Background
Methods
Study population
Definition of LBW, PTB, and SGA
Statistical analysis
Results
Characteristics | Total | 2004–2008 | 2009–2013 | 2014–2018 | 2019–2020 |
---|---|---|---|---|---|
n = 2,958,695 |
n = 708,808 |
n = 975,772 |
n = 980,609 |
n = 293,506 | |
Maternal characteristics | |||||
Age (years, mean \(\pm \mathrm{SD}\)) | 28.0 \(\pm\) 4.7 | 26.9 \(\pm\) 4.6 | 27.3 \(\pm\) 4.7 | 28.9 \(\pm\) 4.6 | 30.1 \(\pm\) 4.4 |
Education (n, %) | |||||
secondary and below | 1,477,447 (49.9) | 490,530 (69.2) | 530,592 (54.4) | 373,030 (38.0) | 83,295 (28.4) |
tertiary | 1,481,248 (50.1) | 218,278 (30.8) | 445,180 (45.6) | 607,579 (62.0) | 210,211 (71.6) |
Gravidity (n, %) | |||||
1 | 1,365,259 (46.1) | 337,315 (47.6) | 469,150 (48.1) | 431,993 (44.1) | 126,801 (43.2) |
2 | 837,105 (28.3) | 209,026 (29.5) | 266,389 (27.3) | 277,072 (28.3) | 84,618 (28.8) |
≥ 3 | 756,331 (25.6) | 162,467 (22.9) | 240,233 (24.6) | 271,544 (27.7) | 82,087 (28.0) |
Parity (n, %) | |||||
0 | 2,033,081 (68.7) | 532,336 (75.1) | 697,308 (71.5) | 620,668 (63.3) | 182,769 (62.3) |
1 | 844,240 (28.5) | 161,191 (22.7) | 248,971 (25.5) | 333,350 (34.0) | 100,728 (34.3) |
≥ 2 | 81,374 (2.8) | 15,281 (2.2) | 29,493 (3.0) | 26,591 (2.7) | 10,009 (3.4) |
Neonatal characteristics | |||||
Sex (n, %) | |||||
Male | 1,565,963 (52.9) | 378,860 (53.5) | 518,926 (53.2) | 515,056 (52.5) | 153,121 (52.2) |
Female | 1,392,732 (47.1) | 329,948 (46.5) | 456,846 (46.8) | 465,553 (47.5) | 140,385 (47.8) |
Birth weight (g, mean \(\pm \mathrm{SD}\)) | 3,334.8 \(\pm\) 442.8 | 3,340.6 \(\pm\) 443.4 | 3,338.0 \(\pm\) 441.0 | 3,333.1 \(\pm\) 442.4 | 3,316.0 \(\pm\) 447.7 |
Gestational age (days, mean \(\pm \mathrm{SD}\)) | 273.3 \(\pm\) 10.3 | 273.0 \(\pm\) 10.4 | 272.4 \(\pm\) 10.2 | 274.2 \(\pm\) 10.1 | 273.7 \(\pm\) 10.3 |
LBW (n, %) | 84,899 (2.9) | 19,372 (2.7) | 26,822 (2.7) | 28,888 (2.9) | 9817 (3.3) |
PTB (n, %) | 138,961 (4.7) | 31,014 (4.4) | 43,814 (4.5) | 48,293 (4.9) | 15,840 (5.4) |
SGA (n, %) | 274,746 (9.3) | 75,968 (10.7) | 93,956 (9.6) | 80,766 (8.2) | 24,056 (8.2) |
Specific trends for LBW, PTB, and SGA
APC effects for LBW, PTB, and SGA
Modela
|
Goodness of fit
|
Model comparison
| |||||||
---|---|---|---|---|---|---|---|---|---|
