Peripheral Nerve Blocks and Fascial Plane Blocks in Labor: Expert Evidence-Based Perspectives

The World Health Organization (WHO) designates epidural analgesia as the “gold standard” for labor pain relief.1 However, inserting epidurals can be challenging or contraindicated in certain situations (eg, thrombocytopenia, coagulopathy). Additional comorbidities may preclude neuraxial techniques, so the need for alternative methods becomes more pressing. Historically, pudendal nerve block (PNB) and paracervical block (PCB) were commonly used, but their use has declined. Recently, there has been growing interest in fascial plane blocks (FPBs), including the ultrasound-guided quadratus lumborum block (QLB) and erector spinae plane block (ESPB). We are not aware of any systematic reviews evaluating the safety or effectiveness of these blocks, and their clinical niche to date seems to lack expert consensus. Here we address this gap by offering our expert opinion, as based on a systematic review of the literature that accompanies the article (Supplementary Digital Content, https://links.lww.com/AA/F693). SUMMARY OF FINDINGS A detailed description of the methodology used for the literature review is available in Supplementary Digital Content, https://links.lww.com/AA/F693. This considers relevant studies involving laboring women aged over 18 years, who received peripheral nerve blocks (PNBs) or FPBs. The primary outcomes evaluated in the studies were maternal satisfaction (pain relief and opioid use). Secondary outcomes included any type of maternal or fetal periprocedural complication related to the analgesic technique used. Randomized clinical trials (RCTs), review, and observational studies on the topic of PCB and PNB were included, and given the limited availability of high-level evidence, we also included case reports, case series, and letters to the editor. A total of 12,575 articles were initially identified, which, after screening and exclusion criteria, left just 16 studies for consideration2–17; details from each included study are summarized in the Table. Table. - Summary of Included Studies Grouped by Block Type Author (year) Study design Interventions Sample Size Outcome Effect size Complications PCB Jensen et al(1984)4 RCT PCB 12 mL of 0.25% Bupivacaine 55 Labor pain reliefNeonatal well-being assessed with Apgar score (after 1 and 5 minutes) PCB provided significantly better pain relief (p<0.05).Apgar similar (9.3/9.9 vs 9.1/10.0) Two cases of transientfetal bradycardia IM injection of 75 mg Meperidine 62 Nikkola et al (2000)3 RCT PCB 10 mL of 0.25% Bupivacaine 7 Labor pain relief assessed with VASNeonatal monitoring Comparable between two groupsHeart rate lower with fentanyl group (p=0,02)Neurological functions slower with fentanyl(p=0.004) Trial stopped due to significant desaturation (SpO2 59%) in one fentanyl group IV Fentanyl PCA 5 Shravage et al(2001)2 RCT PCB 20 mL of 2% Lidocaine 100 Pain relief assessed with VAS PCB significantly better than placebo (RR 32.31; 95% CI 10.6–98.5) Dizziness, sweating and tingling in the woman’s lower extremitiesTransient fetal bradycardia PCB with Distilled Water 98 PNB Nikpoor et al(2013)5 Systematic review (1/4 RCTs analyzed) PNB 20 mL of 1% Lidocaine 92 Pain relief Spinal anesthesia superior to PNB (RR 0.02; 95% CI 0.00–0.27) None observed Spinal Anesthesia 1 mL of 5% Lidocaine 91 Beke(2022)6 Prospective randomized controlled study Peripudendal block 4 mL of 1% Lidocaine (for each side) 236 Episiotomy rateInjury rateNeed for surgical care Lower with Peripudendal block (P <.02)Higher with Peripudendal block (NS)Lower with Peripudendal block (P <.02) None observed No Peripudendal block 421 Waldum et al(2022)7 Observational cohort study PNB (Bupivacaine, Lidocaine or Bupivacaine with Epinephrine) 495 Childbirth Experience assessed with CEQ score No significant differences between spontaneous (mean ARD = −0.05; NS) and instrumental birth (mean ARD = 0.03; NS) Not assessed No PNB 485 Ellouze et al(2024)8 Randomized prospective comparative study Unilateral PNB 15 mL of 0.75% Ropivacaine 35 Pain intensity assessed with VASSuture durationRehabilitation Lower VAS scores in the PNB group at all time points postpartum (OR 1.8-3.2.)Shorter in the PNB group (P <.01)Faster recovery in the PNB group (P <.001, OR = 2.5) None observed Local infiltration with 10 mL of 2% Lidocaine 35 Luxey et