction of placental arterioles
    • thickening of the endothelium of placental blood vessels

      thus interfering with placental well being and maturity as well as nutrient transfer. Carbon monoxide levels in the mother also reduces oxygen availability for foetal tissues.

      Health risks of smoking during pregnancy

    • Retardation in foetal growth; on average a reduction in birth weight of 200 g.
    • It should be highlighted to women that smoking cessation is still beneficial to the foetus at any time during the pregnancy.
    • Those women who stop smoking before becoming pregnant have babies of similar birth weight to women who have never smoked.
    • Women who stop smoking in the initial 3-4 months of pregnancy and abstain for the rest of the pregnancy have similar weight babies as non-smoking women.
    • Even women who stop as late as week 30 of their pregnancy have heavier babies than those women who smoke throughout the entire pregnancy.
    • The risk of low birth weight increases by about a third in mothers who continue to regularly smoke more than 10 cigarettes per day after the fourth month of pregnancy.
    • Congenital malformation – an association has been found between smoking and cleft palate, microcephalus and club foot.
    • Spontaneous abortion – higher rates in women who smoke and is also related to the number of cigarettes smoked.
    • Effects on foetal heart rate – nicotine increases the baby's heart rate and carbon monoxide results in impaired oxygen transport.
    • Paternal and passive smoking also has a harmful effect on the unborn child.
    • Maternal undernutrition.
    • The risk of harmful effects to the foetus is greater in older mothers who smoke than in younger mothers who smoke.

    Perinatal risks

    • Increased risk of perinatal mortality (about 35%)
      • greater incidence of placenta praevia, abruptio placentae, ante partum haemorrhage and premature delivery
      • higher incidence of complications during pregnancy can result in increased likelihood of stillbirths, asphyxia, pneumonia, prematurity and neonatal deaths from respiratory distress syndrome
      • these risks are partly as a consequence of the absorption of harmful chemicals through the placenta, the most important toxin being carbon monoxide.

    Infant risks

  4. Respiratory disorders
    • Sudden Infant Death Syndrome
    • increased incidence of bronchitis, pneumonia, acute otitis media and persistent middle ear effusions, eye, nose and throat disorders and impaired lung development
    • parents and others who smoke can cause as well as aggravate disorders such as asthma, wheezing, and allergies in their children.
  5. Long-term body growth – smoking during and after pregnancy may affect the attainment of final height and also retard the growth of head and chest circumference.
  6. Increased risk of febrile seizures.
  7. School performance may be retarded through repeated absences due to illness, malaise and hearing problems.
  8. Increased risk of meningococcal infection.
  9. Increased problems for children with cystic fibrosis.
  10. Babies can also be at risk from mothers who smoke and breast feed
    • smoking reduces breast milk supply
    • nicotine can pass into the child's bloodstream from the breast milk
    • breast milk is still beneficial to the child, since it protects from infection, but many smoking mothers are unaware of the transmission of harmful chemicals to the child through their breast milk.

    Foetal Tobacco Syndrome

    'Foetal Tobacco Syndrome'Wakefield, M. and Wilson, D. Smoking during pregnancy: a literature review and working paper of the options for intervention. South Australian Health Commission, Adelaide, 1988(10) is a name that has been given to the growth retardation associated with maternal smoking.

    The term can be used when at least three of the four conditions listed below occur:

    1. The mother smoked 5 or more cigarettes per day throughout the pregnancy
    2. The mother had no evidence of hypertension during pregnancy specifically:
      • no preeclampsia
      • documentation of normal blood pressure at least once after the first trimester
    3. The newborn has symmetrical growth retardation at term (37 weeks), defined as:
      • a birthweight less than 2 500 g
      • a ponderal index [(weight in grams)/(length in centimetres)3 x 100] greater than 2.32
    4. There are no other obvious causes of intrauterine growth retardation (eg congenital infection or anomaly).

      Other risks to children

      • Poisoning – by cigarettes and cigarette ash
      • Burns and eye injuries from lit cigarettes
      • Matches and lighters – can cause serious accidents
      • Role models – children are more likely to smoke if their parents do.


