4.2 Discrete Choice Experiment
4.2.4 Data collection and source: the DCE
This section describes the various stages undertaken to conduct the DCE. The data
collection techniques are presented in section 4.2.4.1. The data source is described in
section 4.2.4.2. This section also provides summary statistics on response rates and
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4.2.4.1 Survey distribution and data collection: the DCE
The DCE is distributed across two groups of women attending antenatal care in two
teaching hospitals in Ireland: CUMH and the National Maternity Hospital, Dublin
(NMH) (see Figure 4.2 for breakdown of survey distribution and data collection for
the DCE). CUMH is the sole secondary care setting for a catchment area that caters to
8,000 deliveries per annum in the south west of Ireland (CUMH 2013). The NMH is
located in the east of Ireland, and caters to approximately 9,000 deliveries per annum
(NMH 2013).
To minimise the effect of experience on preferences, women are surveyed during
antenatal care, or before they give birth. Only women who are considered to be at low
risk of obstetric complications are invited to participate in the study; high risk women
are excluded from the analysis as the option of delivering in a MLU is not available to
this group. Low risk is defined according to the NICE guidelines and includes women
between 18 and 39 years of age with no history of obstetric complications or Caesarean
section and no contraindications of morbidities at the time of pregnancy (NICE 2007).
Selecting the appropriate sample size is complex. Lancsar and Louviere (2008)
propose that a sample size of twenty is sufficient to reliably estimate a discrete choice
model. To protect against a poor response rate this analysis invited 400 women to
participate in the study, surveying 200 women from each maternity unit. The study is
referred to as the Maternal Assessment of Maternity Services in Ireland study, or
MAMS.
MAMS is distributed to 400 women by post in booklet form, along with an invitation
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Figure 4.2: Breakdown of survey distribution and data collection for the DCE and CVM.
would like to participate in the study, they are asked to complete and return the survey
in the pre-paid envelope provided, thereby signalling their consent, or return the opt-
out consent form if they do not wish to participate. Three reminders are distributed to
participants who neither return the survey nor opt-out of the study over the course of
eight weeks (see Appendix B.1 for sample invitation letter; information leaflet;
reminders). The data collected is anonymous; women are assigned a unique Study ID.
Respondents are informed of the study’s goals and objectives in the invitation letter and accompanying information leaflet. If women would like to find out any further
Notes:
Abbreviations: MAMS, Maternal Assessment of Maternity Services; DRC, dual response choice; CUMH, Cork University Maternity Hospital; OLOL, Our Lady of Lourdes Hospital Drogheda; CGH, Cavan General Hospital; UHG, University Hospital Galway; NMH, the National Maternity Hospital, Dublin.
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information about the study they are encouraged to contact the researcher directly.
Women are also encouraged to visit the study’s webpage
(http://www.ucc.ie/en/npec/projects/mams/) which discusses the study in greater
detail and provides contact details for and links to important and relevant maternity
care support services. Ethical approval for the study was granted by the Clinical
Research Ethics Committee, Division of Obstetrics and Gynaecology in CUMH, and
the Research Ethics Committee in The NMH, Dublin (Appendix B.2).
The questionnaire comprises four sections (Appendix B.3). The first section asks
women about their obstetric history, if any, and plans for their upcoming delivery.
Section two investigates women’s preferences for each of the attributes in the DCE directly, and asks them to choose their preferred level for each attribute. Women are
also asked to identify the attribute that matters most to them. The DCE is introduced
in the third section, accompanied by a definition of each of the attributes being
considered. Each DCE contains 16 choice sets. A sample choice set is presented in
Figure 4.1. Respondents’ demographics are captured in the fourth section, while the fifth section contains the CVM, described in section 4.3. The survey is provided in
Appendix B.3.
Questionnaire responses were coded and entered into Stata v.12 (StataCorps 2011b).
The discrete choice data are effects coded for the qualitative attributes and
continuously for the quantitative attributes. Effects coding, rather than dummy coding,
is employed as the DCE includes an opt-out alternative. When an opt-out alternative
is included in a DCE, dummy coding cannot differentiate between the effect of a
reference category within a variable from the effect of an opt-out alternative {Bech,
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to differentiate between the reference category and the opt-out alternative. Effects
coding, on the other hand, provides a way to separate these two through the inclusion
of an alternative specific constant, or intercept term specific to the opt-out option
{Bech, 2005 #314}. The alternative specific constant captures the effect of the opt-out
alternative, allowing the effect of the reference category to be internalised in the parameter estimate, or β {Bech, 2005 #314}. Without effects coding it would be difficult to internalise the effect of the reference category in the parameter estimate
given the presence of the opt-out alternative.
