A. C. Turnbull

Relationship between length of gestation and cervical dilatation, uterine contractility, and other factors during pregnancy

Abstract The relationship was examined in healthy young primigravidas between the length of gestation and several factors measured during pregnancy, including the physical and chemical state of the cervix, uterine contractility, smoking, and sexual intercourse. Cervical dilatation and effacement during pregnancy relate to the time in gestation at which labor starts. For example, at the thirty-second week the internal cervical os was one fingerbreadth dilated in all patients who subsequently were delivered before the thirty-eighth week, but in only 10 per cent of those delivered after the forty-first week. The concentration of cervical hydroxyproline did not relate to gestation at labor nor to the physical state of the cervix. There was a highly significant negative correlation between the activity of the uterus at the thirty-sixth week of pregnancy and gestation at the onset of labor. The proportion of patients delivered before the end of the thirty-ninth week was significantly greater for smokers that for nonsmokers. However, the relationship between the length of gestation and cervical dilatation and uterine contractility in pregnancy remained significant in nonsmokers. The frequency of sexual intercourse during pregnancy did not influence the time in gestation when labor began.

TALC AND CARCINOMA OF THE OVARY AND CERVIX

An extraction‐replication technique was used to examine tissue from patients with ovarian and cervical tumours. In both conditions talc particles were found deeply embedded within the tumour tissue. The close association of talc to the asbestos group of minerals is of interest.

FETAL ADRENAL WEIGHT AND THE CAUSE OF PREMATURE DELIVERY IN HUMAN PREGNANCY

In a group of 79 infants delivered before the end of the 36th week of pregnancy, and who either were stillborn or died within 12 hours, the weights of the adrenal glands in relation to fetal weight and gestational age were determined. Three groups were identified according to the clinical cause of the premature labour, namely those due to no known cause, those due to antepartum haemorrhage and those due to pre‐eclampsia.

THE RELATIONSHIP IN ANENCEPHALY BETWEEN THE SIZE OF THE ADRENAL CORTEX AND THE LENGTH OF GESTATION

WORK in sheep has revealed the importance of fetal pituitary-adrenal activity in determining the duration of gestation (Liggins et a]., 1966, 1967). Evidence in the human fetus that the pituitary-adrenal axis is concerned in regulating the onset of labour has been obtained indirectly from studies of anencephaly. Jt is well known that this fetal malformation is almost invariably associated with some degree of hypoplasia of the adrenal cortex, attributed to pituitary insufficiency (Ch’in, 1938; Lanman, 1961 ; Bearn, 1968), and also, if hydramnios does not develop, with very prolonged gestation (Ballantyne, 1902; Malpas, 1933; Comerford, 1965). We have investigated the possibility that the size of the adrenal cortex in anencephaly might relate to the length of gestation.

Automatic oxytocin infusion equipment for induction of labour.

Equipment has been developed for the automatic infusion of oxytocin using a positive pressure peristaltic pump. The automatic setting starts the infusion at 1 milliunit of oxytocin per minute and doubles the dose every 12‐5 minutes. When contractions are of adequate strength and frequency, the “manual” control is used to maintain the oxytocin dose rate, and for immediate and accurate adjustment to any required level. Using this equipment in a series of 130 cases, the average induction‐delivery interval was less than 8 hours. Continuous records of amniotic fluid pressure and fetal electrocardiography showed normal uterine contractions and fetal heart rate patterns.

MATERNAL PLASMA OESTROGEN AND PROGESTERONE LEVELS DURING THERAPEUTIC ABORTION INDUCED BY INTRA‐AMNIOTIC INJECTION OF PROSTAGLANDIN F2α

Plasma 17β‐oestradiol, total unconjugated oestrogens and progesterone levels were measured in ten patients in the second trimester of pregnancy who were undergoing abortion by intra‐amniotic injection of prostaglandin F2α (PGF2α). The correlation between total unconjugated plasma oestrogens and 17β‐oestradiol was highly significant (r =+0.92; p<0.001). A similar positive correlation between total unconjugated plasma oestrogen and progesterone was observed (r =+0.66; p<0.001). The concentration of these steroids in samples, taken at intervals during normal pregnancy, showed considerable variation. Following administration of PGF2α no consistent change was seen in plasma steroid concentrations until after delivery of the fetus and placenta. PGF2α therefore appears to have no direct effect on oestrogen and progesterone biosynthesis and may act principally by direct stimulation of myometrial contractility.

HUMAN FETAL AND MATERNAL PLASMA OESTROGENS AND THE ONSET OF LABOUR

Levels of unconjugated oestrone and oestradiol were measured in maternal peripheral and umbilical arterial and venous plasma. The levels before and after the spontaneous onset of labour were compared, samples being obtained either at elective Caesarean section or at normal delivery following labour of spontaneous onset. In the umbilical circulation, the mean concentrations of both oestrone and oestradiol were higher in the vein than in the artery, but the V‐A difference was highly significant only for oestrone (P<0.001). The main positive finding in relation to labour was that in the umbilical vein plasma, the oestrone level was significantly higher (P<0.01) after labour than before its onset, the mean value (±S.E.) in the patients having an elective Caesarean section being 10.9 (±1–4) ng./ml., compared with a level of 17.1 (±1.6) ng./ml. in the group delivering spontaneously. In the maternal peripheral circulation there was no appreciable change in the level of oestrone or oestradiol in relation to labour. It is concluded that the increase in umbilical vein oestrone may depend on a change in the placental metabolism of oestrogens related to labour, and probably reflects more complex endocrine changes concerned in the control of human parturition.

THERAPEUTIC ABORTION BY INTRAUTERINE INSTILLATION OF PROSTAGLANDIN E2

Intrauterine instillation of prostaglandin E2 was used in an attempt to induce abortion in 20 pregnancies of less than 12 weeks gestation. The technique failed altogether in 7 patients, and achieved only incomplete abortion in the remaining 13. Evidence of uterine infection developed in 4 patients. The results obtained have not encouraged the continuing use of the method for terminating early pregnancy in this centre.

SPONTANEOUS CONTRACTILITY AND OXYTOCIN SENSITIVITY OF THE HUMAN UTERUS IN MID‐PREGNANCY

ALTHOUGH much has been written on the activity of the human uterus and its response to oxytocin in late pregnancy and in labour, there is little information on the behaviour of the uterus in mid-pregnancy, particularly before the 20th week. Caldeyro-Barcia and Poseiro (1959) studied uterine activity and oxytocin sensitivity at the 12th and 20th weeks of pregnancy and reported that although spontaneous activity was very low at these times the uterus responded to “physiological” doses of oxytocin as early as the 12th week. The opportunity to study the human uterus in mid-pregnancy was afforded us by the policy of therapeutic termination of pregnancy by the intra-amniotic injection of hypertonic saline. Before the saline was injected, amniotic fluid pressure was recorded directly by means of an open-ended catheter in the amniotic sac and the response of the uterus to varying doses of oxytocin was assessed. The effect of an increase in amniotic fluid volume on spontaneous and oxytocin-induced uterine activity was also studied in one patient.