# The lifetime risk of maternal mortality: concept and measurement

## John Wilmoth

Volume 87, Number 4, April 2009, 256-262

### Table 1. Illustrative calculation of three measures of the lifetime risk of maternal mortality, LR1, LR2 and LR3, based on age-specific maternal mortality data from Bangladesh for 1998–2001

Age range(years) Exposure timea Maternal deathsb MMRatec (per 1000) Live births Fertility rated MMRatioe (per 100 000) Life-table exposure timef LRMM
Other causes of death ignoredg
Other causes of death considered
From birthh
From age 15 yearsi
LR1 LR2 LR3
15–19 90 099 20.501 0.228 12 068 0.134 169.9 4.545 0.0011 0.0010 0.0011
20–24 67 389 29.559 0.439 12 494 0.185 236.6 4.518 0.0022 0.0020 0.0022
25–29 57 605 30.820 0.535 8 600 0.149 358.4 4.485 0.0027 0.0024 0.0026
30–34 48 931 24.399 0.499 4 727 0.097 516.2 4.443 0.0025 0.0022 0.0024
35–39 40 110 10.490 0.262 2 130 0.053 492.5 4.393 0.0013 0.0011 0.0013
40–44 31 989 12.367 0.387 636 0.020 1945.9 4.337 0.0019 0.0017 0.0019
45–49 21 880 3.256 0.149 134 0.006 2435.4 4.252 0.0007 0.0006 0.0007
Totalj 358 007 131.392 0.367 40 788 3.222 322.2 30.972 0.0125 0.0111 0.0122

LRMM, lifetime risk of maternal mortality; MMRate, maternal mortality rate; MMRatio, maternal mortality ratio.
a Exposure time is the total number of woman-years lived by the survey population during the observation period.
b The numbers of maternal deaths are fractional because they were estimated from survey data using sample weights.
c MMRate = maternal deaths ÷ exposure time.
d Except for the total row, fertility rate = live births ÷ exposure time.
e MMRatio = maternal deaths ÷ live births.
f The life-table exposure time is the number of woman-years lived per female live birth derived from a life table constructed using survey data.
g Except for the total row, elements of the column labelled LR1 = 5 × MMRate = 5 × fertility rate × MMRatio, showing that equivalent measures of lifetime risk can be derived using age-specific values of either the MMRate or the MMRatio.
h Except for the total row, elements of the column labelled LR2 = MMRate × life-table exposure time = fertility rate × MMRatio × life-table exposure time.
i All elements of the column labelled LR3 equal the corresponding element of the column labelled LR2 divided by 0.9115, where 0.9115 is the probability that a female will survive from birth to age 15 years.
j Values in the total row are the sums of their respective column values except for the MMRate, fertility rate and MMRatio. The MMRate for ages 15–49 years combined equals total maternal deaths divided by total exposure time; similarly, the MMRatio for ages 15–49 years combined equals total maternal deaths divided by total live births. Finally, the sum of fertility rates by 5-year age groups is multiplied by 5 to represent the total fertility rate (TFR) or the hypothetical average number of births per woman according to the age-specific birth rates observed in the survey population, under the assumption that death does not occur before menopause.All data are from the Bangladesh Maternal Health Services and Maternal Mortality Survey of 2001.7 Data in the columns labelled Exposure time to MMRatio were taken or derived from table 3.2 of that report. The life-table exposure time and the probability that a female will survive to age 15 years (see note i) were derived by computing a female life-table using all-cause death rates as shown in table 3.8 of that report.