Table 2.

Risk factors for infant mortality, by Indigenous status

	Indigenous infants (n = 25,962)						Non-Indigenous infants (n = 16,712)
	Survived	Died					Survived	Died
	n	n	%	RR	(95% CI)	p-value	n	n	%	RR	(95% CI)	p-value
Infants	25,532	430	1.7				16,596	116	0.7
Demographic factors
Sexa
Male	13,052	240	1.8	1.20	(0.99–1.45)	0.058	8586	64	0.7	1.14	(0.79–1.65)	0.468
Female*	12,438	190	1.5				7991	52	0.6
Maternal Indigenous status
Indigenous	24,321	418	1.7	1.72	(0.97–3.05)	0.062
Non-Indigenous*	1211	12	1.0				16,596	116	0.7
Socioeconomic statusb
Very low (0–5%)	6793	128	1.8	2.16	(1.38–3.39)	0.001	996	15	1.5	3.50	(1.88–6.54)	<.001
Low (6–25%)	11,095	195	1.7	2.02	(1.30–3.13)	0.002	4461	50	1.1	2.62	(1.65–4.15)	<.001
Medium (26–50%)	5054	83	1.6	1.89	(1.18–3.01)	0.008	4517	23	0.5	1.20	(0.69–2.07)	0.523
High (51–100%)*	2546	22	0.9				6584	28	0.4
Geographical remotenessc
Major cities/Inner regional*	10,331	160	1.5				13,574	88	0.6
Outer regional	4185	73	1.7	1.12	(0.85–1.48)	0.404	1811	22	1.2	1.86	(1.17–2.97)	0.009
Remote	4776	75	1.5	1.01	(0.77–1.33)	0.922	834	5	0.6	0.93	(0.38–2.27)	0.865
Very remote	6195	120	1.9	1.25	(0.98–1.58)	0.066	326	< 5	0.3	0.47	(0.07–3.40)	0.458
Baseline Pregnancy Risk Factors
Multiple gestation
Yes	568	23	3.9	2.43	(1.61–3.66)	<.001	414	13	3.0	4.81	(2.73–8.50)	<.001
No*	24,964	407	1.6				16,182	103	0.6
Birth spacing
< 18 months	3011	82	2.7	1.74	(1.37–2.21)	<.001	1112	19	1.7	2.70	(1.66–4.40)	<.001
Firstborn/18 months+*	22,521	348	1.5				15,484	97	0.6
Maternal age
12–19 years	7628	122	1.6	0.91	(0.72–1.17)	0.471	1740	21	1.2	2.36	(1.41–3.94)	0.001
20–24 years	9420	158	1.6	0.96	(0.76–1.20)	0.713	3916	47	1.2	2.35	(1.57–3.52)	<.001
25–34 years*	7533	132	1.7				9054	46	0.5
35 + years	951	18	1.9	1.08	(0.66–1.76)	0.761	1886	< 5	0.1	0.21	(0.05–0.86)	0.030
Parity
Nulliparous	9035	126	1.4	0.82	(0.66–1.03)	0.093	7954	53	0.7	0.99	(0.67–1.45)	0.939
Parity 1–2*	10,847	184	1.7				7539	51	0.7
Parity 3+	5650	120	2.1	1.25	(0.99–1.57)	0.058	1103	12	1.1	1.60	(0.86–2.99)	0.140
Pregnancy complications
Abruptio placentae and other disordersd
Yes	122	8	6.2	3.77	(1.91–7.42)	<.001	90	< 5	4.3	6.31	(2.38–16.8)	<.001
No*	25,410	422	1.6				16,506	112	0.7
Placenta previa
Yes	87	< 5	3.3	2.02	(0.66–6.17)	0.217	109	0	0
No*	25,445	427	1.7				16,487	116	0.7
Premature rupture of membranes
Yes	1200	34	2.8	1.72	(1.22–2.43)	0.002	445	5	1.1	1.63	(0.67–3.97)	0.284
No*	24,332	396	1.6				16,151	111	0.7
Infection related hospitalisation in pregnancye
Yes	2041	34	1.6	0.99	(0.70–1.40)	0.947	388	< 5	0.5	0.73	(0.18–2.96)	0.664
No*	23,491	396	1.7				16,208	114	0.7
Other maternal factors/Exposures during pregnancy
Substance use related service contactf
Yes	397	15	3.6	2.24	(1.35–3.72)	0.002	293	6	2.0	2.99	(1.33–6.76)	0.008
No*	25,135	415	1.6				16,303	110	0.7
Hospitalisation for external causes of injuryg
Yes	1479	38	2.5	1.56	(1.12–2.17)	0.008	278	< 5	1.1	1.55	(0.50–4.86)	0.450
No*	24,053	392	1.6				16,318	113	0.7
Mental health related service contacth
Yes	768	12	1.5	0.93	(0.52–1.64)	0.794	427	5	1.2	1.70	(0.70–4.14)	0.244
No*	24,764	418	1.7				16,169	111	0.7
Sibling in contact with child protectioni
Yes	852	30	3.4	2.13	(1.48–3.07)	<.001	237	6	2.5	3.70	(1.64–8.33)	0.002
Firstborn/No*	24,680	400	1.6				16,359	110	0.7

*Reference category

^a42 Indigenous and 19 non-Indigenous infants missing sex

^b46 Indigenous and 38 non-Indigenous infants missing socioeconomic status

^c47 Indigenous and 51 non-Indigenous infants missing remoteness

^dExcludes placenta previa

^eInfection related hospitalisation in pregnancy

^fSubstance use (including alcohol) or poisoning related service contact (hospital or mental health service)

^gHospitalisation for external causes of injury in pregnancy (excludes poisoning)

^hMental health service contact in pregnancy (excludes substance use) (hospital or mental health service)

ⁱOlder sibling(s) in contact with child protection system in infant’s pregnancy