4.2.4.2 Response rate and participant characteristics: the DCE
Of the 400 surveys distributed, 112 questionnaires were returned, yielding a response
rate of 28 per cent. The response rate from CUMH (36.5 per cent) was higher than the
NMH (19.5 per cent). Three reminder letters were distributed to participants from
CUMH, but no reminders could be delivered to participants from the NMH as the
maternity unit experienced an unforeseen staff shortage problem after the initial
survey was distributed to women. Thirteen per cent of women (52) opted-out of the
study with 54 per cent of this group (28) comprising of first-time mothers who felt
poorly equipped to evaluate maternity services given their inexperience. Some
respondents were removed from the analysis due to the high risk nature of their
pregnancy. One woman was removed due to advanced maternal age.33 Thirteen
women were removed given an obstetric history that included a previous Caesarean
section.34 Two respondents were removed for failing to complete more than 25 per
33 A pregnancy may be classified as low risk if the woman is between 18 and 39 years of age (NICE
2007). At 41 years of age this participant did not meet the inclusion criteria.
34 Best efforts were made to avoid contacting ‘high risk’ women, however, some women with a history
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cent of the choice sets. 96 women comprise the final sample, with participants from
CUMH accounting for two-thirds of this group (64).
The mean age of participants was 30.2, with a median age of 30 (Table 4.3). The
average age of first-time mothers was 29.6, with a median age of 29. The youngest
participant was 20, while the eldest was 39. Less than half the sample was multiparous
(45), while 53.1 per cent were nulliparous with a singleton foetus (53). Women who
had given birth before had 1-4 other children. The median number of births was 1,
with a mean of 1.4. The majority of participants were married, accounting for 53.7 per
cent, with single and cohabitating participants comprising the remaining 18.9 and 27.4
per cent of the sample, respectively. The majority of participants were Irish,
accounting for 74.4 per cent of the group (71), with the remaining 25.6 per cent
comprising of other white (22) and Asian backgrounds (2). Approximately 30 per cent
of participants were in receipt of some form of the medical card, while 39.6 per cent
reported having private health insurance (PHI). Household income varied across
participants, with the majority of participants concentrated in the highest three income
brackets (62.7 per cent).
There were some differences in certain demographics across the two maternity units.
For instance, the mean age of participants in the NMH was higher at 31.5, compared
with 29.5 in CUMH. The number of women in receipt of some form of the medical
card was considerably larger in CUMH, accounting for 32.8 per cent of the group,
compared with just 18.8 per cent of women from the NMH. The number of women
with PHI was also higher among participants from CUMH (62.5 per cent). In the
of Caesarean may be classified as low risk when the pregnancy is occurring within a CLU; hence, the contact details of some women were available on the hospital’s ‘low risk’ antenatal database records.
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Table 4.3: Demographic characteristics of the DCE sample.
