1. CDC Birth certificate data: The Centers for Disease Control and Prevention’s (CDC) National Center for Health Statistics (NCHS) has been collaborating with colleagues in the State vital statistics offices to revise the certificates of live birth and death and the report of fetal death. This process is generally carried out every 10 to 15 years. Prior to 2003, the most recent revisions in effect were implemented in 1989. The 2003 revisions have recently been approved by the HHS Secretary and are going into effect in the States. Some States began the revision process in 2003, but full implementation in all States will be phased in over several years. A critical component of the recommendations for this revision focuses on fundamental changes in the way that data are collected, especially for births. Partly as a consequence of these recommendations, States are engaged in re-engineering their vital statistics systems as they implement the revisions.
https://www.cdc.gov/nchs/nvss/vital_certificate_revisions.html
Strong research question: What is the state-level prevalence of cesarean section?
The CDC birth certificate data consistently asks at the state level about several items, including mode of birth. Mode of birth is less prone to misclassification errors.
Weak research question: Does home birth increase the risk of poor neonatal outcome?
Because of inconsistencies in state reporting of home birth, most birth certificates cannot distinguish between planned and unplanned home birth, or identify home-birth transfers. These create problems of misclassification of the exposure. For instance, unplanned home births can have worse neonatal outcomes (often due to poor prenatal care), and home-birth transfers can also have worse outcomes (because they transferred for a medical reason). Thus, national studies of US home births have been limited in making causal claims. The largest cohort study to date on home birth, the UK Birth Place study, had full ascertainment of home births (better vital statistics in regards to home birth in the UK) and women there need to “book into” a home birth early in pregnancy (thus able to do an intention-to-treat analysis).
2. Diethylstilbestrol Adenosis Project (DESAD) - The DESAD began in 1974 at Baylor College of Medicine, Gundersen Clinic, Massachusetts General Hospital, the Mayo Clinic, and the University of Southern California. The DESAD, the largest DES cohort, included 4,014 DES Daughters and 1,033 unexposed women. Exposed women had documented evidence of DES exposure through review of prenatal records or by physician referral. The DESAD was assembled to conduct studies to determine if DES Daughters were at an increased risk for health problems related associated with their exposure to DES (Labarthe, 1978).
Strong research question: Does in utero DES exposure predict the development of endometrial cancer?
As the largest cohort of DES exposed girls, this is an ideal study question to examine the later-in-life outcomes of in utero DES exposure.
Weak research question: Did DES exhibit any effect-modification with environmental exposures on the outcome of clear cell adeonocarcinoma of the cervix?
Because the DES cohort was assembled only with detailed information gathered from prenatal records about DES, it would be difficult to examine DES’s interaction with any other exposures.
3. NHANES: A primary aim of NHANES is to collect and compile data on the health and nutritional status of study participants through a repeated cross-sectional design. Particular emphasis is placed on data regarding the prevalence of major diseases and risk factors for diseases. Information is derived from participant interviews as well as physical and laboratory examinations. Minority populations are oversampled to produce reliable statistics.
Strong research question: Has there been a change in the prevalence of morbid obesity in African Americans between the last two NHANES surveys? Repeated cross sectional survey designs can give important information about population trends in health.
Weak research question: How does the risk of endometrial cancer for morbidly obese African American women change as they age? Because this design requires individual level data as it changes over time, repeated cross sectional design would not work.