The association between Afghan Women's autonomy and experience of domestic violence, moderated by education status.

This study examines the association between Afghan women's autonomy (WA) and experience of domestic violence (physical, sexual, and emotional) in the previous 12 months, and whether this association is moderated by education status. We used data from 19,098 married women aged 15-49, who completed the 2015 Afghanistan Demographic and Health Survey- the first and only national survey administered in the country. WA was measured across 5 domains (healthcare, visiting family, household purchases, spending, and contraceptive use). Adjusted odds ratios and 95% confidence intervals for the association between domestic violence in the past 12 months (any vs. none) and WA were estimated using multiple logistic regression and adjusted for covariates. Interaction terms between education status and WA were also assessed. We found that the experience of physical, emotional, and sexual violence was 45% 30%, and 7%, and at least 1 in 2 had no autonomy. After adjustment, compared to women without autonomy, WA in healthcare decisions, spending, visiting families, and household purchases significantly decreased the odds of physical violence. Similarly, WA in healthcare decisions and spending significantly decreased the odds of sexual violence. Lastly, WA in spending and not using contraception was associated with reduced odds of emotional violence. We also found a greater protective effect of WA in visiting family among women with any education across each domestic violence outcome. These findings provide insights into areas for intervention to address gender inequalities (Sustainable Development Goal 3) and mitigate adverse health outcomes for mothers and their children (Goal 5).

Functional data analysis to characterize disease patterns in frequent longitudinal data: application to bacterial vaginal microbiota patterns using weekly Nugent scores and identification of pattern-specific risk factors.

BACKGROUND: Technology advancement has allowed more frequent monitoring of biomarkers. The resulting data structure entails more frequent follow-ups compared to traditional longitudinal studies where the number of follow-up is often small. Such data allow explorations of the role of intra-person variability in understanding disease etiology and characterizing disease processes. A specific example was to characterize pathogenesis of bacterial vaginosis (BV) using weekly vaginal microbiota Nugent assay scores collected over 2 years in post-menarcheeal women from Rakai, Uganda, and to identify risk factors for each vaginal microbiota pattern to inform epidemiological and etiological understanding of the pathogenesis of BV. METHODS: We use a fully data-driven approach to characterize the longitudinal patters of vaginal microbiota by considering the densely sampled Nugent scores to be random functions over time and performing dimension reduction by functional principal components. Extending a current functional data clustering method, we use a hierarchical functional clustering framework considering multiple data features to help identify clinically meaningful patterns of vaginal microbiota fluctuations. Additionally, multinomial logistic regression was used to identify risk factors for each vaginal microbiota pattern to inform epidemiological and etiological understanding of the pathogenesis of BV. RESULTS: Using weekly Nugent scores over 2 years of 211 sexually active and post-menarcheal women in Rakai, four patterns of vaginal microbiota variation were identified: persistent with a BV state (high Nugent scores), persistent with normal ranged Nugent scores, large fluctuation of Nugent scores which however are predominantly in the BV state; large fluctuation of Nugent scores but predominantly the scores are in the normal state. Higher Nugent score at the start of an interval, younger age group of less than 20 years, unprotected source for bathing water, a woman's partner's being not circumcised, use of injectable/Norplant hormonal contraceptives for family planning were associated with higher odds of persistent BV in women. CONCLUSION: The hierarchical functional data clustering method can be used for fully data driven unsupervised clustering of densely sampled longitudinal data to identify clinically informative clusters and risk-factors associated with each cluster.

Infant Sex-Specific Associations between Prenatal Food Insecurity and Low Birthweight: A Multistate Analysis.

