Highlights
- •Four risk factors are associated with difficult fetal extraction in emergency CS.
- •Difficult fetal extraction causes maternal blood loss, low Apgar score and low umbilical artery pH.
- •This article suggests a definition of difficult fetal extraction.
Abstract
Introduction
This study aimed to assess risk factors for difficult fetal extraction in emergency caesarean sections, focusing on top-up epidural anesthesia compared to spinal anesthesia. Additionally, this study addressed consequences of difficult fetal extraction on neonatal and maternal morbidity.
Material and Methods
This retrospective registry-based cohort study included 2,332 of 2,892 emergency caesarean sections performed with local anesthesia during 2010–2017. Main outcomes were analyzed by crude and multiple adjusted logistic regression providing odds ratios.
Results
Difficult fetal extraction was found in 14.9% of emergency caesarean sections.
Risk-factors for difficult fetal extraction included top-up epidural anesthesia (aOR:1.37[95 %CI 1.04–1.81]), high pre-pregnancy BMI (aOR:1.41[95 %CI 1.05–1.89]), deep fetal descent (ischial spine: aOR:2.53[95 %CI 1.89–3.39], pelvic floor: aOR:3.11[95 %CI 1.32–7.33]), and anterior placental position (aOR:1.37[95 %CI 1.06–1.77]). Difficult fetal extraction was associated with increased risk of low umbilical artery pH 7.00–7.09 (aOR:3.50[95 %CI 1.98–6.15]) pH ≤ 6.99 (aOR:4.20[95 %CI 1.61–10.91]), five-minute Apgar score ≤ 6 (aOR:3.41[95 %CI 1.49–7.83]) and maternal blood loss (501–1,000 ml: aOR:1.65[95 %CI 1.27–2.16], 1,001–1,500 ml: aOR:3.24[95 %CI 2.24–4.67], 1,501–2,000 ml: aOR:3.94[95 %CI 2.24–6.94] and ≥ 2001 ml: aOR:2.76[95 %CI 1.12–6.82]).
Conclusion
This study identified four risk factors for difficult fetal extraction in emergency caesarean section: top-up epidural anesthesia, high maternal BMI, deep fetal descent and anterior placental position. Additionally, difficult fetal extraction was associated with poor neonatal and maternal outcomes.
Abbreviations:
DFE (Difficult fetal extraction), CS (Caesarean section), BMI (Body Mass Index), Apgar5 (Five-minute Apgar score), ml (milliliters), OR (Odds Ratio), aOR (Adjusted Odds Ratio), g (grams), CI (Confidence Interval)Keywords
Introduction
Difficult fetal extraction(DFE) during emergency cesarean section(CS) may prolong delivery interval and cause adverse outcomes for mother and child [
1
, 2
, 3
, 4
]. Currently, no universal definition of DFE is described and used consistently.Several factors can theoretically be associated with DFE. First, type of anesthesia may influence fetal extraction since emergency CSs are performed with either spinal-, top-up epidural- or general anesthesia [
[5]
]. Second, oxytocin augmentation used to stimulate contractions during delivery [OBSTETRISK ANÆSTESIUDVALG, DASAIM. Anæstesi til kejsersnit [Internet]. 2019. Available from: http://www.dasaim.dk/wp-content/uploads/2019/10/Anæstesi-til-kejsersnit-2019.pdf.
[6]
] may cause a contracted uterine muscle and DFE. Third, high maternal BMI can lead to poor visualization of the surgical field [[7]
], and has been associated with prolonged incision-to-delivery interval [[8]
].Fourth, a deeply engaged head in the pelvis is known to cause DFE in emergency CSs [
1
, 2
, 3
, 4
, 9
]. Furthermore, placental position, rupture of membranes prior to emergency CS, fetal weight and gestational age could also be potential risk factors for DFE. However, neither of these factors have been investigated.Clinical consequences of DFE on maternal and neonatal morbidity have previously been investigated [
1
, 2
, 3
, 4
]. Maternal blood loss is a well-established risk factor for maternal morbidity and mortality [10
, 11
, 12
]. Placental position has been associated with higher risk of postpartum haemorrhage [[13]
].Five-minute Apgar score(Apgar5) is a measure for fetal neurological state at birth, while umbilical artery pH < 7.10 is a predictor for neonatal acidosis [
[14]
]. Neonatal acidosis increases the risk for neonatal mortality [15
, 16
, 17
] and neonatal morbidity [18
, 19
, 20
, 21
, 22
, 23
, 24
, 25
, 26
]. DFE due to an impacted fetal head has in one study been associated with low umbilical artery pH.The aim of this study is to assess risk factors for DFE in emergency CSs with a focus on the risk associated with top-up epidural anesthesia compared to spinal anesthesia. In addition, we investigate how DFE affects neonatal and maternal morbidity.
