Pudendal nerve block is one of the quiet workhorses of obstetric and gynecologic care. It's been used for decades to manage pain during vaginal birth and a range of gynecologic procedures, and when it works, it works well: strong, targeted pain relief without the risks that come with general or neuraxial anesthesia.

The problem is that it doesn't always work.

Published literature puts average failure rates around 20%, with some series reporting failure on at least one side in up to half of cases. That's a wide range for a procedure this common, and it's worth asking why.

~20%
average failure rate in published literature
50%
failure on at least one side in some series
1953
year the landmark technique was established, unchanged since

A Technique Built on Touch

The transvaginal approach to pudendal block depends on the clinician's ability to locate the ischial spine and sacrospinous ligament by feel, then guide a needle to within about a centimeter of a target that isn't visible and sits close to major blood vessels. Done well, it's fast and effective. Done by someone earlier in their training, or on a patient with less typical anatomy, it's easy to miss.

"The literature is fairly direct about where the variability comes from: it points primarily to technique and operator experience, not patient anatomy. That's a meaningful distinction. It suggests the ceiling on consistency isn't set by the biology; it's set by how reliably any given clinician can execute a landmark-based, blind technique under real clinical conditions."

Jimmy Belotte, MD, PhD, MBA, FACOG

It also helps explain why the procedure remains underused in some settings, despite its benefits: patient discomfort with landmark-based injection, understandable concern about nearby structures, and, frankly, limited hands-on training time in many residency programs.

Why This Matters Beyond the Numbers

A failed block isn't just a statistic. It's a patient who doesn't get the pain relief she was counting on, at a moment when there's no good opportunity to simply try again.

It's also a reminder that some of the most established techniques in obstetric and gynecologic care haven't been meaningfully re-examined in a long time, not because they don't matter, but because they've simply always been done this way.

We think that's worth a second look. Procedural consistency (making sure a well-established technique performs the same way regardless of who's holding the needle or how many times they've done it) is a problem worth solving carefully, and it's one we're actively working on at NEG+.

We'll have more to share as that work progresses.

Reference: Ghanavatian S, Leslie SW, Derian A. Pudendal Nerve Block. Updated Sept 2, 2024. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2026. Available at ncbi.nlm.nih.gov/books/NBK551518/.