AIC | Residual Df | Residual Dev | Comparison | Change in Df | Change in Dev | Change in Dev/Df |
P
| Interpretation | |
LBW | |||||||||
Age | 1471.45 | 110 | 530.97 | ||||||
Age-driftb
| 1272.41 | 109 | 329.93 | 2 versus 1 | 1 | 201.05 | 201.05 | < 0.001 | Trend (drift) |
Age-Cohort | 1241.33 | 101 | 282.85 | 3 versus 2 | 8 | 47.08 | 5.88 | < 0.001 | Nonlinear cohort effect |
Age-Period-Cohortc
| 1160.83 | 99 | 198.35 | 4 versus 3 | 2 | 84.50 | 42.25 | < 0.001 | Period effect adjusted for cohort |
Age-Period | 1221.36 | 107 | 274.88 | 4 versus 5 | 8 | 76.53 | 9.57 | < 0.001 | Cohort effect adjusted for period |
5 versus 2 | 2 | 55.05 | 27.52 | < 0.001 | Nonlinear period effect | ||||
PTB | |||||||||
Age | 1476.57 | 110 | 476.48 | ||||||
Age-driftb
| 1240.69 | 109 | 238.60 | 2 versus 1 | 1 | 237.88 | 237.88 | < 0.001 | Trend (drift) |
Age-Cohort | 1206.79 | 101 | 188.71 | 3 versus 2 | 8 | 49.90 | 6.24 | < 0.001 | Nonlinear cohort effect |
Age-Period-Cohortc
| 1171.00 | 99 | 148.92 | 4 versus 3 | 2 | 39.79 | 19.89 | < 0.001 | Period effect adjusted for cohort |
Age-Period | 1222.87 | 107 | 216.79 | 4 versus 5 | 8 | 67.87 | 8.48 | < 0.001 | Cohort effect adjusted for period |
5 versus 2 | 2 | 21.82 | 10.91 | < 0.001 | Nonlinear period effect | ||||
SGA | |||||||||
Age | 2796.16 | 110 | 1736.37 | ||||||
Age-driftb
| 2005.90 | 109 | 944.11 | 2 versus 1 | 1 | 792.26 | 792.26 | < 0.001 | Trend (drift) |
Age-Cohort | 1657.44 | 101 | 579.66 | 3 versus 2 | 8 | 364.46 | 45.56 | < 0.001 | Nonlinear cohort effect |
Age-Period-Cohortc
| 1370.25 | 99 | 288.47 | 4 versus 3 | 2 | 291.19 | 145.59 | < 0.001 | Period effect adjusted for cohort |
Age-Period | 1785.60 | 107 | 719.82 | 4 versus 5 | 8 | 431.35 | 53.92 | < 0.001 | Cohort effect adjusted for period |
5 versus 2 | 2 | 224.30 | 112.15 | < 0.001 | Nonlinear period effect |
Factor | LBW | PTB | SGA | |||
---|---|---|---|---|---|---|
Age
|
Rate
|
95%CI
|
Rate
|
95%CI
|
Rate
|
95%CI
|
15 | 0.068 | ( 0.063 ~ 0.073) | 0.090 | ( 0.084 ~ 0.095) | 0.274 | ( 0.263 ~ 0.285) |
16 | 0.060 | ( 0.056 ~ 0.064) | 0.080 | ( 0.076 ~ 0.084) | 0.247 | ( 0.239 ~ 0.255) |
17 | 0.053 | ( 0.050 ~ 0.056) | 0.072 | ( 0.069 ~ 0.075) | 0.223 | ( 0.217 ~ 0.229) |
