Background
Materials and methods
-
Respiratory distress syndrome (RDS): oxygen-dependence increasing during the first 24 h, typical radiological findings: reduced air content, reticulogranular pattern of the lungs, bronchogram.
-
Transient tachypnea of the newborn (TTN): oxygen supplement requirement during the first 6 h which decreases during the subsequent 18 h, improvement in clinical condition within 6 h and chest x-rays which are either normal or show reduced translucency, infiltrates and hyperinsufflation of the lungs.
-
Apnea: breathing pauses that last for >20 seconds or for >10 seconds if associated with bradycardia or oxygen desaturation.
-
Persistent pulmonary hypertension (PPH): persistent elevation in pulmonary artery pressure with right-left shunt and hypoxia.
-
Air leak: presence of pneumothorax and/or pneumomediastinum.
-
Meconium aspiration syndrome (MAS): respiratory distress in a meconium-stained newborn and chest x-ray indicating aspiration.
-
Respiratory failure: other respiratory clinical conditions not included in previous categories which needed respiratory support.
Results
34 | 35 | 36 | LPI | 37 | 38 | 39 | 40 | 41 | TI | 34-41 | |
---|---|---|---|---|---|---|---|---|---|---|---|
n = 151 | n = 241 | n = 458 |
n = 850
| n = 1149 | n = 2444 | n = 3343 | n = 3729 | n = 2261 |
n = 12926
|
n = 13776
| |
Age
| |||||||||||
Mean (SD) | 32.4(5.4) | 31.7(6.6) | 32.9(4.8) |
32.5(5.5)
| 32.7(5.2) | 32.5(5.1) | 32.1(5.0) | 32.1(5.1) | 31.9(5.0) |
32.2(5.1)
|
32.2(5.2)
|
Number of US
***
| |||||||||||
Mean (SD) | 4.7(2.3) | 5.0(2.8) | 5.2(4.7) |
5.1(4.0)
| 4.5(3.4) | 4.0(2.2) | 3.6(1.6) | 3.5(1.5) | 3.5(2.0) |
3.7(2.0)
|
3.9(2.1)
|
Ethnicity
| |||||||||||
Caucasian | 119(89.5) | 181(85.0) | 357(86.9) |
657(86.8)
| 933(88.0) | 1953(85.8) | 2722(88.1) | 3097(88.6) | 1852(88.0) |
10557(87.8)
|
11214(81.4)
|
African | 7(5.3) | 10(4.7) | 21(5.1) |
38(5.0)
| 51(4.8) | 115(5.1) | 135(4.4) | 155(4.4) | 115(5.5) |
571(4.8)
|
609(4.4)
|
Hispanic | 3(2.3) | 18(8.4) | 22(5.4) |
43(5.7)
| 41(3.9) | 112(4.9) | 138(4.5) | 128(3.7) | 71(3.4) |
490(4.0)
|
533(3.8)
|
Asian | 4(3.0) | 4(1.9) | 11(2.7) |
19(2.5)
| 35(3.3) | 97(4.3) | 94(3.0) | 114(3.3) | 67(3.2) |
407(3.4)
|
426(3.1)
|
ART
***
| |||||||||||
Yes | 4(2.9) | 3(1.3) | 6(1.3) |
13(1.6)
| 16(1.4) | 12(0.5) | 15(0.5) | 14(0.4) | 7(0.3) |
64(0.5)
|
73(0.5)
|
Medical disorders
***
| |||||||||||
Yes | 53(45.7) | 83(40.5) | 128(32.6) |
264(37.0)
| 281(27.6) | 422(18.8) | 265(8.6) | 288(8.4) | 151(7.4) |
