John A.D. Spencer

Maternal and fetal effects of the supine and pelvic tilt positions in late pregnancy

Material and fetal cardiovascular effects of position change were assessed in 20 women in late pregnancy. On changing from the left lateral to the supine position, there was a 45% reduction in leg blood flow, measured by strain guage plethysmography. Arterial resistance, measured with Doppler ultrasound in the femoral, brachial and uterine arteries, remained unchanged, confirming the absence of compensatory vasoconstriction. There was no change in blood pressure (BP) in the leg, indicating no significant aortic compression, but a rise in maternal heart rate in the supine position suggested the presence of inferior vena cava (IVC) compression. Neither the left or the right pelvic-tilt position was associated with a significant change in leg blood flow or maternal heart rate compared to the supine position. A possible sluice effect in the placental circulation was not confirmed, as fetal heart rate and umbilical Doppler resistance did not change in any position. In the absence of active vasoconstriction and significant aortic compression, IVC compression is the likely cause of the decrease in leg blood flow, and also of the previously demonstrated decrease in uterine blood flow. Leg BP and Doppler ultrasound measurements of uterine artery resistance may not be adequate measures of the effect of posture on uteroplacental perfusion.

Fetal acidaemia, the cardiotocograph and the T/QRS ratio of the fetal ECG in labour

Objective To relate the T/QRS ratio of the fetal electrocardiogram (ECG) to the cardiotocogram (CTG) and fetal pH during labour.

Fetal heart rate response to vibroacoustic stimulation during low and high heart rate variability episodes in late pregnancy

In 52 women in late pregnancy, the mean durations of transient fetal tachycardia after vibroacoustic stimulation during low fetal heart rate variability (4.8 minutes) and high fetal heart rate variability (6.3 minutes) were similar. The fetal heart rate continued with high variability in all cases, suggesting that the fetus did not return to its prestimulation state after vibroacoustic stimulation during quiescence. In 10 women, the duration of high variability after vibroacoustic stimulation during low fetal heart rate variability was significantly shorter (mean, 22 minutes) than the preceding (mean, 36 minutes) or subsequent (mean, 43 minutes) high-variability components of complete rest activity cycles. In another 10 women, the duration of high variability after vibroacoustic stimulation during high fetal heart rate variability was similar to preceding and subsequent high-variability episodes. In these 20 women, the next complete rest-activity cycle after vibroacoustic stimulation was not different in duration to the complete cycle recorded on the previous day.

Uteroplacental perfusion after epidural analgesia for elective caesarean section

A recent Doppler ultrasound study concluded that epidural analgesia improved uteroplacental perfusion (Giles et al. 1987) whereas a previous radio-isotope study had suggested that intervillous blood flow may decrease slightly, though not significantly, with epidural analgesia (Jouppila et al. 1978). We report an assessment of the variability of measurements of the uteroplacental blood flow pulsatility index (PI) and the results of a study of the effects of fluid preloading and epidural analgesia on uteroplacental perfusion in women undergoing elective caesarean section.

Fetal heart rate and neonatal condition related to epidural analgesia in women reaching the second stage of labour

The relationship between epidural analgesia and a number of labour and delivery factors, relevant to fetal and neonatal condition, was considered in a prospective study of 200 labours reaching the second stage of labour. The group was representative of the hospital population with regard to the proportion of nulliparous women, the incidence of instrumental vaginal deliveries and the incidence of epidural analgesia (37%). The 8% of labours requiring fetal blood sampling during the first stage, and the labours with fetal heart rate (FHR) decelerations in the hour prior to second stage (25%) and during pushing (50%) were significantly more likely to have been given an epidural. Nulliparity (55%), induced labour (34%), a first stage longer than eight hours (37%), a second stage longer than 60 min (43%), maternal pushing for longer than 36 min (50%), forceps delivery (28%) and a 1 min Apgar score less than 7 (12%) were also factors associated with significantly higher rates of epidural analgesia whereas meconium (15%), a small baby (16%) and umbilical arterial metabolic acidaemia (13%) were not. FHR decelerations in labours reaching the second stage with an epidural reflect adjustments to fetal cardiovascular control and not acidaemia.

