Abstract

BACKGROUND

There is a need to improve our understanding of contraceptive use over the long term. The aims of this study were to describe contraceptive use and pregnancies in the same women followed prospectively from 19 to 44 years of age.

METHODS

In 1981, a postal questionnaire about contraception, pregnancies and reproductive health was sent to a random sample (n = 656) of 19-year-old women resident in Gothenburg, Sweden. The responders were contacted again every fifth year.

RESULTS

At 19 years of age, 74% of the women had already used contraception and this increased to 98% at 44 years. Combined oral contraception was the commonest method currently used up to 29 years of age (48/51/22% at 19/24/29 years of age, respectively) and thereafter an intrauterine device (IUD: 34/39/38% at 34/39/44 years of age, respectively). Condom use alone during the 25-year study period was: 14/12/24/21/21/15% and non-use of contraception was: 35/24/26/20/21/26%. The mean number of pregnancies/children increased from 0.2/0.1 at 19 years of age to 3.1/2.1 at 44 years. Women who had been pregnant and women who had not been pregnant ≤19 years of age were compared up to 44 years of age (months of OC use: 69/107, P < 0.01; months of IUD use: 126/91, P < 0.01; 4.2/2.9 pregnancies, P < 0.001; 2.5/2.1 children, P< 0.09).

CONCLUSIONS

Choice of contraception was strongly related to age and parity, and the cumulative total number of pregnancies at 44 years of age, and contraceptive choice was related to age at first pregnancy.

Introduction

Women's choice of contraceptive method is influenced by her perception of the possible physical and psychological effects of the method (den Tonkelaar and Oddens, 2001; ESHRE Capri Workshop Group, 2005). Contraceptive use is related to many factors, e.g. sexuality, age, parity, accessibility to family planning facilities, social policy, and moral, cultural and religious convictions (Wellings, 2005). The interaction between these factors is complex and single factors are difficult to evaluate. The health beliefs and opinion of both users and prescribers (Burkham, 1999) regarding methods of contraception differ from society to society, which may explain why a method can be popular in some countries while not in others. Contraceptive use varies considerably between the developed world and the developing world (United Nations, 2007), but there are also large differences between countries from the developed world (Rimpelä et al., 1992,Skouby, 2004; Moreau et al., 2007; Rasch et al., 2007; Cibula, 2008; Lindh et al. 2009; Potter et al., 2009) where most contraceptive methods are readily available. The majority of studies regarding the contraceptive use are cross-sectional (Rimpelä et al., 1992 Skouby, 2004; Moreau et al., 2007; Rasch et al., 2007; Cibula, 2008; Lindh et al., 2009; Potter et al., 2009) and there is a lack of longitudinal studies describing the use of contraception in the same women over time.

The occurrence of unplanned pregnancies and legal abortions is high (UK Department of Health, 2004; Abortion Statistics Sweden, 2008; Jones et al., 2008) in many developed countries despite the availability of effective contraceptive techniques. Sweden has, despite the ready availability of contraception, the highest abortion rate in Western Europe (21.3/1000 women in 2008), and 38% of all abortions in 2008 were performed in women who previously had undergone an abortion (Abortion Statistics Sweden, 2008). Studies have shown that there is a continued increased risk of unintended pregnancy in women who already have undergone an abortion (Heikinheimo et al., 2008; Lindh et al., 2009) and that teenagers who give birth constitute a continued high risk for future unintended pregnancies and legal abortion (Falk et al., 2006). Thus, there is a need for prospective longitudinal studies simultaneously assessing the use of contraception and the occurrence of possible pregnancies in order to improve our understanding regarding contraceptive use in the long-term perspective.

In 1981, a prospective longitudinal study was initiated regarding contraceptive use, pregnancies and reproductive health in a random sample of 19-year-old women (Andersch and Milsom, 1982). The same women have now been re-assessed at 5-year intervals up to the age of 44 years. The primary aim of the study was to describe contraceptive use and pregnancies in the same women followed during this 25-year period. A secondary objective was to compare continued contraceptive choice and the number of pregnancies and children in women who had already been pregnant at 19 years of age and women with no pregnancy at that age.

Materials and Methods

Study population

In 1981, a prospective longitudinal population study of women resident in the city of Gothenburg, Sweden, was initiated (Andersch and Milsom, 1982). The women included were born in 1962 and were 19 years of age and this age was chosen in order to be able to deal with women of legal age, enabling information to be collected via the individuals themselves without the necessity of consent from their parents. The study was approved by the Ethics Committee, Faculty of Medicine, University of Gothenburg and the National Data Inspection Board approved the study design and informed consent was obtained from each participant.

