Table 1.
Perinatal, Neonatal, and Current Characteristics of Cases and Controls, Northern Finland, 2009–2011
| Characteristic | Early Preterm (n = 134) |
P Valuea | Late Preterm (n = 242) |
P Valuea | Controls (n = 344) |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No. | % | Mean (SD) | No. Missing | No. | % | Mean (SD) | No. Missing | No. | % | Mean (SD) | No. Missing | |||
| Male | 65 | 48.5 | 0.95 | 120 | 49.6 | 0.86 | 168 | 48.8 | ||||||
| Peri- and neonatal characteristics | ||||||||||||||
| Pregnancy with multiple fetuses | 32 | 23.9 | <0.001 | 34 | 14.0 | <0.001 | 4 | 1.2 | ||||||
| Maternal hypertensionb | 17 | 12.7 | 0 | 0.51 | 36 | 15.2 | 5 | 0.10 | 36 | 10.6 | 4 | |||
| Maternal preeclampsiac | 32 | 23.9 | 0 | <0.001 | 22 | 9.3 | 5 | <0.001 | 16 | 4.7 | 4 | |||
| Maternal gestational diabetes | 4 | 3.5 | 21 | 0.28 | 11 | 5.0 | 24 | 0.03 | 6 | 1.8 | 9d | |||
| Maternal smoking during pregnancy | 21 | 16.5 | 7 | 0.94 | 46 | 19.3 | 4 | 0.44 | 57 | 16.8 | 5 | |||
| Cesarean delivery | 80 | 59.7 | <0.001 | 67 | 27.7 | <0.001 | 41 | 11.9 | ||||||
| Gestational age, weeks | 31.8 (2.0) | <0.001 | 35.8 (0.8) | <0.001 | 40.1 (1.2) | |||||||||
| Birth weight, grams | 1,786 (493) | <0.001 | 2,674 (515) | <0.001 | 3,576 (483) | |||||||||
| Birth weight SD score | −0.73 (1.4) | <0.001 | −0.63 (1.3) | <0.001 | −0.02 (1.0) | |||||||||
| Small for gestational age | 22 | 16.4 | <0.001 | 30 | 12.4 | <0.001 | 7 | 2.0 | ||||||
| Large for gestational age | 4 | 3.0 | 0.91 | 5 | 2.1 | 0.41 | 11 | 3.2 | ||||||
| Respirator treatment | 68 | 50.7 | <0.001 | 28 | 11.6 | <0.001 | 2 | 0.6 | ||||||
| Duration of respirator treatment, dayse | 7.0 (10.4) | 0.55 | 2.8 (2.7) | 0.86 | 2.5 (0.7) | |||||||||
| Supplementary oxygen | 98 | 73.1 | <0.001 | 93 | 38.4 | <0.001 | 7 | 2.0 | ||||||
| Duration of supplementary oxygen, daysf | 9.0 (14.1) | 0.15 | 2.0 (3.6) | 0.59 | 1.3 (1.9) | |||||||||
| Current | ||||||||||||||
| Age, years | 23.1 (1.4) | <0.001 | 23.2 (1.3) | <0.001 | 23.6 (1.1) | |||||||||
| Parental educational level | 1 | 0.51 | 5 | 0.62 | 4 | |||||||||
| Basic or less or unknown | 12 | 9.0 | 19 | 8.0 | 20 | 5.9 | ||||||||
| Secondary | 81 | 60.9 | 134 | 56.5 | 207 | 60.9 | ||||||||
| Lower-level tertiary | 13 | 9.8 | 31 | 13.1 | 45 | 13.2 | ||||||||
| Upper-level tertiary | 27 | 20.3 | 53 | 22.4 | 68 | 20.0 | ||||||||
| Maternal history of hypertension | 19 | 15.1 | 8 | 0.53 | 39 | 16.9 | 3 | 0.18 | 42 | 12.8 | 17 | |||
| Maternal history of diabetes | 3 | 2.4 | 8 | 0.41 | 17 | 7.4 | 12 | 0.08 | 13 | 4.0 | 16 | |||
| Maternal history of myocardial infarction or stroke | 2 | 1.6 | 7 | 0.13 | 4 | 1.7 | 12 | 0.08 | 1 | 0.3 | 17 | |||
| Paternal history of hypertension | 19 | 15.2 | 9 | 0.62 | 39 | 17.3 | 16 | 0.97 | 56 | 17.1 | 17 | |||
| Paternal history of diabetes | 6 | 4.8 | 9 | 0.07 | 20 | 8.8 | 16 | 0.63 | 33 | 10.1 | 17 | |||
| Paternal history of myocardial infarction or stroke | 8 | 6.4 | 9 | 0.81 | 15 | 6.6 | 15 | 0.69 | 19 | 5.8 | 17 | |||
| Self-reported physical activity, MET-hours/week | 23.5 (13.8) | 4 | 0.08 | 24.9 (14.5) | 7 | 0.35 | 26.0 (13.8) | 10 | ||||||
| Daily smoking | 39 | 29.1 | 0.08 | 54 | 22.3 | 0.82 | 74 | 21.5 | ||||||
| Amount of alcohol doses per week | 3 | 0.89 | 9 | 0.31 | 12 | |||||||||
| 0 | 23 | 17.6 | 51 | 21.9 | 57 | 17.2 | ||||||||
| 1–3 | 60 | 45.8 | 87 | 37.3 | 142 | 42.8 | ||||||||
| 4–9 | 24 | 18.3 | 57 | 24.5 | 71 | 21.4 | ||||||||
| 10 or more | 24 | 18.3 | 38 | 16.3 | 62 | 18.7 | ||||||||
| Use of β-blockers | 1 | 1.4 | 0.56 | 2 | 1.6 | 0.52 | 4 | 2.3 | ||||||
| Hormonal contraception (% of women) | 24 | 34.8 | 0.30 | 45 | 36.9 | 0.37 | 74 | 42.0 | ||||||
Abbreviations: MET, metabolic equivalent; SD, standard deviation.
a P values refer to comparisons between subjects who were born preterm and controls, using Student's t test or Pearson's χ2 test (and Fisher's exact test for use of antihypertensive drug).
b Gestational or chronic hypertension.
c Includes superimposed preeclampsia.
d Subjects who had missing data on maternal gestational diabetes included subjects whose mothers did not undergo an oral glucose tolerance test despite risk factors and thus have uncertain gestational diabetes status.
e Among those treated in respirator.
f Among those treated with supplementary oxygen.