28th October 2016, Volume 129 Number 1444

Jacqueline Chesang, Ann Richardson, John Potter, Mary Jane Sneyd, Pat Coope

Since the introduction of oral contraceptives (OCs) in the 1960s,1 there have been substantial advances in the development of contraceptive methods, including transition from high-dose to low-dose OCs, and from inert to copper-bearing and levonorgestrel-releasing intrauterine contraceptive devices.2 Currently, there is a wide range of safe and effective contraceptive methods available. From a public health perspective, up-to-date knowledge of patterns of contraceptive use is important, as contraceptives exert effects that could be beneficial or harmful to some users.

There has also been a significant change in age at first delivery among New Zealand women, which may have affected patterns of contraceptive use. Among women born in the 1960s, 42% had their first child before the age of 25 years, compared with 60% of women born before 1950.3 In 1962, women in their twenties had the highest fertility rates, while in 2014 the highest fertility rates were in women in their thirties. These changes were accompanied by a decrease in fertility rates across all age groups.4

A population-based study on patterns of contraceptive use in New Zealand by Paul et al was published in 1988.5 Women aged 25–54 years were randomly selected from the New Zealand electoral roll. The participants, who were part of the control arm of a population-based case-control study of breast cancer and hormonal contraception, were recruited during 1983 to 1986. A more recent study,6 which recruited participants from North Waikato and Auckland City only, was restricted to women who had ever had sexual intercourse, and did not report age-specific contraceptive use.

The estimates reported in this paper are derived from a recent population-based case-control study designed to assess the association between ovarian cancer and use of contraceptives. The availability of information on contraceptive use among controls offered an opportunity to assess current and recent contraceptive practice in women over 35 years of age. Current patterns of contraceptive use in New Zealand women aged 35–69 years are presented, and comparisons with the previous population-based study for women aged 35–54 years are made.

Methods

Study participants were members of the control arm of a nationwide population-based case-control study on the association between contraceptive use and ovarian cancer. Women were recruited into this study between April 2013 and September 2015. A random sample stratified by five year age-groups of women aged 35 to 69 years was obtained from the electoral roll. All New Zealand citizens and permanent residents 18 years of age and above are required by law to register on the electoral roll. Access to electronic data from the electoral roll for the purposes of health research is allowed under section 112(3) of the Electoral Act 1993. The choice of the age limits 35 to 69 years was constrained by the ovarian cancer and contraception study. Ovarian cancer is generally a disease of post-menopausal women, with the highest incidence at ages 65 to 74 years. The age range 35 to 69 years includes the population that is most affected by ovarian cancer and at the same time allows for recall of contraceptive usage. Approval to conduct the study was obtained from the Southern Health and Disability Ethics Committee (13/STH/26) and the University of Canterbury Human Ethics Committee (HEC2013/08).

Each potential participant was sent a letter on University of Canterbury letterhead, signed by two members of the research team. The letter was accompanied by an information and consent form, a copy of the study questionnaire, and a post-paid addressed envelope for returning the questionnaire and signed consent form. To facilitate the responses, women who did not respond to the initial questionnaire and consent form within three weeks from the date of dispatch, were sent a second study pack. Women who did not respond to the second mail-out were contacted and asked to complete the questionnaire by telephone. If they were willing to do this, a telephone interview was done, using the same questionnaire. All questionnaires were checked for completeness; where necessary, participants were contacted to obtain missing data.

Participants were asked about ever-use, age at first use, time since last use and duration of use of oral contraceptives, DMPA, contraceptive implants and IUDs. History of and age (if applicable) at menopause, hysterectomy, tubal ligation and bilateral oophorectomy were also asked. Information on ever-use and duration of reliance on condoms and vasectomy or other contraceptives was sought. In addition, information on socio-demographic characteristics of the participants and risk factors for ovarian cancer was also gathered. Participants were provided with a calendar of major life events to assist in recall and to record their use of contraceptives.

