Abstract

BACKGROUND

Factors predicting the outcome of the next pregnancy following termination of pregnancy (TOP) are poorly known.

METHODS

A cohort of 1269 women undergoing medical TOP between 2000 and 2002 were followed up until the next pregnancy or until the end of 2006, using registers of induced abortion, births and hospital discharges. Factors associated with repeat TOP, delivery and failed pregnancy were analysed.

RESULTS

During the mean (±SD) follow-up period of 4.2 ± 1.5 years, 446 (35%) women had at least one subsequent pregnancy. Of these, 207 (46%) resulted in delivery, 169 (38%) in repeat TOP and 16% in failed pregnancy. In multivariate analysis, parity [hazard ratio (HR) 3.42, 95% confidence interval (CI) 1.70–6.91] and history of TOP (HR 1.60, 95% CI 1.10–2.33) were risk factors of repeat TOP. Age above 25 years (HR ≤ 0.46) and the use of intrauterine contraception (HR ≤ 0.45) were associated with reduced risks of repeat TOP. However, only age between 25 and 29 years was associated with an increased probability of delivery (HR 2.44, 95% CI 1.45–4.11).

CONCLUSIONS

Risk factors of repeat TOP are more clearly defined than factors associated with delivery. An increased focus on young women, those with a history of TOP and parous women, might be effective in reducing repeat TOP.

Introduction

Pregnancies, both planned and unplanned, are common occurrences in women’s lives. Factors affecting the decision to continue or not to continue an unintended pregnancy have been assessed in several studies. In a recent US study, a woman’s life circumstances, status of the relationship with the male partner and desire for a baby emerged as significant determinants of the fate of an unplanned pregnancy (Santelli et al., 2006). In a Spanish study, low socioeconomic status (SES) was a strong predictor of an induced abortion (Font-Ribera et al., 2007).

Women undergoing termination of pregnancy (TOP) are at an increased risk of another TOP. Risk factors of repeat TOP have been characterized in several studies. In studies performed both in Europe and in North America, factors such as parity, social deprivation, use of hormonal contraception and a history of domestic violence or sexually transmitted diseases have been associated with repeat TOP (John et al., 2004; Fisher et al., 2005; Prager et al., 2007; Rowlands, 2007). Recently, in a prospective study, we showed that young age, parity, a history of abortion and regular smoking were risk factors of repeat abortion in Finland (Heikinheimo et al., 2008).

However, life circumstances may change rapidly during the fertile years. To our knowledge, factors identifiable at the time of TOP and associated with repeat TOP, delivery or failure of subsequent pregnancy (i.e. ectopic pregnancy or spontaneous miscarriage) have not been assessed previously. The objective of the present work was to identify factors, which, at the time of TOP, may be of use in predicting the outcome of the next pregnancy. Knowledge of such factors would be important when counselling and planning services for women undergoing TOP.

Materials and Methods

The cohort of 1269 women established at the time of introduction of medical abortion at our institution (Heikinheimo et al., 2007) was studied further. This medical TOP is referred to as the index abortion. Demographic data of the subjects and data concerning their post-abortal contraception are shown in Table I. In a previous report, we followed the cohort until the end of 2005 and analysed risk factors of repeat TOP (Heikinheimo et al., 2008). In the present work, the follow-up was extended until the end of 2006, and all subsequent pregnancies (those resulting in delivery, TOP as well as failed pregnancies) were included. Thus, the subjects were followed until their next pregnancy or until the end of 2006.

