Calculating abortion rates: why and how – AIMSI

Measuring abortion trends and planning for healthcare

As with any healthcare procedure we want to know how to plan for abortion  services, therefore we need to have an understanding and an idea of how prevalent the procedure is amongst women of childbearing age. We need to know if there are any geographic areas in which the rate is higher or lower, and if there is a significant divergence from the mean rate we might want to analyse and investigate this. We might want to know whether the procedure is more common amongst women of a particular age or even socioeconomic bracket. We might also want to assess how the rate changes over time so that we can assess the impact of new initiatives or services.

In carrying out such analysis with respect to abortion, healthcare planners try to identify how to meet healthcare demands and also to identify how well services and initiatives are performing. With respect to abortion one of the key services that is being evaluated is the provision of contraception services availability and use.

There may be a particular interest in particular geographic areas, for example underprivileged areas or wealthy areas, there may also be an interest in different age groups for example teenagers or older women. The ease of access to services is also of interest and in health care planning the aim is usually equity of access, so that all women who need to access any particular aspect of  women’s healthcare service are able to. We often also want to know how our country s healthcare and women fare with respect to time and also with respect to other countries, so it is vital that we continue to use the same metrics and categories so that direct comparisons can be made through time and space.

The Total Number of Abortions

This is the most crude measure of abortions in any country or region and it simply measures the total number. It doesn’t account for the total number of women living there or the pregnancy rate and it gives no measure of density or spread over a region.

The Abortion Rate

In order to do this, the most commonly used metric is  one that is calculated with respect to women of childbearing age. The focus is the women. The metric is called the abortion rate. The focus is healthcare planning. There is no judgement and no punitive implications. This is called the Abortion Rate

The abortion rate, represents the number of induced abortions occurring in a specified reference period (e.g., one year) per 1,000 women of reproductive age (15-44 or 15-49).

The abortion rate (AR) is calculated as:

# of abortions                                           x 1000
Total mid-year population of women 15-44 (or 49)

Obviously to calculate this rate we need to know the total number of abortions, and the childbearing population.

We cannot really produce such a rate for Ireland, as we only have guesstimates for the former, although the HSE did estimate it as  4.1/1000 in 2014 based on Irish addresses given in Britain and the Netherlands.

In countries where there is an abortion service and the number of abortions and the number of childbearing women  is known, the rate is easy to calculate. Abortion rates are the standardised way of calculating nationwide abortion trends relative to the population.

For example in 2016 the Chief Medical Officer calculated it as 16/1000 (rounded) for England and Wales.

Rates are not and should not be calculated to expose a society or group as permissive or morally corrupt.

Abortion Ratio

Another way of calculating abortion figures is to use a ratio.

The Abortion Ratio for a population, typically measured in a given year  is the number of abortions for every 1000 pregnancies  in the population. It is calculated as follows:

 # of abortions
______________    x       1000
Total # of pregnancies

This measurement is used to try and calculate how likely a woman is to have an abortion were she to become pregnant. It is a measure of intent. It is presented as a proportion of 1000.

The problem with calculating the abortion ratio

In order to calculate this ratio you need the raw number of pregnancies, which no government agency collects directly. Why? There are several reasons for this. Firstly, some pregnancies are virtually impossible to count, because they end in miscarriage. Sometimes this happens before the woman even knows she is pregnant and sometimes before she enters the maternity service. Even if a woman enters the maternity service first trimester miscarriage statistics are often not recorded. Secondly, not all fetuses survive into the second or third trimester. Some babies die in-utero, some babies have fatal fetal conditions and some babies are stillborn.

The Abortion Ratio requires “estimations”

Therefore the total number of pregnancies have to be ESTIMATED. And so enters the first potential error or inaccuracy with this metric as the number of pregnancies can ever only be an estimate.

Another issue is that it is also notoriously difficult to measure intent in a generalised way like this. True intent can only be known by asking individual women what their intent is. If they had an abortion they are likely to say that they intended to end the pregnancy, but if they continued with the pregnancy they are very unlikely to say that they didn’t intend to keep the baby once the baby is born even though we know that approximately half of all pregnancies are unintentional.

If alternatively, the total number of births is used instead of the total number of pregnancies then the metric is no longer measuring the same thing.

 # of abortions
______________  x 1000
Total # of live births

It can no longer be accurately measuring intent as we are no longer looking at the raw number of pregnancies but the final number of live births. Furthermore, the denominator (the number at the bottom of the fraction, or the number that you are dividing by) becomes smaller than if you were using the number of raw pregnancies. What happens when the dividing number becomes smaller? The ratio of abortions to births becomes more similar, and it looks like more people are intending to have abortions.

The Abortion Ratio is dependent on the birth rate

As this figure is a ratio it will become more dramatic based on EITHER an increase in the number of abortions OR a decrease in the birth rate. So the number of abortions might remain the same between two time periods but if the birth rate goes down in the same time period then it appears that there are more abortions. Regions or countries in which the birth rate is quite low and where there is an established abortion service often have quite dramatic ratios.

Abortion Rates for Ireland

So in Ireland we can’t really calculate abortion ratios and abortion rates because we have no accurate figures. We estimate the total number of abortions based on Irish addresses given in abortion clinics in other countries and also on the number of illegal abortion inducing drugs seized by customs. However, in the  2018 Referendum debate on the 8th amendment to the Irish Constitution, the Irish public have been subjected to posters stating that 1 in 5 babies in England are aborted, with the tag line of not wanting this to happen here.

Misleading abortion figures on posters in the Referendum to Repeal the 8th Amendment

These figures are not referring  to the official abortion rate as defined by the Chief Medical Officer for England and Wales, neither is it a metric of abortion ratio per 1000 pregnancies or per 1000 live births, which is the way that abortion ratios should be given.

It is a self calculated metric not produced by a national statistical organisation.

It is calculated in a way to make the numbers appear more impactful. Everyone knows that numbers appear more meaningful when given not as a percentage but as a ratio, for example 10% appears to be quite low, but one in ten appears to be quite high yet they refer to the same thing.

The figures have been calculated for England alone, as including Scotland Wales and Northern Ireland would have made the figures less dramatic. Statistical information needs to be free of bias, you cant just cherry pick what you want to suit what you are saying. In the last week (18th April 2018), the Save the 8th campaign has had to admit that if miscarriages were to be included the ratio would not be 1 in 5 as stated in their posters.

Furthermore, look carefully at what is being said on line and in social media. The posters cite the figure as relating to England. This means that it doesn’t relate to any other jurisdiction across the Irish Sea. It doesn’t relate to the UK, it doesn’t relate to Britain it doesn’t even relate to England and Wales, just England.

Next the figure states it relates to abortion vs babies. This means that it doesn’t relate to pregnancies as it doesn’t include miscarriage. So no one quoting the figure on social media should be saying that it is related to pregnancies and intention with respect to pregnancy because it doesn’t.

The rate of abortion in England and Wales 2016

The officially calculated statistic that is given with respect to measuring abortion in England and Wales is 16 per 1000 women of childbearing age.. This is not a figure we have calculated. It is calculated and published by the Chief Medical Officer in the UK

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