Age of participants was calculated in two ways. For the purpose of comparing with the New Zealand 2013 census population, age was calculated as the difference between each participant’s date of birth and the date she was selected from the electoral roll. For prevalence estimations, the difference between date of birth and date of questionnaire completion was used to calculate age. Level of education was classified by the highest qualification attained using the 2013 census categories. Income was based on the total personal pre-tax income in the last year. Menopause was defined as the age periods stopped, women with natural menopause and those with iatrogenic menopause were classified as postmenopausal. Analysis of current contraceptive use was restricted to women aged 35–54 years. This is because those above 54 years were most probably postmenopausal and would therefore have no need for contraception. Those who were postmenopausal but within 35–54 years of age were included as currently not using a reversible contraceptive method in order to account for all the participants.

In the previous population-based study by Paul et al, study participants were members of the control arm of a nationwide population-based case-control study of breast cancer and hormonal contraception. Women aged 25–54 years were randomly selected from the New Zealand electoral rolls. Only those with traceable telephone numbers were included. Recruitment of participants was done from 1st November 1983 to 5th February 1986, and a response proportion of 84% was achieved.

The study by Paul et al5 included women aged 25–54 years, whereas the current study included women aged 35–69 years. In comparing the two studies, the prevalence estimates were restricted to women aged 35–54 years, the overlapping age-range for the two studies. In addition, proportions were weighted to account for the age structure of both samples. The age-groups used in comparing the two studies are similar to those used in the publication of the study by Paul et al. The lead author was also contacted to verify our accuracy in data extraction from their publication. In both studies, the purpose of examining ethnic groups was to compare the participants with the census population. In the study by Paul et al, prioritised ethnicity was used because this was used at that time by Statistics New Zealand. At the time of our study, prioritised ethnicity was no longer used by Statistics New Zealand. Therefore, in our study, ethnicity was classified according to the 2013 census categories. This was appropriate because we needed to compare the ethnic distribution of the participants with that of similarly aged New Zealand women in order to assess whether they were a representative sample.

Data were analysed using IBM Statistical Package for the Social Sciences (IBM SPSS statistics 22). Descriptive statistics were used to compute frequencies and percentages. The chi-square test was used to examine the associations between socio-demographic characteristics of the participants and the female usually resident population at the 2013 census. Differences in the age standardised prevalence of contraceptive use between the two studies and 95% confidence intervals were estimated in order to assess statistical significance.

Results

There were 904 women selected from the electoral roll. Of these, 59 were not currently residing at the address indicated on the electoral roll and 15 could not communicate in English. Of the remaining 830 women, 255 declined to participate and 184 could not be located. This left 389 women who were available for the analysis (response proportion = 47%).

The age profile of the sample population was representative of the 2013 census female population aged 35–69 years. Although participants had a higher level of education than the general population (χ2=58.455, df=6, p<0.001), other socio-demographic characteristics of the participants were comparable to those of the female usually resident population aged 35–69 years (Table 1).

Table 1: Socio-demographic characteristics of women in the present study and the female usually resident population aged 35–69 years—2013 census.

Characteristic

Women in present study

Female usually resident population—2013 census

 

Number

(%)1

Number2

(%)1

Age (years)

(n=389)

(n=969,111)

35–44

111

(29)

302,835

(31)

45–54

120

(31)

312,723

(32)

55–64

101

(26)

253,089

(26)

65–69

57

(14)

100,464

(10)

Ethnicity3

(n=389)

(n= 921,423)

NZ European4

316

(81)

714,276

(78)

Māori

37

(10)

111,828

(12)

Others5

58

(15)

-

-

Parity

(n=327)

(n = 783,810)

0

47

(14)

120,867

(15)

1

32

(10)

108,414

(14)

2

144

(44)

283,707

(36)

3

66

(20)

166,608

(21)

4

25

(8)

64,860

(8)

5

10

(3)

22,470

(3)

6 and Over

3

(1)

16,884

(2)

Education6

(n=321)

(n=792,375)

No qualification

34

(11)

138,987

(18)