Material and methods
Study design
This is a retrospective cohort study of all women who underwent emergency CS at Nordsjællands Hospital, Hillerød, Denmark, between January 1st, 2010 and March 16th, 2017, and their children.
Study population
All women with singleton pregnancies both cephalic and breech presentation who had emergency CSs classified as category 1, 2 or 3 based on urgency, and maximum tolerated time from decision-to-delivery was 15, 30 or 60 min respectively. Emergency CSs with general anesthesia and/or missing information were excluded.
Data sources
The personal identification number of each woman was extracted through an electronic health record system, DocuLive(Cerner-Corporation, USA). Afterwards, all data regarding mother and child were manually collected through medical charts found in the electronic birth journal KMD-Fødejournal, the local surgery registry Orbit and the EPIC health platform Sundhedsplatformen.
Defining difficult fetal extraction
We defined fetal extraction as difficult if extra ordinary measures were used or if DFE was described in the medical record. A fetal extraction was defined as difficult if at least one of the following descriptions were applied in the medical record when describing the extraction: 1) the words “difficult”, “a little difficult” or related synonyms were used, 2) kiwi cup was used for fetal extraction, 3) midwife/assistant pushed the fetal head up through the vagina, 4) use of terbutaline or glyceryl trinitrate or 5) another surgeon was called to assist with fetal extraction [
2
, 27
].Risk factors for difficult fetal extraction in emergency caesarean sections
The following nine potential risk factors for DFE were included in the statistical analysis.
Maternal age; maternal pre-pregnancy BMI; fetal birth weight; gestational age at delivery; fetal pelvic descent recorded as last noted position prior to emergency CS; rupture of membranes prior to emergency CS; oxytocin augmentation; placental location in the uterus recorded as last noted position determined by ultrasound; and type of anesthesia at the start of fetal extraction defined in Table 1, Table 2.
Table 1Descriptive statistics of the study population at baseline by presence of fetal extraction difficulties.
| Difficult fetal extraction: No | Difficult fetal extraction: Yes | |
|---|---|---|
| n (%) | n (%) | |
| 1984 (85.1) | 348 (14.9) | |
| Maternal age (years) | ||
| ≤25 | 301 (15.2) | 51 (14.7) |
| 26–35 | 1221 (61.5) | 231 (66.4) |
| ≥36 | 462 (23.3) | 66 (19.0) |
| Missing | 0 (0.0) | 0 (0.0) |
| Maternal pre-pregnancy BMI* (kg/m2) | ||
| ≤18.49 | 69 (3.5) | 7 (2.0) |
| 18.50–24.99 | 1097 (55.3) | 174 (50.0) |
| 25.00–29.99 | 476 (24.0) | 101 (29.0) |
| 30.00–34.99 | 195 (9.8) | 35 (10.1) |
