Hip extension at crowning did not reduce significant tears

Design

Pragmatic, non-blinded randomised clinical trial

Population

1,206 nulliparous women with a term singleton who delivered vaginally

Primary outcome

Second-, third- or fourth-degree perineal laceration

Effect

66.6% with hip extension vs 66.2% usual care (P=0.89)

A pragmatic, non-blinded US trial randomised nulliparous women with a term singleton to be asked to lower their legs and extend the hips just before crowning, or to deliver in their usual position, usually with hips flexed. 1,206 women delivered vaginally after randomisation.

Second-, third- or fourth-degree tears occurred in 66.6% with extension and 66.2% with usual care, with no difference by intention to treat. A quarter of the extension group did not adhere. In the as-treated analysis, sphincter injuries were 5.2% with extension versus 9.9% with flexion, but this was no longer significant after adjustment.

The primary answer is clear: telling women to extend their hips did not reduce significant tears. The as-treated signal on sphincter injury is weaker evidence, because women who could extend their hips may differ from those who could not.

For practice, there is no case for actively repositioning women at crowning to protect the perineum. Let women choose the position that suits them, and put the effort into the measures with better evidence.

• There is no need to redirect women into hip extension at crowning to prevent tears
• Let women deliver in the position they find comfortable
• Keep using controlled head delivery and warm compresses to protect the perineum
• Do not quote the as-treated sphincter-injury reduction as an established benefit

Why it matters

It removes one coaching step from the second stage that midwives and obstetricians may have been using.

Don't overread it

The lower sphincter-injury rate came from an as-treated analysis that lost significance after adjustment.

The statistics, in plain English

66.6% versus 66.2% is essentially identical, with P=0.89. The as-treated comparison breaks randomisation, so differences there may reflect who was able to adopt the position rather than the position itself; after adjustment it was not significant.

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