Table 2

Missing data in selected birth outcome variables (2002–2010)

Variable	HES deliveries		HES births		ONS births		NN4B births*
Variable	n missing	Missing, %	n missing	Missing, %	n missing	Missing, %	n missing	Missing, %
Total births or deliveries (2002–2010)	5 545 905		5 534 194		5 727 407		3 333 154
Maternal age	14 605	0.3	2 128 620	38.5	0	0	2	0
Plurality	905 313	16.3	1 563 918	28.3	N/A†		N/A†
Residential postcode	36 185	0.7	4 088 071	73.9	318	0	885	0.0
Government Office Region (GOR)	32 245	0.6	4 086 574	73.8	0	0	6300	0.2
Carstairs score‡	49 526	1	3 473 637	71.4	8625	0.2	6300	0.2
Birth status (live/still)	1 540 412	27.8	2 072 393	37.4	N/A§		N/A§
Birth weight¶	1 300 202	23.4	2 085 549	37.7	36 224	0.6	20 327	0.6
Sex of baby	1 326 373	23.9	5 409 048	97.7	0	0	2	0
Parity (previous children)**	NI		NI		2 480 180	48.4	NI
Mothers’ ethnicity	943 329	17.0	NI		NI		NI
Babies’ ethnicity	NI		1 441 154	26.0	NI		260 112	7.8
Previous pregnancies	2 061 539	37.2	5 390 377	97.4	NI		NI
Delivery method	1 294 750	23.3	1 742 960	31.5	NI		NI
Delivery place	1 881 901	33.9	2 213 562	40.0	NI		NI
Gestational age	2 201 195	39.7	2 227 618	40.3	N/A		32 039	1

*2006 to 2010 only.
†ONS and NN4B codes multiple births as 1, all other births are considered singleton. Coverage is therefore 100%.
‡No data for 2010, results displayed for years 2002–2009, NN4B 2006–2010.
§ONS tables are split into stillbirths and live births. Coverage is therefore 100%.
¶Valid birth weights for HES include 1–7000 g, for ONS 1–9997 g and for NN4B 200–5000 g.
**Applies to live births and stillbirths within marriage only.
HES, Hospital Episode Statistics; ONS, Office for National Statistics; NA, not applicable; NI, not included; NN4B, NHS Numbers for Babies.