Maternal/pregnancy characteristics by small-for-gestational-age (SGA) status (birth weight <10th percentile for gestational age) in the University Hospital Southampton (UHS) maternity population-based cohort (singleton live births 2004–2016, n=65 909)
| Characteristics | SGA | Non-SGA | % SGA | |||
| n | % | n | % | % SGA | 99% CI | |
| Highest qualification | ||||||
| University degree or higher | 1550 | 24.4 | 17 518 | 29.5 | 8.1 | 7.6 to 8.6 |
| College | 2378 | 37.4 | 24 011 | 40.4 | 9.0 | 8.5 to 9.5 |
| Secondary school or lower | 2429 | 38.2 | 17 958 | 30.2 | 11.9 | 11.3 to 12.5 |
| Maternal employment | ||||||
| Employed | 3877 | 61.3 | 40 561 | 68.6 | 8.7 | 8.4 to 9.1 |
| Unemployed | 2446 | 38.7 | 18 533 | 31.4 | 11.6 | 11.1 to 12.2 |
| Partner’s employment | ||||||
| Employed | 4981 | 85.6 | 50 675 | 90.9 | 8.9 | 8.6 to 9.3 |
| Unemployed | 841 | 14.4 | 5079 | 9.1 | 14.2 | 13.0 to 15.4 |
| Partnership | ||||||
| Partnered | 5721 | 90.0 | 55 054 | 92.5 | 9.4 | 9.1 to 9.7 |
| Lone mother | 639 | 10.0 | 4495 | 7.6 | 12.4 | 11.3 to 13.7 |
| Maternal BMI | ||||||
| <18.5 (underweight) | 395 | 6.2 | 1586 | 2.7 | 19.9 | 17.6 to 22.3 |
| 18.5–24.9 (normal weight) | 3641 | 57.3 | 30 758 | 51.7 | 10.6 | 10.1 to 11 |
| 25–29.9 (overweight) | 1425 | 22.4 | 16 083 | 27.0 | 8.1 | 7.6 to 8.7 |
| 30+ (obese) | 899 | 14.1 | 11 122 | 18.7 | 7.5 | 6.9 to 8.1 |
| Smoking | ||||||
| Never smoked | 3059 | 48.1 | 30 791 | 51.8 | 9.0 | 8.6 to 9.4 |
| Ex-smoker | 1492 | 23.5 | 19 758 | 33.2 | 7.0 | 6.6 to 7.5 |
| <10 per day | 1040 | 16.4 | 5557 | 9.4 | 15.8 | 14.6 to 17.0 |
| 10–20 per day | 694 | 10.9 | 3103 | 5.2 | 18.2 | 16.6 to 19.9 |
| >20 per day | 71 | 1.1 | 252 | 0.4 | 22.0 | 16.3 to 28.5 |
| Maternal age | ||||||
| 18–24 | 2004 | 31.5 | 14 364 | 24.1 | 12.2 | 11.6 to 12.9 |
| 25–34 | 3428 | 53.9 | 35 678 | 59.9 | 8.8 | 8.4 to 9.1 |
| 35–39 | 758 | 11.9 | 8004 | 13.5 | 8.6 | 7.9 to 9.4 |
| 40+ | 170 | 2.7 | 1503 | 2.5 | 10.1 | 8.3 to 12.2 |
| Previous live births | ||||||
| None | 3526 | 55.4 | 25 136 | 42.2 | 12.3 | 11.8 to 12.8 |
| One or more | 2834 | 44.6 | 34 413 | 57.8 | 7.6 | 7.2 to 8 |
| Maternal ethnicity | ||||||
| White | 4807 | 75.6 | 49 531 | 83.2 | 8.8 | 8.5 to 9.2 |
| Mixed | 87 | 1.4 | 721 | 1.2 | 10.8 | 8.1 to 13.9 |
| Asian | 810 | 12.8 | 3622 | 6.1 | 18.3 | 16.8 to 19.8 |
| Black/African/Caribbean | 148 | 2.3 | 1096 | 1.8 | 11.9 | 9.6 to 14.4 |
| Chinese | 31 | 0.5 | 429 | 0.7 | 6.8 | 4.1 to 10.4 |
| Other | 116 | 1.8 | 832 | 1.4 | 12.2 | 9.6 to 15.2 |
| Not known | 361 | 5.7 | 3318 | 5.6 | 9.8 | 8.6 to 11.1 |
| Gestational diabetes | ||||||
| Not present in current pregnancy | 6213 | 97.7 | 58 074 | 97.5 | 9.7 | 9.4 to 10.0 |
| Present in current pregnancy | 147 | 2.3 | 1475 | 2.5 | 9.0 | 7.3 to 11 |
| Systolic blood pressure | ||||||
| <140 mm Hg | 6219 | 99.0 | 57 831 | 98.6 | 9.7 | 9.4 to 10 |
| >=140 mm Hg | 64 | 1.0 | 812 | 1.4 | 7.3 | 5.2 to 9.9 |
| Overall | 6360 | 100 | 59 549 | 100 | 9.7 | 9.4 to 9.9 |
| SGA | Non-SGA | P value for t-test | |||
| Mean | SD | Mean | SD | ||
| Maternal BMI | 24.5 | 5.3 | 25.7 | 5.5 | <0.001 |
| Maternal age | 27.9 | 5.8 | 28.8 | 5.5 | <0.001 |
| Maternal systolic blood pressure | 108.7 | 11.5 | 109.9 | 11.3 | <0.001 |
Source: UHS antenatal records for live singleton births (2004–2016). Records with a late antenatal booking (over 24-week gestation) were excluded. Variables with missing information include maternal education (65), maternal employment (492), maternal smoking (92), maternal systolic blood pressure (983) and partner’s employment (4333). The percentage SGA column indicates the percentage of babies born SGA for this characteristic, and the accompanying 99% CI. The t-test indicates whether the mean of each variable differs between those born SGA and non-SGA.
BMI, body mass index.