Aeromedical retrieval for suspected preterm labour or rupture of membranes in the Northern Territory, Australia: may some cases be safely not retrieved?

Background: Suspected preterm labour (PTL) and prelabour rupture of membranes (PPROM) are common indications for aeromedical retrieval in the Top End, Northern Territory, Australia, where many women reside remotely and preterm birth (< 37 completed weeks of gestation) is common. The primary objective of this study was to determine rate of delivery during the index admission following aeromedical transfers from remote clinics to Royal Darwin Hospital for suspected PTL/PPROM.

Methods: A retrospective cohort study of aeromedical transfers for suspected PTL/PPROM from 1 January 2020 to 31 July 2022 was undertaken. Transfers were identified through CareFlight, the regional air ambulance service, and complemented with data from hospital records. Clinical and sociodemographic characteristics were compared by delivery status during the index (post-retrieval) admission using parametric and non-parametric tests and multivariable linear regression analysis.

Results: 238 women with singleton pregnancies were retrieved for suspected PPROM (n = 77, 32.4%) or PTL (n = 161, 67.6%), together accounting for 49.2% of all obstetric transfers (n = 483). Of 77 patients transferred for suspected PPROM, 47 (61.0%) had ruptured membranes confirmed on arrival, and 45 (95.7%) of them delivered during the index admission. None of the 30 women transferred for suspected PPROM with intact membranes on arrival delivered during the index admission. Of 161 patients transferred for suspected PTL, 13 (8.1%) had ruptured membranes confirmed on arrival, and 12 (92.3%) of them delivered during the index admission. Amongst women transferred for suspected PTL with intact membranes confirmed on arrival, 14.9% (22/149) delivered during the index admission. Prior to arrival, 120 women (50.4%) had a documented speculum examination, and 15 (6.3%) and 9 (3.8%) had cervicovaginal swab tests to assess their risks of a PPROM and PTL, respectively. Half of women who did not deliver during the index admission had received antenatal corticosteroids (n = 76).

Conclusions: Many aeromedical retrievals for suspected PTL/PPROM did not result in delivery during the index admission. Women retrieved for suspected PPROM with intact membranes on arrival were less likely to deliver. Upskilling remote clinic staff and better point-of-care testing may reduce retrievals and unnecessary interventions. Prospective cohort studies designed to enable accurate prediction of which cases can be safely not retrieved are required.

Trial Registration: Not applicable.