1407(11.9)
|
1671(12.1)
|
34 | 35 | 36 | LPI | 37 | 38 | 39 | 40 | 41 | TI | 34–41 | |
---|---|---|---|---|---|---|---|---|---|---|---|
n = 151 | n = 241 | n = 458 |
n = 850
| n = 1149 | n = 2444 | n = 3343 | n = 3729 | n = 2261 |
n = 12926
|
n = 13776
| |
Birth weight
***
| |||||||||||
Mean (SD), g | 2128(406) | 2323(431) | 2592(429) |
2433(463)
| 2887(455) | 3115(414) | 3269(385) | 3401(392) | 3545(391) |
3292(442)
|
3289 (489)
|
SGA
***
| 17(11.3) | 40(16.6) | 69(15.1) |
126(14.8)
| 163(14.2) | 257(10.6) | 298(8.9) | 328(8.8) | 156(6.9) |
1202(9.3)
|
1328(9.6)
|
Gender
| |||||||||||
Male | 73(48.3) | 124(51.5) | 242(52.8) |
439(51.6)
| 618(53.8) | 1311(53.6) | 1710(51.2) | 1933(51.8) | 1195(52.9) |
6767(52.3)
|
7206(52.3)
|
Twin
***
| 50(33.1) | 66(27.4) | 105(22.9) |
221(26.0)
| 108(9.4) | 90(3.7) | 14(0.4) | 0 | 0 |
212(1.6)
|
233(1.7)
|
Malformation
**
| 6(4.0) | 7(2.9) | 7(1.5) |
20(2.4)
| 27(2.4) | 35(1.4) | 35(1.1) | 44(1.2) | 23(1.3) |
164(1.3)
|
184(1.3)
|
Delivery
***
| |||||||||||
Spontaneous | 68(45.0) | 116(48.1) | 295(64.4) |
479(56.4)
| 815(70.9) | 1821(74.5) | 2961(88.6) | 3341(89.6) | 1946(86.1) |
10884(84.2)
|
11363(82.5)
|
CS without labor | 53(35.1) | 104(43.2) | 120(26.2) |
277(32.6)
| 246(21.4) | 459(18.8) | 201(6.0) | 79(2.1) | 58(2.6) |
1043(8.1)
|
1320(9.6)
|
CS with labor | 30(19.9) | 21(8.7) | 43(9.4) |
94(11.1)
| 88(7.7) | 164(6.7) | 181(5.4) | 309(8.3) | 257(11.4) |
999(7.7)
|
1093(7.9)
|
Apgar < 7 at 5 min
***
| 5(3.3) | 4(1.7) | 2(0.4) |
11(1.3)
| 6(0.5) | 7(0.3) | 8(0.2) | 6(0.2) | 6(0.3) |
33(0.3)
|
44(0.3)
|
Resuscit. at birth
***
| 19(12.6) | 40(16.6) | 30(6.6) |
89(10.5)
| 61(5.3) | 64(2.6) | 48(1.4) | 50(1.3) | 38(1.7) |
261(2.0)
|
350(2.5)
|
Admission to NICU
***
| |||||||||||
Yes | 81(53.6) | 92(38.2) | 72(15.7) |
245(28.8)
| 88(7.7) | 93(3.8) | 74(2.2) | 83(2.2) | 65(2.9) |
403(3.1)
|
648(4.7)
|
Yes, for resp. disordersa
| 37(45.7) | 38(41.3) | 23(31.9) |
98(40.0)
| 30(34.1) | 26(28.0) | 14(18.9) | 21(25.3) | 12(18.5) |
103(25.6)
|
201(2.2)
|
Length of stay
| |||||||||||
Median (IQR), days | |||||||||||
Total***
| 7.8(5–13.1) | 6(4.3–10.8) | 4.3(3.3–6.3) |
5.3(3.8–8.1)
| 3.6(2.8–4.9) | 3.1(2.6–4.1) | 3(2.5–3.4) | 2.9(2.5–3.4) | 3(2.6–3.6) |
3(2.5–3.8)
|
3(2.6–4)
|
No NICU***
| 5.1(4.3–6.2) | 4.8(3.9–6.3) | 4(3.2–5.4) |
4.3(3.4–5.8)
| 3.4(2.7–4.4) | 3.1(2.6–4) | 2.9(2.5–3.4) | 2.9(2.5–3.4) | 2.9(2.6–3.6) |
3(2.5–3.7)
|
3(2.6–3.8)
|
NICU***
| 12(8.4–17) | 12(7.1–15.2) | 10.4(7.6–16) |
11.6 (8–15.8)
