Stage 1: identifying common characteristics of preconception populations
Search and screening process
The search was conducted in April 2018. Flow of included studies is presented in Fig. 1. Titles and abstracts of 970 papers were screened (with good reliability achieved on a 10% double screened subsample; kappa = 0·8) [17]. Ninety-eight papers were eligible for full text screening (kappa = 0·6 for 10% subsample). Twenty-three papers representing 19 studies were eligible for inclusion. Details pertaining to study characteristics and recruitment methods are presented in Supplementary File 1 and summarised below.
Definitions of preconception
Only one study explicitly defined the preconception population, defined as “women with desire to conceive” [19]. Implicit definitions were similar in theme, primarily centring on intentions for pregnancy or current pregnancy plans. One study focused on women and couples of childbearing age [20], whilst another focused on couples with fertility problems [21].
Inclusion and exclusion criteria
Regarding inclusion criteria of participants, most studies specified recruitment of women only (n = 13), with one solely recruiting men [22]. Age criteria varied, albeit most (n = 12) studies recruited participants aged 18 to 45 years. Twelve studies specified that participants must be planning a pregnancy, including specific time scales such as within 1 year, sometime in the future or currently trying to become pregnant. Relationship status was an explicit criterion in three studies, with two allowing only married participants (conducted in Iraq and Vietnam) [23, 24] and one specifying that participants must be in a stable relationship [25]. Many studies also stipulated health or reproductive history criteria such as absence of fertility or reproductive issues (n = 4) [25,26,27,28], no health risk factors (n = 2) [29, 30], receipt of preconception care consultations (n = 2) [19, 31], being on a waiting list for in vitro fertilisation (n = 1) [21], and previous miscarriage (n = 2) [32, 33]. Exclusion criteria were less specified, however these included ongoing pregnancy or breastfeeding (n = 5) [20, 24, 26, 31, 34], history of infertility or adverse pregnancy events (n = 4) [20, 26, 31, 32], multiple pregnancy (n = 1) [29], and contraceptive use (n = 1) [26].
Participant characteristics
A total of 12,427 participants (131 males and 12,296 females) were included; mean age ranged from 25·4 to 36·7 years (range 14–42). Reporting of other demographic variables was inconsistent, hence data are reported only from the studies that provided information: 669 participants were described as having no children, ranging from 9 to 87% in individual studies and 4541 had one or more children; 5700 were married or living with partner, ranging from 64 to 98% in studies; 704 reported white ethnicity (37–95%); 2657 were employed (35–98%); and 1711 had been educated to university level (7–86%) and 633 to secondary education level (31–66%; see Additional File 1).
Recruitment methods
Studies provided varying detail regarding their recruitment methods. Clinic/hospital settings included premarital clinics (n = 2) [23, 30], preconception clinics (n = 2) [21, 31], obstetric/gynaecological clinics (n = 2) [20, 29], general hospital setting (n = 1) [32], health centres (n = 2) [24, 32], ART clinic (n = 1) [20], and a women’s clinic (n = 1) [35]. Recruitment from the general population occurred primarily via the Internet/websites (n = 5) [22, 25, 26, 34, 36], social media (n = 5) [20, 22, 25, 34, 35], posters/flyers in the community (n = 3) [20, 25, 26], television, print or radio media (n = 2) [25, 26], or word of mouth (n = 2) [20, 36].
Stage 2: concept analysis
Steps 1 and 2: select a concept and determine the aims or purposes of analysis
Our concept of interest was the “preconception population” and the purpose of this analysis was to generate a working definition of a preconception population focused on attributes, using concept analysis principles and existing literature.
Step 3: uses of the concept
A summary of the included studies and papers as they pertain to Steps 3 to 8 are included in Additional File 2. These relevant documents included the report Making the Case for Preconception Care published by Public Health England in 2018 [37]; a chapter on preconception care from the Family-Centered Maternity and Newborn Care: National Guidelines published by the Public Health Agency of Canada in 2017 [9]; a consensus statement from the Clinical Workgroup of the National Preconception Health and Health Care Initiative (USA) [38]; a 2017 statement on pre-pregnancy counselling developed by the Royal Australian and New Zealand College of Obstetricians and Gynaecologists [39]; and various reviews published in academic literature [11, 15, 40].
There was a notable absence of the concept of the “preconception population” in the literature, however the term “preconception” was broadly used in the context of women’s health before or around pregnancy or conception. For example, some documents focused on preconception care and related needs [41, 42], while others were focused on preconception health as a concept [11, 22]. Studies tended to define preconception as a time period rather than a population, for example referring to women before conception [33] or before a pregnancy [24, 28], or using “time to pregnancy” as a measure of the preconception period [33].
