The repeatability of self-reported exposure after miscarriage. ALSPAC Study Team. Avon Longitudinal Study of Pregnancy and Childhood

Validation of maternal recall of early pregnancy medication exposure using prospective diary data

PURPOSE

Data about maternal recall accuracy for classifying early pregnancy medication exposure are meager. Nonetheless, studies often rely on recall to evaluate potential impact of pharmaceuticals on the developing fetus.

METHODS

Right from the Start is a community-based pregnancy cohort that enrolled women from North Carolina, Tennessee, and Texas. A subset of 318 women participated in daily medication diaries initiated before conception (2006-2012). We examined nonsteroidal anti-inflammatory drugs (NSAIDs) as an example of a drug type that is difficult to study due to its intermittent and primarily over-the-counter use as well as its incomplete documentation in medical and pharmaceutical records. Selective serotonin reuptake inhibitors (SSRI) were assessed as a prescription medication comparator. Maternal recall of NSAID and SSRI use in early pregnancy was examined by comparing diary data (gold standard) to first-trimester interview.

RESULTS

Sensitivity and specificity for recall of NSAID exposure were 78.6% and 62.3%, respectively (kappa statistic: 0.41), with 72.3% agreement for exposure classification. Sensitivity and specificity for recall of SSRI exposure were 77.8% and 99.0%, respectively (kappa statistic: 0.79), with 97.8% agreement.

CONCLUSIONS

Our findings suggest the validity of maternal recall varies with medication type and prospective data collection should be prioritized when studying early pregnancy drug exposures.

Cohort Profile: the Avon Longitudinal Study of Parents and Children: ALSPAC mothers cohort

Summary The Avon Longitudinal Study of Children and Parents (ALSPAC) was established to understand how genetic and environmental characteristics influence health and development in parents and children. All pregnant women resident in a defined area in the South West of England, with an expected date of delivery between 1st April 1991 and 31st December 1992, were eligible and 13761 women (contributing 13867 pregnancies) were recruited. These women have been followed over the last 19-22 years and have completed up to 20 questionnaires, have had detailed data abstracted from their medical records and have information on any cancer diagnoses and deaths through record linkage. A follow-up assessment was completed 17-18 years postnatal at which anthropometry, blood pressure, fat, lean and bone mass and carotid intima media thickness were assessed, and a fasting blood sample taken. The second follow-up clinic, which additionally measures cognitive function, physical capability, physical activity (with accelerometer) and wrist bone architecture, is underway and two further assessments with similar measurements will take place over the next 5 years. There is a detailed biobank that includes DNA, with genome-wide data available on >10000, stored serum and plasma taken repeatedly since pregnancy and other samples; a wide range of data on completed biospecimen assays are available. Details of how to access these data are provided in this cohort profile.

Impact of pesticide exposure misclassification on estimates of relative risks in the Agricultural Health Study

BACKGROUND

The Agricultural Health Study (AHS) is a prospective study of licensed pesticide applicators and their spouses in Iowa and North Carolina. We evaluate the impact of occupational pesticide exposure misclassification on relative risks using data from the cohort and the AHS Pesticide Exposure Study (AHS/PES).

METHODS

We assessed the impact of exposure misclassification on relative risks using the range of correlation coefficients observed between measured post-application urinary levels of 2,4-dichlorophenoxyacetic acid (2,4-D) and a chlorpyrifos metabolite and exposure estimates based on an algorithm from 83 AHS pesticide applications.

RESULTS

Correlations between urinary levels of 2,4-D and a chlorpyrifos metabolite and algorithm estimated intensity scores were about 0.4 for 2,4-D (n=64), 0.8 for liquid chlorpyrifos (n=4) and 0.6 for granular chlorpyrifos (n=12). Correlations of urinary levels with kilograms of active ingredient used, duration of application, or number of acres treated were lower and ranged from -0.36 to 0.19. These findings indicate that a priori expert-derived algorithm scores were more closely related to measured urinary levels than individual exposure determinants evaluated here. Estimates of potential bias in relative risks based on the correlations from the AHS/PES indicate that non-differential misclassification of exposure using the algorithm would bias estimates towards the null, but less than that from individual exposure determinants.

CONCLUSIONS

Although correlations between algorithm scores and urinary levels were quite good (ie, correlations between 0.4 and 0.8), exposure misclassification would still bias relative risk estimates in the AHS towards the null and diminish study power.

