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The sympathoadrenal system is activated in both the mother and fetus during parturition. The fetal plasma catecholamines may reach extremely high levels during deliveries complicated by asphyxia.Increased maternal sympathoadrenal activity during labour or caesarean section may negatively affect uteroplacental blood flow with possible adverse effects on the fetus. Such an increase may be avoided by adequate maternal pain relief and by the sympathetic blockade which follows epidural anaesthesia.Fetal sympathoadrenal activation during parturition seems on the contrary to be of positive functional importance both for fetal circulatory regulation in utero a well as for the neonatal adaptation in terms of pulmonary function and metabolic stimulation.

Pethidine (100 mg) was administered i.m. to women in labor at different times before delivery. The interval before respiration in the newborn became sustained was shorter if pethidine was given less than one hour before delivery. The respiratory rate of the newborn increased after naloxone injection in 40 per cent of the cases, mostly when intrauterine exposure to pethidine exceeded one hour. The plasma concentrations of pethidine and norpethidine were measured in mother and newborn. The concentrations in the umbilical vein and artery indicted a continuous net transfer of pethidine from mother to fetus for approximately two hours. This correlated with the clinical finding of maximal neonatal depression 2-3 hours after maternal injection. The concentrations of norpethidine increased with a longer time interval between injection and delivery, but were probably too low to have any effect on the newborn. Neonatal depression seems to be related to the amount of unmetabolized pethidine that has been transferred from mother to fetus but not to norpethidine as had been suspected earlier.

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Twenty-four full-term nulliparae and their babies were studied. Twelve received lumbar epidural analgesia with bupivacaine (Marcain-adrenalin@) and twelve conventional obstetrical analgesia with meperidine (PetidinaD), chlorpromazine (Hibernalm), nitrous oxide and a pudendal nerve block with prilocaine (Citanestm). The acid-base balance was determined in fetal and maternal blood during labour and in neonatal blood after birth. The newborn infants were placed in incubators after birth and several clinical parameters were recorded during the first two hours. Epidural analgesia to the mothers resulted in a lower degree of metabolic acidosis than conventional obstetrical analgesia. The clinical and blood-chemical parameters recorded in this study indicated no harmful effects on the newborn infants after epidural analgesia to the mothers.

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A random sample of 798 primiparas was screened with clinical evaluation and radiologic low-dose pelvimetry of the pelvic outlet. The purpose was to study the accuracy of clinical evaluation in comparison with X-ray pelvimetry and to determine whether clinical evaluation could reveal any other factor influencing labor. A significant agreement between clinical and X-ray pelvimetry was found, but the sensitivity of clinical evaluation was low and as many as half the patients with a contracted pelvis, according to pelvimetry, were not detected. Delivery outcomes in two matched groups with similar pelvic outlet measurements but different clinical evaluation did not differ, indicating that clinical evaluation did not detect any other factor not revealed by X-ray pelvimetry.

The influence of pelvic outlet capacity on labor and the efficiency of routine low-dose radiological pelvimetry to anticipate dystocia during labor were studied prospectively among 1,429 unselected term primiparas, all having fetal head presentation and normal pregnancy. Outlet contraction was found in 0.9% and borderline outlet measurement in 5.3%. In 1,402 cases labor started spontaneously and 83 emergency cesarean sections were done. The incidence of cesarean section because of dystocia increased in inverse proportion to decreasing pelvic outlet capacity. The incidence of other emergency cesarean sections was not influenced by pelvic outlet size. In 79% of cesarean section interventions due to dystocia, pelvic outlet capacity was normal. Apgar score less than 7 at one minute was more commonly associated with a small pelvic outlet. Apgar score at 5 minutes and neonatal morbidity were not influenced by pelvic outlet size. Pelvic outlet capacity had a marked influence on the mode of delivery, but the practical value of radiological pelvimetry by fetal head presentation is rarely considered, except in very selected cases.