Objective:We hypothesize that artificial stimulation of the cervix causes an acute secretion of maternal prolactin (PRL) that mimics PRL secretion during the second stage of human labor.
Methods:Eighteen women scheduled for first-trimester therapeutic abortion had a blood sample drawn at the following times: before and after laminaria tent (LT) insertion for cervical ripening, 18-24 hours later upon entry in the procedure room, after LT removal, during instrumental cervical dilatation and uterine evacuation by suction curretage, soon after evacuation, and ½ hour and 1 hour after evacuation. Local cervical anesthesia, intravenous analgesics, and sedation were administered before the procedure. Blood serum was assayed for PRL, human chorionic gonadotropin (hCG), and estradiol.
Results:The initial PRL levels were 34 ng/mL ± 4.2 standard error of the mean (SEM) and did not change after 18-24 hours of LT placement nor after LT removal. However, PRL increased significantly (t = 5.8; P = .00001) over basal levels by 204% ± 15 at the time of instrumental dilatation and rose to 378% ± 33 at ½ hour postevacuation. After 1 hour, PRL had declined to 173% ± 10%. Serum levels of estradiol and hCG changed only after evacuation.
Conclusion:Artificial stimulation of the cervix causes an immediate surge in PRL levels. We suggest that the acute increase in pituitary PRL secretion that occurs during the second stage of labor results from a neural signal from the cervix and not from endocrine changes associated with labor.
1. Rigg LA, Yen SSC, Multiphasic prolactin secretion during parturition in human subjects. Am J Obstet Gynecol1997;128:215-218.
2.
2. Fernandes PA, Szelazek JT, Reid GJ, Wodzicki AM, Allardice JG, McChosen JA. Phasic maternal prolactin secretion during spontaneous labor is associated with cervical dilatation and second-stage uterine activity. J Soc Gynecol Invest1995;2:597-601.
3.
3. Fernandes PA, Koodoo SR, Wodzicki AM, Allardice JG, McCoshen JA. Maternal prolactin secretion is phasic during induced term and post-term labor. J Soc Gynecol Invest1997;4:81-85.
4.
4. Gorospe WC, Freeman ME. The effects of various methods of cervical stimulation on continuation of prolactin surges in rats. Proc Soc Exp Biol Med1981;167:78-82.
5.
5. Russell KP, Biswas MK. Obstetric analgesia & anesthesia. In: Pernoll ML, ed. Current obstetric and gynecologic diagnosis and treatment. Norwalk, Connecticut: Appleton & Lange, 1991:508-535.
6.
6. Norman GR, Streiner DL. PDQ statistics. Hamilton, Ontario: BC Decker, 1986:47-70.
7.
7. Friesen HG, Hwang P, Guyda H, Tolis G, Tyson J, Meyers R. A radioimmunoassay for human prolactin. In: Boyne AR, Griffiths, eds. Physiological and pharmacological factors which affect the secretion of prolactin. 4th Tenovus Workshop on Prolactin and Carcinogensis. Cardiff: Alpha Omega Publishing, 1972:60-80.
8.
8. Fournier PJR, Desjardins PD, Friesen HG. Current understanding of human prolactin physiology and its diagnostic and therapeutic applications: A review. Am J Obstet Gynecol1974;118:337-343.
9.
9. Bigazzi M, Nardi E. Prolactin and relaxin: Antagonism on the spontaneous motility of the uterus. J Clin Endocrinol Metab1981;53:665-667.
10.
10. Kornyei JL, Lei ZM, Rao CV. Human myometrial smooth muscle cells are novel targets of direct regulation by human chorionic gonadotropin. Biol Reprod1995;49:1149-1157.
11.
11. McCoshen JA, Fernandes PA, Dubyna D, Wodzicki AM, Roberts GK, Boroditsky RS. Studies on maternal and fetal prolactin immunoactivity and bioactivity during pregnancy, labor, and the early postpartum. Endocrinologist1994;4:470-476.
12.
12. McChosen JA, Fernandes PA, Tyson P, Sokolowski J, Tyson JE. Immediate and potential prolongel influence of pregnancy on prolactin secretion. J Soc Gynecol Invest1997;4(Suppl 1):127A-127A.
