Purpose of review Human reproduction is a common process and one that unfolds over a relatively short time, but pregnancy and birth processes are challenging to study. Selection occurs at every step of this process (e.g., infertility, early pregnancy loss, and stillbirth), adding substantial bias to estimated exposure-outcome associations. Here we focus on selection in perinatal epidemiology, specifically, how it affects research question formulation, feasible study designs, and interpretation of results. Recent findings Approaches have recently been proposed to address selection issues in perinatal epidemiology. One such approach is the ongoing pregnancies denominator for gestation-stratified analyses of infant outcomes. Similarly, bias resulting from left truncation has recently been termed “live birth bias,” and a proposed solution is to control for common causes of selection variables (e.g., fecundity, fetal loss) and birth outcomes. However, these approaches have theoretical shortcomings, conflicting with the foundational epidemiologic concept of populations at risk for a given outcome. Summary We engage with epidemiologic theory and employ thought experiments to demonstrate the problems of using denominators that include units not “at risk” of the outcome. Fundamental (and commonsense) concerns of outcome definition and analysis (e.g., ensuring that all study participants are at risk for the outcome) should take precedence in formulating questions and analysis approach, as should choosing questions that stakeholders care about. Selection and resulting biases in human reproductive processes complicate estimation of unbiased exposure- outcome associations, but we should not focus solely (or even mostly) on minimizing such biases.

BackgroundTo study the prevalence and define deferential risk factors for ‘Resistant’ hypertension (RHT) in a hypertensive population of South Asian origin.MethodsA descriptive cross-sectional study was carried out among hypertensive patients attending clinics at the Cardiology Unit, Colombo from July-October 2009. All the patients with hypertension who provided informed written consent were recruited to the study (n = 277). A pre-tested interviewer-administered questionnaire was used for data collection. A binary logistic-regression analysis was performed in all patients with ‘presence of RHT’ as the dichotomous dependent variable and other independent co-variants.ResultsMean age was 61 ± 10.3 years and 50.2% were males. The mean of average systolic and diastolic blood pressures (BP) were 133.04 ± 12.91 mmHg and 81.07 ± 6.41 mmHg respectively. Uncontrolled BP was present in 41.1% (n = 114) of patients, of which RHT was present in 19.1% (n = 53). Uncontrolled BP were due to ‘therapeutic inertia’ in 27.8% of the study population. Those with diabetes mellitus, obesity (BMI > 27.5 kg/m2) and those who were older than 55 years were significantly higher in the RHT group than in the non-RHT group. In the binary logistic regression analysis older age (OR:1.36), longer duration of hypertension (OR:1.76), presence of diabetes mellitus (OR:1.67) and being obese (OR:1.84) were significantly associated with RHT.ConclusionA significant proportion of the hypertensive patients were having uncontrolled hypertension. Nearly 1/5th of the population was suffering from RHT, which was significantly associated with the presence of obesity and diabetes mellitus. Therapeutic inertia seems to contribute significantly towards the presence of uncontrolled BP.

CONTEXT Societal views about sexuality and parenting among people with disabilities may limit these individuals’ access to sex education and the full range of reproductive health services, and put them at increased risk for ­unintended pregnancies. To date, however, no national population‐based studies have examined pregnancy ­intendedness among U.S. women with disabilities. METHODS Cross‐sectional analyses of data from the 2011–2013 and 2013–2015 waves of the National Survey of Family Growth were conducted; the sample included 5,861 pregnancies reported by 3,089 women. The proportion of pregnancies described as unintended was calculated for women with any type of disability, women with each of five types of disabilities and women with no disabilities. Multivariate logistic regression analyses were conducted to examine the relationship of disability status and type with pregnancy intendedness while adjusting for covariates. RESULTS A higher proportion of pregnancies were unintended among women with disabilities than among women without disabilities (53% vs. 36%). Women with independent living disability had the highest proportion of unintended pregnancies (62%). In regression analyses, the odds that a pregnancy was unintended were greater among women with any type of disability than among women without disabilities (odds ratio, 1.4), and were also elevated among women with hearing disability, cognitive disability or independent living disability (1.5–1.9). CONCLUSIONS Further research is needed to understand differences in unintended pregnancy by type and extent of disability. People with disabilities should be fully included in sex education, and their routine care should incorporate discussion of reproductive planning.

