Table 2

Characteristics of included studies: participants, intervention, and outcomes

Trial	Participants	Interventions	Outcomes	Notes
Bonta⁸	43 normal term newborn infants whose mothers received narcotic analgesia within six hours of delivery.	1. Intramuscular naloxone (0.02 mg/kg) (n=22)	Apgar score at five minutes, capillary blood gas values at 1, 2, and 4 hours of life, neurobehavioral assessment at 1, 4, and 24 hours.	Infants delivered in breech presentation or by caesarean section, infants with Apgar score <6 at one minute, were excluded.
		2. Placebo (saline) (n=21)
Brice⁹	50 term newborn infants whose mothers received pethidine within four hours of delivery.	1.Naloxone via umbilical vein (0.01 or 0.02 mg/kg) (n=26)	Time to sustained respiration, expired CO₂ output and alveolar ventilation, Brazelton score and Scanlon score within the first 24 hours of life.	Blinding of outcome measurement for Scanlon score only.
		2. No drug (n=24)
Dick¹⁰ (a)	40 newborn infants, of unspecified gestation, whose mothers had been given pethidine in labour.	1. Naloxone via umbilical vein (0.02–0.04 mg/kg) (n=30)	Capillary blood gas pH and partial pressure of CO₂ and of oxygen at 1, 5, 10, 30, 60, and 120 minutes of life.	Presumed, although not stated explicitly in the report, that naloxone was administered at birth.
		2. No drug (n=10)
Dick¹⁰ (b)	30 newborn infants, of unspecified gestation, whose mothers had been given pethidine in labour.	1. Naloxone via umbilical vein (either 0.04 mg/kg or 0.04 mg total) (n=10)	Capillary blood gas pH, partial pressure of CO₂ and of oxygen, and calculated base excess at 1, 5, 10, 30, 60, and 120 minutes of life.
		2. Placebo (n=20)
Evans¹¹	44 newborn infants, of gestation 38–42 weeks, delivered vaginally, whose mothers had been given pethidine in labour.	1.Naloxone via umbilical vein (0.04 mg total) (n=20)	Time to first breath and onset of sustained respiration, Apgar score at five minutes, alveolar CO₂ tension, alveolar ventilation, and ventilation rate at 10 and 30 minutes of life.	Apgar score, time to first breath and to sustained respiration reported as mean values, but without standard deviations.
		2. No drug (n=24)
Gerhardt¹²	20 term newborn infants, whose mothers received pethidine within three hours before delivery.	1. Intramuscular naloxone (0.01 mg/kg) (n=12)	Respiratory rate, tidal volume, minute ventilation, end-tidal CO₂ tension, and response to inhalation of 4% CO₂.	Only infants born vaginally were eligible for inclusion.
		2. Placebo (n=8)		Naloxone was given at 30 minutes of age.
Welles¹³	27 newborn infants, of gestation 38–42 weeks, whose mothers received pethidine during labour.	1. Intramuscular naloxone (0.1 mg total) (n=14)	Brazelton score at 12–24 hours of life and after a further 48 hours. Broussard neonatal perception inventory at about 72 hours.	Naloxone was given at one hour. Infants with Apgar scores <8 at one minute, or <9 at five minutes were not eligible for inclusion.
		2. Placebo (saline) (n=13)
Wiener¹⁴	28 newborn infants, of gestation 38–42 weeks, whose mothers had been given pethidine in labour.	1.Naloxone via the umbilical vein (0.04 mg total) (n=10)	Alveolar CO₂ tension, CO₂ excretion, alveolar ventilation, feeding behaviour, and habituation to a sound specific stimulus up to 48 hours of life.	Naloxone or normal saline were “chosen blind at random”.
		2. Placebo (saline) (n=18)
Wiener¹⁵	30 newborn infants, of gestation 38–42 weeks, whose mothers had been given pethidine in labour.	1. Intramuscular naloxone at one minute of age (0.2 mg total) (n=15)	Alveolar CO₂ tension, CO₂ excretion, alveolar ventilation, feeding behaviour, and habituation to a sound specific stimulus up to 48 hours.
		2. Placebo (saline) (n=15)