Table 3.

Labour and delivery outcomes of women in the study

		Pregnancy in prison (ii)
		Birth in prison		Birth outside prison			Prison controls (iii)			Community controls (iv)
		n	%	n	%	P value (v)	n	%	P value (v)	n	%	P value (v)
Onset of labour
	Spontaneous	64	64.6	156	77.6	0.5	866	71.0	0.5	24064	61.5	<0.0001
	Induced	22	22.2	28	13.9		232	19.0		10116	25.9
	No labour	13	13.1	17	8.5		122	10.0		4924	12.6
	Missing/not stated	0		0			0			8	0.0
	Total	99	100.0	201	100.0		1220	100.0		39112	100.0
Presentation at birth
	Vertex	88	88.9	180	89.6	0.06	1118	91.6	0.9	35533	90.8	0.21
	Non-vertex	10	10.1	8	4.0		64	5.2		1581	4.0
	Missing/not stated	1	1.0	13	6.5		38	3.1		1998	5.1
	Total	99	100.0	201	100.0		1220	100.0		39112	100.0
Method of birth
	Normal vaginal	66	66.7	162	80.6	0.10	897	73.5	0.8	23669	60.5	<0.0001
	Instrumental vaginal	2	2.0	11	5.5		67	5.5		5126	13.1
	Caesarean section	28	28.3	25	12.4		243	19.9		10191	26.1
	Missing/not stated	3	3.0	3	1.5		13	1.1		126	0.3
	Total	99	100.0	201	100.0		1220	100.0		39112	100.0

(i) For each group, live born singleton births and first births during the study period (index births) only.

(ii) Births to women who were incarcerated for a minimum of five consecutive days during this pregnancy.

(iii) Births to women were not incarcerated during this pregnancy, but were incarcerated at another time during the study period.

(iv) A random 10% sample of births to women who were not incarcerated at all during the study period.

(v) Chi-square tests were used to test for differences between study and control groups in labour and delivery outcomes.