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

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 tissue is highly distensible, allowing significant volumes of blood to accumulate before clinical detection, which often delays recognition of bleeding complications.²² In patients with subclinical markers of abnormal coagulation, the decision to proceed with PNB should be individualized, balancing the potential analgesic benefit against the severity of the hemostatic derangement. PNB risk varies by approach: the transgluteal route is noncompressible and should be avoided, whereas transperineal or transvaginal approaches may be acceptable in selected patients with adequate platelet counts and no bleeding history, provided ultrasound guidance and prolonged compression are applied.^19,22

Careful multidisciplinary evaluation is warranted before performing PNB in patients with any coagulation impairment, and nursing staff should be explicitly alerted to monitor for early clinical signs of hematoma. A perineal hematoma may initially present with localized pain, induration, or a firm swelling, but can rapidly expand and progress to hemodynamic instability if not promptly identified.²² Abdominal or pelvic discomfort may also herald deeper extensions of bleeding, underscoring the need for a high index of suspicion.²² Ultrasound assessment may have a role in bedside evaluation, but in cases of diagnostic uncertainty or clinical deterioration, cross-sectional imaging is more reliable.

Ultrasound-Guided QLB: Summary of Evidence

In a case report by De Haan et al a woman with hemophilia A received a bilateral posterior QLB with 20 mL of 0.5% bupivacaine for each side for labor analgesia.¹⁰ The block resulted in effective pain relief throughout the first stage of labor, for 3 to 4 hours, and culminated in an uncomplicated vaginal delivery with a favorable neonatal outcome.

Ultrasound-Guided QLB: Expert Commentary

The QLB, particularly the type 2 (posterior) and type 3 (anterior/transmuscular) approaches, provides potential visceral and somatic pain relief through spread into the paravertebral space. In contrast, the type 1 QLB offers more limited analgesic coverage. Placement of a QLB in parturients presents unique technical challenges due to the anatomical and hemodynamic changes of pregnancy.²³ Progressive enlargement of the uterus displaces abdominal viscera and alters lumbar paravertebral anatomy, reducing the sonographic windows and increasing the depth of the quadratus lumborum muscle. Increased lumbar lordosis and soft tissue edema, both common in late pregnancy and exacerbated during labor, further limit probe positioning and needle visualization. Intrapartum uterine contractions also modify the spatial relationship between the abdominal wall and retroperitoneal structures, causing dynamic shifts that hinder the stability of the needle trajectory. Additionally, engorgement of paravertebral and abdominal wall blood vessels due to caval compression and increased blood volume raises the risk of inadvertent vascular puncture and hematoma. These factors combined explain why QLB in laboring women should be reserved for select scenarios and performed only by experienced operators under strict ultrasound guidance.

The technique’s dependence on large volumes of local anesthetic also raises concerns about LAST, especially in pregnant patients who may have altered pharmacokinetics.²⁴ The QLB is regarded as a deep, noncompressible plexus block. Therefore, the same precautions and timing for anticoagulant interruption as recommended for neuraxial and other deep plexus blocks should be followed, in accordance with professional society guidelines.^25–27 If the block is undertaken in the setting of adequate platelet count, and corrected hemostasis, it would be advisable to adopt several precautions: meticulous ultrasound guidance with color Doppler to identify lumbar vessels and minimize needle passes, use of the smallest effective needle gauge with a single puncture, conservative local anesthetic volumes and doses to reduce the risk of LAST, close maternal–fetal monitoring, and clear instructions to nursing and obstetric staff to remain vigilant for warning signs such as worsening lumbar or flank pain, femoral paresthesias, hemoglobin drop, or hemodynamic instability. Such findings should prompt a low threshold for imaging and early activation of interventional radiology, given the potential for retroperitoneal or psoas hematoma.