Overseas secondary school qualification

12

(4)

60,657

(8)

Level 1 or 2 certificate

76

(24)

202,962

(26)

Level 3 or 4 certificate

40

(13)

99,240

(13)

Level 5 or 6 diploma

57

(18)

93,669

(12)

Bachelor’s degree and level 7 qualification

70

(22)

129,564

(16)

Postgraduate7

32

(10)

67,296

(8)

1Percentages are on the total stated.
2The total numbers of female usually resident population in the four categories differ because of values that were not stated.
3Some participants identified with more than one ethnicity, hence >100%.
4NZ European includes those who identify themselves as ‘New Zealanders’ as this option was not provided in the study questionnaire.
5’Others’ could not be computed from the NZ 2013 census results.
6The estimates presented for parity and education are limited to 35–64 year old women. This is because the census data does not provide the level of education and parity for the 65–69 years age-group; instead this is given as 65 years and over.
7Postgraduate includes postgraduate honours degree, Master’s degree and doctorate. 

Contraceptive ever-use

The results of contraceptive ever-use are presented in Table 2. Oral contraceptives had the highest prevalence of use (89%), with almost uniform use across age-groups. This was followed by condom use (54%), with the proportion of users lower at higher ages. Implants had the lowest prevalence (1%); only four of the 389 women had used an implant. Overall, ever-use of reversible contraceptives declined with age. In contrast, prevalence of vasectomy, tubal ligation and hysterectomy increased with age. No participant had undergone tubal ligation reversal operation. More than half (52%) of the participants were post-menopausal.

Table 2: Proportion of women who have ever-used various contraceptive methods according to age.

Contraceptive Type2

35–44

45–54

55–64

65–69

Total

No.

(%)1

No.

(%)1

No.

(%)1

No.

(%)1

No.

(%)1

Pills

86

(77)

119

(99)

91

(90)

51

(89)

347

(89)

DMPA3

19

(17)

16

(13)

11

(11)

7

(12)

53

(14)

Implants

3

(3)

1

(1)

-

-

-

-

4

(1)

IUDs4

17

(15)

30

(25)

27

(27)

11

(19)

85

(22)

Condoms

72

(65)

76

(63)

46

(46)

17

(30)

211

(54)

Other5

3

(3)

16

(13)

8

(8)

7

(12)

34

(9)

Tubal ligation

3

(3)

16

(13)

22

(22)

21

(37)

62

(16)

Vasectomy

27

(24)

65

(54)

51

(50)

27

(47)

170

(44)

Bilateral oophorectomy

-

-

4

(3)

8

(8)

5

(9)

17

(4)

Hysterectomy

2

(2)

19

(16)

21

(21)

20

(35)

62

(16)

Periods stopped6

6

(5)

48

(40)

88

(87)

53

(93)

195

(50)

Total number of women

111

(100)

120

(100)

101

(100)

57

(100)

389

(100)

1Percentages weighted to account for the age structure of the sample.
2Some women used more than one method.
3Depo medroxyprogesterone acetate.
4Intrauterine contraceptive devices.
5Other included—diaphragm, cervical cap, natural method, chemical methods and emergency contraceptive pills.
6Includes natural menopause and iatrogenic menopause. 

Current contraceptive use

Of the 389 women who were available for analysis, 231 were aged 35–54 years. The results of the women currently practicing contraception are presented in Table 3. The method with the highest prevalence of current use was the oral contraceptives (9%), closely followed by the IUD (8%). As in ever-use, implants had the lowest prevalence of current use. An inverse relationship between age and prevalence of current use of reversible contraceptive methods was seen.

Table 3:Proportion of women on different contraceptive types according to age.

 

35–39

40–44

45–49

50–54

Total

No.

(%)1

No.

(%)1

No.

(%)1

No.

(%)1

No.