| 8.9(6.6–14.5) | 8.8(6.1–14.3) | 8.7(6.7–10.7) | 7.9(5.6–9.9) | 7.7(5.1–10.2) |
8.4(5.9–12.4)
|
9.2(6.7–14.3)
|
NICU resp. disorders | 12(8–18.2) | 10.5(6.9–14) | 8.2(5.2–13.6) |
10.2(7–15)
| 8.5(5.5–19.2) | 6.9(5.1–12.2) | 8.4(6.9–10.7) | 9.8(8.3–13.2) | 7.9(5.6–11.5) |
8.6(6.1–13.2)
|
9.5(6.7–15)
|
Mortality
***
| 1(0.66) | 3(1.2) | 1(0.22) |
5(0.6)
| 6(0.5) | 2(0.08) | 0(0.0) | 1(0.03) | 1(0.04) |
10(0.08)
|
15(0.1)
|
Age at death
| |||||||||||
Median (IQR), days | 11 | 14(1–59) | 8 |
11(8–14)
| 1(0–22) | 25(23–27) | - | 2 | 0 |
1.5(0–23)
|
8(1–22.5)
|
34 | 35 | 36 | LPI | 37 | 38 | 39 | 40 | 41 | TI | 34-41 | |
---|---|---|---|---|---|---|---|---|---|---|---|
n = 151 | n = 241 | n = 458 |
n = 850
| n = 1149 | n = 2444 | n = 3343 | n = 3729 | n = 2261 |
n = 12926
|
n = 13776
| |
CRM
a***
| 38 (25.2) | 38 (15.8) | 29 (6.3) |
105 (12.4)
| 32 (2.8) | 28 (1.1) | 19 (0.6) | 28 (0.8) | 14 (0.6) |
121 (0.9)
|
226 (1.6)
|
TTN***
| 13 (8.6) | 18 (7.5) | 18 (3.9) |
49 (5.8)
| 15 (1.3) | 17 (0.7) | 10 (0.3) | 14 (0.4) | 8 (0.4) |
64 (0.5)
|
113 (0.8)
|
RDS***
| 17 (11.3) | 16 (6.6) | 7 (1.5) |
40 (4.7)
| 9 (0.8) | 3 (0.1) | 2 (0.1) | 2 (0.1) | 1(0.0) |
17 (0.1)
|
57 (0.4)
|
Apnea***
| 5 (3.3) | 2 (0.8) | 3 (0.7) |
10 (1.2)
| 3 (0.3) | 2 (0.1) | 2 (0.1) | 2 (0.1) | 1 (0.0) |
10 (0.1)
|
20 (0.1)
|
Air leak***
| 5 (3.3) | 3 (1.2) | 3 (0.7) |
11 (1.3)
| 4 (0.3) | 4 (0.2) | 4 (0.1) | 4 (0.1) | 1 (0.0) |
17 (0.1)
|
28 (0.1)
|
PPH***
| 0 (0.0) | 1 (0.4) | 3 (0.7) |
4 (0.5)
| 1 (0.1) | 0 (0.0) | 1 (0.0) | 2 (0.1) | 0 (0.0) |
4 (0.0)
|
8 (0.2)
|
MAS | 0 (0.0) | 0 (0.0) | 0 (0.0) |
0 (0.0)
| 0 (0.0) | 0 (0.0) | 1 (0.0) | 4 (0.1) | 3 (0.1) |
8 (0.1)
|
8 (0.05)
|
Respiratory failure**
| 3 (2.0) | 2 (0.8) | 0 (0.0) |
5 (0.6)
| 4 (0.3) | 6 (0.2) | 1 (0.0) | 4 (0.1) | 1 (0.0) |
16 (0.1)
|
21 (0.15)
|
Respiratory support***
| 33 (21.8) | 31 (12.8) | 20 (4.3) |
84 (9.8%)
| 23 (2) | 15 (0.6) | 11 (0.3) | 14 (0.4) | 10 (0.4) |
73 (0.56)
|
157 (1.14)
|
Mechanical ventilation*
| 7 (4.6) | 4 (1.65) | 2 (0.43) |
13 (1.5)
| 5 (0.43) | 2 (0.08) | 2 (0.06) | 5 (0.13) | 2 (0.08) |
16 (0.12)
|
29 (0.21)
|
Data are expressed as absolute numbers and proportions (%) of observed data in each category. All tests refer to comparisons between late preterm infants (LPI) and term infants (TI). |
34 | 35 | 36 | LPI | 37 | 38 | 39 | 40 | 41 | TI | |
---|---|---|---|---|---|---|---|---|---|---|
n = 38 | n = 38 | n = 29 |
n = 105
| n = 32 | n = 28 | n = 19 | n = 28 | n = 14 |
n = 121
| |