There were 2621 women aged 19 living in the city of Göteborg in 1981 and a random sample of every fourth woman was obtained (n = 656) from the population register. The women were contacted by letter and requested to complete and return an enclosed questionnaire concerning contraception, possible pregnancies, reproductive health and factors such as body weight, height etc. If no reply was received, reminders were sent out after 2 and 4 weeks. Women who returned the questionnaire in 1981 were contacted again every fifth year (1986, 1991, 1996, 2001, and 2006) and requested to answer and return a similar questionnaire.

The questionnaire

The questionnaire contained ∼40 questions concerning contraception, reproductive history and factors such as smoking, body weight and height etc. The women were questioned on each occasion regarding their current method of contraception [duration of use was specifically asked regarding oral contraception, copper releasing intrauterine devices (IUD), Cu-IUD, and the levonorgestrel-releasing intrauterine system, LNG-IUS]. They were also questioned whether or not they had at any time used contraception and if so which methods they had used and why they had chosen this method, and if they had stopped using a method why they had ceased using the method. Information on the number of pregnancies and number of children was requested at each measurement point. Questions were not asked regarding partnership status or sexual activity. The ability to understand the questionnaire and reliability was evaluated in a sub-sample of 30 women and was found to be satisfactory. Reliability was tested by letting 30 women answer the questionnaire twice within a 3-week interval and the agreement of the answers to five specific questions was tested. Ten questions in the inquiry were then selected and the same 30 women were interviewed to see if they understood the meaning of the questions.

Characteristics of the samples and analysis of the non-responders

The questionnaire was completed and returned by 594 of the 656 19-year-old women contacted in 1981 (response rate 91%). The population register contains information regarding civil status, nationality and home address linked to the individual's personal identification number. The socio-economic status (SES) of the district where the woman was resident was classified according to a three-point socio-economic index (low, medium, high SES) based on the mean level of education, income and profession/social group for all the inhabitants resident in each district (Statistics Sweden, 2001). The responders in 1981 were considered representative, as there were no significant differences between responders and non-responders regarding marital status, nationality or the SES of the area where the women were resident. The questionnaire was completed and returned on all six occasions (1981, 1986, 1991, 1996, 2001 and 2006) by 286 women, which constitutes 44% of the original sample of 656 women. There were no significant difference regarding smoking, pregnancies, live birth, contraceptive use and SES of the area where the woman was resident between the responders from all six occasions (n = 286) and the non-responders who had answered the questionnaire at some time during the period 1981–2006 (n = 308).

Data analysis and statistical methods

The accuracy of the data entry was checked on an individual basis for each parameter in all subjects. Fisher's exact test, analysis of variance with Tukey's Studentized Range test for post hoc comparisons (SAS 9.1, SAS Institute, Inc., Cary, NC, USA) or Dunnet were used in the analysis of possible differences in basic characteristics, contraceptive use and the number of pregnancies and children.

Results

The questionnaire was completed and returned on all six occasions by 286 women which constituted 44% of the original sample of 656 women. A flow chart describing the inclusion of the women and their continued participation in this study appears in Fig. 1.

Figure 1

Flow chart illustrating the inclusion of the women and their continued participation in this longitudinal study.

Figure 1

Flow chart illustrating the inclusion of the women and their continued participation in this longitudinal study.

Basic characteristics

A comparison of baseline characteristics in the same women at 19, 24, 29, 34, 39 and 44 years of age is shown in Table I. Women at the age of 44 had a significant greater body weight and higher BMI (P < 0.0001) compared with the same women at the age of 19 years. The proportion of smokers decreased from 39% at the age of 19 to 21% at the age of 44 (P < 0.0001). Smoking was as highest (41%) at the age of 24. Mean menarcheal age was 13.

Table I

Comparison of baseline characteristics in the same women (n = 286) at 19, 24, 29, 34, 39 and 44 years of age.