(%)1

Using a reversible method

Pills

5

(11)

10

(15)

3

(5)

3

 

21

(9)

DMPA2

-

-

2

(3)

1

(2)

-

-

3

(1)

Implants

-

-

1

(2)

1

(2)

-

-

2

(1)

IUDs3

3

(7)

9

(14)

6

(10)

1

 

19

(8)

Not using a reversible method4

Vasectomy

8

(17)

14

(22)

30

(48)

29

(50)

81

(35)

BTL5

-

-

3

(5)

7

(11)

7

(12)

17

(7)

Hysterectomy

-

-

2

(3)

4

(6)

15

(26)

21

(9)

Bilateral oophorectomy

-

-

-

-

1

(2)

3

(5)

4

(2)

Period stopped6

-

-

3

(5)

9

(15)

35

(60)

47

(20)

Total number of women

46

(100)

65

(100)

62

(100)

58

(100)

231

(100)

1Percentages weighted to account for the age structure of the sample.
2Depo medroxyprogesterone acetate.
3Intrauterine contraceptive devices.
4Although it is possible for vasectomy and BTL to be reversed, this rarely occurs, so they have been classified as not reversible.
5Bilateral tubal ligation.
6Includes natural menopause and surgically induced menopause. 

Among non-users of reversible contraceptive methods, 58% (101/175) were either sterilised (BTL/hysterectomy) or have, at some point, had a vasectomised partner (participants were not asked about current use of vasectomy therefore this cannot be reported). However, 13 women who were either sterilised or had a history of a relationship with a vasectomised partner were also on a reversible method of contraception.

Comparison with the 1983–86 estimates of contraceptive use

Contraceptive ever-use

In the study by Paul et al, 767 women were aged 35–54 years; there were 231 in the current study. Among women aged 35 to 54 years, over a span of 30 years, ever-use of condoms has more than doubled (24% to 64%). Increases in ever-use of OCs (75% to 89%), vasectomy (26% to 40%) and DMPA (10% to 15%) were also observed. In contrast, the prevalence of tubal ligation declined from 22% to 8%. The increase in reversible contraceptive use was uniform across age-groups apart from IUDs in which a decline in ever-use was observed in the younger age-group (35 to 44 years). The fall in tubal ligation was largely due to lower prevalence among younger women (Table 4).

Table 4: Comparison of contraceptive ever-use between the present and previous study in women aged 35–54 years.

 

Paul et al: (1983–1986)

Current study (2013–2015)

35–44

45–54

Total

35–44

45–54

Total

No.

(%)

No.

(%)

No.

(%)

No.

(%)

No.

(%)

No.

(%)

Type of contraception

Pill

352

(86)

223

(62)

575

(75)

86

(77)

119

(99)

205

(89)

Injection

52

(13)

28

(8)

80

(10)

19

(17)

16

(13)

35

(15)

IUDs

88

(22)

41

(11)

129

(17)

17

(15)

30

(25)

47

(20)

Condom

78

(19)

107

(30)

185

(24)

72

(65)

76

(63)

148

(64)

Tubal ligation

115

(28)

53

(15)

168

(22)

3

(3)

16

(13)

19

(8)

Vasectomy

120

(29)

82

(23)

202

(26)

27

(24)

65

(54)

92

(40)

Total number of women

408

(100)

359

(100)

767

(100)

111

(100)

120

(100)

231

(100)

Percentages weighted to account for the age structure of the sample.
Some women had used more than one contraceptive. 

Differences in age standardised prevalence between the current and previous study were statistically significant for oral contraceptives (15.0%; 95% CI=10.1–19.9), condoms (39.4%; 95% CI=32.5–46.3), tubal ligation (13.0%; 95% CI=8.5–17.5) and vasectomy (13.8%; 95% CI=7.1–20.6). There was no significant change in use of DMPA (5.0%; 95% CI=-0.1–10.1) or IUDs (4.0%; 95% CI=-1.7–9.8).

