Associations of residential greenness exposure during early pregnancy with the risk of spontaneous abortion: the China Birth Cohort Study

Cui, Yuchen; Gao, Shen; Yang, Boyi; Lin, Lizi; Yue, Wentao; Su, Shaofei; Zhang, Enjie; Liu, Jianhui; Xie, Shuanghua; Zhang, Yue; Zhang, Zheng; Liu, Ruixia; Dong, Guanghui; Yin, Chenghong

doi:10.1186/s12302-024-00869-x

Environmental Sciences Europe

Table 1 Characteristics of participants in the study

From: Associations of residential greenness exposure during early pregnancy with the risk of spontaneous abortion: the China Birth Cohort Study

Variable*	Total (n = 90 890)	Non-SAB (n = 88 073)	SAB (n = 2 817)	P-value
Mothers
Age, year; mean ± SD	29.58 ± 4.27	29.53 ± 4.25	31.05 ± 4.82	< 0.0001
Pre-pregnancy BMI, kg/m²; mean ± SD	21.68 ± 3.26	21.67 ± 3.26	22.07 ± 3.38	0.012
Education (%)				< 0.0001
High school or lower	19 434 (21.4)	18 834 (21.4)	600 (21.3)
College	61 859 (68.1)	60 014 (68.1)	1 845 (65.5)
Master or higher	9 597 (10.5)	9 225 (10.5)	372 (13.2)
Annual family income, CNY (%)				< 0.0001
< 100 000	31 249 (34.4)	30 328 (34.4)	921 (32.7)
100 000–200 000	30 897 (34.0)	30 062 (34.2)	835 (29.6)
> 200 000	28 744 (31.6)	27 683 (31.4)	1 061 (37.7)
Ethnicity (%)				0.019
Han	85 199 (93.7)	82 588 (93.8)	2 611 (92.7)
Others	5 691 (6.3)	5 485 (6.2)	206 (7.3)
Smoke (%)
Yes	2 123 (2.3)	2 058 (2.3)	65 (2.3)	0.919
No	88 767 (97.7)	86 015 (97.7)	2 752 (97.7)
Drink (%)
Yes	2 999 (3.3)	2 886 (3.3)	113 (4.0)	0.032
No	87 891 (96.7)	85 187 (96.7)	2 704 (96.0)
Parity (%)				< 0.0001
0	44 090 (48.5)	42 943 (48.8)	1 147 (40.7)
≥ 1	46 800 (51.5)	45 130 (51.2)	1 670 (59.3)
Urban (%)				0.110
Yes	71 601 (78.8)	69 416 (78.8)	2 185 (77.6)
No	19 289 (21.2)	18 657 (21.2)	632 (22.4)
Environmental factors
NDVI_500m; mean ± SD	0.296 ± 0.128	0.297 ± 0.128	0.283 ± 0.122	0.027
EVI_500m; mean ± SD	0.181 ± 0.088	0.181 ± 0.088	0.172 ± 0.083	0.009
NDVI_250m;mean ± SD	0.274 ± 0.107	0.275 ± 0.107	0.264 ± 0.097	< 0.0001
NDVI_1000m; mean ± SD	0.302 ± 0.109	0.302 ± 0.109	0.294 ± 0.103	0.008
PM₁, μg/m³; mean ± SD	29.981 ± 9.670	29.973 ± 9.674	30.255 ± 9.528	0.076
PM_2.5, μg/m³; mean ± SD	42.325 ± 18.412	42.333 ± 18.477	42.054 ± 16.241	< 0.0001
PM₁₀, μg/m³;mean ± SD	63.185 ± 22.778	63.134 ± 22.806	64.793 ± 21.848	< 0.0001
NO₂, μg/m³;mean ± SD	33.856 ± 10.697	33.827 ± 10.728	34.780 ± 9.641	< 0.0001
O₃, μg/m³;mean ± SD	91.221 ± 35.265	91.186 ± 35.206	92.324 ± 37.062	< 0.0001
Temperature, °C; mean ± SD	16.459 ± 8.023	16.464 ± 8.014	16.286 ± 8.315	< 0.0001
Humidity, %; mean ± SD	63.835 ± 14.990	63.887 ± 14.971	62.196 ± 15.483	< 0.0001

SD, standard deviation; SAB, spontaneous abortion; BMI, body mass index; CNY, China Yuan; PM₁, particulate with aerodynamic diameter ≤ 1 μm; PM_2.5, particulate with aerodynamic diameter ≤ 2.5 μm; PM₁₀, particulate with aerodynamic diameter ≤ 10 μm; NO₂, nitrogen dioxide; O₃, ozone
^* Continuous variables are presented as mean ± standard deviation and categorical variables are presented as numbers (percentage)

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