 19 Years 24 Years 29 Years 34 Years 39 Years 44 Years 
Height, cm (mean) 167.2 167.5 167.5 167.5 167.6 167.5 
(95% CI) 166.5–167.8 166.9–168.1 166.8–168.1 166.9–168.2 166.9–168.2 166.8–168.2 
Weight, kg (mean) 58.5 60.0 62.5 65.1 68.2 69.1 
(95% CI) 57.6–59.3 58.9–61.0 61.4–63.6 63.7–66.5 66.7–69.7 67.5–70.6 
BMI, mean 20.9 21.3 22.3 23.2 24.3 24.6 
(95% CI) 20.6–21.2 21.0–21.6 21.9–22.6 22.7–23.6 23.8–24.8 24.1–25.1 
Menarcheal age (year) [mean (95% CI)] 13.0 (12.9–13.2)       
Smoking [n (%)]       
Smoker 110 (39) 115 (41) 93 (33) 83 (29) 75 (26) 59 (21) 
 19 Years 24 Years 29 Years 34 Years 39 Years 44 Years 
Height, cm (mean) 167.2 167.5 167.5 167.5 167.6 167.5 
(95% CI) 166.5–167.8 166.9–168.1 166.8–168.1 166.9–168.2 166.9–168.2 166.8–168.2 
Weight, kg (mean) 58.5 60.0 62.5 65.1 68.2 69.1 
(95% CI) 57.6–59.3 58.9–61.0 61.4–63.6 63.7–66.5 66.7–69.7 67.5–70.6 
BMI, mean 20.9 21.3 22.3 23.2 24.3 24.6 
(95% CI) 20.6–21.2 21.0–21.6 21.9–22.6 22.7–23.6 23.8–24.8 24.1–25.1 
Menarcheal age (year) [mean (95% CI)] 13.0 (12.9–13.2)       
Smoking [n (%)]       
Smoker 110 (39) 115 (41) 93 (33) 83 (29) 75 (26) 59 (21) 

Significance of difference: body weight and BMI had increased between 19 and 44 years of age (P < 0.0001). The proportion of smokers decreased during the same time period (P < 0.0001) and height was unchanged (NS).

Contraception

At 19 years of age, 74% reported they had already used contraception and this figure increased to 98% at 44 years of age. Combined oral contraception (COC) was the most commonly used method and had been used at some time up to the age of 44 years by 95% of the women. The corresponding figures for condom use and the use of an IUD were 78 and 48%, respectively.

COC was the most commonly used method of contraception up to 29 years of age (Table II), whereas intrauterine methods of contraception (Cu-IUD or the LNG-IUS) were more common after 29 years of age. The use of a condom alone varied during the 25-year study period (12–24%) and was most often used at the ages of 29 (24%), 34 (21%) and 39 (21%). Questions about other methods of contraception, such as sterilization, natural family planning method, coitus interruptus and different kinds of barrier methods except condoms, were asked for the first time at the age of 29 years old. The use of these other methods varied between 14 and 19% from the age of 29 to 44 years. At 44 years of age, 2.4% of the women were using sterilization as a method of contraception. The use of the progestogen-only pill varied between 2 and 5% during the study period. In Sweden, emergency contraception was officially introduced in 1994 and, thus, the use of emergency contraception was only recorded in the postal questionnaire from 1996. Two percent of women reported that they had been using emergency contraception at the age of 34 and 4% at the age of 39 and 44 years. Non-use of contraception varied between 20 and 35%.

Table II

Contraceptive use in the same women (n = 286) at 19, 24, 29, 34, 39 and 44 years of age.

Contraceptive method 19 Years, n (%) 24 Years, n (%) 29 Years, n (%) 34 Years, n (%) 39 Years, n (%) 44 Years, n (%) 
No contraception 101 (35) 69 (24) 74 (26) 57 (20) 61 (21) 75 (26) 
COC 136 (48) 146 (51) 63 (22) 34 (12) 21 (7) 18 (6) 
COC + condom 4 (1) 1 (0) 10 (3) 4 (1) 1 (0) 1 (0) 
Condom alone 39 (14) 35 (12) 69 (24) 59 (21) 61 (21) 42 (15) 
Cu-IUD 3 (1) 32 (11) 53 (19) 58 (20) 54 (19) 47 (16) 
LNG-IUS — — — 41 (14) 57 (20) 63 (22) 
IUD + condom 1 (0) 1 (0) 1 (0) 
POP 12 (4) 6 (2) 8 (3) 13 (5) 12 (4) 12 (4) 
Depot gestagen/implant 3 (1) 10 (3) 4 (1) 
Other method — — 53 (19) 53 (19) 43 (15) 39 (14) 
Contraceptive method 19 Years, n (%) 24 Years, n (%) 29 Years, n (%) 34 Years, n (%) 39 Years, n (%) 44 Years, n (%) 
No contraception 101 (35) 69 (24) 74 (26) 57 (20) 61 (21) 75 (26) 
COC 136 (48) 146 (51) 63 (22) 34 (12) 21 (7) 18 (6) 
COC + condom 4 (1) 1 (0) 10 (3) 4 (1) 1 (0) 1 (0) 
Condom alone 39 (14) 35 (12) 69 (24) 59 (21) 61 (21) 42 (15) 
Cu-IUD 3 (1) 32 (11) 53 (19) 58 (20) 54 (19) 47 (16) 
LNG-IUS — — — 41 (14) 57 (20) 63 (22) 
IUD + condom 1 (0) 1 (0) 1 (0) 
POP 12 (4) 6 (2) 8 (3) 13 (5) 12 (4) 12 (4) 
Depot gestagen/implant 3 (1) 10 (3) 4 (1) 
Other method — — 53 (19) 53 (19) 43 (15) 39 (14) 