Nasal oxygen**
| 0 (0.0) | 1 (2.6) | 2 (6.9) |
3 (2.9)
| 5 (15.6) | 2 (7.1) | 3 (15.8) | 5 (17.9) | 3 (21.4) |
18 (14.9)
|
N-CPAP***
| 26 (68.4) | 26 (68.4) | 16 (55.2) |
68 (64.8)
| 13 (40.6) | 11 (39.3) | 6 (31.6) | 4 (14.3) | 5 (35.7) |
39 (32.2)
|
MV | 7 (18.4) | 4 (10.5) | 2 (6.9) |
13 (12.4)
| 5 (15.6) | 2 (7.1) | 2 (10.5) | 5 (17.9) | 2 (14.3) |
16 (13.2)
|
Surfactant*
| 6 (15.8) | 7 (18.4) | 4 (13.8) |
17 (16.2)
| 5 (15.6) | 0 (0.0) | 0 (0.0) | 3 (10.7) | 0 (0.0) |
8 (6.6)
|
INO | 0 (0.0) | 2 (5.3) | 2 (6.9) |
4 (3.8)
| 3 (9.4) | 0 (0.0) | 0 (0.0) | 2 (7.1) | 0 (0.0) |
5 (4.1)
|
Pleural drainage | 6 (15.8) | 1 (2.6) | 1 (3.5) |
8 (7.6)
| 5 (15.6) | 1 (3.6) | 0 (0.0) | 1 (3.6) | 1(7.1) |
8 (6.6)
|
Data are expressed as absolute numbers and proportions (%) of observed data in each category. All tests refer to comparisons between late preterm infants (LPI) and term infants (TI). |
Odds ratio estimates (95% confidence interval) | ||
---|---|---|
Late preterm birth | CRM | |
Maternal age | 1.002 (0.982–1.021) | 1.007 (0.971–1.043) |
Maternal medical disorders no | 1 | 1 |
Maternal medical disorders yes | 3.8 (3.1–4.7) | 3.3 (2.3–4.7) |
Twins birth no | 1 | 1 |
Twins birth yes | 19.3 (14.6–25.4) | 4.3 (2.6–7.3) |
Odds ratio estimates (95% confidence interval) | |||
---|---|---|---|
CRM | N-CPAP | MV | |
Gest. age, weeks 39–40–41 | 1 | 1 | 1 |
Gest. age, week 38 | 1.5 (0.9– 2.4) | 2.0 (0.9–4.5) | 0.96 (0.3–3.1) |
Gest. age, week 37 | 3.3 (2.0–5.5) | 5.1 (2.3–11.4) | 3.4 (1.2–10.0) |
Gest. age, week 36 | 9.1 (5.1–16.2) | 13.3 (5.5–32.2) | 11.1 (3.2–38.8) |
Gest. age, week 35 | 21.8 (11.5–41.5) | 34.9 (13.5–90.0) | 18.0 (4.2–77.5) |
Gest. age, week 34 | 40.8 (19.7 –84.9) | 55.9 (19.3–162.0) | 34.4 (6.7–180.6) |
Spontaneous delivery | 1 | 1 | 1 |
CS without labor | 3.0 (2.1–4.2) | 3.7 (2.3–6.0) | 2.9 (1.3–6.3) |
CS with labor | 2.2 (1.4–3.4) | 2.5 (1.4–4.8) | 2.1 (0.8–5.6) |
Maternal medical disorders no | 1 | 1 | 1 |
Maternal medical disorders yes | 1.3 (0.9–1.8) | 1.3 (0.7–1.6) | 1.7 (0.8–3.4) |
Twins birth no | 1 | 1 | 1 |
Twins birth yes | 0.9 (0.5–1.4) | 1.0 (0.6–1.7) | 0.3 (0.1–1.3) |
Birth weight, g | 1.0 (0.98–1.1) | 1.0 (0.9–1.05) | 1.1 (0.98–1.2) |
Female | 1 | 1 | 1 |
Male | 1.4 (1.1–1.9) | 1.5 (1.0–2.3) | 1.8 (0.9–3.6) |
Malformation no | 1 | 1 | 1 |
Malformation yes | 8.9 (5.3–15.1) | 2.4 (0.9–6.2) | 26.0 (12.5–54.1) |
Small for gestational age no | 1 | 1 | 1 |
Small for gestational age yes | 1.0 (0.6–1.8) | 0.6 (0.3–1.3) | 2.6 (0.9–7.9) |