Table 6.

Perinatal outcomes by maternal age in low-risk women aged 16 and over

		OU			Non-OU
	Events/births	Weighted*		Events/births	Weighted*
Age (years)	n/N	%	(95% CI)	n/N	%	(95% CI)
Nulliparous
16–19	39/1260	3.2	(2.2 to 4.5)	31/1553	2.9	(1.9 to 4.4)
20–24	89/2610	3.5	(2.5 to 5.0)	94/3700	2.4	(1.9 to 3.2)
25–29	92/3026	3.3	(2.6 to 4.0)	123/5357	2.1	(1.7 to 2.8)
30–34	101/2340	4.2	(3.1 to 5.6)	128/4918	3.0	(2.2 to 4.0)
35–39	37/962	3.9	(2.8 to 5.4)	65/1999	3.0	(2.1 to 4.1)
40+	10/149	7.5	(3.4 to 15.7)	8/195	3.9	(1.0 to 14.0)
Total	368/10 347	3.7	(2.9 to 4.6)	449/17 722	2.6	(2.2 to 3.1)
Multiparous
16–19	6/179	3.0	(1.4 to 6.4)	5/337	1.7	(0.6 to 4.6)
20–24	26/1519	1.8	(1.2 to 2.7)	43/3489	1.3	(0.8 to 2.0)
25–29	41/2547	1.6	(1.2 to 2.3)	73/7032	1.1	(0.8 to 1.6)
30–34	50/2578	2.0	(1.5 to 2.6)	111/8468	1.2	(1.0 to 1.5)
35–39	33/1594	2.1	(1.3 to 3.3)	88/5761	1.6	(1.2 to 2.2)
40+	7/345	2.1	(0.9 to 4.6)	20/978	2.3	(1.3 to 4.1)
Total	163/8762	1.9	(1.5 to 2.4)	340/26 065	1.3	(1.1 to 1.6)

*Percentages are weighted to take account of differences in the probability of a woman being selected for inclusion in the study arising from differences in each unit/trust's period of participation and the stratum-specific probabilities of selection of OUs.

OU, obstetric unit.