      A specific concern with cannabis is the cumulative effect of _9 tetrahydrocannabinol (THC), and how this may affect the child before and after birth. THC, the most active component of cannabis accumulates in the fatty tissues of the brain. At this stage of our knowledge it is difficult to ascertain a causal relationship between cannabis and damage to the foetus, often because mothers use combinations of alcohol, tobacco and cannabis. Health risks pertaining to cannabis use during pregnancy should be considered possible and a conservative approach taken.

      Several abnormalities of foetal development have been reported when pregnant women have used cannabis heavily. It must be emphasised that there is a high prevalence of cigarette and alcohol intake in association with cannabis use. Therefore it is difficult to differentiate the direct effects of cannabis.

      Suggested health risks of smoking cannabis during pregnancy

      • Lower birth weights, length and head circumference
      • Possible impairment of foetal brain development
      • Relative prematurity
      • Malformations
        • toxic effects of the drug may possibly cause foetal anomalies
      • Higher rate of miscarriage and perinatal death
      • Cannabis use may reduce the foetal blood supply
      • Cannabis may exacerbate other risk factors in pregnancy
      • THC accumulates in breast milk
        • may diminish milk supply.

      Effects observed in newborns

      • Lethargic and slow to gain weight
      • Increased startle reflex
      • Tremors
      • Poor self-quieting
      • Failure to habituate to light
      • Possible long-term developmental and behavioural effects are yet unknown.


      Regular use of illicit opiates endangers the health of the woman and her foetus through continual change in blood heroin levels, exposure to a diverse range of drugs and contaminants, and infections consequent upon injecting drug use. Due to lifestyle factors associated with opiate dependency, pregnant women in this population do not usually have adequate nutrition, necessary rest or sufficient antenatal care.

      Health risks of taking opiates during pregnancy

      General medical risks associated with injecting drug use that may affect the health and development of the foetus:

      • HIV
      • hepatitis B and hepatitis C
      • endocarditis
      • malnutrition
      • anaemia
      • sexually transmitted diseases.

      Obstetric complications

      • Increased risk of miscarriage
      • Increased risk of intrauterine growth retardation
      • Increased risk of other obstetric complications – placental insufficiency, foetal distress, intrauterine death
      • Risk of physical dependence in the foetus and subsequent withdrawal in the neonate (known as Neonatal Abstinence Syndrome)
      • Opiate withdrawal or detoxification during pregnancy may induce abortion, or premature labour/foetal distress particularly before the 14th week or after the 32nd week respectively. If withdrawal is to be attempted it ideally should be undertaken between the 14th and 32nd weeks under close supervision.

      Opiate management options for pregnant drug-dependent women

      Opiate-dependent women generally have two management options:

      • reduce opiate intake independently or attempt detoxification. Such a task is enormously difficult and results in many users returning to opiate use. Constantly changing states of intoxication and withdrawal can stress the foetus, particularly in the first and third trimesters
      • enrol in a methadone maintenance program.

      Advantages of methadone maintenance programs

      • It provides the woman with a daily dose of methadone which eliminates the fluctuating heroin blood levels experienced by mother and foetus during illicit opiate use.
      • Women in methadone maintenance programs tend to have longer pregnancies, fewer obstetrical complications and infants who are larger for their gestational age than similar populations not in treatment (Giles et al., 1989).
      • Methadone maintenance programs dramatically reduce the possibility of foetal exposure to unknown drugs and contaminants.
      • Enrolment in methadone maintenance programs may provide the woman with sufficient antenatal care and parenting education and support. This is important for a population who are often highly stigmatised and unsupported.

      Neonatal Abstinence Syndrome (NAS)

      • Many infants born to methadone-maintained women will experience some form of withdrawal, usually within 72 hours of birth.
      • Such withdrawal is characterised by agitation, irritability, or by vomiting, diarrhoea or convulsions in extremely severe cases.
      • This abstinence syndrome tends to respond well to morphine or phenobarbitone.
      • Women who are stable on methadone maintenance programs should be encouraged to breastfeed. The amount of methadone in breast milk is minute and unlikely to harm the infant in the first three to six months of life. When breastfeeding is ceasing, the infant must be weaned slowly as there is a risk of withdrawal.


