Table 1. Clinical characteristics.
| Variable | 1Cases (n = 207) | Controls (n = 217) | 2p |
| Parity | 0 [0–4] | 1 [0–4] | <0.001 |
| Gestational Age (days) | 253 [182–258] | 280 [273–286] | <0.001 |
| Birth weight (grams) | 2810 [950–4000] | 3650 [2610–4970] | <0.001 |
| APGAR at 1 minute (%<7) | 16 (8%) | 12 (6%) | 0.355 |
| APGAR at 5 minutes (%<7) | 3 (1%) | 5 (2%) | 0.522 |
| Maternal Age (yrs) | 29 [20]–[34] | 30 [21]–[34] | 0.203 |
| Smoking (%) | 22 (12%) | 21 (11%) | 0.770 |
Parity is defined as the number of times a woman has given birth.
Medians are reported with the range in brackets.
1
Cases are defined as <37 weeks gestation compared with the women delivering at term between 39–40 weeks (controls).
2
P-values are calculated by Mann Whitney U- test for continuous variables and chi-square test or Fisher's exact test for dichotomous variables.