Step 4: defining attributes
Three defining attributes were present for all cases of preconception participants. These were (1) reproductive age; (2) man or woman; (3) woman or partner were not pregnant. These attributes were encompassed across the literaturee.g.,11,40 and include the majority of the adult population, therefore we broke this down into four definitions where more specific attributes could be applied (see Fig. 2). Firstly, the public health preconception perspective includes the three defining attributes described above, but includes only individuals who are not sexually active. The potential preconception perspective includes three of the four defining attributes in the public health perspective (reproductive age, man/woman, not pregnant), however, the criteria for not being sexually active is changed to include only individuals who are sexually active, including those who partake in intercourse without using effective contraception or who experience contraceptive failure. This encompasses men or women who may go on to experience unplanned pregnancies. The intentional preconception perspective includes the four potential preconception population defining attributes, plus a conscious decision to conceive and/or an element of pregnancy planning. In this way, the intentional perspective focuses on women or men with pregnancy intentions, whether or not specific behavioural changes have been made towards preparing for pregnancy. The life course perspective recognises that preconception health can be addressed throughout the life course by targeting populations that do not meet the criteria for the other definitions, for example adolescents or pregnant women. One final approach should be considered that is cross-cutting across the other perspectives; a systems approach to addressing preconception health is essential to support activities across all other perspectives and includes adequate policies and guidelines regarding lifestyle and health; these were reflected in many of the included documents. All of these perspectives apply equally to men and women, to same sex couples and to solo mothers by choice.
Step 5: model cases
Examples of model cases for the identified perspectives were created through discussion and reference to existing literature and are presented below. Each one contains the defining attributes. Consider the following example model cases:
Public health preconception perspective:
“Toni is 26 years old, is not pregnant, and is not currently sexually active.”
Potential preconception perspective:
“Toni is 26 and not pregnant. She is not currently planning a pregnancy, but she is sexually active. However, she regularly forgets to take her oral contraceptive pill and sometimes her partner does not wear a condom when they have sex.”
“Jaime is 19. He is regularly sexually active with his new girlfriend who is not pregnant. They are careful and use a condom every time.”
Intentional preconception perspective:
“Toni is 26 and not pregnant. After discussion with her partner, she has decided that they would like to start trying to have a baby this year. She has stopped taking her oral contraceptive pill and she and her partner deliberately do not use condoms when they have sex.”
“Jaime is 19 years old. He is regularly sexually active with his new girlfriend who is not pregnant. They have decided they would like to get pregnant as soon as possible.”
Step 6: borderline, related, and contrary cases
There were some instances where studies recruited or referred to populations that did not meet the defining attributes of a preconception population. A borderline case contains most, but not all, of the defining attributes of the concept. The following constructed example illustrates a borderline case from a potential perspective. Here, Sophia has not indicated a specific future pregnancy intention or any pregnancy planning, but might be considered preconception.
“Sophia is 20, not currently pregnant, is not currently sexually active, but is due to marry soon.”
A related case occurs when a concept is related to the concept of interest but does not contain all defining attributes. The following constructed example may more closely align with the concepts of preconception care [43] or reproductive life planning [12], but does not contain all the defining attributes for a preconception population from an intentional perspective.
“Jo is 27. She is not currently pregnant but recently gave birth to her first child. Jo and her partner have resumed intercourse after Jo’s recovery from labour and delivery. They think they would like to try for a sibling for their daughter but would like to wait a bit longer and are using condoms when they have sex. Nevertheless, Jo is careful about her reproductive health and has made an appointment at a preconception care clinic to ensure she is healthy and to make any necessary behavioural changes or preparations for future pregnancies.”
A contrary case is a case that does not meet any of the defining attributes (“not the concept”). The following constructed example is a contrary case for both the potential and intentional perspective because Sarah is not currently partaking in intercourse, experiences a permanent form of contraception and is not planning a future pregnancy.
“Sarah is 32. Recently, after giving birth to her first child, she had medical complications which resulted in a hysterectomy meaning she can no longer become pregnant. She is abstaining from sex with her partner while she recovers.”
Step 7: antecedents and consequences
From the public health perspective, the antecedent to preconception would be childhood or puberty. From a potential perspective, the antecedent is when one becomes sexually active. From an intentional perspective, the antecedent is the decision and action of stopping the use of contraception and/or the act of making a decision that results in a pregnancy intention. Antecedents could be considered flags to identify individuals who may become preconception in the near future.
For the concept of the “preconception population”, there are two consequences. Firstly, a woman (or female partner) becomes pregnant. The second alternative is that the individual exits reproductive age, for example after going through menopause. In the literature, only the consequence of pregnancy was considered in studies which followed women until they reported a pregnancy [33].
Step 8: empirical referents
In the concept of the preconception population, intercourse and the use of contraception may be easily measured by asking a simple question. Pregnancy planning (intentional perspective) is often retrospectively assessed via a single item (e.g., “was your pregnancy planned?” [44]) but can be assessed more comprehensively using the London Measure of Unplanned Pregnancy (LMUP) [45]. The LMUP is a 6-item measure that encompasses contraceptive use, feelings about pregnancy, pregnancy intentions (including discussions with partner) and health actions to prepare for pregnancy. However, the LMUP is designed for use during or after pregnancy, and therefore is retrospective. Whether considering the preconception population from a public health, potential, or intentional perspective, there is a need for a validated scale to assess prospective pregnancy intentions. Key opportunities to assess intentions regarding a future pregnancy include adolescents learning about preconception health and family planning during sexual education classes in school, when women visit a medical practitioner to talk about contraceptive use or for cervical screening, when women marry or attend preconception care clinics or in the postnatal period. A new, validated measure that could be applied in these contexts is the Desire to Avoid Pregnancy scale, a 14-item tool that explores attitudes towards pregnancy across cognitive, affective and practical domains [46].