Table 3

Birth outcomes for the Aboriginal Families Study (AFS) cohort compared to Australian reference data and differentially according to whether cannabis and cigarettes were used in pregnancy

		AFS cohort
					Birth outcomes for those using
	Australian reference data10				Cannabis (with or without cigarettes)		Cigarettes only		Neither
		Full cohort			(20.5%)		(31.9%)		(47.6%)
	Mean	N	Mean	(SD)	Mean	(SD)	Mean	(SD)	Mean	(SD)	p Value*
Gestational age (weeks)	38.8%	308	38.7%†	2.7%	37.8%	3.8%	39.0%	2.0%	38.9%	2.3%	0.014
Birth weight (g)	3367	315	3209‡	698	2781	733	3267	579	3345	690	<0.001
		N
Gestation at birth
Preterm (<37 weeks)	8.5%	36	11.7%§		19.1%		8.3%		10.7%		0.245
Term (≥37 and <42 weeks)	90.9%	268	87.0%		79.4%		89.6%		88.6%
Post-term (≥42 weeks)	0.6%	4	1.3%		1.6%		2.1%		0.7%
Infant birth weight
Low (<2500 g)	6.2%	43	13.7%¶		35.5%		9.1%		7.8%		<0.001
Appropriate (≥2500 and <4000 g)	82.3%	241	76.5%		59.7%		81.8%		79.9%
High (≥4000 g)	11.5%	31	9.8%		4.8%		9.1%		12.3%
Weight for gestational age
Small (<10th centile)	10.0%	64	21.6%**		38.6%		22.6%		14.3%		0.004
Appropriate (≥10th and <90th centile)	80.0%	210	70.7%		54.4%		72.0%		76.2%
Large (≥90th centile)	10.0%	23	7.7%		7.0%		5.4%		9.5%

*p Value comparing mothers who used cannabis, cigarettes or neither during pregnancy (Wald test from linear regression for continuous birth outcomes, χ² test for categorised birth outcomes).
†p Value from one sample t test comparing mean gestational age to full cohort to Australian reference data=0.498.
‡p Value from one sample t test comparing mean birth weight to Australian reference data <0.001.
§p Value from binomial probability test comparing proportion of preterm births to Australian reference data=0.052.
¶p Value from binomial probability test comparing proportion of low birth weight to Australian reference data <0.001.
**p Value from binomial probability test comparing proportion SGA to Australian reference data <0.001.