Current contraceptive use

In both studies the most common currently used contraceptives were pills, followed by IUDs, and DMPA, albeit with an increase in the proportion of users from 5% to 9%, 3% to 8% and 0.3% to 1% respectively. In addition, a fall in female sterilisation and a rise in vasectomy were observed. In both studies, there was a consistent pattern of a higher prevalence of current use of reversible contraceptive methods among the 35–44 year olds compared to the 45–54 year olds. Overall, the prevalence of current use of reversible contraceptive methods was similar in both studies; 19% and 20%. The results are presented in Table 5.

Table 5: Comparison of prevalence of current contraceptive use between the present and previous study in women aged 35–54 years.

 

Paul et al: (1983–1986)

Current study (2013–2015)

35–44

45–54

Total

35–44

45–54

Total

No.

(%)

No.

(%)

No.

(%)

No.

(%)

No.

(%)

No.

(%)

Using a reversible method

Oral contraceptives

26

(6)

10

(3)

36

(5)

15

(14)

6

(5)

21

(9)

DMPA injection

1

(0.2)

1

(0.3)

2

(0.3)

2

(2)

1

(1)

3

(1)

IUD

17

(4)

8

(2)

25

(3)

12

(11)

7

(6)

19

(8)

Not using a reversible method

Sterilised

 

 

 

 

 

 

 

 

 

 

 

 

Tubal Ligation

101

(25)

33

(9)

134

(17)

3

(3)

14

(12)

17

(7)

Vasectomy

103

(25)

50

(14)

153

(20)

22

(20)

59

(49)

81

(35)

Hysterectomy

64

(16)

75

(21)

139

(18)

2

(2)

19

(16)

21

(9)

Postmenopausal

66

(16)

185

(52)

251

(33)

3

(3)

44

(37)

47

(20)

Total number of women

408

(100)

359

(100)

767

(100)

111

(100)

120

(100)

231

(100)

Some women used more than one contraceptive method concurrently.
Percentages weighted to account for the age structure of the sample.
Although it is possible for vasectomy and BTL to be reversed, this rarely occurs, so they have been classified as not reversible. 

In contrast to ever-use, the difference in age standardised prevalence of current use between the current and previous study was not statistically significant for oral contraceptives (4.6%; 95% CI=0.6–8.5), but was significant for IUDs (5.1%; 95% CI=1.3–8.8). Similar to ever-use, the change in use of DMPA was not statistically significant (1.0%; 95% CI=-0.5–2.5).

Paul et al reported differences in contraceptive use according to socio-economic groups. However, in the present study no association between contraceptive use and income levels was observed, nor was there any relationship with level of education (data not shown).

Discussion

In this population-based study of women aged 35–69 years, oral contraceptives had the highest proportion of ever-use (89%), followed by condom use (54%); implants had the lowest prevalence (1%). The prevalence of vasectomy, tubal ligation and hysterectomy showed a positive relationship with age. In contrast to ever-use, the most common currently-used reversible contraceptives were IUDs and OCs. Implants had the lowest prevalence of current use.

Estimates of prevalence of contraceptive use restricted to women aged 35–54 years were compared with the previous study.5 A significant rise in ever-use of the pill (75% to 89%) and a more than two-fold increase in condom use (24% to 64%) were observed. There was a significant increase in ever-use of vasectomy (26% to 40%), accompanied by a fall in tubal ligation (22% to 8%). Only a slight increase in the use of DMPA and IUDs was observed.

Of participants currently not using reversible contraceptives, 58% had a tubal ligation or hysterectomy, or had, at some point, a vasectomised partner. This may explain their non-use of reversible contraceptives. However, 13 women in this group were also on a reversible method of contraception. A subsequent change of partner or the use of contraceptives for non-contraceptive reasons may explain this.

In a report on current contraceptive use in New Zealand women aged 35–49 years, a fall in sterilisation (both male and female sterilisation) and a rise in condom use were observed during 1976 to 2001, the latter being consistent with the current findings. Use of oral contraceptives remained relatively constant during this period. In contrast, a fall in current use of IUDs in younger women (35–39 years) and a rise in older women (40–49 years) were observed.7

The previous study5 reported a positive association between current contraceptive use and socio-economic status. In the current study no relationship was observed between current use and income or level of education. The difference in findings may be attributed to a change in contraceptive use, or to use of different measures of socio-economic status. Paul et al used the Elley-Irving scale for categorising social class. This method uses occupation as the main determinant of social class and is no longer in use. Furthermore, for married women, the occupation of the husband was taken into consideration. In contrast, we used each participant’s own annual income and highest level of education.