Ultrasound-Guided ESPB: Summary of Evidence

In a case series by Vilchis-Renteria et al, four women in the first stage of labor (6–8 cm cervical dilation) received lumbar ESPB at the L4 level.¹¹ The first patient received 20 mL of 0.2% ropivacaine bilaterally; the second, 20 mL of 0.5% ropivacaine unilaterally; the third, 20 mL of 1.5% lidocaine with 1:200,000 adrenaline unilaterally; and the fourth, 20 mL of 0.5% lidocaine with 1:200,000 adrenaline, also administered unilaterally. The rationale for performing unilateral blocks was the documented paravertebral and epidural spread of local anesthetic—confirmed also by Magnetic Resonance Imaging and cadaveric studies—which provides both somatic and visceral coverage and may extend contralaterally.¹¹ All participants reported complete pain relief, with a 3-6 point reduction on the Numerical Rating Scale (NRS), and analgesia duration ranged from 60 to 120 minutes. No procedure-related complications were noted.¹¹ In a 2021 case series, three parturients received bilateral thoracic (T11) ESPB (10 mL of 0.25% bupivacaine for each side) during the first stage of labor, with significant pain reduction on the NRS. However, pain relief was insufficient during the second stage, necessitating rescue analgesia.¹² The largest case series by Niraj et al included 10 nulliparous women who received bilateral lumbar (L4) ESPB due to failure of standard IV tramadol therapy. For the first six women, a mixture containing 30 mL bupivacaine (62.5 mg), lidocaine (100 mg with 1:200,000 epinephrine), and dexamethasone (4 mg) was injected for each side. After observing the effectiveness of a single bolus and considering the technical challenges of catheter placement during active labor, the remaining four women received single-shot bilateral ESPB. All participants experienced complete relief of abdominal pain, although two of the ten cases required cesarean delivery due to fetal distress, which developed later in labor rather than in close temporal relation to the block. The authors did not attribute the fetal compromise to the block, and no mechanism linking ESPB to fetal distress was suggested.¹³ A case report by Martin Serrano et al described a pregnant woman with factor XI deficiency, who received a bilateral lumbar ESPB (20 mL of 0.25% levobupivacaine for each side) for labor analgesia with significant pain reduction.¹⁴

Ultrasound-Guided Sacral ESPB: Summary of Evidence

Based on the idea that sacral sparing contributes to the failure of epidural analgesia and adverse maternal experience, especially during the second stage of labor, Marrone et al proposed in a letter to the editor to combine epidural with sacral-ESPB (S-ESPB).¹⁵ Alternatively, when neuraxial techniques are contraindicated or cannot be feasible, this letter proposes using early bilateral continuous lumbar ESPB (L1–L2) followed by a single-shot S-ESPB with 30 ml of 0.3% ropivacaine in advanced labor stages.¹⁵ A clinical case report by Paventi described the use of S-ESPB (single-shot administration of 30 mL of 0.3% ropivacaine) in a nulliparous woman. The patient reported a significant reduction in pain intensity, from 8 to 2 on the NRS, though she ultimately required a cesarean delivery under spinal anesthesia due to labor arrest.¹⁶

No complications related to LAST or epidural hematoma have been reported with either ESPB or Sacral ESPB. A review of nonobstetric patients in patients treated with anticoagulant or antiplatelet therapy suggested minimal risk of bleeding with ESPB.²⁸

Ultrasound-Guided ESPB and Sacral-ESPB: Expert Commentary

Although there have been no reported cases of LAST or epidural hematoma associated with the ESPB, concerns persist regarding its volume-dependent nature, the potential for systemic toxicity, and the unpredictable distribution of local anesthetic —issues that are particularly relevant in obstetric patients.¹⁷ The physiological changes of pregnancy further amplify the risk of LAST, especially given the high anesthetic volumes usually required for effective ESPB.^23,29 Another critical issue is the unpredictable epidural spread described after thoracic and lumbar ESPB, which may cause motor block or lower limb weakness, thereby compromising maternal mobility and expulsive efforts—both essential for a positive labor experience.³⁰ When ESPB is combined with other FPBs, such as QLB, risks may be compounded by cumulative anesthetic dosing. Performance in conjunction with PCB or additional regional blocks, while theoretically offering complementary visceral and somatic coverage, increases the overall LA dose and thus the likelihood of LAST. Furthermore, if blocks are performed independently by different team members without coordination, there is a tangible risk of overlapping dermatomal coverage, inadequate monitoring, or inadvertent cumulative dosing. For these reasons, such combinations should be reserved for strictly indicated scenarios, always requiring dose adjustment, structured team coordination, and continuous maternal-fetal surveillance.²⁹ Despite growing interest in the ESPB, its overall effectiveness for obstetric analgesia remains highly questionable. Thoracic, lumbar, and sacral ESPB pose significant technical challenges, mainly related to patient positioning. Prone positioning, ideal for optimal needle-probe alignment, is not feasible during labor. Although sitting or lateral positioning may theoretically facilitate alignment—similar to neuraxial block placement—both approaches have limitations: lateral positioning is complicated by difficulty with spinal alignment, whereas the sitting position may reduce maternal tolerance and cooperation during contractions. Moreover, unlike neuraxial techniques, ESPB requires precise fascial plane identification at greater depth, where pregnancy-related edema and anatomical variation further compromise needle visualization. These factors contribute to the persistent technical complexity of ESPB in obstetric practice.