Variable CUMH n (%) NMH n (%) All n (%)
Age in years, mean (SD) 29.5 (3.8) 31.5 (4.8) 30.2 (4.3)
First baby (%) 34 (53.1) 17 (53.1) 51 (53.1)
Age of first-time mothers, mean (SD) 28.8 (3.8) 31.0 (4.8) 29.6 (4.3) Number of children, mean (SD) 1.3 (0.51) 1.5 (0.72) 1.4 (0.60) Marital status (%)*
Single 11 (17.2) 7 (22.6) 18 (18.9)
Married 35 (54.7) 16 (51.6) 51 (53.7)
Cohabitating 18 (28.1) 8 (25.8) 26 (27.4)
Education status (%)
Some primary/primary/junior certificate 1 (1.6) 1 (3.1) 2 (18.9)
Leaving certificate 9 (14.1) 3 (9.4) 12 (12.5) Diploma 22 (34.4) 7 (21.9) 29 (30.2) Primary degree 15 (23.4) 5 (15.6) 20 (20.8) Higher degree 17 (26.6) 16 (50.0) 33 (34.3) Ethnicity (%)* Irish background 49 (77.8) 22 (68.8) 71 (74.4)
Other white background 13 (20.6) 9 (28.1) 22 (23.1)
Asian background 1 (1.6) 1 (3.1) 2 (2.1) Employment status (%) Self-employed 2 (3.1) - 2 (2.0) Employee 43 (67.2) 25 (78.1) 68 (70.8) Homemaker 9 (14.1) 5 (15.6) 14 (14.6) Unemployed 7 (10.9) 1 (3.1) 8 (8.3) Student 1 (1.6) 1 (3.1) 2 (2.1)
Unable to work (illness/disability) 2 (3.1) - 2 (2.1) Medical card status (%)
Full card 18 (28.1) 3 (9.4) 21 (21.8)
GP card only 3 (4.7) 3 (9.4) 6 (6.3)
Not covered 43 (67.2) 26 (81.3) 69 (71.9)
Private health insurance (%)
Yes 24 (37.5) 14 (43.7) 38 (39.6) No 40 (62.5) 18 (56.3) 58 (60.4) Household income (%)* < €834 per month 1 (1.6) - 1 (1.1) €834 - €1,667 per month 8 (12.9) 2 (6.3) 10 (10.6) €1,668 - €2,500 per month 20 (32.3) 4 (12.5) 24 (25.5) €2,501 - €3,333 per month 8 (12.9) 8 (25.0) 16 (17.0) €3,334 - €4,167 per month 14 (22.6) 8 (25.0) 22 (23.4) > €4,167 per month 11 (17.7) 10 (31.2) 21 (22.3) Observations 64 32 96 Notes:
Abbreviations: CUMH, Cork University Maternity Hospital; NMH, the National Maternity Hospital, Dublin. * Contains missing observation(s)
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Table 4.4: Women's preferred scenario for each attribute.
CUMH n (%) NMH n (%) All n (%)
Continuity of care with midwife
You are guaranteed continuity of care with the same midwife 52 (81.3) 30 (93.7) 82 (85.4) You are not guaranteed continuity of care with the same
midwife
12 (18.7) 2 (6.3) 14 (14.6)
Involvement of obstetric doctors
Obstetric doctor(s) will be involved in your care if a complication arises
60 (93.7) 29 (90.6) 89 (92.7) Obstetric doctor(s) will be involved in your care if a
complication arises, but you will have to be transferred to an alongside obstetric unit which is accessed through a corridor
4 (6.3) 3 (9.4) 7 (7.3)
Access to pain relief
Gas and air, Pethidine, and Epidural 42 (65.6) 23 (71.9) 65 (67.7) Gas and air, Pethidine, and Birthing Pool 22 (34.4) 9 (28.1) 31 (32.3)
Women's role in decision-making
Medical staff (midwives/ doctors) keep you informed and involved in decision-making
58 (90.6) 28 (87.5) 86 (89.6)
Medical staff (midwives/ doctors) make all decisions for you, but keep you informed
6 (9.4) 4 (12.5) 10 (10.4)
Preferred length of stay in hospital
6 hours 4 (6.3) 0 4 (4.2) 24 hours 14 (21.9) 9 (28.1) 23 (23.9) 48 hours 21 (32.8) 15 (49.9) 36 (37.5) 72 days 25 (39.0) 8 (25.0) 33 (34.4) Observations 64 32 96 Notes:
Abbreviations: CUMH, Cork University Maternity Hospital; NMH, the National Maternity Hospital, Dublin.
NMH, 56.3 per cent reported having PHI. There was a large difference in income
levels across the two groups. In CUMH, approximately half the sample was
concentrated in the top three income brackets (53.2 per cent). This compares sharply
with the NMH where 81.2 per cent of the sample was concentrated in the top three
income brackets.
Women’s preferred level for each attribute is described in Table 4.4. It describes a model of care that assures continuity of care with the same midwife; provides
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anaesthesia; involves women in decision-making; and facilitates extended periods of
stay in hospital after delivery. A simple rating exercise reveals that each attribute is
important to women, with the majority of participants citing involvement in decision-
making as being very important (Table 4.5). In a follow-up question 29.2 per cent of
women identified continuity of care with the same midwife as the most important
attribute (Table 4.6). Access to epidural anaesthesia was the second most important
attribute to 27.1 per cent of the group, while involvement in decision-making was
identified as the most important attribute to 21.9 per cent of women.
This concludes the description of the data collection techniques used for the DCE and
sample obtained therein. The following section introduces the other stated preference technique employed to explore women’s preferences. The various stages involved in designing and analysing the CVM are presented in section 4.3.