| 35.00–39.99 | 81 (4.1) | 17 (4.9) |
| ≥40.00 | 29 (1.5) | 10 (2.9) |
| Missing | 37 (1.9) | 4 (1.2) |
| Fetal birth weight (gram) | ||
| ≤1999 | 84 (4.2) | 12 (3.5) |
| 2000–2499 | 101 (5.1) | 13 (3.7) |
| 2500–2999 | 222 (11.2) | 35 (10.1) |
| 3000–3499 | 523 (26.4) | 80 (23.0) |
| 3500–3999 | 616 (31.1) | 108 (31.0) |
| ≥4000 | 433 (21.8) | 98 (28.2) |
| Missing | 5 (0.3) | 2 (0.6) |
| Gestational age (weeks+days) | ||
| ≤31+6 | 37 (1.9) | 4 (1.2) |
| 32–36+6 | 187 (9.4) | 29 (8.3) |
| 37–40+0 | 687 (34.6) | 105 (30.2) |
| ≥40+1 | 1073 (54.1) | 210 (60.3) |
| Missing | 0 (0.0) | 0 (0.0) |
| Fetal descent into the pelvis | ||
| Pelvic entrance | 1656 (83.5) | 233 (67.0) |
| Ischial spine | 294 (14.8) | 103 (29.6) |
| Pelvic floor | 22 (1.1) | 9 (2.6) |
| Missing | 12 (0.6) | 3 (0.9) |
| Rupture of membranes prior to fetal extraction | ||
| Yes | 1586 (79.9) | 303 (87.1) |
| No | 398 (20.1) | 45 (12.9) |
| Missing | 0 (0.0) | 0 (0.0) |
| Oxytocin drop prior to fetal extraction | ||
| Yes | 1057 (53.3) | 230 (66.1) |
| No | 927 (46.7) | 118 (33.9) |
| Missing | 0 (0.0) | 0 (0.0) |
| Placental location in the uterus | ||
| Posterior | 857 (43.2) | 127 (36.5) |
| Anterior | 876 (44.2) | 177 (50.9) |
| Fundus | 57 (2.9) | 11 (3.2) |
| Praevia/partial praevia | 26 (1.3) | 1 (0.3) |
| Missing | 168 (8.5) | 32 (9.2) |
| Type of anesthesia at the start of fetal extraction | ||
| Spinal anesthesia | 1386 (69.9) | 206 (59.2) |
| Top-up epidural anesthesia | 598 (30.1) | 142 (40.8) |
| Missing | 0 (0.0) | 0 (0.0) |
| Five-minute Apgar score1 | ||
| ≤6 | 39 (2.0) | 15 (4.3) |
| 7–10 | 1941 (97.8) | 333 (95.7) |
| Missing | 4 (0.2) | 0 (0.0) |
| Umbilical artery pH value1 | ||
| ≤6.99 | 15 (0.8) | 8 (2.3) |
| 7.00–7.09 | 41 (2.1) | 22 (6.3) |
| ≥7.10 | 1582 (79.7) | 262 (75.3) |
| Missing | 346 (17.4) | 56 (16.9) |
| Maternal blood loss (ml)1 | ||
| 0–500 | 1105 (55.7) | 127 (36.5) |
| 501–1000 | 677 (34.1) | 136 (39.1) |
| 1001–1500 | 141 (7.1) | 57 (16.4) |
| 1501–2000 | 41 (2.1) | 21 (6.0) |
| ≥2001 | 19 (1.0) | 7 (2.0) |
| Missing | 1 (0.1) | 0 (0.0) |
| Surgical experience2 | ||
| Junior doctor | 1297 (55.1) | 204 (58.6) |
| Obstetrician | 718 (30.6) | 111 (31.9) |
| Gynecologist | 317 (14.4) | 33 (9.5) |
| Time from skin incision to delivery in minutes3 | ||
| Difficult fetal extraction: No | Difficult fetal extraction: Yes | |
| n (mean (SD)) | n (mean (SD)) | |
| Emergency grade | ||
| Category 1, 2 and 3 | 1928 (4.33 (2.79)) | 338 (7.39 (3.72)) |
| Category 1 | 50 (2.20 (1.71)) | 10 (5.30 (1.89)) |
| Category 2 | 779 (3.78 (2.31)) | 142 (6.38 (3.29)) |
| Category 3 | 980 (4.92 (3.02)) | 175 (8.34 (3.87)) |
Table 2Risk factors for difficult fetal extraction in univariate and adjusted logistic regressions.