18 | 0.047 | ( 0.045 ~ 0.049) | 0.064 | ( 0.062 ~ 0.066) | 0.201 | ( 0.197 ~ 0.205) |
19 | 0.042 | ( 0.040 ~ 0.043) | 0.057 | ( 0.055 ~ 0.059) | 0.182 | ( 0.179 ~ 0.185) |
20 | 0.037 | ( 0.036 ~ 0.038) | 0.051 | ( 0.050 ~ 0.053) | 0.164 | ( 0.161 ~ 0.167) |
21 | 0.033 | ( 0.032 ~ 0.034) | 0.046 | ( 0.045 ~ 0.047) | 0.148 | ( 0.145 ~ 0.151) |
22 | 0.030 | ( 0.029 ~ 0.031) | 0.042 | ( 0.041 ~ 0.043) | 0.132 | ( 0.130 ~ 0.134) |
23 | 0.027 | ( 0.026 ~ 0.028) | 0.040 | ( 0.039 ~ 0.041) | 0.117 | ( 0.115 ~ 0.119) |
24 | 0.026 | ( 0.025 ~ 0.027) | 0.040 | ( 0.039 ~ 0.041) | 0.106 | ( 0.105 ~ 0.107) |
25 | 0.026 | ( 0.025 ~ 0.027) | 0.041 | ( 0.040 ~ 0.042) | 0.098 | ( 0.096 ~ 0.099) |
26 | 0.026 | ( 0.025 ~ 0.027) | 0.042 | ( 0.041 ~ 0.043) | 0.091 | ( 0.089 ~ 0.093) |
27 | 0.026 | ( 0.025 ~ 0.027) | 0.042 | ( 0.041 ~ 0.044) | 0.086 | ( 0.084 ~ 0.088) |
28 | 0.027 | ( 0.026 ~ 0.027) | 0.043 | ( 0.042 ~ 0.044) | 0.082 | ( 0.081 ~ 0.084) |
29 | 0.028 | ( 0.027 ~ 0.028) | 0.046 | ( 0.045 ~ 0.047) | 0.080 | ( 0.079 ~ 0.081) |
30 | 0.030 | ( 0.029 ~ 0.031) | 0.049 | ( 0.048 ~ 0.050) | 0.078 | ( 0.077 ~ 0.080) |
31 | 0.031 | ( 0.030 ~ 0.032) | 0.052 | ( 0.050 ~ 0.053) | 0.075 | ( 0.074 ~ 0.077) |
32 | 0.033 | ( 0.032 ~ 0.034) | 0.055 | ( 0.053 ~ 0.057) | 0.072 | ( 0.071 ~ 0.073) |
33 | 0.035 | ( 0.034 ~ 0.036) | 0.059 | ( 0.057 ~ 0.061) | 0.070 | ( 0.068 ~ 0.071) |
34 | 0.037 | ( 0.036 ~ 0.039) | 0.063 | ( 0.062 ~ 0.065) | 0.068 | ( 0.067 ~ 0.069) |
35 | 0.040 | ( 0.039 ~ 0.042) | 0.068 | ( 0.066 ~ 0.070) | 0.067 | ( 0.066 ~ 0.068) |
36 | 0.043 | ( 0.042 ~ 0.045) | 0.074 | ( 0.072 ~ 0.076) | 0.066 | ( 0.065 ~ 0.067) |
37 | 0.046 | ( 0.045 ~ 0.048) | 0.079 | ( 0.077 ~ 0.082) | 0.065 | ( 0.064 ~ 0.067) |
38 | 0.050 | ( 0.048 ~ 0.052) | 0.086 | ( 0.083 ~ 0.088) | 0.065 | ( 0.063 ~ 0.066) |
39 | 0.054 | ( 0.052 ~ 0.056) | 0.093 | ( 0.090 ~ 0.096) | 0.064 | ( 0.062 ~ 0.066) |
40 | 0.058 | ( 0.055 ~ 0.060) | 0.100 | ( 0.097 ~ 0.104) | 0.063 | ( 0.061 ~ 0.065) |
41 | 0.062 | ( 0.059 ~ 0.065) | 0.108 | ( 0.104 ~ 0.112) | 0.063 | ( 0.060 ~ 0.065) |
42 | 0.067 | ( 0.063 ~ 0.071) | 0.117 | ( 0.111 ~ 0.122) | 0.062 | ( 0.059 ~ 0.064) |
43 | 0.072 | ( 0.067 ~ 0.077) | 0.126 | ( 0.120 ~ 0.132) | 0.061 | ( 0.059 ~ 0.064) |