Table I

Subject demographics and contraception started at the index abortion

 n = 1269 
Age, years (mean ± SD) 28.2 ± 7.1 
Parous 490 (38.6%) 
Previous induced abortion 392 (30.9%) 
Smoker* 564 (44.4%) 
Duration of pregnancy, days (mean ± SD) 48.0 ± 6.9 
Socioeconomic class  
 Upper white-collar worker 171 (13.5%) 
 Lower white-collar worker 379 (29.9%) 
 Blue-collar worker 131 (10.3%) 
 Students 385 (30.3%) 
 Other 100 (7.9%) 
 Unknown 103 (8.1%) 
Contraception started**  
 COC 613 (49.5%) 
 POP 28 (2.3%) 
 Implant 18 (1.5%) 
 Cu-IUD 124 (10.0%) 
 LNG-IUS 136 (11.0%) 
 Uncertain 312 (25.2%) 
 Sterilization 7 (0.6%) 
 n = 1269 
Age, years (mean ± SD) 28.2 ± 7.1 
Parous 490 (38.6%) 
Previous induced abortion 392 (30.9%) 
Smoker* 564 (44.4%) 
Duration of pregnancy, days (mean ± SD) 48.0 ± 6.9 
Socioeconomic class  
 Upper white-collar worker 171 (13.5%) 
 Lower white-collar worker 379 (29.9%) 
 Blue-collar worker 131 (10.3%) 
 Students 385 (30.3%) 
 Other 100 (7.9%) 
 Unknown 103 (8.1%) 
Contraception started**  
 COC 613 (49.5%) 
 POP 28 (2.3%) 
 Implant 18 (1.5%) 
 Cu-IUD 124 (10.0%) 
 LNG-IUS 136 (11.0%) 
 Uncertain 312 (25.2%) 
 Sterilization 7 (0.6%) 

Data are presented as n (%) unless stated otherwise.

*Defined as daily smoking.

**Assessed among the 1238 subjects attending the follow-up visit at the clinic within 2 weeks to 2 months after the index TOP.

Before initiation of the present study, approval was obtained from the administrative head of the Department of Obstetrics and Gynaecology, Helsinki University Central Hospital, the National Research and Development Centre for Welfare and Health, as well as from the Ministry of Social Affairs and Health. Demographic risk factors regarding repeat TOP, delivery and failed pregnancy were studied among all 1269 women. The effect of contraceptive choices made at the time of abortion was studied among the 1238 women assessed at follow-up, performed between 2 weeks and 2 months after the index TOP (Heikinheimo et al., 2007).

Repeat TOPs were identified through the Finnish Registry of Induced Abortions, deliveries were identified through the Finnish Medical Birth Registry and failed pregnancies were identified through the National Hospital Discharge Registry (www.stakes.fi). The Finnish Registry of Induced Abortions includes TOPs performed according to national legislation, up to 24 weeks of gestation (Gissler et al. 1996). The Medical Birth Registry includes pregnancies ending at 22 weeks of pregnancy or more, or resulting in delivery of an infant weighing 500 g or more.

The occupation noted in the Registry of Induced Abortions was electronically transformed into an occupation code and subsequently a socioeconomic group as defined by Statistics Finland (Statistics Finland, 1987, 1989, 1992). Classification of SES into six groups was carried out as follows: Group I, upper white-collar workers, Group II, lower white-collar workers, Group III, blue-collar workers, Group IV, students, Group V, all other groups (entrepreneurs, farmers, unemployed, retired and housewives) and Group VI included 103 subjects with no SES information available (unknown).

In statistical analysis, age and duration of pregnancy at the index abortion were considered as both continuous and categorical variables. The continuous variables were analysed using the Mann–Whitney U-test. The effects of various factors concerning sociodemographic characteristics, history of TOP and post-abortal contraception on the probabilities of subsequent repeat TOP, delivery or failed pregnancy were analysed using Cox’s proportional hazards model. The effect of each factor alone was assessed using a univariate Cox’s model. The factors that were statistically significantly different in univariate analysis of any pregnancy outcome were included in a multivariate Cox’s model. The respective hazard ratios (HRs) with 95% confidence intervals (95% CIs) were calculated. In addition, the cumulative risks associated with selected factors were assessed and displayed using the Kaplan–Meier curves. A two-sided P-value of ≤0.05 was considered statistically significant. Statistics were computed using SAS® software (version 9.1) from the SAS Institute Inc. (Cary, NC, USA).

Results

The different pregnancy outcomes are summarized in Fig. 1. More than half (65%) of the women did not have another pregnancy during follow-up, whereas 16% had a pregnancy resulting in delivery, 13% underwent another TOP and 6% had a failed pregnancy.

