1. Early pregnancy losses in in vitro fertilization and oocyte donation
Carlos Simón, M.D., Jose Landeras, M.D., Jose L Zuzuarregui, Ph.D., Julio Cesar Martı́n, Ph.D., José Remohı́, M.D., Antonio Pellicer, M.D. 
Fertility and Sterility 
Volume 72, Issue 6, Pages (December 1999)
DOI: /S (99)

2. FIGURE 1
Results of oocyte donation and IVF cycles. ∗The highest urine β-hCG value obtained in the control group for each technique studied was considered the threshold level. Any value above the threshold for 2 consecutive days was considered positive for the purposes of the study. †Number of patients with positive urinary β-hCG from day 6 to 14 after transfer with a negative pregnancy test at day 16. Numbers in parentheses are percentages.
Simón. Early pregnancy losses. Fertil Steril 1999.
Fertility and Sterility  , DOI: ( /S (99) )