A cohort study of maternal and neonatal morbidity in relation to use of sequential instruments at operative vaginal delivery.

Objective: To evaluate the risk factors and maternal and neonatal morbidity associated with sequential use of instruments (vacuum and forceps) at operative vaginal delivery.

Study Design: A cohort study of 1360 nulliparous women delivered by a single instrument (vacuum or forceps) or by both instruments, within two university teaching hospitals in Scotland and England. Outcomes were compared for use of sequential instruments versus use of any single instrument. A sub-group analysis compared sequential instruments versus forceps alone. Outcomes of interest included anal sphincter tears, postpartum haemorrhage, urinary retention, urinary incontinence, prolonged hospital admission, neonatal trauma, low Apgar scores, abnormal cord bloods and admission to the neonatal intensive care unit (NICU).

Results: Use of sequential instruments at operative vaginal delivery was associated with fetal malpositions, Odds Ratio (OR) 1.8 (95% Confidence Interval (CI) 1.3-2.6), and large neonatal head circumference (>37 cm) (OR 5.0, 95% CI 2.6-9.7) but not with maternal obesity or grade of operator. Sequential use of instruments was associated with greater maternal and neonatal morbidity than single instrument use (anal sphincter tear 17.4% versus 8.4%, adjusted OR 2.1, 95% CI 1.2-3.3; umbilical artery pH <7.10, 13.8% versus 5.0%, adjusted OR 3.3, 95% CI 1.7-6.2). Sequential instrument use had greater morbidity than single instrument use with forceps alone (anal sphincter tear OR 1.8, 95% CI 1.1-2.9; umbilical artery pH <7.10 OR 3.0, 95% CI 1.7-5.5).

Conclusions: The use of sequential instruments significantly increases maternal and neonatal morbidity. Obstetricians need training in the appropriate selection and use of instruments with the aim of completing delivery safely with one instrument.