Table 2

Population characteristics of included studies

Population characteristic	Study
	1*	2	3
	Martin et al 38	Sarkola et al 40	Terplan et al 41
Age (years)	18–41	Mean: 27 (SD±6) 12% teenage.	≤19: 6.2% 20–39: 91.1% ≥40: 2.7%
Education level	Mean number of years in education: ~11	Completed secondary education or vocational training: 25.2%	Less than high school: 10.6% High school only: 26.1% Greater than high school: 63.2%
Employment	Employed: 4–19%	Unemployed at time of birth: 72.7%	NR
Out-of-home care: mothers as children	NR	9.4%	NR
Out-of-home care: previous child	NR	7.3%	NR
Other socioeconomic characteristics	Criminally unencumbered: 71–88%	Homeless or living in institution: 21.6%	Annual income (USD) <10 000: 14.1% 10 000–14 999: 7.5% 15 000–24 000: 12.0% 25 000–50 000: 20.1% ≥$50 000: 46.3%
Ethnicities	White 83% Black 14% Other 2%	NR	White 74.9%, Black 11.9%, Hispanic 7.9%, Other 5.3%
Gravidity	NR	NR	NR
Parity	NR	NR	NR
Gestational age at recruitment	16–20 weeks	NR	Postpartum
Tobacco smoking	~95%	78.4%	NR
Principal drug(s) of choice	Opioids: 100% Multidrug use common - including heroin, cocaine, alcohol, benzodiazepines.	Alcohol: 25% before pregnancy, 11% during pregnancy, Opioids: 12% before pregnancy, 6% during pregnancy, 15%: anxiolytics/hypnotics	Alcohol
Pattern of drug use	NR	NR	Mixed - reports on binge and non-binge drinking
Severity of drug use	Mean addiction severity index 0.29–0.34	14% have a history of regular contact with AOD healthcare	All alcohol use reported, subset of heavy use

*Demographic data obtained from primary study (this study is a secondary analysis).39
NR, not reported; SD, standard deviation; USD, US dollars.