44 | 0.077 | ( 0.072 ~ 0.083) | 0.136 | ( 0.128 ~ 0.144) | 0.060 | ( 0.058 ~ 0.063) |
Period
|
RR
|
95%CI
|
RR
|
95%CI
|
RR
|
95%CI
|
2004 | 1.035 | ( 1.027 ~ 1.043) | 1.020 | ( 1.014 ~ 1.026) | 1.028 | ( 1.023 ~ 1.032) |
2009 | 0.970 | ( 0.960 ~ 0.979) | 0.979 | ( 0.972 ~ 0.987) | 0.986 | ( 0.981 ~ 0.991) |
2014 | 0.987 | ( 0.979 ~ 0.995) | 0.998 | ( 0.992 ~ 1.005) | 0.970 | ( 0.965 ~ 0.974) |
2019 | 1.065 | ( 1.048 ~ 1.082) | 1.027 | ( 1.014 ~ 1.040) | 1.088 | ( 1.077 ~ 1.099) |
Cohort
|
RR
|
95%CI
|
RR
|
95%CI
|
RR
|
95%CI
|
1960 | 0.711 | ( 0.647 ~ 0.780) | 0.693 | ( 0.643 ~ 0.747) | 1.818 | ( 1.716 ~ 1.926) |
1961 | 0.718 | ( 0.658 ~ 0.783) | 0.704 | ( 0.657 ~ 0.754) | 1.753 | ( 1.661 ~ 1.851) |
1962 | 0.725 | ( 0.669 ~ 0.786) | 0.715 | ( 0.670 ~ 0.762) | 1.691 | ( 1.608 ~ 1.778) |
1963 | 0.732 | ( 0.679 ~ 0.789) | 0.726 | ( 0.684 ~ 0.771) | 1.631 | ( 1.557 ~ 1.708) |
1964 | 0.739 | ( 0.690 ~ 0.792) | 0.738 | ( 0.699 ~ 0.779) | 1.573 | ( 1.507 ~ 1.641) |
1965 | 0.747 | ( 0.701 ~ 0.795) | 0.749 | ( 0.713 ~ 0.787) | 1.517 | ( 1.458 ~ 1.577) |
1966 | 0.754 | ( 0.712 ~ 0.798) | 0.761 | ( 0.728 ~ 0.796) | 1.463 | ( 1.411 ~ 1.515) |
1967 | 0.762 | ( 0.723 ~ 0.802) | 0.773 | ( 0.743 ~ 0.805) | 1.410 | ( 1.366 ~ 1.457) |
1968 | 0.769 | ( 0.734 ~ 0.806) | 0.785 | ( 0.757 ~ 0.815) | 1.360 | ( 1.322 ~ 1.400) |
1969 | 0.777 | ( 0.745 ~ 0.810) | 0.798 | ( 0.772 ~ 0.825) | 1.312 | ( 1.278 ~ 1.346) |
1970 | 0.785 | ( 0.755 ~ 0.815) | 0.811 | ( 0.786 ~ 0.836) | 1.265 | ( 1.236 ~ 1.295) |
1971 | 0.792 | ( 0.764 ~ 0.821) | 0.823 | ( 0.800 ~ 0.847) | 1.220 | ( 1.195 ~ 1.246) |
1972 | 0.800 | ( 0.773 ~ 0.828) | 0.836 | ( 0.813 ~ 0.860) | 1.177 | ( 1.154 ~ 1.199) |
1973 | 0.808 | ( 0.781 ~ 0.836) | 0.850 | ( 0.827 ~ 0.874) | 1.135 | ( 1.114 ~ 1.155) |
1974 | 0.818 | ( 0.790 ~ 0.846) | 0.865 | ( 0.841 ~ 0.889) | 1.095 | ( 1.076 ~ 1.115) |
1975 | 0.829 | ( 0.802 ~ 0.858) | 0.881 | ( 0.858 ~ 0.904) | 1.061 | ( 1.042 ~ 1.080) |
1976 | 0.845 | ( 0.818 ~ 0.872) | 0.899 | ( 0.875 ~ 0.922) | 1.035 | ( 1.017 ~ 1.053) |
1977 | 0.864 | ( 0.835 ~ 0.894) | 0.916 | ( 0.891 ~ 0.943) | 1.021 | ( 1.004 ~ 1.039) |
1978 | 0.884 | ( 0.852 ~ 0.917) | 0.924 | ( 0.897 ~ 0.951) | 1.020 | ( 1.001 ~ 1.040) |
