Table 1

 Characteristics of study population by year, Flanders, 2002–11. Values are medians (10–90th centiles) unless stated otherwise

YearTotal birthsAll preterm birthsMild pretermModerate pretermExtreme preterm
No of birthsMaternal age (years)Birth weight (g)% SGA% LBW% RateBirth weight (g)% RateBirth weight (g)% RateBirth weight (g)% RateBirth weight (g)
Spontaneous delivery
200238 65829.3 (23.3–35.3)3320 (2690–3910)10.985.637.412510 (1480–3170)5.812650 (2120–3230)0.791985 (1390–2480)0.821220 (750–1795)
200338 99029.4 (23.3–35.4)3318 (2690–3910)10.495.697.422520 (1535–3130)5.902650 (2100–3190)0.781940 (1440–2460)0.741195 (740–1793)
200442 07729.4 (23.5–35.6)3330 (2705–3920)9.925.507.522550 (1495–3180)5.832680 (2110–3240)0.791990 (1490–2485)0.891250 (732–1800)
200543 29029.4 (23.6–35.7)3330 (2705–3920)10.155.397.382520 (1470–3170)5.802655 (2090–3250)0.761963 (1483–2435)0.821160 (715–1700)
200645 00329.4 (23.6–35.8)3330 (2700–3925)9.825.327.362540 (1530–3140)5.742660 (2100–3200)0.851940 (1475–2.400)0.761250 (720–1735)
200746 27629.4 (23.6–35.8)3330 (2720–3920)9.835.126.932520 (1511–3145)5.372655 (2140–3200)0.791995 (1490–2450)0.771210 (740–1775)
200847 89329.5 (23.6–35.9)3345 (2720–3940)9.245.227.152510 (1510–3130)5.582650 (2110–3200)0.781990 (1490–2400)0.791250 (712–1850)
200948 23729.5 (23.6–35.9)3345 (2720–3940)9.695.156.982515 (1480–3150)5.382660 (2120–3220)0.821984 (1380–2400)0.781240 (750–1795)
201049 16629.7 (23.8–35.9)3350 (2730–3940)9.244.856.842530 (1470–3135)5.282655 (2120–3200)0.761980 (1470–2470)0.811220 (705–1770)
201148 93029.7 (23.8–36.0)3350 (2730–3940)9.624.896.802510 (1450–3145)5.262660 (2120–3220)0.721963 (1405–2418)0.821240 (720–1765)
Total448 52029.5 (23.6–35.8)3335 (2710–3930)9.865.267.162520 (1490–3150)5.582660 (2115–3215)0.781975 (1448–2430)0.801220 (730–1780)
Overall delivery
200255 27529.3 (23.2–35.3)3350 (2730–3950)10.744.915.992520 (1540–3180)4.742650 (2100–3250)0.591970 (1390–2460)0.611220 (750–1790)
200355 63929.3 (23.2–35.4)3350 (2720–3950)10.344.895.982530 (1600–3140)4.842640 (2090–3200)0.591940 (1440–2460)0.551200 (740–1790)
200458 04129.4 (23.4–35.7)3360 (2740–3960)9.904.876.262555 (1540–3180)4.962680 (2100–3240)0.621990 (1490–2493)0.681250 (730–1800)
200559 36829.4 (23.5–35.7)3360 (2740–3960)10.084.736.192535 (1510–3180)4.962660 (2080–3260)0.611970 (1490–2450)0.621160 (713–1700)
200660 87129.4 (23.5–35.8)3360 (2730–3960)9.814.736.162540 (1560–3155)4.902660 (2090–3210)0.661935 (1470–2400)0.601260 (720–1740)
200761 84729.4 (23.5–35.9)3360 (2740–3960)9.774.645.862520 (1560–3145)4.612650 (2120–3200)0.641990 (1480–2430)0.611210 (740–1770)
200863 99929.5 (23.5–36.0)3370 (2750–3980)9.304.696.112520 (1550–3145)4.842650 (2100–3210)0.631990 (1490–2410)0.631255 (710–1850)
200963 41529.5 (23.5–36.0)3370 (2740–3975)9.714.746.072520 (1528–3150)4.772655 (2090–3220)0.671980 (1385–2400)0.631240 (750–1798)
201064 37229.6 (23.7–36.0)3375 (2750–3980)9.434.595.982530 (1520–3135)4.692650 (2090–3195)0.651975 (1470–2465)0.641220 (705–1770)
201164 05029.7 (23.8–36.0)3370 (2750–3980)9.654.525.882510 (1490–3155)4.622650 (2090–3220)0.611955 (1400–2408)0.651240 (712–1765)
Total606 87729.5 (23.5–35.8)3360 (2740–3965)9.854.736.042530 (1540–3155)4.792650 (2100–3220)0.631970 (1450–2430)0.621220 (725–1780)

SGA = Small for gestational age. LBW = Low birth weight (<2500 g).

Preterm categories: mild = 34–36 weeks gestation, moderate = 32–33 weeks, extreme= <32 weeks.

Parity was constant over the study period: median (10–90th centile) = 2 (1–3).