      Health risks of taking barbiturates during pregnancy

      • Neonatal Abstinence Syndrome
      • Increased risk of congenital malformations such as dysmorphic facial features, digital hypoplasia and growth retardation.


      Neurobehavioural abnormalities develop in the children of cocaine-addicted mothers. These children show signs of deficiencies in mood control and abnormal motor development. In addition, such infants may develop a non-specific syndrome of cocaine withdrawal.

      Health risks of taking cocaine during pregnancy

      • Increased risk of ante partum haemorrhage and abruptio placentae
      • Significantly increases the rate of spontaneous abortions
      • Smaller head circumference and body length
      • Intrauterine growth retardation
      • Restrictions in foetal growth have been observed which may be due to reduced oxygen supply to the baby caused by the blood vessel-constricting properties of such drugs
      • Premature birth.

      Effects observed in newborn

      • Excessive tremulousness
      • Irritability
      • Hypertonia
      • Labile skin circulation with colour changes
      • Persistent pulmonary hypertension
      • Increased incidence of Sudden Infant Death Syndrome
      • Neonatal Abstinence Syndrome
        • depressed interactive behaviour
        • excessive sleep
        • poor feeding.

      A number of adverse effects upon the offspring of crack cocaine users have been reported overseas. These include transient neurological symptoms, which occur as a result of crack inhalation during pregnancy or passively after birth.


      The extent of harm associated with amphetamine use is unclear. Research is made difficult by the confounding effects of other drug use, poor nutritional status and lack of information on the frequency and dose of drug used (Wickes, 1992).

      Health risks of taking amphetamines during pregnancy

      • There is a possible link between amphetamine use and congenital abnormalities
      • Increased risk of spontaneous abortion
      • Placental abruption
      • Premature labour
      • Foetal distress
      • Small-for-date babies and growth-retarded babies
      • Neonatal Abstinence Syndrome
        • excessive sleep
        • decreased interactive behaviour
        • poor feeding.


      Health risks of taking benzodiazepines during pregnancy

      • Some benzodiazepines may cause respiratory depression, hypotonia, poor feeding and impaired thermogenesis in the neonate – floppy baby syndrome
      • Neonatal Abstinence Syndrome, particularly if used in conjunction with other drugs.


      Health risks of taking LSD during pregnancy

      The evidence is confusing and conflicting due to the difficulties with research as mentioned before.


      Little is known about the effects of the use of ecstasy on foetal development. The majority of evidence is based on animal studies.

      Health risks of taking ecstasy during pregnancy

      As yet, no study has been reported citing risks of ecstasy use during pregnancy. Since ecstasy is derived from amphetamine, the risks associated with amphetamine use during pregnancy would probably apply here also.

      Solvents and other volatile hydrocarbons

      Volatile organic solvents have been shown to have teratogenic effects on the growing foetus, such as physical malformations or functional impairment.

      Health risks of inhaling solvents during pregnancy

      • Inhaled solvents reduce oxygen levels in body tissue thus reducing oxygen supply to the foetal brain
      • Solvent inhalation may cause neonatal renal problems
      • Exposure to some inhalants may decrease body weight and size
      • Some solvents are embryotoxic
      • Damage reproductive cells and thus impair future conception and pregnancy
      • At high doses can cause the death of the foetus or even the mother
      • Cleft palate
      • Prenatal exposure may affect learning in early childhood.


      Health risks of taking caffeine during pregnancy

      • There may be an association between lower birth-weight and drinking in excess of five cups of coffee or tea, or six cans of cola drinks a day.
      • Irregular foetal heart rate may be associated with excessive amounts of caffeine intake late in pregnancy.
      • Neonatal Abstinence Syndrome has been observed in babies whose mothers used excessive amounts of caffeine.

      Further information

      Further information is available from:

      Drugs in Pregnancy Service
      Royal Prince Alfred Hospital
      Missenden Road
      Camperdown NSW 2050
      Telephone (02) 516 7583
      Fax (02) 516 8970

      Drug Use in Pregnancy Service
      Clinic E
      Westmead Hospital
      Westmead NSW 2145
      Telephone (02) 633 6445.

      Chemical Dependency Unit
      Royal Womens Hospital
      Carlton Vic. 3053
      Telephone (03) 344 2363.

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