Table 1.

Distribution of maternal characteristics in the study categories.

	Mid-trimester (n = 65)	Term not in labor (n = 22)	Term in labor (n = 47)	Preterm labor (n = 209)
Maternal age (years)	37 (35–38)	28.5 (21.8–32)	23 (20–28)	23.9 (20–27)
Gravity	3 (2–3)	3 (2–4)	2 (1–3.3)	3 (2–4)
Gestational age at amniocentesis (weeks)	16 (16–17)	39.3 (38.4–40)	39 (38–40)	28.5 (24.7–32.4)
Amniotic fluid sample storage time (years)	11.7 (10.9–12.2)	16.6 (16.5–16.6)	16.6 (16.6–16.7)	5.2 (4.7–6.1)
Gestational age at delivery (weeks)	39 (38–40)	39.3 (38.4–40)	39 (38–40)	33.1 (28.7–37.7)
Birth weight (grams)	3345 (3144–3632)	3405 (3130–3688)	3220 (3090–3680)	2044 (1110–2760)

Values are expressed as median (interquartile range).