Vulvar lichen sclerosus linked to more sphincter injuries at birth

Design

Regional retrospective matched cohort, Denmark 2019 to 2024

Population

277 births to women with vulvar lichen sclerosus and 533 control births

Primary outcome

Second-degree tears and obstetric anal sphincter injury

Effect

Second-degree tear RR 1.37 (95% CI 1.14 to 1.65); sphincter injury RR 3.37 (1.30 to 8.76)

A Danish regional study (AJOG, 7 October) compared 277 births to women with diagnosed vulvar lichen sclerosus with 533 matched births to unaffected women in North Denmark between 2019 and 2024, using medical records.

After adjusting for parity, birth weight, head circumference and vacuum delivery, lichen sclerosus was associated with more second-degree tears (RR 1.37, 95% CI 1.14 to 1.65) and with more obstetric anal sphincter injuries (RR 3.37, 1.30 to 8.76). Within the lichen sclerosus group, sphincter injury was more common with a narrowed introitus (RR 6.20), symptoms during pregnancy (RR 3.98), nulliparity and vacuum delivery.

Lichen sclerosus is under-diagnosed in women of reproductive age and rarely asked about at booking. This study suggests it is worth asking, examining when symptoms are reported, and flagging to the birth team, particularly where the introitus is narrowed. It is observational and small, with wide intervals, so it does not by itself justify recommending caesarean.

• Ask about known vulvar lichen sclerosus, itch or soreness at booking.
• Where lichen sclerosus is present, examine for narrowing of the introitus in the third trimester and record it.
• Flag a narrowed introitus or active symptoms in the birth plan so the attending team anticipates perineal risk.
• Consider optimising disease control with the usual topical treatment before birth where symptoms are active.
• Be cautious with vacuum delivery in these women, which carried the highest sphincter injury risk in the series.

Why it matters

It adds a skin condition most antenatal histories skip to the list of factors that should prompt closer perineal care at birth.

Don't overread it

This is a small observational study with wide confidence intervals; it does not show that caesarean or any intervention prevents these injuries.

The statistics, in plain English

A relative risk of 3.37 for sphincter injury means about three times the risk of unaffected women, but the interval runs from 1.3 to 8.8, so the true figure is uncertain. The within-group risk factors come from unadjusted bivariate analyses on few events and are weaker evidence than the headline comparison.

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