COC, combined oral contraceptive; POP, low-dose progestogen-only pill and medium dose progestogen only pill; Cu-IUD, Copper intrauterine device; LNG-IUS, levonorgestrel releasing intrauterine system. Other method: sterilization, barrier methods except condom, natural family planning and coitus interruptus. Some women may have answered two choices of contraceptive and therefore in some columns it is more than 100%.

The relationship between the use of contraception and pregnancies is illustrated in Fig. 2. There was a noticeable change in contraceptive choice at the age of 29 which corresponds to the mean age of the woman when she has her first child in Sweden. There was an increase in the use of intrauterine methods of contraception as the proportion of women in the study had been pregnant and had given birth to a child.

Figure 2

Contraceptive choice, number of pregnancies and births and the cumulative mean number of pregnancies and children at different ages in the same women (n = 286) followed longitudinally from 19 to 44 years of age. COC, combined oral contraceptive pill; IUD, intrauterine device.

Figure 2

Contraceptive choice, number of pregnancies and births and the cumulative mean number of pregnancies and children at different ages in the same women (n = 286) followed longitudinally from 19 to 44 years of age. COC, combined oral contraceptive pill; IUD, intrauterine device.

Pregnancies

The cumulative number of pregnancies and children is shown in Fig. 2. At 19 years of age, 17% of the women reported that they had been pregnant and this figure had increased to 96% at the age of 44. One pregnancy was reported by 13.7% of the women at the age of 19 and more than one pregnancy was reported by 3.7%. At the age of 19, 5% of the women had given birth to a child and this figure had increased to 93% at 44 years of age. The mean number of pregnancies/children increased from 0.2/0.1 at 19 years of age to 3.1/2.1 at 44 years of age. At 44 years of age, 4% of the women had not been pregnant and 7% reported that they had not given birth to a child.

Teenage pregnancy

Two hundred and eighty-six women returned the questionnaire on all six occasions and 271 women answered the question about the number of pregnancies and children at the age of 19. Among these 271 women, 224 women reported no pregnancies ≤19 years of age and 47 women reported a mean number of 1.2 pregnancies ≤19 years. There was no significant difference in menarcheal age between the two groups of women (224/47: 13.0/12.7). A comparison regarding pregnancies up to the age of 44 and contraceptive use was made between the women who had already been pregnant ≤19 years of age (n = 47) and the remainder (n = 224) who had not been pregnant ≤19 years of age (Fig. 3). At 44 years of age, the mean number of pregnancies (P < 0.001) and children (P < 0.09) was greater in the group of women who had been pregnant ≤19 years of age (4.2 and 2.5, respectively) compared with women who had not been pregnant ≤19 years of age (2.9 and 2.1, respectively).

Figure 3

Comparison of the use of the COC pill or an IUD, and the cumulative mean number of pregnancies and children at different ages from 19 to 44 years in the women grouped according to whether the woman had been pregnant or not ≤19 years of age.

Figure 3

Comparison of the use of the COC pill or an IUD, and the cumulative mean number of pregnancies and children at different ages from 19 to 44 years in the women grouped according to whether the woman had been pregnant or not ≤19 years of age.

At 24 years of age, the mean number of pregnancies had increased more (P < 0.01) in the group of women who had been pregnant ≤19 years of age (from 1.2 to 2.3) compared with women who had not been pregnant ≤19 years of age (from 0 to 0.5). There was, however, no further increase in the number of pregnancies between groups from 24 to 44 years of age (Fig. 3).