Similar to other studies,1,8,9 oral contraceptives had the highest prevalence of ever-use. Oral contraceptives have been in use for longer than some other methods, and they are also used for the management of some medical conditions. In addition, a high level of satisfaction among users of oral contraceptives has been reported8 and they may be more acceptable than DMPA which has been available for almost the same duration.10 Contraceptive implants were only recently introduced9 and this may partly explain the low uptake seen in the present study. The need for special training in insertion techniques, affordability, side-effects and awareness of availability of the method are additional factors that may contribute to low prevalence of use, however, reasons for discontinuation or choice of a method were not sought in this study. Choice of method of contraception may also be influenced by health policy and funding such that changes in such policies may lead to changes in the prevalence of use of certain contraceptives.

The observed increase in the use of condoms has also been reported in other studies.1,11 A US study attributed the increase in women currently using contraceptives from 56% in 1982 to 64% in 1995 to a rise in condom use.11 With the advent of HIV/AIDs, public education has promoted the use of condoms as a way of reducing the risk of sexually transmitted infections; this may explain the increase in use of condoms.1,8 The use of condoms in our study may have been under-reported because participants were asked about condom ever-use as a contraceptive and not as protection against sexually transmitted infections. Indeed, studies have reported a higher prevalence of condom use in combination with other contraceptives as compared to use of condoms as the primary method; one study reported a rise from 20% to 23% and another from 16% to 25%.8, 11

Over 30 years in New Zealand, an increase in ever-use of vasectomy (26% to 40%) was observed. In a study conducted during 1997 to 1999, men aged 40–74 years were asked about their personal history of vasectomy; a prevalence of 44% was reported.12 The prevalence of vasectomy may have been under-reported in our study because women may not be aware of the vasectomy status of their partners. The increase in prevalence of sterilisation with increasing age is expected because younger women may still desire to have children.

From the findings of the current study, the prevalence of use of permanent methods of contraception (vasectomy and tubal ligation) in New Zealand has not changed in the last 30 years. What has changed is a couple’s choice of sterilisation procedure, such that with the fall in the prevalence of tubal ligation there is a compensatory rise in the prevalence of ever-use of vasectomy. The shift to vasectomy may be due to ease of performing the procedure, lower risk of complications and change in men’s attitude towards sterilisation.

A decline in hysterectomy by half (18% to 9%) in women aged 35 to 54 years was observed. This is consistent with estimates of the prevalence of hysterectomy made for setting outcome targets for the New Zealand National Cervical Screening Programme.13

Strengths of this study are the nationwide population-based design, and that it is representative of the age-distribution and ethnicity of New Zealand women in the 35 to 69 years age-range. Some potential limitations of this study should be considered. The low response proportion (47%) may have introduced selection bias. Women with higher levels of education were over-represented in this study, but response did not differ by age-group. When response by geographic region was assessed, a higher response proportion was noted in the South Island compared to the North Island. However, when only participants where contact was achieved were considered, excluding those who could not be located, participation was equal across regions. This difference may also be explained by high population mobility in the North Island. The Auckland region has the highest proportion of people who change residences between censuses, with some areas having only 10% of the population living at the same address between the 2001 and 2006 censuses.4 Similar studies in New Zealand in the 1980s5 and 1990s12 had higher response proportions (84% and 85% respectively). In contrast to the current study, the inclusion criteria for those studies required participants to have traceable telephone numbers. Household access to a landline telephone has decreased in New Zealand accompanied by a rise in the use of cell phones.4

The study relied on self-reported exposures which were not verified by medical records. However, in previous New Zealand studies in which corroborative information was obtained from medical practitioners, information on contraceptive use provided by the participants was consistent with that on their medical records.5, 12 In addition, it is expected that participants may forget patterns of use of a particular contraceptive (age of onset, duration of use and last age), but not the type of contraceptive used.

