Table 1.

Descriptive Statistics of All Live Births and Preterm Births (PTB) in Shenzhen, China during 2003–2012

	Live births	Term births		Spontaneous preterm births b				Medically induced preterm birth
				PROM-PTB		S-PTB
		N	%	N	%	N	%	N	%
All live birth	1,385,882	1,307,570	94.35	7436	0.54	40,104	2.89	30,712	2.21
Maternal age (years)
≤ 20	81,436	75,759	93.03	315	0.39	4375	5.37	987	1.21
21-35	1,230,521	1,164,107	94.60	6477	0.53	33,773	2.74	26,164	2.13
≥ 36	73,865	67,704	91.66	644	0.87	1956	2.65	3561	4.82
Maternal education
Less than high school	599,640	565,404	94.29	2397	0.40	21,037	3.51	10,802	1.80
High school and college	498,618	469,616	94.18	2993	0.60	13,912	2.79	12,097	2.43
Bachelor	263,880	250,133	94.79	1884	0.71	4765	1.81	7098	2.69
Postgraduate	23,684	22,417	94.65	162	0.68	390	1.65	715	3.02
Parity
0	857,543	808,052	94.23	5277	0.62	25,120	2.93	19,094	2.23
≥ 1	523,788	495,377	94.58	2139	0.41	14,778	2.82	11,494	2.19
Missing data	4491	–	–	–	–	–	–
APNCU index a
Inadequate	635,795	590,381	92.86	3711	0.58	27,182	4.28	14,521	2.28
Intermediate	388,153	366,230	94.35	2427	0.63	9716	2.50	9780	2.52
Appropriate	164,493	157,253	95.60	876	0.53	2458	1.49	3906	2.37
Appropriate plus	197,234	193,572	98.14	421	0.21	744	0.38	2497	1.27
Missing	147	–	–	–	–	–	–
Maternal chronic conditions
Yes	3152	2629	83.41	80	2.54	102	3.24	341	10.82
No	1,382,670	1,304,941	94.38	7356	0.53	40,002	2.89	30,371	2.20
Gestational hypertension
Yes	5008	4496	89.78	72	1.44	101	2.02	339	6.77
No	1,380,814	1,303,074	94.37	7364	0.53	40,003	2.90	30,373	2.20
Preeclampsia or eclampsia
Yes	16,208	12,644	78.01	102	0.63	309	1.91	3153	19.45
No	1,369,614	1,294,926	94.55	7334	0.54	39,795	2.91	27,559	2.01
Infant sex
Male	752,163	707,283	94.03	4306	0.57	23,432	3.11	17,142	2.28
Female	633,466	600,123	94.74	3130	0.49	16,648	2.63	13,565	2.14
Hermaphrodite	193	164	84.97	0.00	0.00	24	12.44	5	2.59

^aAPNCU the adequacy of prenatal care utilization

^bPROM-PTB preterm birth following premature rupture of membranesm, S-PTB preterm birth due to spontaneous preterm labor