1 Physiology of pain in labour

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Reflex responses do not necessarily signify pain, British Medical Journal, 313, 797, 10.1136/bmj.313.7060.797 Lowe, 1987, Parity and pain during parturition, Obstetrics, Gynecology and Neonatal Nursing, 340, 10.1111/j.1552-6909.1987.tb01593.x Lowe, 1989, Explaining the pain of active labour: the importance of maternal confidence, Research in Nursing Health, 12, 237, 10.1002/nur.4770120406 Lyrenas, 1987, Endorphin activity in cerebrospinal fluid prior to elective Caesarean section and in early puerperium, Upsala Journal of Medical Sciences, 92, 37, 10.3109/03009738709178676 Mahomed, 1995, Labour experience, maternal mood and cortisol and catecholamine levels in low-risk primiparous women, Journal of Psychosomatic Obstetrics and Gynecology, 16, 181, 10.3109/01674829509024467 Malmberg, 1993, Spinal nitric oxide synthesis inhibition blocks NMDA-induced thermal hyperalgesia and produces antinociception in the formalin test in rats, Pain, 54, 291, 10.1016/0304-3959(93)90028-N Maves, 1992, Anti-nociception synergy between intrathecal morphine and lidocaine during visceral and somatic nociception in the rat, Anesthesiology, 76, 91, 10.1097/00000542-199201000-00014 McCullagh, 1997, Do fetuses feel pain? Can fetal suffering be excluded beyond reasonable doubt?, British Medical Journal, 314, 302, 10.1136/bmj.314.7076.302a Medina, 1993, 17 β-estradiol and progesterone positively modulate spinal cord dynorphin: relevance to the analgesia of pregnancy, Neuroendocrinology, 58, 310, 10.1159/000126555 Meller, 1992, Production of endogenous nitric oxide and activation of soluble guanate cyclase are required for N-methyl-d-aspartate produced facilitation of the nociceptive tail-flick reflex, European Journal of Pharmacology, 214, 93, 10.1016/0014-2999(92)90102-A Melzack, 1984, The myth of painless childbirth, Pain, 19, 321, 10.1016/0304-3959(84)90079-4 Melzack, 1989, Labour pain: correlations with menstrual pain and acute lower back pain before and during pregnancy, Pain, 36, 225, 10.1016/0304-3959(89)90027-4 Melzack, 1991, Labour pain: effect of maternal position on front and back pain, Journal of Pain Symptom Management, 6, 476, 10.1016/0885-3924(91)90003-M Melzack, 1981, Labour is still painful after prepared childbirth training, Canadian Medical Association Journal, 125, 357 Melzack, 1984, Severity of labour pain: influence of physical as well as psychological variables, Canadian Medical Association Journal, 130, 579 Molina, 1997, Pain in the first stage of labor: relationship to patients position, Journal of Pain Symptom Management, 13, 98, 10.1016/S0885-3924(96)00270-9 Moran, 1982, Attitudinal and demographic factors influencing mother's choice of childbirth procedures, American Journal of Obstetrics and Gynecology, 142, 846, 10.1016/S0002-9378(16)32530-3 Neumark, 1985, Effects of epidural analgesia on plasma catecholamines and cortisol in parturition, Acta Anaesthesiologica Scandinavica, 29, 555, 10.1111/j.1399-6576.1985.tb02253.x Niven, 1989, Do low levels of labour pain reflect low sensitivity to noxious stimulation?, Social Science and Medicine, 29, 585, 10.1016/0277-9536(89)90204-9 Olofsson, 1997, Increased cerebrospinal fluid concentration of aspartate but decreased concentration of nitric oxide breakdown products in women experiencing visceral pain during active labour, Neuroreport, 8, 995, 10.1097/00001756-199703030-00035 Pearson, 1973, The effect of continuous lumbar epidural analgesia upon maternal acid base balance and arterial lactate concentration during the second stage of labour, Journal of Obstetrics and Gynaecology of the British Commonwealth, 80, 225, 10.1111/j.1471-0528.1973.tb02189.x Pearson, 1974, The effect of continuous lumbar epidural analgesia upon fetal acid-base status during the second stage of labour, Journal of Obstetrics and Gynaecology of the British Commonwealth, 81, 975, 10.1111/j.1471-0528.1974.tb00417.x Peters, 1987, Sensory innervation of the external and internal genitalia of the female rat, Brain