Abortion is an important contributing factor to women’s
health and it could even result in mother’s death.
Although in many societies, abortion has been associated
with legal restrictions as well as social, cultural and religious
International Journal of Fertility and Sterility
Vol 13, No 3, October-December 2019, Pages: 209-214
Legal restrictions and stigmata around abortion make it
invisible, as those who had abortion are not willing to disclose
it. This in turn might lead to inaccurate data on the
annual number of abortions (
Due to the social stigma and legislations, direct estimation
of abortion rate with face-to-face interviews
might result in under-estimation of the true prevalence.
In this context, indirect methods were proposed for estimation
of the size of hidden and stigmatized subpopulations
Single sample count (SSC) technique is another efficient
indirect method. In this method, a list of statements
including several insensitive statements with certain distribution
plus a sensitive one is given to the participants
Results of the studies which were designed to estimate
intentional abortion rate in Iran are inconsistent, ranging
from 1 to 20%. In a meta-analysis study, the annual prevalence
was estimated to be 8.9 per 1000 women of fertile
This cross-sectional study was conducted in Kerman, south east of Iran. In this study, 1020 women aging 18- 49 years were selected through street-based multistage sampling proportional to the age distribution of women in the 2011 census. At the first step, the city was classified into three categories based on socioeconomic status (SES): high, medium and low. To do so, we asked for the governor’s office experts' opinion. Secondly, 5 regions were selected from each SES category. Finally, from each of 15 regions, 68 women were recruited through the convenience sampling method in streets. We adopted street-based sampling, as our previous experiences showed that in case of sensitive issues, other sampling schemes such as household or telephone-based methods do not work.
The eligible participants were women aging 18-49 years, who had been living in Kerman for the past five years and verbally consented to participate in the study. Data was collected through a structured, face-to-face interview both in the morning and evening times, performed by trained female interviewers. The proposal of this study was approved by the Ethical Committee of Kerman University of Medical Sciences (ir.kmu. rec.1394.223).
In the first section of the questionnaire, general explanations
about the study and the aims were provided for
participants. In the next section, NSU questions were asked “how many
women do you know in the city of Kerman, who experienced
an abortion within the last year?” In order to minimize
the recall bias, this question was stratified. We asked
participants to tell the number of such individuals they
know among their relatives, husband relatives (in case
she was married), and acquaintances (involving neighbor,
friend, colleague, etc.). These questions were followed by
questions on type of abortion (intentional, therapeutic, or
spontaneous), and age of mother. The standard definition
of ‘know’ was as follows: “you know them by name and
face, and have had at least one contact through phone,
mail, or meeting in person within the past two years, and
are able to contact them at any time through one of the
above-mentioned methods” (
The first requirement of using NSU is knowing the network
size (C) of the participants. In this study we needed
the number of women at reproductive age known by residents
of Kerman. This had been assessed previously (
The following formulas were applied to estimate the crude size of abortion and its standard error (SE):
Where i and j stand for respondent and hidden group (i.e. abortion), respectively, m is the number of abortions known by each respondent, c is the average network, and t is the total population of 18-49 year old females living in Kerman city, which was about 155,644 according to the latest Iranian census.
It is possible that those who had abortion, do not reveal
it to their network members. This is known as visibility
bias. We already designed a study to measure visibility of
different types of abortion. It was determined 11, 70, and
60%, for intentional, therapeutic, and spontaneous abortion,
In the SSC section, a five-statement list, including four insensitive questions plus a sensitive question on intentional abortion, was given to each participant. The prevalence of each of insensitive questions in the society was 50%. Then, the participant was required to determine how many statements were true for her case. We emphasized that it is not necessary to explain which ones, but simply declare the number of statements that apply to her. In this study, we only estimated the prevalence of intentional abortion. The five statements were as follows: i. My national ID card number is even, ii. My date of birth is in the first 15 days of the month, iii. The year of my birth is even, iv. I was born in the first six month of the year, and v. I had intentional abortion within the past year.
The probability of a ‘yes’ response to each of non- sensitive items was 50%. We assumed that each of them follows a binomial distribution with 50% probability of success. Therefore, the expected mean of replies to four insensitive questions was two. Therefore, any deviation from two can be attributed to the sensitive statements. The formulas used for calculating prevalence rate and its confidence interval are given below. Here, λ and n show the number of ‘yes’ replies and sample size, respectively.
Finally, at the last section, in the direct method, the participants were provided with a questionnaire about their own experience of abortion within the preceding year. This was conducted regardless of participants’ marital status. Moreover, the questions were self-administrated and the completed questionnaires were collected through a ballot box to be more comfortable for the participants and increase the accuracy of responses. Data were analyzed using stata version 11 and Excel software.
Among 1451 female who were residents of Kerman and
aged 18-49 years and were invited to join the study, 1020
consented to participate, giving a response rate of 70.3%.
The youngest and the oldest participants were 18, and 49
years old, respectively. The mean (SD) age of the participants
was 30.84 year (8.57). About two-third of the
participants were married, and nearly half of them had
university educations (i.e. more than 12 years of education).
