Birth defects surveillance programs assess, describe and count pregnancy outcomes for
a population within a given geographical area within a given period of time (such as one year).
In this video, we will provide an overview on how to monitor pregnancy outcomes for a population-based birth defects surveillance program.
A population-based surveillance program consists of a population of births in a given
geographic area collected during a given period of time.
The first step is to define the geographic area that your program will monitor.
This area of interest is known as the "catchment area." It can be a country, a region, a community, city, or town.
A population-based birth defects surveillance program will focus on collecting
all pregnancies affected by birth defects occurring among a population that lives in the catchment area.
These could include elective terminations of pregnancy due to fetal anomaly (ETOPFA), stillbirths or live births.
Most programs usually include at least live births and stillbirths with birth defects.
Another component of population-based programs is the need to define whether a mother of a baby born with a birth defect is
a resident within the catchment area.
Most birth defects surveillance programs consider resident mothers as mothers whose primary address is
within the catchment area at the time of delivery.
So, with this definition in mind, there are two main points to consider regarding residency:
If a resident mother gives birth outside of the catchment area, whether or not this birth is affected by a birth defect,
ideally this birth should becounted because the mother is still considered a “resident.”
If a non-resident mother gives birth inside the catchment area, her birth should not be counted in the surveillance program
because the mother is not considered a “resident”.
The next step is to determine which data sources are available for your program to use for capturing
stillbirths and live births with birth defects within the catchment area.
Data might be available from:
health facilities that capture all births and stillbirths
vital records such as birth and death certificates that might contain information about birth defects
referral treatment centers for individuals with birth defects defined by the age inclusion criteria used by the registry
administrative databases such as hospital discharge records
home birth data, and/or
another source from which a stillbirth or live birth with a birth defect can be identified.
Once you have established your catchment area, determined the birth defects and outcomes of pregnancy that will be monitored,
and identified which data sources to use, you are ready to calculate the birth prevalence of birth defects among the population.
Using numbers from the collected data, you use a standard equation to calculate the prevalence.
First, count the number of all live births and stillbirths to resident mothers. This number is the denominator.
Next, from those same births, count the number of stillbirths and live births with birth defects. This number is the numerator.
Finally, divide the numerator by the denominator, and multiply the result by 10,000.
For example, if in one year 450 stillbirths and live births with birth defects are
divided by 15,000 total births and then multiplied by 10,000, the result is 300 cases of birth defects per 10,000 births.
One could summarize this result as 3% of the total births are affected by birth defects.
In this example, data on pregnancy outcomes are used to estimate and describe the
prevalence of birth defects within a catchment area and within a time period of one year.