Research, 408, 199, 10.1016/0006-8993(87)90372-6 Price, 1987, Sensory-affective relationships among different types of clinical and experimental pain, Pain, 28, 297, 10.1016/0304-3959(87)90065-0 Ranta, 1995, The effect of maternal obesity of labour and labour pain, Anaesthesia, 50, 322, 10.1111/j.1365-2044.1995.tb04608.x Ranta, 1995, Paracervical block—a viable alternative for labour pain relief?, Acta Obstetrica Scandinavica, 74, 122, 10.3109/00016349509008919 Reading, 1985, Psychosocial predictors of labour pain, Pain, 22, 309, 10.1016/0304-3959(85)90031-4 Romano, 1988, Estrogen increases proenkephalin messenger ribonucleic acid levels in the ventromedial hypothalamus of the rat, Molecular Endocrinology, 2, 1320, 10.1210/mend-2-12-1320 Sander, 1987, Spinal cord mediation of the opioid analgesia of pregnancy, Brain Research, 408, 389, 10.1016/0006-8993(87)90412-4 Sander, 1989, Spinal dynorphin involvement in the analgesia of pregnancy: effects of intrathecal dynorphin antisera, European Journal of Pharmacology, 159, 205, 10.1016/0014-2999(89)90708-5 Sangoul, 1975, Effect of regional analgesia on maternal oxygen consumption during the first stage of labour, American Journal of Obstetrics and Gynecology, 12, 1080, 10.1016/S0002-9378(16)33592-X Shnider, 1979, Uterine blood flow and plasma norepinephrine changes during maternal stress in the pregnant ewe, Anaesthesiology, 50, 524, 10.1097/00000542-197906000-00010 Stein, 1993, Peripheral mechanisms of opioid analgesia, Anesthesia and Analgesia, 76, 182, 10.1213/00000539-199301000-00031 Steinbrook, 1982, Dissociation of plasma and cerebrospinal fluid beta-endorphin like immunoactivity levels during pregnancy and parturition, Anesthesia and Analgesia, 61, 893, 10.1213/00000539-198211000-00001 Tarapacki, 1992, Gastric vagotomy blocks opioid analgesia enhancement produced by placental ingestion, Physiological Behaviour, 52, 179, 10.1016/0031-9384(92)90449-C Tarapacki, 1993, Ingestion of amniotic fluid by postpartum rats enhances morphine antinociception without liability to maternal behaviour, Physiology and Behavior, 57, 209, 10.1016/0031-9384(94)00275-A Toniolo, 1987, Spontaneous maternal analgesia during birth in rats, vol. 15, 100 Tseng, 1995, Differential ontogenesis of thermal and mechanical antinociception induced by morphine and beta-endorphin, European Journal of Pharmacology, 277, 71, 10.1016/0014-2999(95)00064-R Varrassi, 1989, Effects of physical activity on maternal plasma beta-endorphin levels and perception of labour pain, American Journal of Obstetrics and Gynecology, 160, 707, 10.1016/S0002-9378(89)80065-1 Viscomi, 1997, Duration of intrathecal labour analgesia: early versus advanced labour, Anesthesia and Analgesia, 84, 1108, 10.1213/00000539-199705000-00028 Waldenstrom, 1996, The complexity of labour pain: experiences of 278 women, Journal of Psychosomatic Obstetrics and Gynecology, 17, 215, 10.3109/01674829609025686 Ward, 1997, Acute pain and the obstetric patient: recent developments in analgesia for labour and delivery, International Anesthesiology Clinics, 35, 83, 10.1097/00004311-199703520-00007 Weisenberg, 1989, Cultural and educational influences on pain of childbirth, Journal of Pain Symptom Management, 4, 13, 10.1016/0885-3924(89)90059-6 Westgren, 1986, Maternal and fetal endocrine stress response at vaginal delivery with and without epidural block, Journal of Perinatal Medicine, 14, 235, 10.1515/jpme.1986.14.4.235 Whipple, 1985, Elevation of pain threshold by vaginal stimulation in women, Pain, 21, 357, 10.1016/0304-3959(85)90164-2 Whipple, 1990, Sensory thresholds during the antepartum, intrapartum and post partum periods, International Journal of Nursing Studies, 27, 213, 10.1016/0020-7489(90)90036-I Woolf, 1993, Preemptive analgesia—treating postoperative pain by preventing the establishment of central sensitization, Anesthesia and Analgesia, 77, 362, 10.1213/00000539-199377020-00026 Wuitchik, 1990, Relationships between pain, cognitive activity and epidural analgesia during labour, Pain, 41, 125, 10.1016/0304-3959(90)90016-7