A PROSPECTIVE, RANDOMIZED STUDY OF THE CHORIONIC GONADOTROPIN-TIME RELATIONSHIP IN EARLY GESTATION - CLINICAL IMPLICATIONS

Objective: To investigate the hCG-time relationship in early pregnancy . Design: Prospective, randomized study. Setting: Pregnant human volun teers in a university-based clinical research environment. Patients: N ormal pregnant women with viable singleton pregnancies, conceived spon taneously or after ovulation induction. Interventions: Vaginal ultraso und was performed, and blood samples were obtained for hormone paramet ers between 20 and 30 days after conception. The timing of the tests w as determined by random assignment using sealed envelopes. Main Outcom e Measure: Serum hCG. Results: The log hCG-time relationship was linea r, both during the first 20 days and between 20 and 30 days after conc eption. The inclusion of a quadratic term in either regression was not statistically significant. The slopes of the two regression lines wer e also not statistically different. Conclusion: For practical purposes , the hCG-time relationship in early pregnancy can be treated as log-l inear, but short sampling intervals should be used if doubling times a re to be calculated from paired samples.