Figure 1

Distribution of subsequent pregnancy outcomes (delivery, repeat TOP, failed pregnancy and no pregnancy) during the follow-up period.

Figure 1

Distribution of subsequent pregnancy outcomes (delivery, repeat TOP, failed pregnancy and no pregnancy) during the follow-up period.

Altogether, 446 (35%) of the 1269 women included in the present cohort had at least one pregnancy within the mean (±SD) follow-up period of 4.2 ± 1.5 years (range 0.1–6.4 years). Nearly half (207; 46%) of the first post-abortal pregnancies resulted in delivery, whereas 169 (38%) of the women underwent another TOP. The proportion of failed pregnancies was 16%.

The time (mean ± SD) to the first post-abortal pregnancy resulting in delivery was 3.1 ± 1.3 years, whereas the time to repeat TOP was 2.3 ± 1.4 years (P < 0.0001). The time to failed pregnancy was also 2.3 ± 1.4 years. The mean age of the women at the time of repeat TOP was 25.8 ± 6.3 (SD) years, at the time of delivery, 26.8 ± 5.3 years and at the time of failed pregnancy, 29.1 ± 6.7 years. The mean duration of pregnancy at the time of repeat TOP was 7.8 ± 2.0 (SD) weeks.

Table II shows the incidences of repeat TOP, delivery and failed pregnancy according to different variables. Statistical significance, derived from univariate analyses, is also shown. Only variables associated with a significantly different rate of repeat TOP or delivery are shown. Duration of pregnancy at the time of index TOP, and SES, did not have significant effects on the risk of repeat TOP, failed pregnancy or the probability of delivery. As there were only a few failed pregnancies, none of the variables studied was associated with significantly different rates of failed pregnancy.

Table II

Rates of repeat TOP, delivery and failed pregnancy (ectopic pregnancy and spontaneous miscarriage) according to different variables

 Total Repeat TOP
 
Delivery
 
Failed pregnancy
 
 No Yes Incidencea P-valueb No Yes Incidencea P-valueb No Yes Incidencea P-valueb 
 n = 1069 n = 169 29.3  n = 1031 n = 207 35.9  n = 1168 n = 70 11.6  
Age, years             
 <20 132 33 44.5  143 22 29.5  158 8.5  
 20–24 236 54 40.5 n.s234 56 38.3 n.s274 16 9.6 n.s
 25–29 231 33 26.4 <0.05 193 71 62.7 <0.005 253 11 10.0 n.s
 30–34 229 33 25.9 <0.05 217 45 34.8 n.s239 23 17.6 <0.1 
 35–39 179 16 14.1 <0.002 182 13 15.3 <0.05 186 8.8 n.s
 40 or more 62 0.0 n.s62 0.0 n.s58 16.2 n.s
Parous             
 No 665 96 26.3  614 147 41.4  721 40 10.0  
 Yes 404 73 32.5 n.s417 60 26.4 <0.005 447 30 14.4 n.s
History of abortion             
 No 750 105 26.1  706 149 36.5  807 48 10.8  
 Yes 319 64 34.4 <0.05 325 58 33.6 n.s361 22 12.4 n.s
Smoking daily             
 No 569 75 23.1  537 107 34.6  609 35 11.2  
 Yes 457 93 38.3 <0.001 460 90 36.4 n.s517 33 11.6 n.s
 Missing 62 3.2 n.s45 18 53.6 n.s42 10.1 n.s
Use of LARC*             
 Yes 258 20 14.0  250 28 21.2  268 10 6.9  
 No 552 89 30.8 <0.005 521 120 40.5 <0.002 597 44 13.7 <0.1 
 Other 259 60 44.3 <0.05 260 59 41.2 n.s303 16 10.0 n.s
Type of contraception             
 COC 527 86 31.0  501 112 39.3  570 43 14.0  
 POP 25 24.7 n.s20 68.3 n.s27 8.1 n.s
 Implant 15 35.6 n.s15 37.4 n.s18 0.0 n.s
 Cu-IUD 114 10 14.1 <0.1 109 15 27.0 <0.1 121 5.1 <0.1 
 LNG-IUS 129 11.0 <0.01 126 10 14.2 <0.005 129 9.4 n.s
 Sterilization n.s0.0 n.s7 0 0.0 n.s
 Uncertain 252 60 46.3 <0.05 252 60 44.5 n.s296 16 10.4 n.s
 Total Repeat TOP
 