BACKGROUND: Low birthweight is associated with increased risk of neonatal mortality and adverse outcomes among survivors. As maternal sociodemographic factors do not explain all of the risk in low birthweight, exploring exposures occurring during critical periods, such as maternal food insecurity, should be considered from a life course perspective. OBJECTIVES: To explore the association between prenatal food insecurity and low birthweight, as well as whether or not there may be a sex-specific response using a multistate survey. METHODS: Pregnancy Risk Assessment Monitoring System (PRAMS) data of live births from 11 states during 2009-2017 were used, restricting to women with a singleton birth. Food insecurity was determined by a single question in PRAMS, and low birthweight was defined as a birth <2500 g. Multivariable logistic regression was used, stratified by infant sex and adjusted for maternal sociodemographic and prepregnancy health characteristics. RESULTS: There were n = 50,915 women from 2009 to 2017, with 9.1% experiencing food insecurity. Unadjusted results revealed that food-insecure mothers had an increased odds ratio of delivering a low-birthweight baby (OR: 1.38; 95% CI: 1.25, 1.53). Adjustment for covariates appeared to explain the association among male infants, whereas magnitudes remained greater among female infants (adjusted OR: 1.13; 95% CI: 0.94, 1.35). CONCLUSIONS: Findings suggest a sex-specific response to prenatal food insecurity, particularly among female offspring. Future studies are warranted with more precise measures of food insecurity and to understand the difference by infant sex.

The role of doulas in respectful care for communities of color and Medicaid recipients.

BACKGROUND: Despite the tenets of rights-based, person-centered maternity care, racialized groups, low-income people, and people who receive Medicaid insurance in the United States experience mistreatment, discrimination, and disrespectful care more often than people with higher income or who identify as white. This study aimed to explore the relationship between the presence of a doula (a person who provides continuous support during childbirth) and respectful care during birth, especially for groups made vulnerable by systemic inequality. METHODS: We used data from 1977 women interviewed in the Listening to Mothers in California survey (2018). Respondents who reported high levels of decision making, support, and communication during childbirth were classified as having "high" respectful care. To examine associations between respectful care and self-reported doula support, we conducted multivariable logistic regressions. Interactions by race/ethnicity and private or Medi-Cal (Medicaid) insurance status were assessed. RESULTS: Overall, we found higher odds of respectful care among women supported by a doula than those without such support (odds ratios [OR]: 1.4, 95% CI: 1.0-1.8). By race/ethnicity, the association was largest for non-Hispanic Black women (2.7 [1.1-6.7]) and Asian/Pacific Islander women (2.3 [0.9-5.6]). Doula support predicts higher odds of respectful care among women with Medi-Cal (1.8 [1.3-2.5]), but not private insurance. CONCLUSIONS: Doula support was associated with high respectful care, particularly for low-income and certain racial/ethnic groups in California. Policies supporting the expansion of doulas for low-income and marginalized groups are consistent with the right to respectful care and may address disparities in maternal experiences.

Trends in time-to-pregnancy in the USA: 2002 to 2017.

STUDY QUESTION: Has there been there a temporal change in time-to-pregnancy (TTP) in the USA. SUMMARY ANSWER: Overall, TTP was stable over time, but a longer TTP for women over 30 and parous women was identified. WHAT IS KNOWN ALREADY: Fertility rates in the USA have declined over the past several years. Although these trends have been attributed to changing reproductive intentions, it is unclear whether declining fecundity (the biologic ability to reproduce measured by TTP in the current report) may also play a role. Indeed, trends based on declining sperm quality and higher utilisation of infertility treatment suggest fecundity may be falling. STUDY DESIGN, SIZE, DURATION: This cross-sectional survey data from the National Survey of Family Growth was administered from 2002 to 2017. The surveys are based on nationally representative samples of reproductive-aged women in the USA. Interviews were conducted in person or through computer-assisted self-administration of sensitive questions. PARTICIPANTS/MATERIALS, SETTING, METHODS: The study included women who self-reported time spent trying to become pregnant allowing utilisation of the current duration approach to estimate the total duration of pregnancy attempt (i.e. TTP). In all, 1202 participants were analysed over each study period. To estimate a TTP distribution overall and by parity, we used a piecewise constant proportional hazards model that accounts for digit preference. Accelerated-failure-time regression models, which were weighted to account for the sampling design, were used to estimate time ratios (TRs). Models were adjusted for age, BMI, race, education, relationship status, parity, pelvic inflammatory disease treatment and any reproductive problems. MAIN RESULTS AND THE ROLE OF CHANCE: Of the participants analysed, the average age was 31.8 and BMI was 28.6, which was similar across the survey periods. Relationship status was the only demographic characteristic that changed over time. All other variables remained constant across the study periods. Overall, TRs comparing TTP between 2002 and 2017 increased slightly (TR: 1.02, 95% CI: 0.99, 1.04). When stratified by parity, parous women had a longer TTP over the later years of the study (TR: 1.04, 95% CI: 1.01, 1.06). TTP remained constant for nulliparous women. Similarly, TTP also increased over time for women over age thirty (TR: 1.02, 1.00, 1.05) but not for women under age thirty. LIMITATIONS, REASONS FOR CAUTION: Small changes in data collection over time may have impacted the findings. We accounted for this in sensitivity analyses using imputed data. Overall, TRs were slightly attenuated using the imputed data, but represented similar patterns to the original data. Results for parous women and women over 30 remained consistent in the sensitivity analyses. WIDER IMPLICATIONS OF THE FINDINGS: Consistent with reports of falling fertility rates and sperm counts, this study suggests parous and older couples in the USA may be taking longer to become pregnant. Although trends were suggestive of a small overall increase in TTP, particularly for parous women and women over age thirty, additional data are needed to attempt to understand these trends given the societal, economic and public health implications related to fecundity. STUDY FUNDING/COMPETING INTEREST(S): Funding was provided by National Institutes of Health grant R03HD097287 to A.C.M. There are no competing interests. TRIAL REGISTRATION NUMBER: N/A.

