450 drug-dependent women prescribed substitute methadone delivered babies of singleton pregnancies at the Princess Royal Maternity in Glasgow over three years from 1 January 2004 to 31 December 2006. The hospital has a comprehensive care pathway to deal with such women from the pre- to the postnatal periods.

Researchers found a strong association between social deprivation and drug misuse in pregnancy, with 77.8% of women residing in areas assigned the lowest two social deprivation scores. Almost 90% of women were regular smokers and a third had evidence of active hepatitis C infection. 18.2% of the women were reported to suffer from depression and two-thirds of these women were on antidepressants. Alongside the prescribed doses of methadone, around 80% of women continued to use illicit drugs during their pregnancy. The drugs most frequently used were benzodiazepines (tranquillizers), heroin and cannabis. A small group of women used cocaine. Amphetamine use was uncommon.

45.5% of the infants born to these women needed pharmacological treatment for Neonatal Abstinence Syndrome (NAS) or baby withdrawals. For women who had continued to use other drugs, there was a significantly increased likelihood of the infant requiring treatment for NAS. However, the most important factor determining the likelihood of the infant requiring treatment was the prescribed maternal dose of methadone.

Although the hospital allows treatment of NAS in the postnatal ward, 48.8% of infants were admitted to the neonatal unit after birth. The reasons for admission included prematurity (15.8%), respiratory distress (12.6%) and a range of social reasons (13%). Infants born to drug misusing mothers constituted 2.9% of hospital births, but occupied almost a fifth of neonatal cot days.

Doctors also found that when women breastfed their babies for more than 72 hours there was a significantly reduced odds of the infants receiving treatment for NAS. Apart from the benefits of breast milk and the way breastfeeding soothes agitated babies, researchers note that small traces of the drugs taken by the mother may find their way into the breast milk, thus lessening the baby's withdrawal symptoms.

Based on their findings, researchers recommend that drug-misusing mothers should be encouraged to breastfeed their babies. A prolonged postnatal stay is recommended to help healthcare professionals observe for signs of NAS, conduct social work assessment and arrange for parenting and community support for the mothers prior to discharge.

Dr Helen Mactier, consultant neonatologist who headed the study, said "Drug misuse in pregnancy is an emotive issue - prescription of substitute methadone stabilises lifestyle and reduces the incidence of preterm birth but it does not prevent ongoing drug misuse and is commonly associated with Neonatal Abstinence Syndrome. Infants born to drug misusing mothers tend to be born a bit early, and to be small, with correspondingly low intrauterine head growth.

"Our research has shown that breastfeeding seems to protect against the risk of developing neonatal abstinence syndrome, with the likelihood of receiving treatment halved in those infants who breastfed for more than three days. Our advice is for pregnant drug misusing women to be maintained on the lowest dose of methadone compatible with stability and for them to be encouraged and supported to breastfeed."

Professor Philip Steer, BJOG editor-in-chief, said "Caring for pregnant women with a history of substance misuse is complicated and difficult because of the complex social and lifestyle factors influencing maternal drug use.

"This piece of research has revealed that a higher methadone dose is associated with an increased chance of NAS in infants. This will help inform future policy on the treatment of pregnant women blighted by substance misuse."


BJOG: An International Journal of Obstetrics and Gynaecology is owned by the Royal College of Obstetricians and Gynaecologists (RCOG) but is editorially independent and published monthly by Wiley-Blackwell. The journal features original, peer-reviewed, high-quality medical research in all areas of obstetrics and gynaecology worldwide. Please quote 'BJOG' or 'BJOG: An International Journal of Obstetrics and Gynaecology' when referring to the journal.


Dryden C, Young D, Hepburn M, Mactier H. Maternal methadone use in pregnancy: factors associated with the development of neonatal abstinence syndrome and implications for healthcare resources. BJOG 2008; DOI: 10.1111/j.1471-0528.2008.02073.x.

Royal College of Obstetricians and Gynaecologists