How often does transperitoneal transmigration of sperm occur in effecting human pregnancy?

Abstract

Objective: To determine how often sperm transmigrates across the peritoneal cavity to effect intrauterine human pregnancy. Design: Two-hundred seventy-two women were identified with non-communicating rudimentary uterine horn pregnancies who had prior parity data available. All pregnancies in the “blind” rudimentary horns had no direct communication to the cervix or vagina and necessarily resulted from transperitoneal transmigration of either sperm or fertilized ova. All prior clinical pregnancies occurred in the unicornuate hemi-uterus with communication to the cervix. In 187 cases, the population fertility rate that was specific to each patient’s age, era, and country of origin was also available, such that the expected prior parity for each woman could be calculated. Materials and Methods: Between 1900–1999, 272 women with non-communicating uterine horn pregnancies were identified in the world literature who had prior pregnancy information. The total number of observed pregnancies prior to the incident rudimentary horn pregnancies was determined. For a subset of 187 women who had age, country, and era-specific fertility rate information available, the total number of expected prior pregnancies was also calculated. The proportional rudimentary horn pregnancy results were used as upper and lower bounds to infer the per pregnancy sperm transperitoneal transmigration rate. The actual prior parity frequency distribution for the 272 women was also determined and the best-fit per pregnancy probability of attaining a rudimentary horn pregnancy was calculated using the method of maximum likelihood estimation. Results: The total number of observed pregnancies prior to the incident 272 rudimentary horn pregnancies was 292, yielding a ratio of actual rudimentary to non-rudimentary uterine horn pregnancies of 0.93. For the subset of 187 women who had age, country, and era-specific fertility rate information available, the total number of actual prior pregnancies was 166 and the total number of expected prior pregnancies was 218 (ratios of rudimentary to non-rudimentary horn pregnancies of 1.13 and 0.86, respectively). These proportional rudimentary horn pregnancy results directly imply maximum and minimum per pregnancy sperm transmigration rates of 0.53 and 0.46, respectively. The actual prior parity frequency distribution for all 272 women was P0=136, P1=67, P2=30, P3=18, P4=8, P5=3, P6=8, P7=1, P8=0, and P9=1. Using maximum likelihood estimation, the best-fit probability of attaining a rudimentary horn gestation per pregnancy was 0.51 (Figure), with a range from 0.48 to 0.56 (p >0.05 in all cases, indicating no statistically significant difference between the actual prior parity distribution and the calculated parity distribution over this range). Conclusion: Intraperitoneal sperm transmigration occurs approximately half the time in effecting human pregnancy. In view of this result, it can be suggested that in order to minimize the risk of ectopic tubal pregnancy in cases where a woman has a unilaterally damaged fallopian tube and a normal contralateral salpinx, salpingectomy is the preferred surgical treatment rather than attempting tubal salvage and repair.