Delivery
 
Failed pregnancy
 
 No Yes Incidencea P-valueb No Yes Incidencea P-valueb No Yes Incidencea P-valueb 
 n = 1069 n = 169 29.3  n = 1031 n = 207 35.9  n = 1168 n = 70 11.6  
Age, years             
 <20 132 33 44.5  143 22 29.5  158 8.5  
 20–24 236 54 40.5 n.s234 56 38.3 n.s274 16 9.6 n.s
 25–29 231 33 26.4 <0.05 193 71 62.7 <0.005 253 11 10.0 n.s
 30–34 229 33 25.9 <0.05 217 45 34.8 n.s239 23 17.6 <0.1 
 35–39 179 16 14.1 <0.002 182 13 15.3 <0.05 186 8.8 n.s
 40 or more 62 0.0 n.s62 0.0 n.s58 16.2 n.s
Parous             
 No 665 96 26.3  614 147 41.4  721 40 10.0  
 Yes 404 73 32.5 n.s417 60 26.4 <0.005 447 30 14.4 n.s
History of abortion             
 No 750 105 26.1  706 149 36.5  807 48 10.8  
 Yes 319 64 34.4 <0.05 325 58 33.6 n.s361 22 12.4 n.s
Smoking daily             
 No 569 75 23.1  537 107 34.6  609 35 11.2  
 Yes 457 93 38.3 <0.001 460 90 36.4 n.s517 33 11.6 n.s
 Missing 62 3.2 n.s45 18 53.6 n.s42 10.1 n.s
Use of LARC*             
 Yes 258 20 14.0  250 28 21.2  268 10 6.9  
 No 552 89 30.8 <0.005 521 120 40.5 <0.002 597 44 13.7 <0.1 
 Other 259 60 44.3 <0.05 260 59 41.2 n.s303 16 10.0 n.s
Type of contraception             
 COC 527 86 31.0  501 112 39.3  570 43 14.0  
 POP 25 24.7 n.s20 68.3 n.s27 8.1 n.s
 Implant 15 35.6 n.s15 37.4 n.s18 0.0 n.s
 Cu-IUD 114 10 14.1 <0.1 109 15 27.0 <0.1 121 5.1 <0.1 
 LNG-IUS 129 11.0 <0.01 126 10 14.2 <0.005 129 9.4 n.s
 Sterilization n.s0.0 n.s7 0 0.0 n.s
 Uncertain 252 60 46.3 <0.05 252 60 44.5 n.s296 16 10.4 n.s

aPer 1000 woman-years.

bUnivariate comparison with first mentioned variable in each category.

*LARC, Long-acting reversible methods of contraception (i.e. Cu-IUD, LNG-IUS and implants).

Includes uncertain and sterilization.

Contraception was assessed among the 1238 women who participated in the follow-up visit.

The incidence of repeat TOP was higher than that of delivery in the youngest age groups of <20, and 20–24 years. However, the incidence of delivery exceeded that of abortion in the age groups of 25 years and more, and reached its peak in the group who were between 25 and 29 years of age at the time of index abortion. Parity was associated with a lower incidence of delivery but was not associated with the incidence of repeat TOP. A history of induced abortion was associated with an increased risk of repeat TOP but not associated with an altered incidence of delivery.

Figure 2 shows the results of the Kaplan–Meier analysis of the effect of age on the cumulative incidence of repeat abortion and delivery. The first repeat TOP occurred at only a few months following the index TOP. The younger the women were at the time of the index TOP, the higher the rate of cumulative repeat TOP. However, the cumulative rate of delivery was highest at all times among women who were between 25 and 29 years of age at the time of the index abortion.

Figure 2

Cumulative incidence of repeat TOP (left) and delivery (right) among different age groups at the time of the index abortion.

