A CHALLENGE TO THE CONCEPT OF TUBAL REFLUX TO EXPLAIN THE RISE AND FALL OF CA125 IN SERUM DURING THE FIRST TRIMESTER

Although amniotic fluid concentrations of cancer antigen (CA) 125 rise during the first two trimesters of pregnancy, the serum concentration s of CA125 peak during the first trimester and drop to non-pregnant va lues in the second and third trimester, A previous hypothesis to expla in this phenomenon was that in the early first trimester decidual CA12 5 gains access to the maternal compartment via 'tubal reflux' and subs equent absorption by peritoneal lymphatics, However, as pregnancy adva nces, the decidua capsularis fuses with the decidua parietalis, thus o bliterating the endometrial cavity at 10-12 weeks; the Fallopian tubes thus become functionally obstructed, To test this hypothesis, we eval uated early first trimester CA125 concentrations in women conceiving b y in-vitro fertilization (IVF) and embryo transfer with patent tubes ( group 1) and in those conceiving by IVF and embryo transfer with bilat eral tubal occlusion (group 2), We also compared those conceiving with human menopausal gonadotrophin therapy for ovulation induction withou t assisted reproduction (group 3) and those conceiving without fertili ty drugs in assisted reproduction (group 4). Mean CA125 concentrations were similar in groups 1-3; the mean CA125 concentration in group 4 w as lower but this difference was not statistically significant, probab ly due to the small sample size, These data do not support the concept that tubal reflux explains the rise and fall of serum concentrations of CA125, since these were equal in IVF conceptions with os without tu bal patency.