Racial and Ethnic Disparities in Maternal Mortality in the United States Using Enhanced Vital Records, 2016‒2017.

Objectives. To better understand racial and ethnic disparities in US maternal mortality. Methods. We analyzed 2016-2017 vital statistics mortality data with cause-of-death literals (actual words written on the death certificate) added. We created a subset of confirmed maternal deaths that had pregnancy mentions in the cause-of-death literals. Primary cause of death was identified and recoded using cause-of-death literals. We examined racial and ethnic disparities both overall and by primary cause. Results. The maternal mortality rate for non-Hispanic Black women was 3.55 times that for non-Hispanic White women. Leading causes of maternal death for non-Hispanic Black women were eclampsia and preeclampsia and postpartum cardiomyopathy with rates 5 times those for non-Hispanic White women. Non-Hispanic Black maternal mortality rates from obstetric embolism and obstetric hemorrhage were 2.3 to 2.6 times those for non-Hispanic White women. Together, these 4 causes accounted for 59% of the non-Hispanic Black‒non-Hispanic White maternal mortality disparity. Conclusions. The prominence of cardiovascular-related conditions among the leading causes of confirmed maternal death, particularly for non-Hispanic Black women, necessitates increased vigilance for cardiovascular problems during the pregnant and postpartum period. Many of these deaths are preventable.

Risk and protective factors associated with BV chronicity among women in Rakai, Uganda.

OBJECTIVES: To assess risk and protective factors associated with bacterial vaginosis (BV) chronicity ascertained by Nugent score criteria. METHODS: A longitudinal cohort study included 255 sexually experienced, postmenarcheal women who provided weekly self-collected vaginal swabs for up to 2 years. Vaginal swabs were scored using Nugent criteria and classified as normal (≤3), intermediate (4-6) and Nugent-BV (≥7). Detailed behavioural/health information were assessed every 6 months. A per-woman longitudinal summary measure of BV chronicity was defined as the percentage of each woman's weekly vaginal assessments scored as Nugent-BV over a 6-month interval. Risk and protective factors associated with BV chronicity were assessed using multiple linear regression with generalised estimating equations. RESULTS: Average BV chronicity was 39% across all follow-up periods. After adjustment, factors associated with BV chronicity included baseline Nugent-BV (ß=35.3, 95% CI 28.6 to 42.0) compared with normal baseline Nugent scores and use of unprotected water for bathing (ie, rainwater, pond, lake/stream) (ß=12.0, 95% CI 3.4 to 20.5) compared with protected water sources (ie, well, tap, borehole). Women had fewer BV occurrences if they were currently pregnant (ß=-6.6, 95% CI -12.1 to 1.1), reported consistent condom use (ß=-7.7, 95% CI -14.2 to 1.3) or their partner was circumcised (ß=-5.8, 95% CI -11.3 to 0.3). CONCLUSIONS: Factors associated with higher and lower values of BV chronicity were multifactorial. Notably, higher values of BV chronicity were associated with potentially contaminated bathing water. Future studies should examine the role of waterborne microbial agents in the pathogenesis of BV.