Figure 2

Cumulative incidence of repeat TOP (left) and delivery (right) among different age groups at the time of the index abortion.

The use of long-acting reversible methods of contraception (LARC) following the index abortion was associated with a reduced incidence of pregnancy. Specifically, in comparison with COCs, use of the LNG-IUS was associated with reduced incidences of both repeat TOP and delivery. The effect of Cu-IUD use was of borderline significance (P < 0.1). Postponing initiation of post-abortal contraception (i.e. uncertain) was associated with an increased incidence of repeat TOP, but it did not have a significant effect on the incidence of delivery (Table II). The highest initial rates of delivery were seen among women starting implant contraception, followed by POP users after 4 years of follow-up. The cumulative rates of repeat TOP and delivery according to the method of post-abortal contraception are shown in Fig. 3.

Figure 3

Cumulative incidence of repeat TOP (left) and delivery (right) according to contraceptive choices made at the time of the index abortion.

Figure 3

Cumulative incidence of repeat TOP (left) and delivery (right) according to contraceptive choices made at the time of the index abortion.

Figure 4 shows the HRs and 95% CIs associated with repeat TOP and delivery according to different variables. In these multivariate analyses, the risk of repeat TOP was reduced among women who were over 25 years of age at the time of the index TOP when compared with women <20 years of age. In addition, the risk of repeat TOP was significantly increased among parous women and those with a history of abortion. The effect of regular smoking was of borderline significance. The risk of repeat TOP was lower among women who chose either the Cu-IUD or the LNG-IUS for post-abortal contraception. However, delaying initiation of contraception was not associated with a significantly changed risk of repeat TOP.

Figure 4

HRs and 95% CIs of repeat TOP (left) and delivery (right) according to multivariate analyses.

Figure 4

HRs and 95% CIs of repeat TOP (left) and delivery (right) according to multivariate analyses.

In multivariate analysis, the probability of the next pregnancy resulting in delivery was significantly increased only among women who were between 25 and 29 years of age at the time of the index TOP. Contraceptive choices made at the time of the index abortion had only a minor effect on the probability of the next pregnancy resulting in delivery. In comparison with COCs, women who used the LNG-IUS showed a lower probability of delivery, but the difference was of borderline significance.

Discussion

In the present study, pregnancies following induced abortion were common and more than one-third of all women underwent another pregnancy during the ∼4 year follow-up period. Nearly half of all pregnancies resulted in delivery and approximately one-third resulted in repeat TOP. The characteristics of women whose next pregnancy ended in repeat TOP differed from those whose next pregnancy resulted in delivery. In multivariate analysis, young age, history of TOP and parity were associated with an increased risk of repeat abortion. However, the factors associated with delivery were less clear: only age between 25 and 29 years was related to an increased probability of the next pregnancy resulting in delivery.

The strengths of the present study include its prospective nature and long follow-up period. In addition, the abortion and birth registers cover practically all abortions and deliveries in Finland (Gissler et al., 1996; Heikinheimo et al., 2008). However, the data on failed pregnancies, collected from hospital discharge records, may be less reliable, as some of these pregnancies are likely to have been attended to outside the public hospital system. As the study was registry-based, no information on which of the subsequent pregnancies were planned or unplanned is available. In addition, women choosing medical abortion might differ slightly from those choosing surgical abortion. Nevertheless, nearly 70% of all early abortions in Finland are currently performed medically (www.stakes.fi).

In previous reports, from the USA and Spain, a quarter of pregnancies resulted in TOP (Henshaw, 1998; Font-Ribera et al., 2007). Of all the present pregnancies, one-third resulted in repeat TOP. Given the overall rate of TOP of ∼15% in Finland (www.stakes.fi), the present figure is high. This is most likely a result of the fact that the present subjects represent a young, highly fertile population having undergone previous TOP(s).

The rate of failed pregnancy was low (16%) and in line with commonly cited rates of spontaneous miscarriages of clinically recognized pregnancies (Katz, 2007). Because of their low number, no statistically significant risk factors regarding failed pregnancies emerged in univariate analysis.

