The objective of this study was to develop and validate algorithms to detec
t pregnancies from the time of first clinical recognition by using Kaiser P
ermanente automated databases from Portland, Oregon. In 1993-1994, the auth
ors evaluated these databases retrospectively to identify markers indicativ
e of initial clinical detection of pregnancy and pregnancy outcomes. Pregna
ncy markers were found for 99% of the women for whom pregnancy outcomes wer
e included in the automated databases, and pregnancy outcomes were identifi
ed for 77% of the women for whom there were pregnancy markers. The earliest
marker most predictive of a pregnancy outcome was a positive human chorion
ic gonadotropin test; least predictive was an obstetric outpatient visit. M
edical record review indicated that in a sample of women with pregnancy mar
kers in the database, an estimated 6% of pregnancy outcomes (primarily earl
y fetal deaths and elective terminations) were lost. Pregnancies were first
captured in automated databases 6-8 weeks after the last menstrual period,
and a combination of a positive human chorionic gonadotropin test and an o
utpatient obstetric visit was the most sensitive and specific early marker
of pregnancy. When combined with automated pharmacy records, these database
s may be valuable tools for evaluating prescription drug effects on all maj
or outcomes of clinically recognized pregnancies.