Value and disvalue of the pregnancy checkbox on death certificates in the United States-impact on newly released 2018 maternal mortality data.

Maternal mortality is a sentinel health indicator. To improve the identification of maternal deaths, a pregnancy question was added during the 2003 revision of the US standard death certificate. Its adoption across all states in the United States took 16 years (2003-2018), and therefore the National Center for Health Statistics did not provide the national maternal mortality rate between 2007 and 2018. During this time, researchers raised questions about the accuracy of the checkbox information, particularly regarding its contribution to overreporting of maternal deaths in the United States. Checkbox errors were especially evident for women aged >40 years and for nonspecific causes of death. In January 2020, the NCHS resumed the reporting of maternal mortality data and provided the 2018 figures using a new coding method (ie, the 2018 method). Despite internal analyses suggesting the presence of both high false positive and high false negative pregnancy checkbox errors, the National Center for Health Statistics reported identification of 658 maternal deaths nationwide and a maternal mortality rate of 17.4 deaths per 100,000 live births for 2018. The 2018 coding method restricts the entry of checkbox information to decedents aged 10-44 years; the information cannot, therefore, be entered for women aged >45 years when no pregnancy-related cause of death information is indicated on the death certificate. Reported deaths with a pregnancy or obstetrical condition entered in the cause of death section of the death certificate continue to be coded as maternal deaths regardless of age. The 2018 method likely corrects errors introduced by the use of the checkbox for women aged >45 years, but whether it provides accurate maternal mortality figures remains unknown. We call for efforts to urgently and systematically validate the pregnancy checkbox information. Post hoc coding adjustments cannot substitute for providing accurate and actionable maternal mortality data.

The association between interpregnancy interval and severe maternal morbidities using revised national birth certificate data: A probabilistic bias analysis.

BACKGROUND: Severe maternal morbidity continues to be on the rise in the US. Short birth spacing is a modifiable risk factor associated with maternal morbidity, yet few studies have examined this association, possibly due to few available data sources to examine these rare events. OBJECTIVE: To examine the association between interpregnancy interval (IPI) and severe maternal morbidity using near-national birth certificate data and account for known under-reporting using probabilistic bias analysis. METHODS: We used revised 2014-2017 birth certificate data, restricting to resident women with a non-first-born singleton birth. We examined the following: (a) maternal blood transfusion, (b) admission to intensive care unit (ICU), (c) uterine rupture (among women with a prior caesarean delivery) and (d) third- or fourth-degree perineal laceration (among vaginal deliveries) by IPI categories (<6, 6-11, 12-17, 18-23, 24-59 and 60+ months). Risk ratios and 95% confidence intervals were estimated using log-binomial regression, adjusting for select maternal characteristics. Probabilistic bias analyses were performed. RESULTS: Compared with IPI 18 to 23 months, adjusted models revealed that the risk of maternal transfusion followed a U-shaped curve with IPI, while risk of ICU admission and perineal laceration increased with longer IPI. Risk of uterine rupture was highest among IPI <6 months. With the exception of maternal transfusion, these findings persisted regardless of the extent or type of misclassification examined in bias analyses. CONCLUSIONS: Associations between IPI and maternal morbidity varied by outcome, even after adjusting for misclassification of SMM. Differences across maternal health outcomes should be considered when counselling and making recommendations regarding optimal birth spacing.

Examining interpregnancy intervals and maternal and perinatal health outcomes using U.S. vital records: Important considerations for analysis and interpretation.

BACKGROUND: Numerous studies use birth certificate data to examine the association between interpregnancy interval (IPI) and maternal and perinatal health outcomes. Substantive changes from the latest birth certificate revision have implications for examining this relationship. METHODS: We provide an overview of the National Vital Statistics System and recent changes to the national birth certificate data file, which have implications for assessing IPI and perinatal health outcomes. We describe the calculation of IPI using birth certificate information and related measurement issues. Missing IPI values by maternal age, race and education using 2016 birth certificate data were also compared. Finally, we review and summarise data quality studies of select covariate and outcome variables (sociodemographic, maternal health and health behaviours, and infant health) conducted after the most recent 2003 birth certificate revision. RESULTS: Substantive changes to data collection, dissemination and quality have occurred since the 2003 revision. These changes impact IPI measurement, trends and associations with perinatal health outcomes. Missing values of IPI were highest for older ages, lower education and non-Hispanic black women. Minimal differences were found when comparing IPI using different gestational age measures. Recent data quality studies pointed to substantial variation in data quality by item and across states. CONCLUSION: Future studies examining the association of IPI with maternal and perinatal data using vital records should consider these aspects of the data in their research plan, sensitivity analyses and interpretation of findings.