1979 | 0.899 | ( 0.870 ~ 0.929) | 0.915 | ( 0.892 ~ 0.938) | 1.022 | ( 1.003 ~ 1.042) |
1980 | 0.910 | ( 0.880 ~ 0.940) | 0.917 | ( 0.894 ~ 0.941) | 1.018 | ( 1.004 ~ 1.033) |
1981 | 0.931 | ( 0.904 ~ 0.959) | 0.952 | ( 0.929 ~ 0.976) | 1.013 | ( 0.997 ~ 1.030) |
1982 | 0.947 | ( 0.911 ~ 0.985) | 0.975 | ( 0.945 ~ 1.006) | 1.012 | ( 0.991 ~ 1.034) |
1983 | 0.950 | ( 0.910 ~ 0.991) | 0.956 | ( 0.924 ~ 0.990) | 1.007 | ( 0.986 ~ 1.028) |
1984 | 0.975 | ( 0.951 ~ 1.001) | 0.971 | ( 0.954 ~ 0.989) | 1.001 | ( 0.986 ~ 1.017) |
1985 |
Reference
| |||||
1986 | 0.993 | ( 0.975 ~ 1.012) | 1.003 | ( 0.979 ~ 1.027) | 1.000 | ( 0.988 ~ 1.011) |
1987 | 0.977 | ( 0.939 ~ 1.017) | 0.996 | ( 0.966 ~ 1.028) | 0.996 | ( 0.977 ~ 1.017) |
1988 | 0.980 | ( 0.943 ~ 1.019) | 0.990 | ( 0.964 ~ 1.017) | 0.989 | ( 0.968 ~ 1.011) |
1989 | 0.991 | ( 0.960 ~ 1.023) | 0.987 | ( 0.962 ~ 1.013) | 0.975 | ( 0.958 ~ 0.991) |
1990 | 0.994 | ( 0.964 ~ 1.025) | 0.987 | ( 0.962 ~ 1.012) | 0.951 | ( 0.936 ~ 0.966) |
1991 | 0.989 | ( 0.960 ~ 1.019) | 0.988 | ( 0.963 ~ 1.013) | 0.921 | ( 0.907 ~ 0.935) |
1992 | 0.980 | ( 0.951 ~ 1.011) | 0.990 | ( 0.965 ~ 1.017) | 0.889 | ( 0.875 ~ 0.902) |
1993 | 0.971 | ( 0.939 ~ 1.004) | 0.993 | ( 0.965 ~ 1.021) | 0.857 | ( 0.842 ~ 0.871) |
1994 | 0.961 | ( 0.925 ~ 0.999) | 0.996 | ( 0.964 ~ 1.028) | 0.826 | ( 0.810 ~ 0.842) |
1995 | 0.952 | ( 0.911 ~ 0.995) | 0.998 | ( 0.963 ~ 1.035) | 0.796 | ( 0.779 ~ 0.815) |
1996 | 0.943 | ( 0.896 ~ 0.992) | 1.001 | ( 0.960 ~ 1.043) | 0.768 | ( 0.748 ~ 0.789) |
1997 | 0.934 | ( 0.880 ~ 0.990) | 1.003 | ( 0.958 ~ 1.051) | 0.741 | ( 0.718 ~ 0.763) |
1998 | 0.924 | ( 0.865 ~ 0.988) | 1.006 | ( 0.955 ~ 1.060) | 0.714 | ( 0.690 ~ 0.739) |
1999 | 0.915 | ( 0.850 ~ 0.986) | 1.008 | ( 0.952 ~ 1.069) | 0.688 | ( 0.662 ~ 0.716) |
2000 | 0.907 | ( 0.835 ~ 0.985) | 1.011 | ( 0.948 ~ 1.078) | 0.664 | ( 0.635 ~ 0.694) |
2001 | 0.898 | ( 0.820 ~ 0.983) | 1.014 | ( 0.945 ~ 1.087) | 0.640 | ( 0.610 ~ 0.672) |
2002 | 0.889 | ( 0.805 ~ 0.982) | 1.016 | ( 0.942 ~ 1.097) | 0.617 | ( 0.585 ~ 0.651) |
2003 | 0.880 | ( 0.790 ~ 0.981) | 1.019 | ( 0.938 ~ 1.106) | 0.595 | ( 0.562 ~ 0.630) |
2004 | 0.872 | ( 0.776 ~ 0.979) | 1.021 | ( 0.935 ~ 1.116) | 0.574 | ( 0.539 ~ 0.611) |