12. Drugs in pregnancy

Introduction
Health risks associated with non-medical drug use during pregnancy
Special effects of individual drugs

INTRODUCTION

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.

HEALTH RISKS ASSOCIATED WITH NON-MEDICAL DRUG USE DURING PREGNANCY

Increased risk of a low birth weight and developmental delay
Increased perinatal mortality
Increased risk of complications during pregnancy such as HIV, hepatitis B, hepatitis C, malnutrition, anaemia, sexually transmitted diseases and respiratory depression, all of which can affect the unborn child as well as the mother
Higher incidence of congenital abnormalities
Higher incidence of Sudden Infant Death Syndrome (4-5 fold) in infants born to drug-dependent mothers.

Further Information

Alcohol

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:

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.
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.
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)

Alcohol intake – the foetal effects of alcohol are related to quantity, frequency and timing of use. A single dose of more than 5 drinks very early in pregnancy or an average of 2 drinks per day in later pregnancy (second or third trimester) has been associated with subsequent learning difficulties in childhood (Streissguth, Barr and Sampson, 1990).
Nutritional status of the mother – those who are undernourished can attain higher blood alcohol levels and decrease their capacity to metabolise alcohol
Parity – short intervals between births has been found to be associated with an increased risk of congenital malformations and severity of FAS
Alcohol-related conditions that may complicate pregnancy:
- cirrhosis
- other liver problems
- anaemia
- gastritis
- gastrointestinal bleeding
- delirium tremens
- diabetes
- pancreatitis
- sexually transmitted diseases
- tuberculosis.
Multiple drug use – women who drink heavily are also more likely to smoke heavily and possibly to use other drugs, all of which may have a cumulative harmful effect on the developing foetus
Medication – alcohol reduces the effectiveness of anaesthetics and analgesics
Increased risk of spontaneous abortion – with heavy and even moderate alcohol consumption
Increased risk of complicated birth – higher risk of breech birth (15% as opposed to 3%).

Characteristics of Foetal Alcohol Syndrome (FAS)

A diagnosis of Foetal Alcohol Syndrome requires: (9)

growth retardation
- prenatal and/or postnatal growth retardation
- weight and/or height below the 10th percentile when corrected for gestational age.
CNS abnormalities
- eg neurological abnormality, developmental delay, behavioural dysfunction or deficit, intellectual impairment and/or structural abnormalities such as microcephaly or brain malformation.
facial abnormalities
- underdevelopment of the 'middle 1/3' of the face including short palpebral fissures, an elongation mid-face, a long and flattened philtrum, thin upper lip and flattened maxilla.
Other abnormalities include:
- increased neonatal death rate
- slow physical development in the first few years of life
- other physical features
  - cardiac defects
  - ear anomalies
  - large haemangiomata
  - small nails
  - altered palmar crease patterns
  - joint and limb abnormalities.
Tobacco
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

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.

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.

Increased risk of febrile seizures.

School performance may be retarded through repeated absences due to illness, malaise and hearing problems.

Increased risk of meningococcal infection.

Increased problems for children with cystic fibrosis.

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:

Contents | Feedback | Search | DRCNet Home Page | Join DRCNet

DRCNet Library | Schaffer Library | Alcohol