Risk of preterm birth in the subsequent pregnancy following caesarean section at full cervical dilatation compared with mid-cavity instrumental delivery.

BACKGROUND: Expediting delivery in the second stage of labour often involves a choice between a caesarean section at full dilatation or mid-cavity instrumental delivery. Accumulating evidence suggests that the mode of delivery may influence the risk of preterm birth in the subsequent pregnancy. AIMS: To directly compare first birth caesarean section at full dilatation with mid-cavity instrumental delivery for the risk of preterm birth in the subsequent pregnancy (second birth). A further aim was to identify predictive factors associated with these index modes of delivery. MATERIALS AND METHODS: This is a retrospective cohort study involving three maternity hospitals in western Sydney over the period of 2006-2017. Inclusion criteria were nulliparous women with a singleton term cephalic first birth delivered by caesarean section at full dilatation or mid-cavity instrumental delivery, and whose second birth also occurred under our care. Data were analysed separately for first and second births. RESULTS: There were 425 caesarean section at full dilatation and 874 mid-cavity instrumental cases which met inclusion criteria. The risk of preterm birth in the second birth was 5.7% compared to 3.2%, respectively (risk ratio 1.76; 95% CI 1.04-3.00; P = 0.035). After excluding causes of preterm birth not related to previous mode of delivery, the risk of spontaneous preterm birth was 4.3% compared to 2.0%, respectively (risk ratio 2.18; 1.14-4.19; P = 0.019). CONCLUSION: Caesarean section at full dilatation is associated with a significantly higher rate of preterm birth in the subsequent pregnancy compared to a mid-cavity instrumental delivery. This should be considered in second-stage mid-cavity decision-making.

Point-of-care measurement of fetal blood lactate - Time to trust a new device.

BACKGROUND: Point-of-care lactate devices are used worldwide for intrapartum decision making. Current practice is often based on Lactate Pro (Arkray) but its imminent product discontinuation necessitates determination of an optimal replacement device. AIMS: To evaluate the performance of Lactate Pro and two other point-of-care devices, Lactate Pro 2 (Arkray) and StatStrip (Nova Biomedical), and to derive scalp lactate cut-offs equivalent to the current intervention trigger of >4.8 mmol/L. MATERIALS AND METHODS: Paired umbilical cord arterial and venous blood samples from 109 births were tested on the three point-of-care products (two devices each), cross-compared with the reference method blood gas analyser. RESULTS: All brands deviate from the blood gas analyser, with Lactate Pro and StatStrip results consistently lower and Lactate Pro 2 consistently higher. Standard deviation from the blood gas analyser was smallest for StatStrip (0.78 mmol/L, cord artery), and largest for Lactate Pro 2 (1.03 mmol/L, cord artery). Within-brand variation exists and is similar for all brands (mean absolute difference on cord artery 0.23-0.30 mmol/L). Equivalent values to the 4.8 mmol/L intervention threshold based on Lactate Pro are 4.9-5.0 mmol/L for StatStrip and 5.3-5.9 mmol/L for Lactate Pro 2, calculated by receiver-operating characteristic analysis. CONCLUSIONS: StatStrip appears superior to Lactate Pro 2 to replace the original Lactate Pro. Using StatStrip, the 4.8 mmol/L intervention threshold equivalent was 4.9-5.0 mmol/L. The variation in accuracy of point-of-care lactate devices may exceed the small increments (eg <4.2 mmol/L vs >4.8 mmol/L) that guide obstetric decisions.

Rapid identification of group B streptococcus carriage by PCR to assist in the management of women with prelabour rupture of membranes in term pregnancy.

BACKGROUND: Management of prelabour rupture of membranes at term (37 weeks gestation or later) (TPROM) remains complicated in the absence of a rapid assay for group B streptococcus (GBS) colonisation. AIMS: To evaluate the accuracy and clinical utility of a commercial PCR assay, compared with culture, for detection of GBS colonisation in pregnant women presenting with TPROM. METHODS: A prospective study of women presenting with TPROM conducted in a large tertiary hospital (Westmead Hospital, Australia). Five hundred and seventy-four consecutive women with TPROM were enrolled between July 2006 and November 2007. Paired low vaginal and anal swabs were collected from women presenting with TPROM for PCR and culture on GBS selective agar following broth enrichment. Primary outcomes were sensitivity and specificity of PCR compared with GBS selective enrichment culture. Secondary analyses included comparison with a historical but otherwise similar cohort regarding clinical utility, maternal and neonatal outcomes. RESULTS: PCR sensitivity and specificity were 89.0% (95% CI - 82.8-93.6%) and 97.9% (95% CI - 96.0-99.0%), respectively, compared with culture. 72.3% of women were aware of their GBS PCR status within 3 h of presentation. Compared with the historical cohort, PCR reduced the requirement for intrapartum antibiotics by 25.6% (P < 0.001). There were no significant differences in maternal outcomes or combined rates of admissions to neonatal intensive care or special care nursery. CONCLUSIONS: Group B streptococcus PCR is an accurate, rapid, safe and practical alternative to culture for detection of GBS colonisation in pregnant women at the time of TPROM. This method has the potential advantage to reduce costs associated with length of hospital stay.

Lactate study using umbilical cord blood: agreement between Lactate Pro hand-held devices with blood gas analyser and evaluation of lactate stability over time.

BACKGROUND: Lactate measurements have become increasingly preferred over pH analysis in the evaluation of fetal acidaemia in labour. In a busy labour ward, often the umbilical cord may be sampled late and as a result yield unreliable lactate values. AIM: To investigate the agreement of hand-held device Lactate Pro with a reference method blood gas analyser and evaluate the stability of umbilical cord lactate values over time. METHODS: Prospective study carried out at elective caesarean section. Sixteen umbilical cords were double clamped immediately after delivery with paired arterial and venous blood samples collected by an independent researcher, at varying time intervals, and processed by two Lactate Pro devices and a reference method blood gas analyser. RESULTS: A significant difference of -0.41 to 0.10 mmol/L was found when different groups of Lactate Pro devices were compared with blood gas analyser at lactate values up to 5.70 mmol/L, with average lactate value of 2.45 mmol/L. Over time, there is progressive rise in lactate samples obtained from the umbilical cord. CONCLUSION: Lactate Pro devices have a significant difference, but when used in clinical practice on cord blood after delivery, this is unlikely to be meaningful. In intrapartum fetal surveillance, a systematic overestimation might lead to unnecessary intervention. It is possible to retrospectively predict the likely level of lactate at birth in delayed cord samples.