Nitric oxide metabolites in cervical fluid during pregnancy: further evidence for the role of cervical nitric oxide in cervical ripening.
OBJECTIVE
Cervical tissue expresses all the isoenzymes of nitric oxide synthase. We studied the concentrations of nitric oxide metabolites in the cervical fluid in nonpregnant (n = 11) and pregnant women (n = 106).


METHODS
Cervical fluid was collected into a Dacron polyester swab, and nitric oxide metabolites were eluted into physiologic saline solution, which was assayed for nitric oxide metabolites with the Griess reaction. The detection limit of the method is 0.2 micromol/L.


RESULTS
Cervical fluid nitric oxide metabolite was detectable in 46% of nonpregnant women (median, <0.2 micromol/L; 95% CI, 0-49), in 63% of women in early pregnancy (median, 11 micromol/L; 95% CI, 0-23) and in 82% of women in late pregnancy (median, 128 micromol/L; 95% CI, 21-276). In late pregnancy, the cervical fluid nitric oxide metabolite level was higher in women with Bishop score of > or =6 (median, 163 micromol/L; 95% CI, 105-276) than in women with Bishop score of <6 (median, 86 micromol/L; 95% CI, 21-99). Cervical fluid nitric oxide metabolite concentration before the onset of labor in parous women (median, 97 micromol/L; 95% CI, 78-283) was higher (P =.008) than that in nulliparous women (median, 28 micromol/L; 95% CI, 0-95). Cervical fluid nitric oxide metabolites before the initiation of labor (median, 33 micromol/L; 95% CI, 0-95) rose to 3.5-fold (median, 115 micromol/L; 95% CI, 78-284) after the commencement of uterine contractions and showed a significant relationship to Bishop score (r = 0.39, P =.01). Cervical fluid nitric oxide metabolite concentrations were not relative to simultaneous plasma nitric oxide metabolite levels (n = 41 women, r = 0.14, P =.41). Rupture of fetal membranes tended to decrease cervical fluid nitric oxide metabolite levels, whereas gentle cervical manipulation elevated it 6.6-fold in 1 minute. The administration of glyceryl trinitrate (0.5 mg, nitric oxide donor) intracervically resulted in a significant rise in the cervical fluid nitric oxide metabolite level in 2 minutes.


CONCLUSIONS
Cervical fluid nitric oxide metabolite level rises after cervical ripening, nitric oxide donor administration, or cervical manipulation, which supports a role for cervical nitric oxide in cervical ripening.
Väisänen-Tommiska
Mervi
M
Department of Obstetrics and Gynecology, Helsinki University Central Hospital, Finland.
Nuutila
Mika
M
Aittomäki
Kristiina
K
Hiilesmaa
Vilho
V
Ylikorkala
Olavi
O
D000287:Administration, Topical; D000328:Adult; D001826:Body Fluids / Q000378:metabolism*; D020070:Cervical Ripening / Q000502:physiology*; D002584:Cervix Uteri / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006801:Humans; D007743:Labor, Obstetric / Q000378:metabolism; D009569:Nitric Oxide / Q000097:blood / Q000378:metabolism*; D005996:Nitroglycerin / Q000008:administration & dosage; D011247:Pregnancy / Q000378:metabolism*; D015149:Tocolytic Agents / Q000008:administration & dosage
D015149:Tocolytic Agents; D009569:Nitric Oxide; D005996:Nitroglycerin