Transplacental Transfer of Cefuroxime in Uncomplicated Pregnancies and Those Complicated by Hydrops or Changes in Amniotic-Fluid Volume

The transplacental transfer of cefuroxime was determined at antenatal fetal blood sampling in a cross sectional study of 78 patients between 15-35 weeks gestation, 8-138 minutes after a maternal intravenous dose of 750 mg. Mean serum cefuroxime concentration, measured by high performance liquid chromatography, was 7.4 (95% confidence interval (CI) 6.8 to 8.1) mg/l in control fetuses; concentrations in hydropic fetuses were similar (6.2 mg/l, CI 4.7 to 7.7) but in fetuses with oligohydramnios they were significantly lower, (4.9 mg/l, CI 3.6 to 6.2). Antibiotic concentration did not correlate with gestational age and remained unchanged by transfusion of packed red cells. We conclude that (i) fetal serum concentrations of cefuroxime obtained after a maternal dose of 750 mg are only adequate for prophylaxis against organisms with a minimum inhibitory concentration of < 4 mg/l and (ii) transplacental passage of cefuroxime is significantly reduced in the presence of oligohydramnios.

Intra-amniotic pressures following vaginal gemeprost prior to first and second trimester termination of pregnancy.

Intra-amniotic pressures were measured following 1 mg gemeprost for cervical preparation before first trimester vacuum aspiration (n = 10) and following 2 mg gemeprost before second trimester dilatation and evacuation (n = 15). Twenty-five women, matched for gestational age and parity, who did not receive gemeprost served as controls. Compared to control values (2-8 mmHg), basal intra-amniotic pressure (IAP) was significantly increased after 1 mg and 2 mg of gemeprost (median 20.0, range 4-45 mmHg, median 20.0, range 8-60 mmHg, respectively). Uterine contractions were recorded in 8 of 10 subjects after 1 mg (median delta IAP 28.0, 95% CI 10.0-42.6 mmHg) and 14 of 15 subjects after 2 mg (median delta IAP 52.5, 95% CI 26.7-60.3 mmHg). Gemeprost produces an increase in uterine contractility which may be additional to cervical softening properties and which may be responsible for the adverse effects of pain and bleeding experienced by some women prior to termination.

The placental transfer of cefuroxime at parturition

Maternal and fetal serum concentrations of cefuroxime were determined at birth in 39 women who were given a single intravenous dose of either 750 mg or 1500 mg of cefuroxime before delivery. Mean serum cefuroxime concentrations in maternal venous and umbilical venous blood were dose dependent, being significantly higher after 1500 mg of cefuroxime (55.0 mg/l, 95% CI 33.4-80.9 and 19.5 mg/l, 95% CI 9.5-26.3, respectively) than after 750 mg (14.7 mg/l, 95% CI 10.5-21.1 and 8.8 mg/l 95% CI 5.8-9.4, respectively). Antibiotic concentration in maternal blood correlated with sampling time but a similar relationship was not found in cord blood. Fetal concentrations did not correlate with mode of delivery or initial maternal blood pressure. No relationship could be demonstrated between cefuroxime concentration in maternal or cord blood and maternal weight, maternal weight gain, birthweight of baby or volume of fluid infused prior to epidural anaesthesia. It is concluded that maternal and fetal concentrations likely to be effective for prophylaxis before delivery require a maternal dose of 1500 mg of cefuroxime and are independent of these physiological variables.

Cervical preparation with gemeprost for dilatation and evacuation

Dilatation of the pregnant cervix above 12 mm, for termination of pregnancy, has resulted in concern regarding the risk of trauma and subsequent cervical integrity (Johnstone ef al. 1976; Obel 1979). In the USA, preoperative cervical dilatation using Laminaria japonica tents improves the ease and safety of operative termination (Grimes & Schulz 1985) but takes between 18 and 36 h (Castadot 1986). Gemeprost, a prostaglandin E, analogue, administered as a vaginal pessary, was found to be easier to administer and faster acting than Lamicel for adequate cervical preparation before first trimester dilatation and suction evacuation (Helm ef al. 1988). We report our experience of the use of vaginal gemeprost for cervical preparation in 141 consecutive patients having second trimester dilatation and evacuation.