Moreover, about 30% of them were employed. We
asked married women to provide demographic characteristics
of their husbands. Nearly one third of husbands had
university educations, and more than half of them were
In total, 41.8% of participants did not know any woman who had an abortion in the past year. The mean (± SD) number of abortions known by respondents was 1.07 (± 1.55). Poisson regression model revealed that married and widowed subjects were respectively 39 and 12% more likely to reveal abortion than single participants. Those in age groups of 25-34 and 18-24 years, in comparison with those aged 35-49 years, were respectively 72 and 57% more likely to report abortion cases in their network. Employees and self-employed women were respectively 43 and 28% more likely to report abortion.
Demographic characteristics of participants
|Age (Y)||18-24||301 (29.5)|
|Marital status||Single||354 (34.7)|
|Education||≤9 years||136 (13.4)|
|12 years||392 (38.4)|
|12-16 years||403 (39.5)|
|Husband’s job||Employee||196 (30.5)|
|Husband’s education||≤9 years||158 (24.6)|
|12 years||271 (42.1)|
|12-16 years||165 (25.7)|
As summarized in Table 2, NSU estimates for intentional, therapeutic, and spontaneous abortions were 9, 3, and 11 per 1000 women of reproductive ages. In SSC method, the average positive answers for five-item list were 2.015. This suggested an annual prevalence of intentional abortion at 15 per 1000 women of reproductive ages. The estimates of direct method for three types of abortion namely intentional, therapeutic, and spontaneous were 10, 4, and 15 abortions per 1000 women of reproductive ages, respectively.
The annual abortion rate determined by the three methods
|Type of abortion||Direct% (CI 95%)||NSU% (CI 95%)||SSC% (CI 95%)|
|Intentional||0.98 (0.38-1.58)||0.9 (0.73-1.1)||1. 5 (0-7.6)|
|Therapeutic||0.39 (0.006-0.77)||0.29 (0.25-0.33)|
|Spontaneous||1.47 (0.73-2.21)||1.12 (1.04-1.2)|
NSU; Network Scale UP, SSC; Single Sample Count, and CI; Confidence Interval.
In this study, using the NSU and direct method, the annual rate of abortion per 1000 women aging 18-49 years was calculated to be about 23 (9 intentional, 3 therapeutic, and 11 spontaneous abortion) and 29 (10 intentional, 4 therapeutic, and 15 spontaneous abortion), respectively. Also, using SSC method, intentional abortion was estimated to be 15 per 1000 women aging 18-49 years.
The results of direct and NSU methods were fairly close with overlap in their confidence intervals. The estimates of the direct method were slightly higher than those of the NSU method. This might be due to this issue that since for direct estimation, a self-administered questionnaire at the end of interview was submitted to the respondents and the forms were returned through a ballot box, the anonymity the response was maximized. This indicates that use of direct methods with consideration of methodological issues can provide useful statistics. It also implies the usefulness of NSU. In comparison with direct and item counts methods, the confidence intervals of NSU method were narrower. Within the NSU method, each person responds about the intended behavior of the whole network members rather than one individual. Therefore, the sample size required for NSU studies is much smaller than that of direct methods.
We applied SSC method only for intentional abortion.
The SSC estimate was higher than those of the other
methods and its confidence interval was wider, which
might be due to the nature of this method (
Our estimate for intentional abortion (9-15 cases per
1000 women aging 18-49 years) was slightly higher than
that reported by two national studies in Iran (
The denominator in our study included all women of
reproductive ages, in order to make our results comparable
with those of WHO and studies conducted in other
Zare and Dastouri (
Nojomi et al. (
The worldwide estimate of intentional abortions per
1000 women aging 15-44 years is 35 (27 and 37 in developed
and developing countries, respectively). This
corresponded to 25% of pregnancies. Globally, married
and single women account for 73 and 27% of abortions,
respectively. The range of intentional abortion in
Asia was reported to be 35-37, as well (
Based on the world statistics, more than half of the
unplanned pregnancies (about 57%) ends in intentional
Although abortion is considered against social norms
and standard services are not available for that in Iran,
we believe that its rate is still considerable. This is alarming
and policy makers should be informed to explore for
possibility of new legislations. Women need more assistance
and guide from health care providers to make better
decisions in their reproductive life. Moreover, providing
enough resources for reproductive health services for
them is vital (
One of the limitations of our study was that, due to ethical issues, we could not recruit those aged under 18. Moreover, street-based interviews does not guarantee access to a random sample. However, it was a trade-off between representativeness of the sample and accuracy of replies. On the other hand, our study had several strengths. It was the first study that compared performance of direct and indirect methods in estimation of abortion rate. We showed that even direct methods are applicable, if methodological issues are concerned and anonymity is preserved. We provided an updated figure for the abortion situation in Iran.
Estimates derived in our study are alarming and flashes the need for new legislations. The results of three methods are close confirming the internal validity of methods and methodologies. While direct method with methodological considerations might still provide an acceptable estimate, NSU method has practical appeal as it requires a much smaller sample size in sensitive issues with relatively low prevalence. In addition, it is possible to estimate size of several hidden groups in one study. Furthermore, these indirect methods might be useful and are suggested in estimating other sensitive issues through increasing the response and honesty rate. In addition, such methods enjoy from some advantages, like cost-effectiveness, quickness, and simplicity in performance and analysis, which make them an appropriate tool in low and middle income countries, where an accurate registration system is lacking.