al(2024)9 Systematic review (1/79 RCTs analyzed) Unilateral PNB 15 mL of 0.75% Ropivacaine 20 Pain scores at rest and during activity assessed with VASNeed for additional analgesia Lower pain scores with PNB (P <.05)Less rescue analgesia with PNB (ARR 70%, RR 0.18, NNT 1.4, p=0.001) None observed PNB 15 mL of Saline 20 pQLB De Haan et al(2020)10 Case report pQLB 20 mL of 0.5 % Bupivacaine (for each side) 1 Pain assessment (patient’s verbal report) Pain reduced in the first stage of labor No uterine contraction feeling during the second stage of labor Apgar score 9 at 1 min 10 at 5 min ESPB Vilchis-Renteria et al(2020)11 Case series 1) ESPB 20 mL of 0.2 % Ropivacaine (for each side) 4 Labor pain relief assessed with NRS Mean ΔNRS = 4 Cesarean delivery under spinal anesthesia due to obstructed labor - patient two 2) Unilateral ESPB 20 mL of 0.5 % Ropivacaine 3) Unilateral ESPB 20 mL of 1.5 % Lidocaine + 1:200 000 Adrenaline 4) Unilateral ESPB 20 mL of 0.5 % Lidocaine + 1:200 000 Adrenaline Yasar et al(2021)12 Case series ESPB 10 mL of 0.25% Bupivacaine (for each side) 3 Labor pain relief assessed with NRS Mean ΔNRS = 3 Tachycardia, hypertension, and NRS pain score increase (7–8/10) during the second stage of labor – all three patients Niraj et al(2024)13 Case series ESPB 30 mL of 62.5 mg Bupivacaine + 100 mg Lidocaine (with 1:200.000 Epinephrine) + 4 mg Dexamethasone (for each side) 10 Labor pain relief assessed with NRS Abdominal pain: mean ΔNRS = 8Perineal pain: mean ΔNRS = 5 Cesarean delivery due to fetal distress in 2 cases Martin Serrano et al(2024)14 Case report S-ESPB 20 mL of 0.25% Levobupivacaine (for each side) 1 Labor pain relief assessed with VAS ΔVAS = 4 None observed S-ESPB Paventi et al(2024)16 Case report S-ESPB 30 mL of 0.3% Ropivacaine 1 Labor pain relief assessed with NRS ΔNRS = 6 Cesarean delivery under spinal anesthesia due to labor arrest Δ pain score: difference between pre- and postintervention pain scores (eg, VAS 8 → 4 = ΔVAS 4).Mean Δ pain score: average Δ pain score across patients (eg, 4, 5, 3 → mean ΔVAS 4).For bilateral blocks, the reported volume refers to the dose per side unless otherwise specified.Definitions of maternal satisfaction and pain relief varied among studies; outcomes are presented as reported in the original publications.Abbreviations: 95% CI, confidence interval, ARD, absolute risk difference, ARR, absolute risk reduction, CEQ, childbirth experience questionnaire, ESPB, erector spinae plane block, NNT, number needed to treat, NS, the difference was not significant, NRS, numerical rating scale, OR, odds ratio, PCB, paracervical block, pQLB, posterior quadratus lumborum block, PNB, pudendal nerve block, RCT, randomized controlled trial, RR, relative risk, S-ESPB, sacral-erector spinae plane block, SpO2, peripheral oxygen saturation, VAS, visual analogue scale. PCB: Summary of Evidence One RCT involving 198 women found that PCB with 20 mL of 2% lidocaine was significantly more effective than a placebo (relative risk [RR], 32.31; 95% confidence interval [CI], 10.60–98.54).2 However, it also reported side effects such as transient fetal bradycardia, as well as maternal side effects including dizziness, sweating, and tingling in the lower extremities.2 In one RCT by Nikkola et al, PCB (10 mL of 0.25% bupivacaine injected into four locations at the cervix) provided analgesia comparable to patient-controlled intravenous fentanyl.3 The study was halted after 12 participants when one neonate in the fentanyl group experienced significant desaturation, requiring naloxone. Neonates in the fentanyl group also exhibited lower heart rates and less favorable neurological outcomes.3 In another RCT by Jensen et al, women who received PCB with 12 mL of 0.25% bupivacaine (30 mg) reported higher satisfaction with analgesia compared to those who received intramuscular pethidine (odds ratio [OR], 2.52; 95% CI 1.65–3.83).4 Importantly, neonatal outcomes in both studies were favorable, with Apgar scores ≥ 7 at 5 minutes postdelivery.3,4 PCB: Expert Commentary PCB entails a non-negligible risk of maternal complications—ranging from inadvertent intravascular injection and neuropathic injury due to sacral plexus trauma, to the formation of pelvic hematomas and abscesses. The technique is highly operator-dependent, a factor that has likely contributed to its gradual decline in favor of more reliable