Table 4

Comparison of all live, all eligible, linked and unlinked datasets

CharacteristicsAll live births
(n=1 250 490)
All eligible births
(n=1 170 790)
Linked
(n=1 073 115)
Unlinked
(n=97 675)
P value*
n%n%n%n%
Ethnicity
 Bangladeshi16 7301.316 2811.415 3561.49251.0<0.0001
 Indian32 2412.631 2872.728 9702.723182.4
 Pakistani48 5703.947 3524.043 7024.136483.7
 Black African24 4612.023 3942.021 5042.018881.9
 Black Caribbean86680.782000.774200.77810.8
 White British788 98563.0738 88763.1675 34062.963 55265.1
 White other91 3117.386 9187.480 6117.563066.5
 Other102 0488.297 3628.389 0438.383188.5
 Missing137 47611.0121 10910.3111 16910.4993910.2
Mother's age
 Under 2052 6054.251 3124.446 8034.445094.6<0.0001
 20–24216 76817.3208 68817.8190 72917.817 96018.4
 25–29306 60324.5290 13224.8266 00224.824 13024.7
 30–34363 31229.1337 32328.8309 60428.927 71828.4
 35–39244 95219.6223 25619.1204 99019.118 26318.7
 40+66 2505.360 0795.154 9875.150955.2
Nulliparous
 No587 83447.0562 20748.0523 05248.739 15240.1<0.0001
 Yes570 12945.5548 25846.8505 98047.242 27943.3
 Missing92 5277.460 3255.244 0834.116 24416.6
IMD Score (quintiles)
 Q1333 80926.7318 83027.2292 31227.226 51327.10.001
 Q2263 21221.1247 77921.2227 08021.220 70021.2
 Q3221 72017.7206 64817.7189 75817.716 89117.3
 Q4200 89116.1186 16515.9170 31315.915 85116.2
 Q5195 38215.6181 04115.5165 76615.515 27715.6
 Missing35 4762.830 3272.627 8862.624432.5
Sex
 Male639 61751.2599 71551.2549 23251.250 48451.70.002
 Female610 87348.9571 07548.8523 88348.847 19148.3
Mother UK born
 No274 65922.0259 17122.1237 66322.221 50422.00.413
 Yes974 06577.9909 96177.7833 94377.776 02277.8
 Missing17660.116580.115090.11490.2
Registration status
 Married716 85857.3665 76456.9612 06357.053 69855.0<0.0001
 Sole registration85 5006.881 0806.974 1586.969227.1
Joint registration, same address339 64127.2320 09827.3292 33827.227 76228.4
 Joint registration, different address108 4918.7103 8488.994 5568.892939.5
Region of birth
 East Midlands87 3107.082 3117.077 7507.345614.7<0.0001
 East of England126 92510.1118 49110.1106 96110.011 53011.8
 London248 34119.9228 98019.6208 22219.420 75621.3
 North East61 0074.957 4914.954 5695.129223.0
 North West170 50413.6159 85913.7142 85513.317 00317.4
 South Central88 7987.183 6107.178 4517.351595.3
 South East Coast96 6067.790 8757.883 9567.869217.1
 South West107 3768.6101 1208.698 4389.226822.8
 West Midlands137 85911.0129 22311.0108 06210.121 16021.7
 Yorkshire/Humber125 76510.1118 83010.2113 85110.649815.1
Month of birth
 January100 6048.194 2338.185 7468.084878.7<0.0001
 February93 4567.587 6837.578 3337.393509.6
 March104 0698.397 5268.385 7798.011 74712.0
 April99 9778.093 6338.086 7018.169337.1
 May104 9928.498 3138.490 8568.574557.6
 June105 1248.498 1498.490 0828.480718.3
 July108 2498.7101 3308.693 9088.874217.6
 August109 9688.8103 2298.895 6748.975557.7
 September109 7178.8102 7528.894 9188.978338.0
 October108 4858.7101 3018.694 4218.868817.0
 November102 5178.295 8488.287 9388.279108.1
 December103 3328.396 7938.388 7598.380328.2
Birth weight (g)
 <150015 1301.211 0731.010 0160.910561.1<0.0001
 1500–199919 2821.513 4391.212 4541.29851.0
 2000–249960 0124.847 8254.144 0894.137383.8
 2500–2999213 07317.0195 55416.7179 23616.716 31916.7
 3000–3499447 03035.8427 60036.5391 92636.535 67536.5
 3500–3999357 50528.6342 60629.3314 06029.328 54029.2
 4000–4499116 4849.3111 7089.5102 5349.691769.4
 4500+20 7301.719 9401.718 3281.716111.7
 Missing12440.110451.04720.05750.6
Gestational age
 <2860710.546610.440610.46000.6<0.0001
 2820350.215240.113820.11420.2
 2923330.217390.216020.21370.1
 3029990.222610.220710.21890.2
 3138160.327910.225700.22210.2
 3253670.438200.335090.33110.3
 3375200.655810.551930.53880.4
 3412 2611.092250.885060.87190.7
 3518 0491.414 1701.213 0491.211221.2
 3633 7012.727 5352.425 2712.422642.3
 3771 6435.762 0345.356 9175.351175.2
 38168 88713.5156 20013.3142 97513.313 22613.5
 39272 46921.8260 44322.3238 74122.321 70722.2
 40337 79327.0322 74827.6296 39927.626 34727.0
 41242 26419.4234 54720.0215 21720.119 32519.8
 4248 2403.947 2374.043 5214.137163.8
 43+50630.448930.445780.43150.3
 Missing99790.893810.875530.718291.9
  • All live births = all live births within the Office for National Statistics (ONS) birth cohort.

  • All eligible births = all live, singleton, NHS hospital births to mothers living in England within the ONS birth cohort.

  • Linked = all eligible births from ONS birth cohort that successfully linked with an Hospital Episode Statistics (HES) birth record.

  • Unlinked = all eligible births from ONS birth cohort that did not successfully link with an HES birth record.

  • 2 test: linked versus unlinked.

  • IMD, Index of Multiple Deprivation.