Carl Wood

Autonomic control of fetal heart rate

Abstract The role of sympathetic and parasympathetic nerves in the control of fetal heart rate was elucidated by using the sympathetic blocking drug, propranolol, and the parasympathetic blocking drug, atropine. The sinoatrial node of the fetal heart is stimulated by parasympathetic drive comparable to the neonate and young adult. Sympathetic drive is also present but its extent could not be determined because of limitations of the experimental procedure. During contractions sympathetic drive often increases. A fast fetal heart rate may be due to changes in either sympathetic or parasympathetic control of the sinoatrial node. The maternal heart rate may increase or decrease during contractions and this change usually involves the parasympathetic nervous system.

MATERNAL AND FŒTAL KETONE CONCENTRATIONS IN PLASMA AND URINE

Abstract The plasma and urinary ketone concentrations of twenty-two pregnant women were measured under standard conditions. The findings suggest that pregnancy is associated with an increased susceptibility to develop ketosis. The maternal and foetal plasma-ketone concentrations were closely related, at the time of delivery, with a gradient from mother to foetus which produces a transfer of ketones in that direction. Both levels were elevated when labour was prolonged, but no relation with acid-base status or with blood-glucose was found. Foetal levels were relatively elevated when preeclampsia was present, suggesting that fœtal-fat catabolism may take place in circumstances where placental function is disturbed. The intravenous infusion of 50 g. of dextrose reduced elevated maternal plasma-ketone levels.

Oxygen transfer from mother to fetus during labor

The present study was aimed at determining the effect of maternal inhalation of 10, 50, and 100 per cent oxygen upon fetal blood PO 2 and acid-base status during labor. As maternal capillary blood PO 2 increases or decreases, fetal scalp capillary blood PO 2 changes in the same manner. In both normal and abnormal patients inhalation of oxygen enriched mixtures increased fetal blood PO 2 . The most effective way of increasing fetal blood PO 2 was by administering 100 per cent oxygen by mask. The increase in fetal blood PO 2 was usually rapid. Fetal base deficit sometimes increased during the experiments. This change was associated with a decrease of fetal capillary blood PCO 2 .

THE EFFECT OF ADRENERGIC RECEPTOR BLOCKING DRUGS ON THE HUMAN UTERUS

THE classical papers of Langley (1905) and Dale catecholamines (Stander, 1967). Adrenaline has (1906) first introduced the concept of a receptive been shown to act on both a and p receptors in mechanism related to the sympathetic nervous the human uterus, the excitatory response of system. Ahlquist (1948) postulated two types of adrenaline being reversed in the presence of the adrenergic receptors, alpha and beta. Since then, a blocking agent phenoxybenzamine, and the evidence has accumulated which confirms the resulting inhibition being blocked by the @ presence of these receptors in many types of blocking agent propranolol (Nakanishi et al., smooth muscle and with the development of 1967). Adrenaline produces an inhibitory redrugs with specific actions on a and p receptors, sponse in vivo which is changed to excitation after knowledge of their function and significance has administration of the p blocking agent proincreased. pranolol (Wansbrough et al., 1967). Alpha excitatory and beta inhibitory receptors Thus the evidence for the presence of a and p have been described in the uterus of several receptors in the human uterus is fairly conclusive species including the guinea pig (Clegg, 1963), although little is known of their significance in the rabbit, the rat and the dog (Maughan et al., relation to control of uterine activity. In order to 1967; Willems et al., 1965). Pharmacological extend our knowledge of this we have examined studies have confirmed the presence of a and p the effects of some sympathetic stimulating and receptors in the human uterus (Nakanishi et al., blocking agents on uterine activity in pregnant 1967). The excitatory response produced by and non-pregnant patients. noradrenaline and adrenaline was inhibited by administration of the CI blocking agents phenoxybenzamine and phentolamine, and the inhibitory response produced by isoprenaline was blocked The studies were carried out on 10 normal by administration of the p blocking agents pregnant women at the beginning of the first propranolol and dichloroisoproterenol. In their stage of labour and 20 non-pregnant women studies on the uterine activity of pregnant women admitted to hospital for curettage or hysterecat term Eskes et al. (1965) demonstrated an tomy. The patients volunteered for the study inhibitory response to Cc-25, a (3 mimetic agent, after the experimental procedure had been which was partially antagonized by administraexplained to them. The phase of the menstrual tion of the p blocking agents pronethalol and cycle was determined by histological examinapropranolol. Propranolol itself has been observed tion of the endometrium and classified as to produce an increase in uterine activity in proliferative or secretory. Uterine activity was pregnant women at term, and the mechanism of recorded continuously using an intrauterine this effect was thought to be due to its blocking balloon containing 1 to 2.5 ml. of sterile water effect on the inhibitory action of endogenous connected by a closed water system to a strain MATERIAL AND METHODS