The time to delivery was significantly longer than that to repeat TOP. However, given the fact that nearly all of the repeat TOPs were performed in the first trimester, both classes of pregnancy began at approximately the same time. Thus, life circumstances affecting decisions concerning pregnancy can change rapidly.

The observed factors affecting repeat TOP versus delivery reflect the current fertility trends in Finland well. Between 2000 and 2006, the fertility rate in Finland was ∼1.8 (www.tilastokeskus.fi). In univariate analysis, women who were nulliparous at the time of the index abortion had an increased chance of the next pregnancy ending in delivery, whereas parous women had an increased risk of repeat abortion. However, in multivariate analysis only the increased risk of repeat TOP seen in parous women persisted.

Of the various factors studied, age had the most pronounced effect on the outcome of the next pregnancy. In the groups below 25 years of age, repeat TOP was the most likely pregnancy outcome. However, among older women, most of the pregnancies resulted in delivery. The reasons for this are likely to be multifactorial. The mean age of all parturients in the Helsinki area in the early part of this century has been ∼29 years (www.stakes.fi). Analogously, the highest rate of delivery was seen among women who were between 25 and 29 years of age at the time of the index abortion.

In a recent Spanish study, SES had an important effect on the fate of an unplanned pregnancy (Font-Ribera et al., 2007). This is in contrast to French results, according to which SES had a dual effect—high SES was associated with an increased use of contraception but a higher rate of induced abortion in cases of unintended pregnancy (Rossier et al., 2007). In the present study, SES did not emerge as a significant predictor of pregnancy outcome. However, different societies are likely to differ greatly in this respect. In addition, many of the present subjects were young students. Thus, the SES of their family and/or partner might have been a better variable to assess. Unfortunately, such data are not recorded in the currently used registers.

Contraceptive choices made at the time of the index abortion were significantly related to the outcome of the next pregnancy. Intrauterine contraception, especially use of the LNG-IUS, was associated with the lowest incidence of pregnancy. Yet, in multivariate analysis, initiation of intrauterine contraception was associated only with a significantly decreased risk of repeat TOP. As the study was not randomized, the women choosing intrauterine contraception were likely to have been highly motivated. This may be highlighted in the case of the LNG-IUS, which requires a relatively large single investment. Contraceptive cultures vary from country to another. Despite their high contraceptive efficacy (Meirik et al., 2003), only few women chose contraceptive implants, and none chose depot medroxyprogesterone acetate injections for post-abortal contraception. This may be typical in Finland with long tradition of oral contraceptive and IUD/IUS use. Nevertheless, access to contraception might be a contributing factor regarding repeat TOP among some women.

The present results have practical implications. Contraceptives are not provided free of charge in Finland. On the basis of the present data, contraceptive provision to parous women and young women undergoing TOP is important. Accordingly, the rate of teenage abortion declined in Norway following provision of contraception free-of-charge to girls and women between 16 and 20 years of age (www.fhi.no). The nature of the contraception provided is also relevant and on the basis of the present data, effective provision of LARCs might be important. Immediate post-abortal provision of intrauterine contraception has been suggested to significantly decrease the rate of repeat abortion (Goodman et al., 2008). As the LNG-IUS is increasingly being used among nulliparous women (Suhonen et al., 2004), its use among young women undergoing TOP might be especially beneficial.

In conclusion, at the time of induced abortion, the factors affecting repeat TOP are more clearly defined than those affecting delivery later on. The various factors also mirror the prevalent fertility trends—in a setting of a relatively low fertility rate, previous delivery was a significant risk factor as regards repeat TOP. Selection of post-abortal contraception had an important effect on the rate of repeat TOP, but less effect on the rate of delivery. Thus, enhanced investment (such as easier access to contraceptive services) among young women, especially those who are parous and those who have a history of abortion, might be efficacious and result in a decreased rate of repeat TOP.

Funding

Funding from the Helsinki University Central Hospital Research Funds and Schering Ag Finland research funds is gratefully acknowledged.

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Clinical performance of a levonorgestrel-releasing intrauterine system and oral contraceptives in young nulliparous women: a comparative study
Contraception
 , 
2004
, vol. 
69
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407
-
412
)