The changes observed in contraceptive practice in New Zealand are a marked increase in the prevalence of vasectomy and condom use, and a slight increase in ever-use of oral contraceptives. In contrast, there was a fall in female sterilisation. New Zealand has a high prevalence of vasectomy and ever-use of oral contraceptives compared to other countries.1, 8, 9 For example, in 2003, among women aged 15–49 years in five European countries (France, Germany, Italy, Spain and the UK), 85% were ever-users of oral contraceptives and 11% used sterilisation methods (both female and male sterilisation).Patterns of contraceptive use may be changing; therefore monitoring is required in order to meet the contraceptive needs of the New Zealand population. Knowledge of this may influence public health policy. The use of permanent sterilisation and long-acting reversible contraceptives (LARCs) affect the rate of unintended pregnancy and abortion rates, which are of public health importance. Population-based estimates of the prevalence of contraceptive use are also useful for calculating population attributable fractions for diseases related to contraceptive use.14

Summary

A study of contraceptive use among New Zealand women aged 35–69 found that 89% of women have used oral contraceptives at some stage. The next most commonly used types of contraception were condoms and vasectomy. Over the last 25–30 years, ever-use of the pill and condoms has become more common. There has also been an increase in the ever-use of vasectomy, but a decline in female sterilisation.

Abstract

Aim

To estimate the prevalence of contraceptive use among New Zealand women and to measure changes in contraceptive use since the last population-based prevalence estimates were published in 1988.

Method

Nine hundred and four women, aged 35–69 years were randomly selected from the electoral roll. A postal questionnaire was used to gather information on contraceptive use, socio-demographic characteristics and risk factors for ovarian cancer. Data were collected in 2013–2015. Estimates of current and ever-use of contraceptives were made and compared with the findings of the 1988 study by Paul et al. In both studies, participants were members of the control arm of case-control studies.

Results

The study by Paul et al had a response proportion of 84%, whereas that of the current study was 47%. Oral contraceptives had the highest prevalence of ever-use among women aged 35–69 years (89% [347/389]), followed by condom use (54% [211/389]) and vasectomy (44% [170/389]). Compared to the previous study, there has been an increase in ever-use of condoms (24% [185/767] to 64% [148/231]), vasectomy (26% [202/767] to 40% [92/231]) and oral contraceptives (75% [575/767] to 89% [205/231]) among women aged 35–54 years. In contrast, a lower prevalence of tubal ligation (22% [168/767] to 8% [19/231]) was observed.

Conclusion

The study demonstrates a change in patterns of contraceptive use among women aged 35–54 years. The prevalence of ever-use of oral contraceptives and vasectomy remains high in New Zealand compared with other countries.

Author Information

Jacqueline Chesang, School of Health Sciences, University of Canterbury, Christchurch; Ann Richardson, School of Health Sciences, University of Canterbury, Christchurch; John Potter, School of Health Sciences, University of Canterbury, Christchurch; Preventive and Social Medicine,  University of Otago, Dunedin; Pat Coope, Health and Human Development, University of Canterbury, Christchurch.

Acknowledgements

We gratefully acknowledge the support of the Wayne Francis Charitable Trust and the Genesis Oncology Trust. 
We are grateful to Emeritus Professor Charlotte Paul for her very helpful comments on an earlier draft of this paper. We would also like to thank Catriona Mackay for her help in data collection, and the women who participated in this study.

Correspondence

Jacqueline Chesang, School of Health Sciences, University of Canterbury, Christchurch.

Correspondence Email

jjc95@uclive.ac.nz

Competing Interests

Dr Coope, Dr Chesang, Dr Sneyd and Dr Richardson report grants from Genesis Oncology Trust and Dr Richardson reports grants from Wayne Francis Charitable Trust during the conduct of the study.

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