Serum concentration of CA-125 during the first trimester of normal and abnormal pregnancies.

A prospective study was initiated to closely examine maternal serum concentrations of CA-125 during the early first trimester of normal and abnormal pregnancies. Sequential serum specimens were obtained from 43 women with a normal intrauterine pregnancy, 20 with a surgically confirmed ectopic gestation and 10 whose pregnancies ended in spontaneous abortion. In normal pregnancies the CA-125 levels increased significantly from the first week after the missed menses (39.9 +/- 8.2 U/mL [mean +/- SEM]) to the second week (48.3 +/- 6.9 U/mL) (P less than .05) and from the second to the third week (62.5 +/- 9.8) (P less than .05). After the third week after the missed menses the mean CA-125 serum concentrations plateaued, but levels observed during the fourth (59.6 +/- 8.8 U/mL) and fifth (48.8 +/- 7.2 U/mL) weeks were still significantly greater than at week 1. In addition, the mean CA-125 concentrations were significantly higher in normal pregnancies than in ectopic gestations during the second, third and fourth weeks after the missed menses. Although there was a tendency for the CA-125 levels to be lower in women who had a spontaneous abortion when compared to normals, these differences were not statistically significant. Serum levels of CA-125 may prove useful in monitoring early pregnancy.