S-ESPB presents additional concerns. By potentially interfering with the Ferguson reflex—a key trigger of effective expulsive effort—this block may hinder natural labor progression.²⁹ This concern is particularly relevant for patients seeking a less invasive alternative to neuraxial analgesia. However, in scenarios where neuraxial techniques are contraindicated (eg, in women with Harrington rods or spina bifida), the potential risk of blunting the Ferguson reflex may be considered acceptable, as the same limitation exists with neuraxial blocks and obstetric providers can provide coached pushing to support the expulsive phase. The mechanism by which ESPB might provide visceral analgesia remains uncertain. Proposed explanations include local anesthetic spread into the paravertebral or epidural space with partial sympathetic blockade, but evidence is inconsistent and inconclusive in obstetric patients.^11,30

In patients with thrombocytopenia or coagulopathy, ESPB and S-ESPB are generally considered to carry a lower bleeding risk compared to deep, noncompressible plexus blocks, as the injection site is more superficial and accessible to compression.^19,25 However, given the paucity of obstetric-specific data, these techniques should still be approached with caution, applying the same principles used for neuraxial or deep peripheral blocks: multidisciplinary assessment, strict ultrasound guidance, minimal needle passes, and close postprocedure monitoring for occult bleeding.

Main Findings

The findings suggest that these techniques provide varying degrees of pain relief during labor, with specific advantages and limitations depending on the technique and stage of labor. PCB was shown to be effective in the first stage of labor, when compared with systemic opioids, but has not been compared with neuraxial analgesia. PNB showed limited and inconsistent efficacy during the second stage of labor, remaining less effective than spinal anesthesia. The posterior QLB has been described in a single case report, where it provided effective analgesia during the first stage of labor. A total of 18 cases of ESPBs were identified, with reports of reduction in pain during the first but not the second stage of labor. Finally, a single case report suggests that the S-ESPB may offer analgesia during the second stage of labor, although further studies are needed to confirm its efficacy and safety.

The quality of the available evidence was limited. Case reports and small series often lacked detail and consistency in reporting outcomes, whereas observational studies carried risks of bias, particularly in participant selection and control of confounding factors. Randomized trials showed uneven rigor, with some limitations in design and execution. Reviews generally provided useful insights but were sometimes limited by incomplete literature searches or insufficient data presentation, reducing their overall reliability. The summary provided here is focused on highlighting evidence gaps and methodological limitations rather than duplicating existing reviews.

Indications for Peripheral Nerve Blocks

Peripheral nerve blocks for labor and delivery may be considered for patients who wish to avoid neuraxial analgesia, for patients with an anatomical spine abnormality that contraindicates neuraxial analgesia, and as a supplement to neuraxial analgesia for patients with breakthrough pain. Careful attention to total local anesthetic dose will limit the risk of LAST when multiple regional blocks are combined.

Safety of Nerve Blocks in Thrombocytopenia and Coagulopathy

When neuraxial techniques are contraindicated due to thrombocytopenia or coagulopathy, the safety of peripheral and FPBs depends mainly on needle depth and site compressibility. In general, deep and noncompressible blocks should be avoided, particularly the PCB, transgluteal PNB, and pQLB. Superficial, compressible approaches, such as the transvaginal PNB and the ESPB, are theoretically safer, although evidence is insufficient to exclude serious risk, mandating multidisciplinary discussion, individualized assessment of benefits and risks, and shared decision making before use.^19,25 In obstetrics, a platelet count ≥70×10⁹/L is usually regarded as low risk for neuraxial hematoma in otherwise healthy women, and comparable or stricter thresholds are applied for deep blocks, whereas superficial blocks may occasionally be performed at slightly lower counts.^19,25,29 Careful preprocedure evaluation, preference for single-shot ultrasound-guided techniques at compressible sites, and vigilant postprocedure monitoring remain essential.^19,25,29

Study Limitations

Our findings were based on a heterogeneous group of studies, differing in design, sample size, and outcome reporting. Neonatal outcomes, for example, were often limited to Apgar scores without in-depth neurological evaluation, and maternal pain assessments lacked long-term follow-up. Although we applied different validated tools (Supplementary Digital Content, https://links.lww.com/AA/F693), this approach hindered direct comparisons across studies and introduced potential assessor-related bias, particularly in domains with insufficient reporting. We did not assess inter-rater reliability or involve a third reviewer. The inclusion of case reports and small case series carries a high risk of bias; although both can illustrate possible scenarios, neither provides evidence of association or causation. Finally, although individual complications were discussed per technique, their overall impact on maternal and neonatal outcomes remains uncertain due to limited follow-up and small sample sizes.