techniques. Notably, none of the available studies directly compared PCB with neuraxial analgesic techniques; this gap underscores the need for further comparative research. Given the rich vascularity of the paracervical region, PCB carries a higher bleeding risk and should be avoided in patients with active coagulopathy or inadequate platelet count.18,19 Particularly concerning is its contraindication in cases of utero-placental insufficiency and nonreassuring cardiotocographic (CTG) patterns.18 In the specific context of intrauterine fetal demise, PCB may still be considered. If performed, several technique modifications may minimize maternal risk even when coagulation is normal: using the smallest effective needle gauge, minimizing punctures, performing incremental injections with aspiration before each dose, and avoiding vasoconstrictors that might mask bleeding. Although vasoconstrictors could theoretically promote local hemostasis by reducing vascular perfusion, their use may delay recognition of ongoing hemorrhage, which is particularly concerning in patients with thrombocytopenia or coagulopathy.20 Continuous maternal monitoring during the procedure and careful postprocedure observation would be advisable to promptly detect signs of pelvic hematoma (pelvic/abdominal pain or hemodynamic instability). Clinicians should also consider the possibility of retroperitoneal hematoma, which may present with nonspecific abdominal or hemodynamic findings.21 Abdominal ultrasound can miss both pelvic and retroperitoneal collections; therefore, abdominal CT should be performed when there is clinical suspicion, with subsequent management through interventional radiology or exploratory laparotomy as appropriate. PNB: Summary of Evidence In a systematic review by Nikpoor et al, spinal anesthesia was found to be more effective than PNB for operative vaginal delivery (OR 3.36; 95% CI, 2.46–4.60), with better maternal satisfaction.5 Beke et al’s RCT of bilateral PNBs (4 mL of 2% lidocaine for each side) during the second stage of labor compared to no blocks showed that bilateral PNBs significantly reduced the episiotomy rate due to enhanced perineal relaxation.6 However, this same relaxation increased the risk of spontaneous perineal tears, mostly of first and second degree, with no significant rise in severe (third-degree) injuries.6 In an observational cohort study by Waldum et al, women’s birth experiences (Childbirth Experience Questionnaire, CEQ) were not enhanced by PNB (with bupivacaine, lidocaine, or bupivacaine with epinephrine)7 when compared with no PNB. This result was valid for both spontaneous deliveries (mean absolute risk difference: −0.05, P = .36) and instrumental deliveries (mean absolute risk difference: 0.03, P = .61).7 Other studies reported varying degrees of satisfaction and efficacy with PNB. Postdelivery PNB for episiotomy repair was studied in a prospective randomized study by Ellouze et al where one group received a unilateral nerve stimulator-guided PNB on the side of the lateral episiotomy with 15 mL of 0.75% ropivacaine, and the other received 10 mL of 2% lidocaine infiltration along the length of the incision. The trial was single-blinded, as the operator and assisting nurse knew the assigned technique, whereas outcomes were assessed by a second anesthetist, and patients could not reliably distinguish between treatments. Pain scores were significantly lower in the PNB group (P <.01), although the authors noted that complete patient blinding could not be guaranteed, representing a methodological limitation.8 In contrast, a systematic review by Luxey et al in 2024 recommended against PNB for postpartum pain relief due to insufficient evidence.9 PNB: Expert Commentary Although multiple anatomical approaches exist for PNB—whether transvaginal, transperineal, or transgluteal, with or without ultrasound guidance—no particular approach has demonstrated consistent efficacy or patient comfort. A key limitation remains the anatomical challenge of targeting the pudendal nerve—deeply embedded near the ischial spine and often obscured by connective tissue.22 Ultrasound guidance, although potentially helpful, requires considerable pressure, often resulting in pain, which can hinder both localization and cooperation. Moreover, the single-shot nature of PNB yields a short duration of action, limiting its value during prolonged