Beyond birth outcomes: Interpregnancy interval and injury-related infant mortality.

BACKGROUND: Several studies have examined the association between IPI and birth outcomes, but few have explored the association between interpregnancy interval (IPI) and postnatal outcomes. OBJECTIVE: We examined the association between IPI and injury-related infant mortality, a leading cause of postneonatal mortality. METHODS: We used 2011-2015 US period-linked birth-infant death vital statistics data to generate a multiyear birth cohort of non-first-born singleton births (N = 9 782 029). IPI was defined as the number of months between a live birth and the start of the pregnancy leading to the next live birth. Causes of death in the first year of life were identified using ICD-10 codes. Hazard ratios (HR) for IPI categories were estimated using Cox proportional hazards models adjusted for birth order, county poverty level, and maternal characteristics (marital status, race/ethnicity, education, age at previous birth). RESULTS: After adjustment, overall infant mortality (48.1 per 10 000 births) was higher for short and long IPIs compared with IPI 18-23 months (reference): <6, aHR 1.61, 95% CI 1.54, 1.68; 6-11, aHR 1.22, 95% CI 1.17, 1.26; and 60+ months, aHR 1.12, 95% CI 1.08, 1.16. In comparison, the risk of injury-related infant mortality (4.4 per 10 000 births) decreased with longer IPIs: <6, aHR 1.77, 95% CI 1.55, 2.01; 6-11, aHR 1.41, 95% CI 1.25, 1.59; 12-17, aHR 1.25, 95% CI 1.10, 1.41; 24-59, aHR 0.78, 95% CI 0.69, 0.87; and 60+ months, aHR 0.55, 95% CI 0.48, 0.62. CONCLUSION: Unlike overall infant mortality, injury-related infant mortality decreased with IPI length. While injury-related deaths are rare, these patterns suggest that the timing between births may be a marker of risk for fatal infant injuries. The first year postpartum may be an ideal time for the delivery of evidence-based injury prevention programmes as well as family planning services.

Good practices for the design, analysis, and interpretation of observational studies on birth spacing and perinatal health outcomes.

BACKGROUND: Meta-analyses of observational studies have shown that women with a shorter interpregnancy interval (the time from delivery to start of a subsequent pregnancy) are more likely to experience adverse pregnancy outcomes, such as preterm delivery or small for gestational age birth, than women who space their births further apart. However, the studies used to inform these estimates have methodological shortcomings. METHODS: In this commentary, we summarise the discussions of an expert workgroup describing good practices for the design, analysis, and interpretation of observational studies of interpregnancy interval and adverse perinatal health outcomes. RESULTS: We argue that inferences drawn from research in this field will be improved by careful attention to elements such as: (a) refining the research question to clarify whether the goal is to estimate a causal effect vs describe patterns of association; (b) using directed acyclic graphs to represent potential causal networks and guide the analytic plan of studies seeking to estimate causal effects; (c) assessing how miscarriages and pregnancy terminations may have influenced interpregnancy interval classifications; (d) specifying how key factors such as previous pregnancy loss, pregnancy intention, and maternal socio-economic position will be considered; and (e) examining if the association between interpregnancy interval and perinatal outcome differs by factors such as maternal age. CONCLUSION: This commentary outlines the discussions of this recent expert workgroup, and describes several suggested principles for study design and analysis that could mitigate many potential sources of bias.

Report of the Office of Population Affairs' expert work group meeting on short birth spacing and adverse pregnancy outcomes: Methodological quality of existing studies and future directions for research.

