Abstract
Study question
What is the prevalence of female infertility among UK military personnel and does it differ from the Metropolitan Police Service (MPS) and civilian populations?
Summary answer
Prevalence of self-reported infertility was higher in servicewomen (31.7%) and female MPS officers (36.3%) than in civilian women (24.4%).
What is known already
Arduous employment is associated with numerous potential occupational hazards and behaviours that may be relevant to fertility. These include physical and psychological stress, smoking, alcohol drinking and other lifestyle factors. A preliminarily report in 2016 indicated that UK servicewomen over 30 years of age were more likely to present with fertility problems compared with reported civilian infertility data for age-matched women. Few previous studies have compared infertility prevalence of servicewomen with civilians, and none have compared infertility prevalence with other occupations.
Study design, size, duration
A cross-sectional study was undertaken in 2019 to determine prevalence of infertility. All eligible UK servicewomen (14,650) and MPS officers (8,262) aged 18–60 years were invited to participate with sisters of participants recruited as controls using a snowball technique. Data including pregnancy history, time to each pregnancy and self-reported infertility risk-factors were collected using an online questionnaire. We estimated a sample of 4898 servicewomen would give a precision of 1% around infertility prevalence estimates.
Participants/materials, setting, methods
The questionnaire was developed, piloted and adapted for electronic distribution. The occupational groups were invited by email to complete the questionnaire on three occasions. Prevalence of infertility was defined as the proportion of women at risk of pregnancy who had not become pregnant within 12 months. Only women with pregnancy outcomes, or fully tested for fertility (12 months or more of exposure), were included in the denominator.
Main results and the role of chance
Participants included 4806 (33%) women serving in the UK Armed Forces, 1237 (15%) female MPS officers and 435 (estimated 8%) non-military, non-MPS sisters (biological, half, step or adopted) of both groups. 98.4% of responses were complete. Prevalence of self-reported 12-month infertility was 31.7% (95% CI 29.9–33.5) in servicewomen, 36.3% (95% CI 33.1–39.7) in MPS officers and 24.4% (95% CI 19.6–29.8) in civilian women. Age, history of polycystic ovary syndrome, endometriosis, fibroids, tubal and pelvic surgery, hysterectomy and a short General Health Questionnaire (GHQ 12) score of > 4 (suggesting a minor psychiatric disorder) were associated with infertility and adjusted for in logistic regression models to estimate odds ratios. The adjusted odds ratio (aOR) of infertility in servicewomen was 1.0 (95% CI 0.8–1.2) compared with MPS officers and 1.5 (95% CI 1.1–2.0) in both servicewomen and MPS officers compared with sisters.
Limitations, reasons for caution
The major limitation is the low response rate, particularly in the two control groups, potentially resulting in response bias. Prevalence of infertility could have been further over-estimated if fertile women are more likely to have left the military or MPS. There is scope for residual confounding.
Wider implications of the findings: Further analyses will explore the key risk factors to identify what aspects of these occupations contribute to infertility and which may be modifiable. Future cohort studies would be helpful to extend the understanding of the influence of occupation on infertility.
Trial registration number
Not applicable
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