Evaluation of cesarean delivery rates and factors associated with cesarean delivery among women enrolled in a pregnancy cohort study at two tertiary hospitals in Thailand.

BACKGROUND: Cesarean delivery rates have increased globally resulting in a public health concern. We estimate rates of cesarean deliveries among Thai women using the World Health Organization (WHO) Robson Classification system and compare rates by Robson group to the Robson guideline for acceptable rates to identify groups that might benefit most from interventions for rate reduction. METHODS: In 2017 and 2018, we established cohorts of pregnant women aged ≥ 18 years seeking prenatal care at two tertiary Thai hospitals and followed them until 6-8 weeks postpartum. Three in-person interviews (enrollment, end of pregnancy, and postpartum) were conducted using structured questionnaires to obtain demographic characteristics, health history, and delivery information. Cesarean delivery indication was classified based on core obstetric variables (parity, previous cesarean delivery, number of fetuses, fetal presentation, gestational week, and onset of labor) assigned to 10 groups according to the Robson Classification. Logistic regression was used to identify factors associated with cesarean delivery among nulliparous women with singleton, cephalic, term pregnancies. RESULTS: Of 2,137 participants, 970 (45%) had cesarean deliveries. The median maternal age at delivery was 29 years (interquartile range, 25-35); 271 (13%) participants had existing medical conditions; and 446 (21%) had pregnancy complications. The cesarean delivery rate varied by Robson group. Multiparous women with > 1 previous uterine scar, with a single cephalic pregnancy, ≥ 37 weeks gestation (group 5) contributed the most (14%) to the overall cesarean rate, whereas those with a single pregnancy with a transverse or oblique lie, including women with previous uterine scars (group 9) contributed the least (< 1%). Factors independently associated with cesarean delivery included age ≥ 25 years, pre-pregnancy obesity, new/worsen medical condition during pregnancy, fetal distress, abnormal labor, infant size for gestational age ≥ 50th percentiles, and self-pay for delivery fees. Women with existing blood conditions were less likely to have cesarean delivery. CONCLUSIONS: Almost one in two pregnancies among women in our cohorts resulted in cesarean deliveries. Compared to WHO guidelines, cesarean delivery rates were elevated in selected Robson groups indicating that tailored interventions to minimize non-clinically indicated cesarean delivery for specific groups of pregnancies may be warranted.

Bayesian Estimation of Human Population Toxicokinetics of PFOA, PFOS, PFHxS, and PFNA from Studies of Contaminated Drinking Water.

BACKGROUND: Setting health-protective standards for poly- and perfluoroalkyl substances (PFAS) exposure requires estimates of their population toxicokinetics, but existing studies have reported widely varying PFAS half-lives (T½) and volumes of distribution (Vd). OBJECTIVES: We combined data from multiple studies to develop harmonized estimates of T½ and Vd, along with their interindividual variability, for four PFAS commonly found in drinking water: perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS). METHODS: We identified published data on PFAS concentrations in human serum with corresponding drinking water measurements, separated into training and testing data sets. We fit training data sets to a one-compartment model incorporating interindividual variability, time-dependent drinking water concentrations, and background exposures. Use of a hierarchical Bayesian approach allowed us to incorporate informative priors at the population level, as well as at the study level. We compared posterior predictions to testing data sets to evaluate model performance. RESULTS: Posterior median (95% CI) estimates of T½ (in years) for the population geometric mean were 3.14 (2.69, 3.73) for PFOA, 3.36 (2.52, 4.42) for PFOS, 2.35 (1.65, 3.16) for PFNA, and 8.30 (5.38, 13.5) for PFHxS, all of which were within the range of previously published values. The extensive individual-level data for PFOA allowed accurate estimation of population variability, with a population geometric standard deviation of 1.57 (95% CI: 1.42, 1.73); data from other PFAS were also consistent with this degree of population variability. Vd estimates ranged from 0.19 to 0.43L/kg across the four PFAS, which tended to be slightly higher than previously published estimates. DISCUSSION: These results have direct application in both risk assessment (quantitative interspecies extrapolation and uncertainty factors for interindividual variability) and risk communication (interpretation of monitoring data). In addition, this study provides a rigorous methodology for further refinement with additional data, as well as application to other PFAS. https://doi.org/10.1289/EHP10103.

Performance of Symptom-Based Case Definitions to Identify Influenza Virus Infection Among Pregnant Women in Middle-Income Countries: Findings From the Pregnancy and Influenza Multinational Epidemiologic (PRIME) Study.

BACKGROUND: The World Health Organization (WHO) recommends case definitions for influenza surveillance that are also used in public health research, although their performance has not been assessed in many risk groups, including pregnant women in whom influenza may manifest differently. We evaluated the performance of symptom-based definitions to detect influenza in a cohort of pregnant women in India, Peru, and Thailand. METHODS: In 2017 and 2018, we contacted 11 277 pregnant women twice weekly during the influenza season to identify illnesses with new or worsened cough, runny nose, sore throat, difficulty breathing, or myalgia and collected data on other symptoms and nasal swabs for influenza real-time reverse transcription-polymerase chain reaction (rRT-PCR) testing. We calculated sensitivity, specificity, positive-predictive value, and negative-predictive value of each symptom predictor, WHO respiratory illness case definitions, and a de novo definition derived from results of multivariable modeling. RESULTS: Of 5444 eligible illness episodes among 3965 participants, 310 (6%) were positive for influenza. In a multivariable model, measured fever ≥38°C (adjusted odds ratio [95% confidence interval], 4.6 [3.1-6.8]), myalgia (3.0 [2.2-4.0]), cough (2.7 [1.9-3.9]), and chills (1.6 [1.1-2.4]) were independently associated with influenza illness. A definition based on these 4 (measured fever, cough, chills, or myalgia) was 95% sensitive and 27% specific. The WHO influenza-like illness (ILI) definition was 16% sensitive and 98% specific. CONCLUSIONS: The current WHO ILI case definition was highly specific but had low sensitivity. The intended use of case definitions should be considered when evaluating the tradeoff between sensitivity and specificity.