Preparing linked population data for research: cohort study of prisoner perinatal health outcomes

Table 2 Reasons for data censoring women by prisoner and mental health morbidity (MHM) status

	Non-prisoners				Prisoners^a				All MHM^b		All Prisoners		All study women
	No MHM^b		MHM^b		No MHM^b		MHM^b		All MHM^b		All Prisoners		All study women
Person records:	37,533		25,857		935		2,152		28,009		3,087		66,477
Reason censored	N	‰	N	‰	N	‰	N	‰	N	‰	N	‰	N
Duplicated births	5	0.1	4	0.2	1	1.1	0	0	4	0.1	1	0.3	10
Too many maternities	8	0.2	6	0.2	1	1.1	7	3.3	308	10.9	8	2.6	22
Non-chronological maternities	25	0.7	29	1.1	4	4.3	26	12.1	55	2	30	9.7	84
Concurrent maternities	42	1.1	37	1.4	6	6.4	20	9.3	57	2	36	11.7	115
Inconsistent incarceration data	–	–	–	–	29	31.0	314	145.9	312	11.1	343	111.1	343
Missing incarceration data	–	–	–	–	18	19.3	41	19.1	41	1.5	59	19.1	59
Conception in prison	–	–	–	–	28	29.3	35	16.3	35	1.2	63	20.4	63
Maternity reason^c	64	1.7	62	2.4	10	10.7	42	19.5	104	3.7	52	16.8	178
Study mothers:	37,469		25,795		850		1,739		27,534		2,589		65,853
Censored %	0.2		0.2		9.1		19.2		1.7		16.1		0.9

Notes:
^a Prisoners were also divided into incarceration of 5 days or more (5 + days) or less than 5 days (<5 days). These results are shown in the [see Additional file 2: Table S2A]
^b Women with mental health morbidity (MHM) had either a mental health admission episode or were authorised or receive opiate substitution therapy (OST)
^c Women censored for inconsistent maternity data have one or more of the first four listed reasons for data censoring
^dThese mothers were retained in the study and their linked records used for further analysis
‰ rate per 1,000 person records % rate per 100 person records – not applicable

ISSN: 1471-2288