The prevalence of COC use and IUD use varied between the two groups (Fig. 3). However, there were only minor differences between the groups with regard to condom use or the non-use of contraception with one exception (condom use at 19 years of age was greater in the group of women who had been pregnant ≤19 years, 26 versus 12%, P < 0.05). At 19 years of age, COC was the commonest method in both groups (51% for the women who had been pregnant ≤19 years of age and 52% for women who had not been pregnant ≤19 years of age) and there were few IUD users (4 and 0%, respectively). At 24 years of age, COC use was still high in the group of women who had not been pregnant ≤19 years of age (56%) but was lower (P < 0.01) in the group of women who had been pregnant ≤19 years of age (34%), where IUD use had increased to 32% compared (P < 0.001) with 7% among women who had not been pregnant ≤19 years of age. The mean number of months of COC use at 44 years of age (107 months) was higher (P < 0.01) among the women who had not been pregnant ≤19 years of age compared with the group of women who had been pregnant ≤19 years of age (69 months). This was in contrast to the mean number of months of IUD use which was higher (P < 0.01) in the group of women who had been pregnant ≤19 years of age (126 months) compared with the group of women who had not been pregnant ≤19 years of age (91 months).

Discussion

Choice of contraception during the 25-year study period was strongly related to age and parity, and the cumulative number of pregnancies at 44 years of age was related to age at first pregnancy. Women who had been pregnant ≤19 years of age reported more pregnancies at 44 years of age compared with women who had not been pregnant ≤19 years of age. Choice of contraception in a life-time perspective also differed between these two groups.

The majority of earlier studies describing birth control have been cross-sectional and often based on selected populations, such as women attending family planning clinics, student health clinics or abortion clinics. Such studies provide valuable information but are not truly representative of the total population as they relate to the clientele attending these clinics. In addition, the majority of studies has investigated the prevalence of contraception alone and have not related contraceptive practice to reproductive history.

The women included in this study were selected at random from the total population of women resident in the city of Gothenburg in 1981 and the use of contraception and pregnancies has been followed in the same women at 5-year intervals from 19 to 44 years of age. It has been possible to trace the women during this 25-year period using the individual's personal identification number that has been used in Sweden since 1947. In total, 44% of the women originally included in 1981 responded on all occasions to this questionnaire study. It was also possible to compare the responders and non-responders regarding smoking, pregnancies, live birth, contraceptive use and SES and no differences were found. However, there may have been some differences between responders and non-responders in their acceptance of their chosen contraceptive method and hence compliance. The study provides a unique possibility to follow the same women with regard to their contraceptive choice and pregnancies during the majority of their fertile years of life.

In the present study, 65–80% of the women during the major part of their fertile years were using some form of contraception and at 44 years of age, 98% reported that they had used contraception at some time in their lives. Our figures from Sweden can be compared with data from the UK Omnibus Survey performed in 2005/2006 (Taylor et al., 2006) which cited that 74% of women under 50 years of age were using contraception. These figures can also be compared with recent figures published by the Guttmacher Institute (2008) regarding contraceptive use in the USA, where it was reported that 62% of the 62 million fertile women were currently using some form of contraception and that 98% of women 15–44 years of age had used contraception. However, it should be noted that some of the women both in our study and in the Guttmacher report who were not currently using contraception did not actually need contraception owing to the fact that they were already pregnant, were post-partum, had no relationship and therefore no need or were infertile. In both reports, it is not possible to assess the proportion of women who were sexually active without the desire of becoming pregnant and who were not using contraception. These figures from Sweden and USA can be compared with other European countries where absence of contraception was reported to vary between 21 and 30%. Skouby (2004) studied the non-use of contraception in more detail and excluded women who were not sexually active, women who were pregnant or wanting to become pregnant and women who were infertile and concluded that 6.5% of the studied population were at risk for an unwanted pregnancy because of non-use of contraception.

COC was the most commonly used method of contraception up to 29 years of age. In this respect, Sweden does not differ from other European countries (Skouby, 2004; Cibula, 2008) and USA (Guttmacher Institute, 2008) where COC are the commonest form of contraception for women in their teens and twenties.

