Prenatal diagnostic technology makes it possible to offer women the option of electively terminating pregnancies affected by birth defects. Excluding these pregnancies from epidemiologic studies may affect study results. We explored this effect using examples from the literature. We calculated the bias in the odds ratio caused by excluding prenatally diagnosed pregnancies when the exposure of interest is not correlated with the likelihood of terminating an affected pregnancy and when it is correlated with an increase or decrease in this likelihood. We assumed that control infants did not have birth defects. When the exposure is not associated with the likelihood of a pregnancy termination, studies excluding terminations suffer a loss of precision. When the exposure is associated with an increase or decrease in this likelihood, the odds ratios are biased toward or away from the null, respectively. The magnitude of the bias will vary according to characteristics of the study population such as the prevalence of the exposure and the frequency with which prenatal diagnosis and elective termination are used. Whenever possible, pregnancies terminated after prenatal diagnosis must be included in epidemiologic studies.
Prenatal diagnosis of fetal anomalies during the second trimester of pregnancy: their characterization and delineation of defects in pregnancies at risk
The absence of a relation between the periconceptional use of vitamins and neural-tube defects. National Institute of Child Health and Human Development Neural Tube Defects Study Group
Severity of abnormality influences decision to terminate pregnancies affected with fetal neural tube defects
Impact of prenatal diagnosis and elective termination on prevalence and risk estimates of neural tube defects in California, 1989-1991
Impact of prenatal diagnosis and elective termination on the prevalence of selected birth defects in Hawaii
Prenatal diagnosis and elective termination of Down syndrome in a racially mixed population in Hawaii, 1987-1996
Impact of demographic factors on prenatal diagnosis and elective pregnancy termination because of abdominal wall defects, Hawaii, 1986-1997
Current and potential impact of fetal diagnosis on prevalence and spectrum of serious congenital heart disease at term in the UK. British Paediatric Cardiac Association
Benzodiazepine use in pregnancy and major malformations or oral clefts. Pooled results are sensitive to zero transformation used
Patterns of first-year survival among infants with selected congenital anomalies in Texas, 1995-1997
Exploring adoption with clients: the need for adoption education within the genetic counseling profession
Residence, delivery and referral patterns of infants and fetuses with birth defects delivered in Hawaii, 1986-1999
Parental hope confronting scientific uncertainty: a test of ethics in maternal-fetal surgery for spina bifida
Estimating the proportion of all observed birth defects occurring in pregnancies terminated by a second-trimester abortion
Trends in congenital malformations, 1974-1999: effect of prenatal diagnosis and elective termination
Congenital malformations in the newborn population: a population study and analysis of the effect of sex and prematurity
Evolution of the frequency of congenital defects in newborn infants and fetuses from terminations of pregnancy after prenatal diagnosis in the period 1982-2009
Increasing detection rates of birth defects by prenatal ultrasound leading to apparent increasing prevalence. Lessons learned from the population-based registry of birth defects of Barcelona
The effect of terminations of pregnancy for fetal abnormalities on trends in mortality to one year of age in Western Australia
Feasibility of using the national hospital discharge survey to estimate the prevalence of selected birth defects
Including prenatal diagnoses in birth defects monitoring: Experience of the Metropolitan Atlanta Congenital Defects Program
Pregnancy termination following prenatal diagnosis of anencephaly or spina bifida: a systematic review of the literature
Importance of including all pregnancy outcomes to reduce bias in epidemiologic studies of neural tube defects--Texas, 1999 to 2005
The association between mountaintop mining and birth defects among live births in central Appalachia, 1996-2003
Is ambient heat exposure levels associated with miscarriage or stillbirths in hot regions? A cross-sectional study using survey data from the Ghana Maternal Health Survey 2007
Status of Comorbid Congenital Anomalies and Their Influence on Resource Use in Pediatric Inpatients: A Serial Cross-Sectional Study in Shanghai, China.
Original article: is the protective association between hyperemesis gravidarum and birth defects biased by pregnancy termination?
Birth defects encompass structural and functional alterations that occur during embryonic or fetal development and are present since birth. The cause may be genetic, environmental or unknown and can result in physical and/or mental impairment. Here is the latest research on birth defects.