second-stage labor. Beyond technical concerns, the impact on postpartum bladder function should not be underestimated. PNB can disrupt both sensory and motor components of micturition, increasing the risk of urinary retention. In contemporary obstetric practice, PNB may retain utility for episiotomy repair, but its routine use in the second stage of labor appears increasingly difficult to justify in light of these limitations. The safety profile of PNB requires particular consideration, and it is contraindicated in patients with frank coagulopathy. Perineal is highly significant of to before clinical which often recognition of bleeding In patients with of the to with PNB should be the analgesic against the of the PNB risk by the is and should be whereas or approaches may be in patients with platelet and no bleeding provided ultrasound and prolonged are is before performing PNB in patients with any coagulation and should be to for clinical signs of A perineal hematoma may initially present with pain, or a but can and to hemodynamic not promptly Abdominal or pelvic may also of the need for a of Ultrasound assessment may a in but in cases of or clinical is more Summary of Evidence In a case report by De Haan et al a with A received a bilateral posterior with 20 mL of bupivacaine for each side for labor The block in effective pain relief the first stage of for 3 to 4 and in an vaginal delivery with a favorable neonatal Expert Commentary The particularly the type 2 and type 3 and pain relief through into the In contrast, the type 1 more limited analgesic of a in technical due to the anatomical and hemodynamic of of the abdominal and reducing the and increasing the of the quadratus lumborum and both in and during further and needle uterine also the between the abdominal and retroperitoneal that hinder the of the needle of and abdominal due to and increased volume the risk of inadvertent vascular and in laboring women should be for and performed by experienced under ultrasound The on of local also in patients who may The is as a plexus the same and for as recommended for neuraxial and other plexus blocks should be in with If the block is in the of platelet and it would be advisable to several ultrasound with to and minimize needle use of the smallest effective needle with a local and to the risk of and to and obstetric to for signs such as or pain, or hemodynamic should a for and of interventional given the for retroperitoneal or Summary of Evidence In a case series by Vilchis-Renteria et al, four women in the first stage of labor received ESPB at the The first patient received 20 mL of the 20 mL of the 20 mL of lidocaine with and the 20 mL of lidocaine with also The for performing unilateral blocks was the and epidural of local also by and both and and may participants reported complete pain with a on the and analgesia duration from to No were In a case series, three received bilateral ESPB (10 mL of 0.25% bupivacaine for each side) during the first stage of with significant pain on the However, pain relief was insufficient during the second rescue case series by Niraj et al included 10 women who received bilateral ESPB due to of IV the first a 30 mL bupivacaine lidocaine mg with and (4 mg) was injected for each the effectiveness of a and the technical of during active the four women received single-shot bilateral participants experienced complete relief of abdominal pain, although two of the cases delivery due to fetal which in labor than in to the The authors not the fetal to the block, and no ESPB to fetal distress was A case report by Martin Serrano et al a with factor who received a bilateral ESPB mL of 0.25% for each side) for labor analgesia with significant pain Summary of Evidence on the that sacral to the of epidural analgesia and maternal during the second stage of et al in a to the to epidural with when neuraxial are contraindicated or be this using bilateral ESPB by a single-shot S-ESPB with 30 of 0.3% in labor A clinical case report by Paventi the use of S-ESPB of 30 mL of 0.3% in a The patient reported a significant in pain from 8 to 2 on the NRS, a delivery under spinal anesthesia due to labor No related to or epidural hematoma been reported with ESPB or A review of patients in patients with or risk of bleeding with ESPB and Expert Commentary Although there been no reported cases of or epidural hematoma with the ESPB, its