Antenatal corticosteroids for short cervix: When is it indicated - a cohort study

Antenatal corticosteroids (ACS) improve outcomes for children born before 34 weeks, with timing being crucial. Administration within seven days before birth is optimal. After longer intervals the benefits are less clear and ACS might even be harmful if delivery occurs at term. We aimed to assess the rate of optimally timed ACS across different indications and explore strategies to improve timing.

We conducted a 10-year retrospective cohort study of all pregnant patients receiving ACS at a single center from 2014 to 2023. Patients lost to follow-up < 14 days were excluded. Clinical characteristics and birth outcomes were collected. ACS timing was categorized by interval to birth: <2 days (late), 2-7 days (optimal), 7-14 days (suboptimal), and > 14 days (early). Timing accuracy was evaluated per indication. Four alternative administration strategies were modeled to assess potential improvements.

Among 4578 patients, the most common indications were threatened preterm birth (24%), PPROM (19%), and short cervix (16%). Overall, 33% received ACS within 7 days of delivery and 44% within 14 days, with no improvement over the decade. In patients with a short cervix (23% of the cohort), ACS timing was late in 1%, optimal in 9%, suboptimal in 7%, and early in 84%. Restricting ACS to those with an open cervix would result in 50% receiving ACS within 14 days of birth. For patients with a short but closed cervix, administering ACS only when symptoms developed would result in late or missed ACS in 4%. Withholding ACS in asymptomatic patients could avoid or delay treatment in 76% while increasing optimal/suboptimal timing to 45%.

ACS for asymptomatic short cervix is rarely optimally timed. Targeted administration based on cervical status and symptoms may substantially improve timing accuracy.