The Mothers and Children's Environmental Health (MOCEH) study

The MOCEH study is a prospective hospital- and community-based cohort study designed to collect information related to environmental exposures (chemical, biological, nutritional, physical, and psychosocial) during pregnancy and childhood and to examine how exposure to environmental pollutants affects growth, development, and disease. The MOCEH network includes one coordinating center, four local centers responsible for recruiting pregnant women, and four evaluation centers (a nutrition center, bio-repository center, neurocognitive development center, and environment assessment center). At the local centers, trained nurses interview the participants to gather information regarding their demographic and socioeconomic characteristics, complications related to the current gestation period, health behaviors and environmental factors. These centers also collect samples of blood, placenta, urine, and breast milk. Environmental hygienists measure each participant's level of exposure to indoor and outdoor pollutants during the pre- and postnatal periods. The participants are followed up through delivery and until the child is 5 years of age. The MOCEH study plans to recruit 1,500 pregnant women between 2006 and 2010 and to perform follow-up studies on their children. We expect this study to provide evidence to support the hypothesis that the gestational environment has an effect on the development of diseases during adulthood. We also expect the study results to enable evaluation of latency and age-specific susceptibility to exposure to hazardous environmental pollutants, evaluation of growth retardation focused on environmental and genetic risk factors, selection of target environmental diseases in children, development of an environmental health index, and establishment of a national policy for improving the health of pregnant women and their children.

Risk factors for first trimester miscarriage--results from a UK-population-based case-control study

OBJECTIVE

The aim of this study was to examine the association between biological, behavioural and lifestyle risk factors and risk of miscarriage.

DESIGN

Population-based case-control study.

SETTING

Case-control study nested within a population-based, two-stage postal survey of reproductive histories of women randomly sampled from the UK electoral register.

POPULATION

Six hundred and three women aged 18-55 years whose most recent pregnancy had ended in first trimester miscarriage (<13 weeks of gestation; cases) and 6116 women aged 18-55 years whose most recent pregnancy had progressed beyond 12 weeks (controls).

METHODS

Women were questioned about socio-demographic, behavioural and other factors in their most recent pregnancy.

MAIN OUTCOME MEASURE

First trimester miscarriage.

RESULTS

After adjustment for confounding, the following were independently associated with increased risk: high maternal age; previous miscarriage, termination and infertility; assisted conception; low pre-pregnancy body mass index; regular or high alcohol consumption; feeling stressed (including trend with number of stressful or traumatic events); high paternal age and changing partner. Previous live birth, nausea, vitamin supplementation and eating fresh fruits and vegetables daily were associated with reduced risk, as were feeling well enough to fly or to have sex. After adjustment for nausea, we did not confirm an association with caffeine consumption, smoking or moderate or occasional alcohol consumption; nor did we find an association with educational level, socio-economic circumstances or working during pregnancy.

CONCLUSIONS

The results confirm that advice to encourage a healthy diet, reduce stress and promote emotional wellbeing might help women in early pregnancy (or planning a pregnancy) reduce their risk of miscarriage. Findings of increased risk associated with previous termination, stress, change of partner and low pre-pregnancy weight are noteworthy, and we recommend further work to confirm these findings in other study populations.

The National Children's Study: a 21-year prospective study of 100,000 American children

Prospective, multiyear epidemiologic studies have proven to be highly effective in discovering preventable risk factors for chronic disease. Investigations such as the Framingham Heart Study have produced blueprints for disease prevention and saved millions of lives and billions of dollars. To discover preventable environmental risk factors for disease in children, the US Congress directed the National Institute of Child Health and Human Development, through the Children's Health Act of 2000, to conduct the National Children's Study. The National Children's Study is hypothesis-driven and will seek information on environmental risks and individual susceptibility factors for asthma, birth defects, dyslexia, attention-deficit/hyperactivity disorder, autism, schizophrenia, and obesity, as well as for adverse birth outcomes. It will be conducted in a nationally representative, prospective cohort of 100,000 US-born children. Children will be followed from conception to 21 years of age. Environmental exposures (chemical, physical, biological, and psychosocial) will be assessed repeatedly during pregnancy and throughout childhood in children's homes, schools, and communities. Chemical assays will be performed by the Centers for Disease Control and Prevention, and banks of biological and environmental samples will be established for future analyses. Genetic material will be collected on each mother and child and banked to permit study of gene-environment interactions. Recruitment is scheduled to begin in 2007 at 7 Vanguard Sites and will extend to 105 sites across the United States. The National Children's Study will generate multiple satellite studies that explore methodologic issues, etiologic questions, and potential interventions. It will provide training for the next generation of researchers and practitioners in environmental pediatrics and will link to planned and ongoing prospective birth cohort studies in other nations. Data from the National Children's Study will guide development of a comprehensive blueprint for disease prevention in children.

Effects of occupational solvent exposure on reproductive hormone concentrations and fecundability in men

BACKGROUND

Little is known about the effects of organic solvents on male reproductive health. To assess fertility and reproductive endocrine function in solvent-exposed men, we investigated time-to-pregnancy using a retrospective cohort design and cross-sectionally measured reproductive hormone concentrations in painters and millwrights compared to a reference group of carpenters.

METHODS

Detailed occupational, exposure, medical, and time-to-pregnancy histories were obtained by telephone interview. Plasma luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone concentrations were determined by immunoassay. Exposure indices, which summarized working life exposure to total solvents, chlorinated solvents, aromatic solvents, and thinners, degreasers, varnishes, and adhesives as a category were calculated from exposure histories.

