Abstract
Most studies of spontaneous abortion are subject to left truncation, because conception is not observed and thus pregnant women are enrolled postconception. Cox regression can account for left truncation but uses gestational age data, which may be inaccurate. Dating is affected by reporting errors and variability in the day of ovulation. These errors may be differential by outcome, because gestational ages are more likely to be clinically corrected in continuing pregnancies than in pregnancies ending in spontaneous abortion. Errors may be differential by exposure status as well, if exposures affect the time of ovulation. The authors designed a simulation to examine bias caused by errors in gestational age. Pregnancies were assigned true and alternative gestational ages using different assumptions about random reporting error and error due to variation in the time between the last menstrual period and ovulation. In separate scenarios, the errors were differential by outcome, differential by exposure, differential by both exposure and outcome, or nondifferential. Hazard ratios were compared using accurate versus erroneous gestational ages. For proportional hazards, bias was only introduced when the error in gestational age was differential by exposure status. Bias was greatest when the magnitude of error for pregnancies at higher risk was much larger than that for pregnancies at lower risk.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1126-1136 |
| Number of pages | 11 |
| Journal | American Journal of Epidemiology |
| Volume | 164 |
| Issue number | 11 |
| DOIs | |
| State | Published - Dec 2006 |
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Keywords
- Abortion, spontaneous
- Bias (epidemiology)
- Gestational age
- Pregnancy
- Proportional hazards models
ASJC Scopus subject areas
- Epidemiology
Cite this
Misclassification of gestational age in the study of spontaneous abortion. / Howards, Penelope P.; Hertz-Picciotto, Irva; Weinberg, Clarice R.; Poole, Charles.
In: American Journal of Epidemiology, Vol. 164, No. 11, 12.2006, p. 1126-1136.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Misclassification of gestational age in the study of spontaneous abortion
AU - Howards, Penelope P.
AU - Hertz-Picciotto, Irva
AU - Weinberg, Clarice R.
AU - Poole, Charles
PY - 2006/12
Y1 - 2006/12
N2 - Most studies of spontaneous abortion are subject to left truncation, because conception is not observed and thus pregnant women are enrolled postconception. Cox regression can account for left truncation but uses gestational age data, which may be inaccurate. Dating is affected by reporting errors and variability in the day of ovulation. These errors may be differential by outcome, because gestational ages are more likely to be clinically corrected in continuing pregnancies than in pregnancies ending in spontaneous abortion. Errors may be differential by exposure status as well, if exposures affect the time of ovulation. The authors designed a simulation to examine bias caused by errors in gestational age. Pregnancies were assigned true and alternative gestational ages using different assumptions about random reporting error and error due to variation in the time between the last menstrual period and ovulation. In separate scenarios, the errors were differential by outcome, differential by exposure, differential by both exposure and outcome, or nondifferential. Hazard ratios were compared using accurate versus erroneous gestational ages. For proportional hazards, bias was only introduced when the error in gestational age was differential by exposure status. Bias was greatest when the magnitude of error for pregnancies at higher risk was much larger than that for pregnancies at lower risk.
AB - Most studies of spontaneous abortion are subject to left truncation, because conception is not observed and thus pregnant women are enrolled postconception. Cox regression can account for left truncation but uses gestational age data, which may be inaccurate. Dating is affected by reporting errors and variability in the day of ovulation. These errors may be differential by outcome, because gestational ages are more likely to be clinically corrected in continuing pregnancies than in pregnancies ending in spontaneous abortion. Errors may be differential by exposure status as well, if exposures affect the time of ovulation. The authors designed a simulation to examine bias caused by errors in gestational age. Pregnancies were assigned true and alternative gestational ages using different assumptions about random reporting error and error due to variation in the time between the last menstrual period and ovulation. In separate scenarios, the errors were differential by outcome, differential by exposure, differential by both exposure and outcome, or nondifferential. Hazard ratios were compared using accurate versus erroneous gestational ages. For proportional hazards, bias was only introduced when the error in gestational age was differential by exposure status. Bias was greatest when the magnitude of error for pregnancies at higher risk was much larger than that for pregnancies at lower risk.
KW - Abortion, spontaneous
KW - Bias (epidemiology)
KW - Gestational age
KW - Pregnancy
KW - Proportional hazards models
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U2 - 10.1093/aje/kwj327
DO - 10.1093/aje/kwj327
M3 - Article
C2 - 16985078
AN - SCOPUS:33845213761
VL - 164
SP - 1126
EP - 1136
JO - American Journal of Epidemiology
JF - American Journal of Epidemiology
SN - 0002-9262
IS - 11
ER -