Objective To establish reference intervals for cancer antigen 125 (CA-125) in women with expected normal pregnancy, delivery, and early postpartum period. Design Prospective observational study. Setting Department of Clinical Biochemistry and Obstetrics, Copenhagen University Hospital, Gentofte, Denmark.
Population Eight hundred and one women with expected normal pregnancies were investigated. Of these, 640 delivered vaginally, 82 by emergency cesarean section, and 79 by elective cesarean section; 720 women had uncomplicated pregnancies.
Methods Samples were collected at gestational weeks 13-20, 21-28, 29-34, 35-42, during labor, and on first and second day postpartum. Reference intervals were calculated for each gestational period as recommended by the International Federation of Clinical Chemistry and Laboratory Medicine.
Main outcome measures Concentration of serum CA-125 during the gestational period and around delivery.
Results CA-125 was fairly stable below 35 U/mL during pregnancy but increased markedly during vaginal delivery, to a minor degree during emergency cesarean section, and only slightly during elective cesarean section. In the early postpartum period, CA-125 decreased with an apparent half-life of 24 h.
Conclusions The CA-125 cut-off value (<35 U/mL) used for non-pregnant women can be used for women during pregnancy after gestational week 13 as a supplement to ultrasound evaluation of ovarian cysts. The wide range of CA-125 concentration during normal pregnancies makes it unlikely that small fluctuations in CA-125 can be clinically useful for identifying other conditions. Measuring CA-125 around the time of delivery is not recommended. Gestational age-specific reference intervals during normal pregnancy are not needed.