RESULTS

FSH concentrations increased significantly with increasing exposure indices for all solvents and for chlorinated solvents. There were no significant associations of solvent exposure indices with LH or testosterone levels. LH, FSH, and testosterone concentrations also did not differ by job title. Using Cox regression, time-to-pregnancy was non-significantly longer in the painters and millwrights than the carpenters. There was no significant association between time-to-pregnancy and any of the solvent exposure indices; however, it should be noted that some of the pregnancies occurred more than 20 years previously, potentially reducing the reliability of the retrospectively collected pregnancy and exposure data.

CONCLUSIONS

The significant associations between FSH levels and solvent exposure indices suggest the potential for adverse effects of solvent exposures on reproductive function in men.

The National Women's Health Study: assembly and description of a population-based reproductive cohort

Background

Miscarriage is a common event but is remarkably difficult to measure in epidemiological studies. Few large-scale population-based studies have been conducted in the UK.

Methods

This was a population-based two-stage postal survey of reproductive histories of adult women living in the United Kingdom in 2001, sampled from the electronic electoral roll. In Stage 1 a short "screening" questionnaire was sent to over 60,000 randomly selected women in order to identify those aged 55 and under who had ever been pregnant or ever attempted to achieve a pregnancy, from whom a brief reproductive history was requested. Stage 2 involved a more lengthy questionnaire requesting detailed information on every pregnancy (and fertility problems), and questions relating to socio-demographic, behavioural and other factors for the most recent pregnancy in order to examine risk factors for miscarriage. Data on stillbirth, multiple birth and maternal age are compared to national data in order to assess response bias.

Results

The response rate was 49% for Stage 1 and 73% for the more targeted Stage 2. A total of 26,050 questionnaires were returned in Stage 1. Of the 17,748 women who were eligible on the grounds of age, 27% reported that they had never been pregnant and had never attempted to conceive a child. The remaining 13,035 women reported a total of 30,661 pregnancies. Comparison of key reproductive indicators (stillbirth and multiple birth rates and maternal age at first birth) with national statistics showed that the data look remarkably similar to the general population.

Conclusions

This study has enabled the assembly of a large population-based dataset of women's reproductive histories which appears unbiased compared to the general UK population and which will enable investigation of hard-to-measure outcomes such as miscarriage and infertility.

Fever in pregnancy and risk of fetal death: a cohort study

BACKGROUND

Hyperthermia acts as a teratogen in some animals where it can induce resorption of the fetus and fetal death. Fever during pregnancy, especially in the period of embryogenesis, is also suspected as being a risk factor for fetal death in human beings. We did a large cohort study in Denmark to investigate this possibility.

METHODS

We interviewed 24040 women who were recruited in the first half of pregnancy to the Danish National Birth Cohort Study, and obtained information on the number of fever incidents during the first 16 weeks of pregnancy. For each fever episode, the highest measured body temperature, duration of incident, and gestational age were recorded. Outcomes of pregnancies were identified through linkage with the Civil Registration System and the National Discharge Registry. Cox's regression with time-dependent variables was used to estimate the relative risk of fetal death, taking delayed entry into account.

FINDINGS

1145 pregnancies resulted in a miscarriage or stillbirth (4.8%). During the first 16 pregnancy weeks 18.5% of the women experienced at least one episode of fever. However, we found no association between fever in pregnancy and fetal death before or after adjustment for known risk factors of fetal death (relative risk 0.95 [95% CI 0.80-1.13]). This finding was consistent irrespective of measured maximum temperature, duration and number of fever incidents, or the gestational time of the fever incident, and was observed for fetal death in all three trimesters of pregnancy.

INTERPRETATION

We found no evidence that fever in the first 16 weeks of pregnancy is associated with the risk of fetal death in clinically recognised pregnancies.

Reliability of reporting on life-style and agricultural factors by a sample of participants in the Agricultural Health Study from Iowa

Repeat interviews from 4,088 Iowa pesticide applicators participating in the Agricultural Health Study provided the opportunity to evaluate the reliability of self-reported information on pesticide use and various demographic and life-style factors. Self-completed questionnaires were administered 1 year apart when participants returned to county agricultural extension offices for pesticide certification or training. Percentage agreement for ever-/never-use of specific pesticides and application practices was quite high, generally ranging from 70% to more than 90%, and did not vary by age, educational level, or farm size. Agreement was lower (typically 50-60%) for duration, frequency, or decade of first use of specific pesticides. Level of agreement regarding pesticide use in this population is similar to that generally found for factors typically used in epidemiologic studies such as tobacco use and higher than typically reported for diet, physical activity, and medical conditions.

The North Cumbria Community Genetics Project

The aim of the North Cumbria Community Genetics Project is to establish a store of DNA, plasma, and viable cells from a cohort of around 8000 Cumbrian infants. To meet this objective, specimens of umbilical cord blood and tissue will be collected with maternal consent from babies born at the West Cumberland Hospital, Whitehaven over a five year period from January 1996. These samples will be used in a series of genetic and epidemiological studies investigating the interaction between genes, the environment, and health. There is little population movement in West Cumbria and so it will be possible to follow many of the babies throughout their childhood and to investigate the relationship between their genetic constitution and health outcome.