Improving birth outcomes for women who are substance using or have mental illness: a Canadian cohort study comparing antenatal midwifery and physician models of care for women of low socioeconomic position

Table 2 Frequencies and adjusted odds ratios for small-for-gestational-age birth by antenatal model of care and psychosocial risk characteristics, British Columbia, April 1, 2008-December 31, 2012

Small-for-gestational-age birth by model of care
	MW n = 3391	GP n = 25,733	OB n = 4742	MW vs. GP	MW vs. OB	GP vs. OB
	n(%)	n(%)	n(%)	aOR (95% CI)	aOR (95% CI)	aOR (95% CI)
Mental illness^a
Yes	42/1011 (4.15)	340/4912 (6.92)	45/545 (8.26)	0.64 (0.46–0.89)	0.49 (0.32–0.77)	0.77 (0.55–1.08)
No	129/2380 (5.42)	1461/20,821 (7.02)	361/4197 (8.60)	0.76 (0.63–0.92)	0.63 (0.51–0.78)	0.83 (0.73–0.94)
Substance use^b
Yes	6/152 (3.95)	222/2275 (9.76)	23/182 (12.64)	0.41 (0.18–0.93)	0.31 (0.12–0.78)	0.75 (0.46–1.21)
No	165/3239 (5.09)	1579/23,458 (6.73)	383/4560 (8.40)	0.75 (0.63–0.89)	0.62 (0.51–0.75)	0.83 (0.73–0.94)
Teen mother
Yes (14–19 yrs.)	8/117 (6.84)	181/2582 (7.01)	21/205 (10.24)	0.94 (0.45–1.98)	0.56 (0.24–1.34)	0.60 (0.36–0.99)
No (25–29 yrs.)	55/1159 (4.75)	537/7697 (6.98)	126/1370 (9.20)	0.71 (0.53–0.94)	0.55 (0.39–0.76)	0.78 (0.63–0.96)
Mental illness, substance use
Both	5 or less /95^c	90/927 (9.71)	10/76 (13.16)	0.33 (0.10–1.07)	0.22 (0.06–0.87)	0.68 (0.32–1.43)
Neither	126/2322 (5.43)	1324/19,424 (6.82)	348/4086 (8.52)	0.78 (0.64–0.94)	0.64 (0.51–0.79)	0.82 (0.72–0.94)

Abbreviations: MW midwife, GP general practitioner, OB obstetrician, OR odds ratio, CI confidence interval
^aMental illness included any of the following diagnoses prior to, or during the current pregnancy: anxiety disorder, depression, postpartum depression, bipolar disorder, other/unknown (including schizophrenic, mood, and psychotic disorders). Aside from mild anxiety or depression, a physician would diagnose mental illness
^bSubstance use included any indication in the medical record of heroin/opioids, cocaine, methadone, solvents, marijuana or other/unknown drugs used by the mother at any time during pregnancy, as well as prescription or other drug use identified as a risk by the provider
^cPercentage suppressed due to small cell size
*Outcomes had statistically significant tests of interaction (p < 0.10) comparing difference of effect across strata (yes vs. no)
Models adjusted for all variables listed except stratifying variables: maternal age, parity, pre-pregnancy BMI, infant sex, smoking status, substance use, mental illness/disorder, and Local Health Area (LHA) socioeconomic rank
Odds ratios based on 2378 births with SGA and 33,866 total births with no missing information for this analysis

ISSN: 1471-2393