The pH as an important determinant of sperm-mucus interaction.

OBJECTIVE

To determine the clinical significance of endocervical mucus pH on sperm-mucus interaction during infertility investigation.

PATIENTS AND MATERIAL

Two hundred sixteen couples with a median duration of infertility of 4 years (range, 1 to 19 years) presenting at the infertility unit of the Women's University Hospital of Heidelberg, Germany.

MAIN OUTCOME MEASURES

Determination of endocervical pH by colorimetric and electrometric measurement and correlation of results with the outcome of postcoital testing (PCT) and other parameters of infertility investigation (semen and cervical mucus [CM] quality, microbial colonization of cervix and ejaculates, medical history, hormonal status, and specific medication) and the subsequent fertility in a prospective study. In vitro experiments with the sperm-cervical mucus penetration test (SCMPT) used as biological model.

RESULTS

The colorimetric determination of endocervical mucus pH is an easy method, suitable for routine clinical use, correlating significantly with electrometric measurement of pH. Median pH was 7.0 (range, 5.4 to 8.2). The mucus pH was significantly related with the results of PCT, even when mucus and semen variables were taken into account. No significant relationship was seen between the cervical index and mucus pH and the microbial colonization of cervix and ejaculates. The pH of endocervical secretions correlated with the peripheral hormonal status: low pH levels were significantly more frequent in patients with hyperandrogenemia, indicated by high testosterone and/or dehydroepiandrosterone sulfate levels before medication was started, and in hyperandrogenemic patients treated with dexamethasone than in the other women. Oral administration of estrogens led to a subtle alkalinization of the CM. With regard to subsequent fertility 6 months after pH testing, the pregnancy rate was significantly lower in women offering reduced mucus pH on occasion of the PCT in the group of couples with primary infertility and in couples with oligozoospermia of the male partner. The significant influence of pH on sperm-mucus interaction was confirmed in vitro with the SCMPT.

CONCLUSIONS

The results indicate that the pH of the CM, easily determined with pH indicator paper, is an important parameter of mucus quality with significant influence on spermatozoal viability in CM, which correlates with peripheral hormonal status and can be affected by oral medication with estrogens. Therefore the routine determination of pH on occasion of the PCT is recommended during infertility investigation.