Background: Recent research suggests that latent phase of labor may terminate at 6 rather than 4 centimeters of cervical dilation. The objectives of this study were to: (a) characterize duration of the latent phase of labor among term, low-risk, United States women in spontaneous labor using the women's self-identified onset; and (b) quantify associations between demographic and maternal/newborn health characteristics and the duration of the latent phase. Methods: This prospective study (n = 1281) described the duration of the latent phase of labor in hours, stratified by parity at the mean, median, and 80th, 90th, and 95th percentiles. The duration of the latent phase was compared for each characteristic using t tests or Wilcoxon rank-sum tests and regression models that controlled for confounders. Results: In this sample of predominantly white, healthy women, duration of the latent phase of labor was longer than described in previous studies: The median duration was 9.0 hours and mean duration was 11.8 hours in nulliparous women. The median duration was 6.8 hours and mean duration was 9.3 hours in multiparous women. Among nulliparous women, longer duration was seen in women whose fetus was in a malposition. Among multiparous women, longer durations were noted in women with chorioamnionitis and those who gave birth between 41 and 41 + 6 weeks' gestation (vs between 40 and 40 + 6 weeks' gestation).

Background Prior studies have found that women with disabilities who give birth are more likely to have preterm deliveries and low birthweight infants. However, it is not known what proportion of pregnant women with disabilities experience live birth, versus miscarriage or abortion. Objective To compare proportions of live birth, miscarriage, and abortion among women with basic action difficulties, women with complex activity limitations, and women without disabilities in a nationally representative sample. Methods We analyzed pooled Medical Expenditure Panel Survey (MEPS) data from Panels 1–11 (covering years 1996–2007), which included a Pregnancy Detail module assessing outcomes for women who were pregnant during panel participation. We used chi-square tests and multivariable logistic regression to compare disability groups on pregnancy outcomes. Results Among women with a recorded pregnancy outcome, women with disabilities were less likely to have live births (80.8% of women with basic action difficulties and 75.3% of women with complex activity limitations versus 85.0% of women without disabilities), but differences related to disability were not significant when adjusting for covariates. Women with complex activity limitations were significantly more likely to report miscarriages, even when controlling for covariates. Disability was not significantly associated with abortion in the adjusted analysis. Conclusions Our findings add to the growing literature on pregnancy outcomes among women with disabilities, providing important information about outcomes that are not reflected in delivery records. We found few differences between women with and without disabilities, and good likelihood of live birth among women with disabilities experiencing pregnancy.

Objectives:The aim of this study was to understand the associations between hypertensive disorders of pregnancy (HDP) and postpartum complications throughout the newly defined 12 week postpartum transition. Study design:We conducted a retrospective cohort study of the associations of HDP (any/ subtype) with postpartum complications among 2.5 million California births, 2008-2012. We identified complications from discharge diagnoses from maternal hospital encounters (emergency department visits and readmissions) in the 12 weeks after giving birth. We compared rates of complications, overall and by diagnostic category, between groups defined by HDP. In survival analyses, we calculated the adjusted hazard ratios of postpartum complications associated with HDP. We adjusted for maternal age, race/ethnicity, prepregnancy obesity, chronic diabetes, gestational diabetes, insurance, delivery mode, gestational age and birth outcome (term and size).Results: Among women with and without HDP, 12.8 and 7.7%, respectively, had a hospital encounter within 12 weeks of giving birth [adjusted hazard ratio 1.5, 95% confidence interval (95% CI): 1.5-1.5]. HDP was associated with increased risk across all major categories of complications: hypertension-related, adjusted hazard ratio 11.8 (95% CI: 11.2-12.3); childbirth related, 1.4 (1.3-1.4); and other, 1.4 (1.4-1.4). Risk of any complication differed by hypertensive subtype: chronic hypertension with super-imposed preeclampsia, adjusted hazard ratio 1.8 (95%

For those desiring a TOL after two previous CDs, prospective studies are needed to assess interventions that limit gestational weight gain as well as the safety and optimal timing of an induction of labor. The decision to attempt a TOL should be guided by counseling regarding the risks, benefits, and chances of a successful TOL.

Although Apgar scores are commonly used as proxy outcomes, little evidence exists in support of the most common cutpoints (<7, <4). We used 2 data sets to explore this issue: one contained planned community births from across the United States (n = 52,877; 2012–2016), and the other contained hospital births from California (n = 428,877; 2010). We treated 5-minute Apgars as clinical “tests,” compared against 18 known outcomes; we calculated sensitivity, specificity, positive and negative predictive values, and the area under the receiver operating characteristic curve for each. We used 3 different criteria to determine optimal cutpoints. Results were very consistent across data sets, outcomes, and all subgroups: The cutpoint that maximizes the trade-off between sensitivity and specificity is universally <9. However, extremely low positive predictive values for all outcomes at <9 indicate more misclassification than is acceptable for research. The areas under the receiver operating characteristic curves (which treat Apgars as quasicontinuous) were generally indicative of adequate discrimination between infants destined to experience poor outcomes and those not; comparing median Apgars between groups might be an analytical alternative to dichotomizing. Nonetheless, because Apgar scores are not clearly on any causal pathway of interest, we discourage researchers from using them unless the motivation for doing so is clear.