BACKGROUND: The World Health Organization (WHO) recommends that women wait at least 24 months after a livebirth before attempting a subsequent pregnancy to reduce the risk of adverse maternal, perinatal, and infant health outcomes. However, the applicability of the WHO recommendations for women in the United States is unclear, as breast feeding, nutrition, maternal age at first birth, and total fertility rate differs substantially between the United States and the low- and middle-resource countries upon which most of the evidence is based. METHODS: To inform guideline development for birth spacing specific to women in the United States, the Office of Population Affairs (OPA) convened an expert work group meeting in Washington, DC, on 14-15 September 2017 among reproductive, perinatal, paediatric, social, and public health epidemiologists; obstetrician-gynaecologists; biostatisticians; and experts in evidence synthesis related to women's health. RESULTS: Presentations and discussion topics included the methodological quality of existing studies, evaluation of the evidence for causal effects of short interpregnancy intervals on adverse perinatal and maternal health outcomes, good practices for future research, and identification of research gaps and priorities for future work. CONCLUSIONS: This report provides an overview of the presentations, discussions, and conclusions from the expert work group meeting.

Breastfeeding Initiation by WIC Receipt After Formula Shortages in 2022.

This study assesses differences in breastfeeding initiation trends between Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) participants and WIC-eligible nonparticipants before, during, and after the 2022 infant formula disruption.

Trends in Texas maternal mortality by maternal age, race/ethnicity, and cause of death, 2006-2015.

BACKGROUND: Maternal mortality is a sentinel indicator of health care quality. Our purpose was to analyze trends in Texas maternal mortality by demographic characteristics and cause of death, and to evaluate data quality. METHODS: Maternal mortality data were initially analyzed by single years, but then were grouped into 5-year averages (2006-2010 and 2011-2015) for more detailed analyses. Rates were computed per 100 000 live births. A two-proportion z test or Poisson regression for numerators <30 was used to evaluate differences. RESULTS: The Texas maternal mortality rate increased from 18.6 in 2010 to 38.7 in 2012, and then declined nonsignificantly to 32.5 in 2015. The 2011-2015 rate (34.2) was 87% higher than the 2006-2010 rate (18.3). In 2011-2015, the maternal mortality rate for women ≥40 years (558.8) was 27 times higher than for women <40 years (20.7). From 2006-2010 to 2011-2015, the maternal mortality rate increased by 121% for women ≥40 years and by 55% for women <40 years. The rate increased by 132% for nonspecific causes of death, and by 54% for specific causes. Rates for women <40 years for specific causes increased by 36%. CONCLUSIONS: The observed increase in maternal mortality in Texas from 2006-2010 to 2011-2015 is likely a result of both a true increase in rates and increased overreporting of maternal deaths, as indicated by implausibly high and increasing rates for women aged ≥40 years and among nonspecific causes of death. Efforts are needed to strengthen reporting of death certificate data, and to improve access to quality maternal health care services.

Measuring US Maternal Mortality.

This Viewpoint discusses the importance of collaboration among the agencies responsible for documenting rates of maternal mortality to ensure more accurate, reliable, and timely estimates.

Plurality of Birth and Infant Mortality Due to External Causes in the United States, 2000-2010.

Risk of death during the first year of life due to external causes, such as unintentional injury and homicide, may be higher among twins and higher-order multiples than among singletons in the United States. We used national birth cohort linked birth-infant death data (2000-2010) to evaluate the risk of infant mortality due to external causes in multiples versus singletons in the United States. Risk of death from external causes during the study period was 3.6 per 10,000 live births in singletons and 5.1 per 10,000 live births in multiples. Using log-binomial regression, the corresponding unadjusted risk ratio was 1.40 (95% confidence interval (CI): 1.30, 1.50). After adjustment for maternal age, marital status, race/ethnicity, and education, the risk ratio was 1.68 (95% CI: 1.56, 1.81). Infant deaths due to external causes were most likely to occur between 2 and 7 months of age. Applying inverse probability weighting and assuming a hypothetical intervention where no infants were low birth weight, the adjusted controlled direct effect of plurality on infant mortality due to external causes was 1.64 (95% CI: 1.39, 1.97). Twins and higher-order multiples were at greater risk of infant mortality due to external causes, particularly between 2 and 7 months of age, and this risk appeared to be mediated largely by factors other than low-birth-weight status.

Estimating infertility prevalence in low-to-middle-income countries: an application of a current duration approach to Demographic and Health Survey data.