MENOPAUSAL HOT FLUSHES : A DOUBLE BLIND COMPARISON OF PLACEBO, ETHINYL OESTRADIOL AND NORGESTREL

A double blind crossover study was planned in order to compare the effects of oestrogen, progestogen and placebo on hot flushes. The 49 women studied had previously undergone hysterectomy and bilateral oophorectomy. The drug regimen consisted of three months each of ethinyl oestradiol 50 μg/day, d norgestrel 250 μg/day, a combination of these two substances (‘ordiol’) and a placebo. The predominant reason for requesting a change of medication was intolerable hot flushes associated with placebo use. All hormonal preparations were found to be significantly more effective than placebo in reducing hot flush frequency and intensity. Oestrogen containing medications were more effective than the progestogen (norgestrel).

Methods of recording fetal movement.

Patient, observer and instrumental methods for recording fetal movements are described. Significant correlations between both patient and observer, and patient and instrumental fetal movement counts, were found. Significant diurnal, daily and weekly variation in fetal movement counts occurred which need to be considered in the interpretation of the frequency of fetal movements as an indication of fetal welfare.

A TRIAL OF ORAL RITODRINE FOR THE PREVENTION OF PREMATURE LABOUR

A double blind clinical trial of oral ritodrine for prevention of premature labour was conducted in 38 primigravidae in whom the internal os of the cervix was one or more fingerbreadths dilated at 28 to 32 weeks gestation. The results suggest that oral ritodrine may not be effective in preventing premature labour.

Fetal acid-base balance. I. Interdependence of maternal and fetal PCO2 and bicarbonate concentration.

This paper presents the results of measurements of the acid-base and gaseous status of maternal and fetal capillary blood at the time of amniotomy, before the onset of labor. The correlation coefficient between maternal and fetal bicarbonate concentration is 0.6, and that between maternal and fetal PCO2 is 0.31. From the results obtained, as well as from a survey of other work in the field, it is proposed that the diffusion of carbon dioxide across the placenta could not explain some of the findings and that bicarbonate concentrations equilibrate across the placenta.

CHOLINERGIC MECHANISMS IN THE HUMAN UTERUS

The intrinsic cholinergic nerve supply of the human myometrium was studied by using electrical transmural stimulation and was found to be postganglionic and minimal. The pharmacological findings indicated that the human nonpregnant myometrium possessed sensitive cholinergic muscarinic receptors, but during pregnancy the sensitivity of the muscarinic receptors was markedly reduced. These results support our hypothesis that the human pregnant myometrium is protected from autonomic influence.

LACK OF AGREEMENT ON NORMAL VALUES FOR FETAL SCALP BLOOD

There are significant differences between authors in the values given for the normal range of p H and blood gases in fetal scalp blood during the first stage of labour. Oxygen tensions show the least agreement. The differences cannot be explained by the ways the normal study group were selected (clinically normal; normal monitored fetal heart rate; healthy newborn infants) nor by choice of measuring system. Both inaccuracy of measurement and variation in the arterial and venous contributions to scalp capillary blood are probably involved.