Table 3.

Descriptive statistics of age at first birth by age cohort, female adolescents, Nairobi informal settlements, 2007

	15–17 year cohort	18–19 year cohort	Total
Proportion having a first birth by age (years):
12	0%	0%	0%
13	0%	1%	0%
14	1%	1%	1%
15	1%	3%	2%
16	2%	4%	3%
17	8%	16%	13%
18	–	24%	21%
19	–	31%	29%
Age at:
First quartile	na	18.9	19.0
Median	na	na	na
Third quartile	na	na	na
Person-years at risk	8164.4	7365.1	15,529.5
N	498	399	897
Events	23	109	132

na=not attained.