STUDY QUESTION: Can infertility prevalence be estimated using a current duration (CD) approach when applied to nationally representative Demographic and Health Survey (DHS) data collected routinely in low- or middle-income countries? SUMMARY ANSWER: Our analysis suggests that a CD approach applied to DHS data from Nigeria provides infertility prevalence estimates comparable to other smaller studies in the same region. WHAT IS KNOWN ALREADY: Despite associations with serious negative health, social and economic outcomes, infertility in developing countries is a marginalized issue in sexual and reproductive health. Obtaining reliable, nationally representative prevalence estimates is critical to address the issue, but methodological and resource challenges have impeded this goal. STUDY DESIGN, SIZE, DURATION: This cross-sectional study was based on standard information available in the DHS core questionnaire and data sets, which are collected routinely among participating low-to-middle-income countries. Our research question was examined among women participating in the 2013 Nigeria DHS (n = 38 948). Among women eligible for the study, 98% were interviewed. PARTICIPANTS/MATERIALS, SETTING, METHODS: We applied a CD approach (i.e. current length of time-at-risk of pregnancy) to estimate time-to-pregnancy (TTP) and 12-month infertility prevalence among women 'at risk' of pregnancy at the time of interview (n = 7063). Women who were 18-44 years old, married or cohabitating, sexually active within the past 4 weeks and not currently using contraception (and had not been sterilized) were included in the analysis. Estimates were based on parametric survival methods using bootstrap methods (500 bootstrap replicates) to obtain 95% CIs. MAIN RESULTS AND THE ROLE OF CHANCE: The estimated median TTP among couples at risk of pregnancy was 5.1 months (95% CI: 4.2-6.3). The estimated percentage of infertile couples was 31.1% (95% CI: 27.9-34.7%)-consistent with other smaller studies from Nigeria. Primary infertility (17.4%, 95% CI: 12.9-23.8%) was substantially lower than secondary infertility (34.1%, 95% CI: 30.3-39.3%) in this population. Overall estimates for TTP >24 or >36 months dropped to 17.7% (95% CI: 15.7-20%) and 11.5% (95% CI: 10.2-13%), respectively. Subgroup analyses showed that estimates varied by age, coital frequency and fertility intentions, while being in a polygynous relationship showed minimal impact. LIMITATIONS, REASONS FOR CAUTION: The CD approach may be limited by assumptions on when exposure to risk of pregnancy began and methodologic assumptions required for estimation, which may be less accurate for particular subgroups or populations. Unrecognized pregnancies may have also biased our findings; however, we attempted to address this in our exclusion criteria. Limiting to married/cohabiting couples may have excluded women who are no longer in a relationship after being blamed for infertility. Although probably rare in this setting, we lack information on couples undergoing infertility treatment. Like other TTP measurement approaches, pregnancies resulting from contraceptive failure are not included, which may bias estimates. WIDER IMPLICATIONS OF THE FINDINGS: Nationally representative estimates of TTP and infertility based on a clinical definition of 12 months have been limited within developing countries. This approach represents a pragmatic advance in our ability to measure and monitor infertility in the developing world, with potentially far-reaching implications for policies and programs intended to address reproductive health. STUDY FUNDING/COMPETING INTERESTS: There are no competing interests and no financial support was provided for this study. Financial support for Open Access publication was provided by the World Health Organization.

Is human fecundity changing? A discussion of research and data gaps precluding us from having an answer.

Fecundity, the biologic capacity to reproduce, is essential for the health of individuals and is, therefore, fundamental for understanding human health at the population level. Given the absence of a population (bio)marker, fecundity is assessed indirectly by various individual-based (e.g. semen quality, ovulation) or couple-based (e.g. time-to-pregnancy) endpoints. Population monitoring of fecundity is challenging, and often defaults to relying on rates of births (fertility) or adverse outcomes such as genitourinary malformations and reproductive site cancers. In light of reported declines in semen quality and fertility rates in some global regions among other changes, the question as to whether human fecundity is changing needs investigation. We review existing data and novel methodological approaches aimed at answering this question from a transdisciplinary perspective. The existing literature is insufficient for answering this question; we provide an overview of currently available resources and novel methods suitable for delineating temporal patterns in human fecundity in future research.