Case 53: Illegal drug use in pregnancy

 

Case 53: Illegal drug use in pregnancy

CASE 53: ILLEGAL DRUG USE IN PREGNANCY

History

A 19-year-old woman is referred to the antenatal clinic by her general practitioner. She is

currently 22 weeks’ gestation in her second pregnancy. She had a son by normal vaginal delivery 18 months ago, who was taken into social services care initially and now lives with his

grandparents (the father’s parents). Since then, the woman has been having very infrequent

periods and only discovered she was pregnant when she attended the emergency department with a presumed urinary tract infection 2 weeks ago. At that stage abdominal palpation

revealed a mass, and ultrasound scan confirmed the singleton gestation.

The GP letter informs that the woman has been a user of crack cocaine and heroin in the past

but that she has been on a methadone replacement programme for the last 8 weeks. The current prescribed regime is 60 mL methadone, which she collects daily from the pharmacist.

The woman reports that she still injects street heroin several times per week but has not used

crack cocaine for several months. She says that she drinks minimal alcohol but she smokes

20–25 cigarettes per day.

There is no other medical history of note.

She lives in a council flat with her partner who is also taking prescribed methadone. She

denies any domestic violence within the relationship.

Examination

The woman appears thin and anxious. The blood pressure is 107/65 mmHg and pulse 90/min.

The abdomen is distended with the fundus palpable at the umbilicus. The fetal heartbeat is

heard with a hand-held Doppler device.

INVESTIGATIONS

Rubella: immune

Syphilis: negative

Hepatitis B surface antigen: positive

HIV1/2: negative

Haemoglobin: 11.4 g/dL

Blood group: A positive

Questions

• What other investigations should be arranged?

• What are the risks associated with drug use in pregnancy?

• How would you manage this woman during the pregnancy?100 Cases in Obstetrics and Gynaecology

140

ANSWER 53

The woman has been found to be hepatitis B surface antigen positive. This needs further

investigation with e antigenicity to determine risk of transmission, and liver function tests.

Assuming the hepatitis B is related to needle sharing, she is also at significant risk of hepatitis

C and this should also be tested for at this stage.

A urine toxicology screen should be performed with the woman’s consent, to confirm the

drug history she has given and what the risks to the fetus may be.

! Illegal Drug Use Risks

Crack cocaine: crack cocaine use is associated with placental abruption and hence

increased risk of perinatal death or prematurity. It is also known to cause intrauterine growth restriction by way of arterial vasoconstriction.

Heroin: opiates are not teratogenic but are associated with intrauterine growth restriction and premature delivery.

Cannabis: cannabis is not known to have specific risks in pregnancy, but the tobacco

use associated and the possibility of other associated drug use makes it an important risk factor.

Tobacco: tobacco use is associated with fetal growth restriction and low birth weight.

There is also the risk of respiratory disease in the infant from passive smoking.

Management of the pregnancy

Multidisciplinary team

Most units have a specialist team for management of drug-using women in pregnancy. This

should include specialists in substance misuse, a social worker, a specialist midwife and an

interested obstetrician.

Opiate replacement

The woman needs to be encouraged to engage more fully with the methadone replacement

programme. This may well mean increasing the methadone regime to allow her to stop the

street heroin. Once this has been achieved then she can gradually reduce the dose needed,

with appropriate support. It is better to be still taking a maintenance dose of methadone

through the pregnancy than to try and stop too quickly, resulting in unquantifiable amounts

of illegal drugs being taken during the pregnancy.

Fetal monitoring

The fetus should be assessed for growth during the pregnancy in view of the increased risk of

intrauterine growth restriction.

Delivery

Labour should be managed as for any non-drug-using woman. The difference may be that

the usual doses of opiates needed for analgesia (epidural or systemic) may be insufficient and

need to be titrated up to ensure adequate pain control.

Fetal blood sampling should be avoided in labour due to the risk of vertical transmission of

hepatitis B antigen.Case 53: Illegal drug use in pregnancy

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Postpartum

The baby should be administered hepatitis B immunoglobulin at delivery and be given the

accelerated hepatitis B immunization course.

Babies of opiate-using mothers may have initial respiratory depression as a result of the opiates but then develop withdrawal symptoms. They need immediate transfer to the neonatal

unit for management of the symptoms, with reducing doses of opiates.

Issues of care for the baby should be established between the social services, medical team

and the parents, prior to delivery.

KEY POINTS

• Women who use illegal drugs have high-risk pregnancies.

• A team approach that encourages trust and engagement from the woman is likely

to be most effective.

• Fetal growth should be monitored and the fetus transferred to the neonatal unit at

delivery for management of respiratory depression and withdrawal.