the for and the of local that are particularly relevant in obstetric The of further the risk of given the for effective is the epidural after and ESPB, which may motor block or lower maternal and for a labor ESPB is with other such as may be by in with PCB or additional blocks, theoretically offering and the dose and the of blocks are performed by without there is a risk of inadequate or inadvertent these such should be for requiring dose and growing interest in the ESPB, its effectiveness for obstetric analgesia remains highly and sacral ESPB significant technical related to patient for is not during labor. Although or lateral may theoretically to neuraxial block approaches lateral is by with spinal whereas the may maternal and during Moreover, neuraxial techniques, ESPB requires fascial plane at where and anatomical further needle to the technical of ESPB in obstetric S-ESPB additional potentially with the key of effective block may hinder labor This is particularly relevant for patients a less alternative to neuraxial However, in where neuraxial are contraindicated (eg, in women with or the risk of the may be as the same limitation with neuraxial blocks and obstetric can to the The by which ESPB might analgesia remains local into the or epidural with but is and in obstetric In patients with thrombocytopenia or ESPB and S-ESPB are to a lower bleeding risk compared to plexus blocks, as the injection is more and to However, given the of these should still be with the same used for neuraxial or peripheral ultrasound guidance, needle and postprocedure monitoring for bleeding. The that these varying degrees of pain relief during with specific and on the technique and stage of labor. PCB was to be effective in the first stage of when compared with but has not been compared with neuraxial PNB showed limited and efficacy during the second stage of less effective than spinal The posterior has been in a case where it provided effective analgesia during the first stage of labor. A total of 18 cases of were identified, with of in pain during the first but not the second stage of labor. a case report that the S-ESPB may analgesia during the second stage of although further studies are needed to its efficacy and The of the available was Case and series often and in whereas observational studies of particularly in and of Randomized trials showed with in design and provided but were limited by literature or insufficient reducing their The provided is on and methodological than for nerve blocks for labor and delivery may be for patients who to neuraxial for patients with an anatomical spine that neuraxial and as a to neuraxial analgesia for patients with to total local dose the risk of when multiple blocks are of in and neuraxial are contraindicated due to thrombocytopenia or the safety of peripheral and on needle and In and blocks should be particularly the PCB, PNB, and such as the PNB and the ESPB, are theoretically although is insufficient to risk, assessment of and and before In a platelet is as risk for neuraxial hematoma in otherwise and comparable or are for blocks, whereas blocks may be performed at lower for single-shot ultrasound-guided at and postprocedure monitoring Study were based on a group of in and for were often limited to Apgar scores without neurological and maternal pain Although we (Supplementary Digital Content, this approach across studies and particularly in with insufficient We not or a The of case and case series carries a risk of although both can of or although were per technique, their impact on maternal and neonatal outcomes remains due to limited and Although alternative anesthesia as PCB, PNB, ESPB, and demonstrated varying degrees of effectiveness in labor we based on our literature review that be reliable for neuraxial anesthesia in routine obstetric Although each technique specific key a lack of to the of insufficient of both and pain, to and use may be in clinical as when neuraxial anesthesia is or be with into their in increase the risk of any analgesic although and approaches hematoma can with any of the obstetric all the blocks are and by anatomical in Moreover, none of the evaluated both of labor In PNBs and during labor should be and to studies should their the technique, and into labor analgesia without maternal or neonatal of This was The authors would to the for the and the time in the of the