Inverse ratio of hCG in peritoneal fluid to that in serum in normal and tubal pregnancies.

The ratio of hCG in peritoneal fluid (PF) to that in serum (S) was studied in 60 patients with normal pregnancies (5th-15th wk of gestation = control group) and in 12 tubal pregnancies, 7 tubal abortions (5th-10th wk of amenorrhea) and one case of an early interstitial pregnancy (8th wk). The PF level in the control group was in every patient lower than in S independent of the gestational age. The ratio PF to S ranged from 0.24 to 0.87 (mean +/- S.E.: 0.51 +/- 0.02). In contrast to this, the patients with tubal pregnancy and tubal abortion showed in each case higher PF levels than in S. The ratio in the group with tubal pregnancy ranged from 1.1 to 374 (54 +/- 30) and in the group with tubal abortion from 1.2 to 162 (33 +/- 23). The difference in the ratio between the control group and both tubal pregnancy and tubal abortion was highly significant (P less than 0.001). The ratio of PF to S in the patient with interstitial pregnancy (0.73) did not differ from the control group. At the time of investigation, the S levels in all but 2 patients with ectopic pregnancy were below the range for normal pregnancy of the same gestational age. These findings indicate that the hCG ratio of PF to S may be dependent on the location of the gestational product.