Table 4.

Changes in preterm birth rates and gestational-age-specific caesarean section rates stratified by obstetric complications in singleton pregnancies in women aged 25–29 years in China, 2012–18

		Year							Change 2012–18	p value for trend
		2012	2013	2014	2015	2016	2017	2018
Antepartum complications (n=733 504)
Number of births		70 339	81 503	10 8380	99 864	13 1833	12 3135	11 8450	68·4	..
Caesarean section rate (per 100 deliveries)
	28–31 weeks	57·0%	59·3%	57·6%	54·4%	57·3%	59·0%	62·6%	9·8	0·02
	32–33 weeks	66·2%	67·3%	64·8%	66·0%	66·2%	65·7%	64·8%	−2·1	0·12
	34–36 weeks	63·7%	63·9%	60·1%	58·3%	57·0%	58·0%	57·8%	−9·2	<0·0001
	≥37 weeks	64·9%	62·9%	57·1%	53·5%	50·1%	48·9%	48·3%	−25·2	<0·0001
Preterm birth rate (per 100 deliveries)*
	Very preterm	1·3%	1·3%	1·2%	1·2%	1·2%	1·1%	1·2%	−4·0	0·05
	Moderate preterm	1·8%	1·6%	1·6%	1·5%	1·5%	1·5%	1·5%	−16·5	<0·0001
	Late preterm	9·1%	8·5%	8·5%	8·3%	8·5%	8·3%	8·3%	−8·1	<0·0001
	All preterm	12·1%	11·4%	11·3%	11·0%	11·1%	10·9%	11·0%	−8·9	<0·0001
Medical diseases (n=253 933)
Number of births		17 535	23 552	34 780	34 414	46 966	46 807	49 879	184·5	..
Caesarean section rate (per 100 deliveries)
	28–31 weeks	28·1%	47·5%	38·0%	34·9%	28·9%	36·5%	46·5%	65·9	0·10
	32–33 weeks	51·2%	54·0%	47·6%	51·5%	47·8%	52·5%	53·2%	3·9	0·35
	34–36 weeks	63·1%	61·7%	59·0%	56·7%	56·0%	57·9%	60·1%	−4·7	0·02
	≥37 weeks	56·9%	53·5%	48·7%	45·4%	42·5%	42·2%	56·9%	−28·2	<.0001
Preterm birth rate (per 100 deliveries)*
	Very preterm	0·4%	0·4%	0·4%	0·4%	0·4%	0·4%	0·4%	−20·5	0·24
	Moderate preterm	0·7%	0·7%	0·6%	0·6%	0·5%	0·5%	0·6%	−14·9	0·002
	Late preterm	4·9%	4·4%	3·8%	3·8%	3·7%	3·5%	3·6%	−27·3	<0·0001
	All preterm	6·0%	5·4%	4·7%	4·8%	4·6%	4·3%	4·5%	−25·5	<0·0001

Very preterm babies were born after 28–31 completed weeks' gestation. Moderate preterm babies were born after 32–33 weeks' gestation. Late preterm babies were born after 34–36 weeks' gestation.

^*Adjusted for the sampling distribution of the population.