Infant mortality rates

Between 1999 and 2008, the number of registered live births per annum for mothers having their residence in the Flemish Region roughly ranged between 60,000 and 70,000, with boys slightly outnumbering girls (sex ratio close to 1.05). The lowest number of births was recorded in 2002 (60,161), the highest in 2008 (69,276).

Figure shows the probability of infant mortality by gender, i.e. the probability among registered live births of dying before the first anniversary. A slight though not steady decrease is observed over the years: from 5.4 in 1999 to 4.6 deaths per thousand live births in 2008 (-14%) for boys, and from 4.6 in 1999 to 3.5 per thousand live births in 2008 (-24%) for girls.

In addition, the figure displays (a) the probability of dying in the year of birth and (b) the probability of dying in the next year before the infant's first anniversary. This clearly shows that the large majority of those who died before their first anniversary actually did so in their year of birth. The average share for all observation years is 85% in males and 87% in females (*P *= 0.68).

The probability of dying in the year of birth decreases from 4.6 to 4.0 per thousand live births (‰) between 1999 and 2008 in boys and from 3.8 to 3.2‰ in girls, with some fluctuations over that period. Note that a significant difference between both gender groups was found only for the years 2001 (*P *= 0.0071) and 2002 (*P *= 0.019).

The probability of dying after the year of birth but before the first anniversary is much lower, with stable mortality rates well below 1 per thousand. The average for all observation years is 0.7‰ in males and 0.5‰ in females (*P *= 0.34).

Mean time-to-event in the year of birth

Figure displays, for the calendar year 2008, the survival curves by gender in the year of birth according to the days lived. Most of the deaths are concentrated in the first days of life. Half of the infants who were born and died in 2008 lived less than 1 week (the median survival time is 4.5 days in males and 3.5 days in females). The mean survival time for that year is equal to 29.6 days for the deceased boys and 31.0 days for the deceased girls. Expressed as a proportion of the calendar year, this gives *k1 *equal to 0.081 in males and 0.085 in females. Note that the difference in survival graphs between both gender groups is not statistically significant.

Table summarizes the mean survival time value of the deceased in their year of birth as well as the resulting mean proportion lived during that year (*k1*) for all observation years by gender. The value of *k1 *is quite stable over the years, on average 0.085 in males and 0.090 in females. Between the gender groups, no significant differences in survival graphs are reported.

| **Table 1**Mean survival time of the deceased in their year of birth |

Mean time-to-event in the next year yet before the first anniversary

From Table we learn that the mean survival time for those dying in the year after their year of birth yet before their first anniversary, expressed as a proportion of the calendar year *(k2)*, fluctuates between 0.43 (year of birth 2006) and 0.55 (2000) in males and between 0.36 (2002) and 0.67 (2008) in females. The average proportion for all observation years approaches 0.5, i.e. 0.502 in males and 0.495 in females.

| **Table 2**Mean survival time of the deceased in the year after the year of birth |

Differences in survival graphs of the gender groups are generally not statistically significant on a yearly basis, the one exception being the year of birth 2000.