Fetal bradycardia due to intrathecal opioids for labour analgesia: a systematic review Chahe ´ Mardirosoff a, * , Lionel Dumont b , Michel Boulvain c , Martin R. Trame `r b Objective To evaluate fetal and maternal adverse effects of intrathecal opioid analgesia during labour. Data sources A systematic search was performed, in Medline, Embase, the Cochrane Library, bibliographies, and personal contact with authors, in any language, up to February 2001. Study selection Full reports on randomised comparisons of any analgesia with intrathecal opioid (experimental group) with any non-intrathecal opioid regimen (control group) during labour. Data extraction Dichotomous data from 24 trials (3513 women). Results With intrathecal opioids, there was a significant increase in the risk of fetal bradycardia: odds ratio 1.8 (95% confidence interval 1.0 to 3.1), number-needed-to-harm 28. The risk of caesarean section due to fetal heart rate abnormalities was similar (6.0% versus 7.8%). The incidence of pruritus was significantly higher with intrathecal opioids: relative risk 29.6 (95% CI 13.6 to 64.6), number-needed-to-harm 1.7. Conclusions Intrathecal opioids for labour increase the risk of fetal bradycardia and maternal pruritus. The risk of subsequent caesarean section is not increased. INTRODUCTION In 1996, 13.5% of the French population received an anaesthetic; of those 9% were for labour 1 . Extrapolating these numbers to the UK indicates that 700,000 women receive an anaesthetic during labour each year. Intrathecal opioid analgesia, the injection of an opioid into the cere- brospinal fluid, has become a widely used technique for pain relief during labour. The main advantages of this method compared with the conventional epidural analgesia with a local anaesthetic are the lack of motor weakness enabling ambulation of the women, the faster onset of analgesia, and the reliability of the spinal injection 2 . Recently, fetal heart rate abnormalities including severe bradycardia have been reported following the administra- tion of intrathecal opioids during the first stage of labour 3 . It has been suggested that the risk of subsequent caesarean section may be increased 4 . Given the potentially higher incidence of side effects with intrathecal opioids, it may not be justified to use this technique as a routine analgesia in labour 5 . However, several large series were unable to confirm an increased risk with intrathecal opioids 6–8 .A recent review of both randomised and observational studies suggested that fetal heart rate abnormalities ‘‘occurred with similar frequencies in association with any method of effective pain relief ’’ 9 . For rational decision-making we need to know if there is a causal relationship between intrathecal opioids and fetal bradycardia, and if this adverse effect increases the risk of emergency caesarean section. We also need to quantify these risks. The objective of this systematic review was to evaluate the adverse effects related to the adminis- tration of intrathecal opioids for labour. METHODS We included reports of randomised comparisons of any intrathecal opioid with or without a local anaesthetic (experimental group) with any analgesic regimen that excluded intrathecal opioids (control group) for labour analgesia. Relevant studies had to report dichotomous data on adverse effects. We searched systematically in Medline, Embase, and the Cochrane library (issue 1, 2001), using the free text terms combined spinal epidural, intrathecal, spinal, subarach- noid, labor, labour, opioid, randomized, randomised, con- trolled and, control, and combinations of the above. The last electronic search was performed on 25 January 2001. We hand searched locally available anaesthesia journals including the non-indexed International Journal of Obste- tric Anaesthesia up to January 2001. We checked biblio- graphies of retrieved reports. No language restriction was applied. When there was ambiguity about data or when BJOG: an International Journal of Obstetrics and Gynaecology March 2002, Vol. 109, pp. 274–281 D RCOG 2002 BJOG: an International Journal of Obstetrics and Gynaecology PII:S1470-0328(02)01380-0 www.bjog-elsevier.com a Department of Anaesthesiology, Polyclinique de Savoie, Annemasse, France b Division of Anaesthesiology, Geneva University Hospitals, Geneva, Switzerland c Department of Gynaecology and Obstetrics, Geneva University Hospitals, Geneva, Switzerland * Correspondence: Dr C. Mardirosoff, De ´partement d’Anesthe ´sie- Re ´animation, Polyclinique de Savoie, 8 Rue Fernand-David, 74100 Annemasse Cedex, France.