The abortion rate in women aged 20–24 years in Sweden (Abortion Statistics Sweden, 2008) is high (34.7/1000 women) despite the fact that more than 50% of the women reported current use of COC in this phase of life. One of the limitations of our study is that we were unable to assess contraception compliance, adherence to therapy and persistence of use. However, it is well known that the efficacy of oral contraception in clinical practice is reduced owing to missed tablets (Rosenberg and Waugh, 1998; Lete et al., 2008) and that some women stop taking the pill because of side effects (Lindh et al., 2009) even if the need for contraception remains. In this respect, poor continuation over time may be an important limiting factor and emphasises the need for follow-up when prescribing oral contraception in order to provide continued motivation and discuss possible side effects. Counselling methods with motivational interviews may be a possible means of improving contraceptive compliance (Petersen et al., 2004). The mean age for the birth of a woman's first child in Sweden is currently 29 years and the age of the sexual debut is ∼16 years. Thus, a large proportion of women do not desire to become pregnant during the first 13 years of their fertile life although many are sexually active. The questions therefore arise if it would not be beneficial to recommend more often the use of ‘forgettable contraception’, a term recently described by Grimes (2009) that includes the use of long-acting forms of contraception (i.e. requires no user attention for at least 3 years), such as IUDs and implants, which helps overcome human fallibility.

Some support for the use of long-acting reversible contraception in this age group can be derived from this study where we have compared contraceptive use and pregnancies up to the age of 44 years in women who had already been pregnant ≤19 years of age with women who had not been pregnant ≤19 years of age. When comparing these two groups, there was a continued increase in the mean number of pregnancies up to 24 years of age in the group of women who had been pregnant ≤19 years of age compared with women who had not been pregnant ≤19 years of age. However, after 24 years of age, pregnancies and children were comparable in the two groups of women. A possible explanation may be the different pattern of contraceptive use from 24 years of age compared with that observed at 19 years of age between the two groups. At 19 years of age, COC was the commonest form of contraception and IUDs were uncommon in both groups. At 24 years of age, IUDs were more commonly used among women who had been pregnant ≤19 years of age which may explain why there was no further increase in pregnancy rate between the groups.

Information regarding contraception is given to Swedish school children and there is a ready availability of youth clinics but unintended pregnancies still occur. However, the use of both condoms and COC has not been as widespread as, for example, in the Netherlands. More emphasis on this combined approach could be advocated. There is also a continued increased risk of unintended pregnancy in women who have already undergone an abortion (Heikinheimo et al., 2008; Lindh et al., 2009) and teenagers who give birth constitute a continued high risk for future unintended pregnancies and legal abortion (Falk et al., 2006). It is therefore imperative that resources are devoted to contraceptive counselling in women attending abortion clinics. In particular, a follow-up visit to assess contraceptive acceptability in women prescribed contraception following an abortion is extremely important.

There is still a need for effective contraception in women who are 40+ years as the decline in fertility with age does not provide adequate protection against unplanned pregnancy. More than 40% of the women in fact reported no contraception or the use of less effective forms of contraception. According to the UK Omnibus Survey (Taylor et al., 2006), 30% of women aged 40–44 were not using contraception: this survey also assessed whether women at various ages were sexually active or not; and according to the 2005/2006 survey, 45% of women aged 40–44 were at risk of pregnancy. The results of our study can also be compared with the results presented in a recent review of female contraception in women over 40 years old where 66–90% used some form of contraception (ESHRE Capri Workshop Group, 2009). The commonest reported method in this review, which covered 10 countries from Europe and North America, was female sterilization. In this respect, the situation in Sweden is very different and in the present study intrauterine methods, such as the Cu-IUD and the LNG-IUS, were the most commonly used methods after 29 years of age, and in women aged 39–44, approximately 40% of the women were using an intrauterine method. Sterilization, both in the male and female is uncommon in Sweden. The high-dosed Cu-IUDs and the LNG-IUS are highly effective forms of reversible contraception, with a long-term efficacy comparable to tubal occlusion. The LNG-IUS also has the added advantage for many women that they have a reduced blood loss during menstruation or become amenorrhoeic which is particularly important and attractive for women in the later stages of the fertile years where menorrhagia is more common.

In conclusion, choice of contraception during the 25-year study period was strongly related to age and parity and the cumulative number of pregnancies at 44 years of age was related to age at first pregnancy. Women who had been pregnant ≤19 years of age reported more pregnancies at 44 years of age compared with women who had not been pregnant ≤19 years of age. Choice of contraception in a life-time perspective also differed between these two groups.

Funding

The study was supported by grants from The Göteborg Medical Society, Hjalmar Svenssons Fund and a National LUA/ALF grant no. 11315.

Acknowledgements

We thank Ms Marianne Sahlen and Ms Anja Andersson for help with data registration and Björn Areskoug MSc for expertise in statistical programming.

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