Fetal Scalp Stimulation Versus Fetal Blood Sampling in Labour (FIRSST)

Fetal Scalp Stimulation (FSS) Versus Fetal Blood Sampling (FBS) to Assess Fetal Wellbeing in Labour - a Multi-centre Randomised Controlled Trial.

University College Cork, University of Limerick, Royal College of Surgeons, Ireland, National University of Ireland, Galway, Ireland, Health Research Board, Ireland, Health Research Board - Trials Methodology Research Network

Pregnant women have routine monitoring of the baby's heart rate when in labour. Women with complicated pregnancies require continuous monitoring using an electronic recorder called a CTG. The CTG produces a paper based recording which is interpreted by the midwife as showing normal, suspicious or abnormal features of the baby's heart rate. Babies quite commonly demonstrate abnormal features from time to time during the course of labour. In some cases the abnormal features are of sufficient concern to warrant delivery by emergency caesarean section. In most of these cases the baby is born in good condition and the question arises whether the caesarean section was unnecessary. In order to reduce the chance of an unnecessary caesarean section additional "second-line" tests can be offered. One such test is where a small drop of blood is taken from the baby's scalp. This test involves an internal examination with an instrument to visualise the baby's head and a small scratch to the baby's scalp. The blood is tested for acid which is an indicator of whether or not the baby is receiving enough oxygen. The test is called a fetal blood sample or FBS. An alternative test is where the doctor or midwife performs a vaginal examination with two fingers and gently rubs the baby's scalp in an attempt to cause an increase in the baby's heart rate. This is a healthy response suggesting that the baby is receiving enough oxygen. The test is called digital fetal scalp stimulation or dFSS. These two "second-line" tests have never been compared in a properly conducted head-to-head comparison. This study aims to compare dFSS and FBS in a large clinical trial completed within four of Ireland's largest maternity hospitals. This trial will generate important evidence of direct relevance to clinical care and patient outcomes.

Continuous electronic fetal heart rate recording with cardiotocography (CTG) is a standard approach to monitoring fetal wellbeing in labour and is recommended for high-risk pregnancies. The aim is to identify fetal compromise early and intervene in order to reduce serious adverse events such as cerebral palsy and perinatal death. CTG abnormalities are relatively common and can lead to the decision to deliver by emergency caesarean section. In most cases the fetus is subsequently found to have been compensating for the stress of labour and is not actually compromised. Fetal blood sampling (FBS) is a second-line invasive test that provides information on the acid-base status of the fetus, reflecting hypoxia. It is used to provide either reassurance that labour can continue, or more objective evidence that delivery needs to be expedited. Clinical guidelines in the United Kingdom and Ireland have treated FBS as a gold standard test. Recent studies have questioned the validity and reliability of FBS, and also the logistic challenges of achieving a result in a timely manner. Fetal scalp stimulation (dFSS) by digital rubbing is an alternative less invasive test of fetal wellbeing in labour and is recommended in preference to FBS in US guidelines. This research aims to compare digital FSS and FBS in women with term singleton pregnancies and an abnormal intrapartum CTG, where additional information on fetal wellbeing is required. A multi-centre randomised controlled trial will be conducted. The clinical outcomes of interest will include caesarean section, assisted vaginal birth, low Apgar scores, cord blood acidosis, and admission to the neonatal unit. This trial will generate important evidence of direct relevance to clinical care and patient outcomes.

randomised controlled trial, fetal blood sampling, fetal scalp stimulation, cardiotocography, caesarean section

The primary and perinatal secondary outcomes will be recorded from the computerised delivery record without knowledge of the allocation. The principal investigator will play no role in the care of the patient or assessment of outcomes.

Fetal capillary blood samples will be collected in heparinised tubes and analysed in the delivery suite using the locally available gas analyser. The result of the first technically reliable sample, or the lowest reliable sample if multiple samples are tested, will be interpreted and acted upon according to the protocol, taking account of the clinical circumstances and the stage of labour: pH ≥7.25 normal, continue and if indicated repeat in 60 minutes; pH 7.21-7.24 borderline, repeat in 30 minutes; pH ≤ 7.20 abnormal, deliver.

The examiner will stimulate the fetal scalp digitally with the index and middle finger over a period of 30-60 seconds.The CTG will be observed over a 5-10 minutes interval after the dFSS and if a fetal heart rate acceleration (>15 bpm for 15 seconds) is observed the test will be considered normal. If there is an episode of normal variability (5-25 bpm) but there is no clear acceleration, the test will be considered borderline. If there is no FHR acceleration and no episode of normal variability with ongoing abnormal features, the test should be interpreted as abnormal in the same way as an abnormal FBS result. FHR acceleration normal, if indicated repeat in 60 min; Uncertain acceleration/ normal variability borderline, repeat in 30 minutes; No Acceleration/ongoing abnormal features abnormal, deliver.

Vaginal examination, insert amnioscope through cervix, visualise fetal scalp, clean fetal scalp, apply ethyl chloride spray, wipe scalp with petroleum gel, small scalp scratch with sharp instrument, collect sample in heparinised capillary tube, analyse sample.

Vaginal examination, insert one or two fingers through cervix onto fetal scalp, rub fetal scalp digitally for approximately 30-60 seconds, withdraw fingers and observe CTG for 5-10 minutes.

Inclusion Criteria: Nulliparous women Singleton pregnancy Cephalic presentation Gestational age 37+0 weeks or greater Abnormal CTG that requires second-line testing (FBS or dFSS) Exclusion Criteria: Contraindication to FBS Limited understanding of English At the discretion of the responsible obstetrician in cases where there is urgency

Hughes O, Murphy DJ. Comparing second-line tests to assess fetal wellbeing in Labor: a feasibility study and pilot randomized controlled trial. J Matern Fetal Neonatal Med. 2022 Jan;35(1):91-99. doi: 10.1080/14767058.2020.1712704. Epub 2020 Jan 12.

Murphy DJ, Shahabuddin Y, Yambasu S, O'Donoghue K, Devane D, Cotter A, Gaffney G, Burke LA, Molloy EJ, Boland F. Digital fetal scalp stimulation (dFSS) versus fetal blood sampling (FBS) to assess fetal wellbeing in labour-a multi-centre randomised controlled trial: Fetal Intrapartum Randomised Scalp Stimulation Trial (FIRSST NCT05306756). Trials. 2022 Oct 4;23(1):848. doi: 10.1186/s13063-022-06794-9.