| Risk factors | Crude OR | [95% CI] | Adjusted OR | [95% CI] |
|---|---|---|---|---|
| Maternal age (years) | ||||
| ≤25 | 0.9 | [0.64–1.24] | 0.91 | [0.63–1.30] |
| 26–35 | 1 | 1 | 1 | 1 |
| ≥36 | 0.75 | [0.56–1.01] | 0.81 | [0.59–1.11] |
| Maternal pre-pregnancy BMI* (kg/m2) | ||||
| ≤18.49 | 0.64 | [0.29–1.42] | 0.56 | [0.22–1.44] |
| 18.50–24.99 | 1 | 1 | 1 | 1 |
| 25.00–29.99 | 1.34 | [1.03–1.75] | 1.41 | [1.05–1.89] |
| 30.00–34.99 | 1.13 | [0.76–1.68] | 1.3 | [0.85–1.98] |
| 35.00–39.99 | 1.32 | [0.77–2.29] | 1.25 | [0.69–2.24] |
| ≥40.00 | 2.17 | [1.04–4.54] | 1.85 | [0.81–4.23] |
| Fetal birth weight (grams) | ||||
| ≤1999 | 0.82 | [0.43–1.54] | 1.04 | [0.38–2.85] |
| 2000–2499 | 0.73 | [0.40–1.36] | 0.8 | [0.34–1.89] |
| 2500–2999 | 0.9 | [0.60–1.36] | 1.11 | [0.67–1.85] |
| 3000–3499 | 0.87 | [0.64–1.19] | 0.93 | [0.66–1.31] |
| 3500–3999 | 1 | 1 | 1 | 1 |
| ≥4000 | 1.29 | [0.96–1.74] | 1.21 | [0.87–1.68] |
| Gestational age (weeks+days) | ||||
| ≤31+6 | 0.71 | [0.25–2.03] | 1.11 | [0.27–4.55] |
| 32–36+6 | 1.02 | [0.65–1.58] | 1.44 | [0.75–2.79] |
| 37–40+0 | 1 | 1 | 1 | 1 |
| ≥40+1 | 1.28 | [0.99–1.65] | 1 | [0.74–1.35] |
| Fetal descent into the pelvis | ||||
| Pelvic entrance | 1 | 1 | 1 | 1 |
| Ischial spine | 2.49 | [1.91–3.24] | 2.53 | [1.89–3.39] |
| Pelvic floor | 2.91 | [1.32–6.40] | 3.11 | [1.32–7.33] |
| Rupture of membranes prior to caesarean section | ||||
| Yes | 1.69 | [1.21–2.36] | 1.01 | [0.65–1.57] |
| No | 1 | 1 | 1 | 1 |
| Oxytocin augmentation | ||||
| Yes | 1.71 | [1.35–2.17] | 1.2 | [0.88–1.64] |
| No | 1 | 1 | 1 | 1 |
| Placental location in the uterus | ||||
| Posterior | 1 | 1 | 1 | 1 |
| Anterior | 1.36 | [1.07–1.75] | 1.37 | [1.06–1.77] |
| Fundus | 1.3 | [0.67–2.55] | 1.58 | [0.79–3.15] |
| Praevia/partial praevia | 0.26 | [0.04–1.93] | 0.33 | [0.04–2.63] |
| Type of anesthesia at the start of fetal extraction | ||||
| Spinal | 1 | 1 | 1 | 1 |
| Top-up epidural | 1.6 | [1.26–2.02] | 1.37 | [1.04–1.81] |
Clinical consequences of difficult fetal extraction
To assess the clinical consequences of DFE, neonatal and maternal morbidity were evaluated as secondary outcomes.
Maternal morbidity was assessed by measured maternal blood loss and was adjusted for the following confounders [
[27]
]: maternal pre-pregnancy BMI; maternal age; maternal parity; maternal diseases; emergency CS indications; induced labor; oxytocin augmentation; and fetal birth weight defined in Table 1, Table 4.Sensitivity analysis
In the first sensitivity analysis we redefined DFE to accommodate other views of the definition, and we only included instances where: 1) the words “difficult”, “a little difficult” or related synonyms were used, 2) midwife/assistant pushed the fetal head up through the vagina or 3) use of terbutaline or glyceryl trinitrate.
The purpose of the second and third sensitivity analyses was to investigate the stability of the top-up epidural anesthesia as a risk factor for DFE. Hence, in the second sensitivity analysis, we restricted the population in four different ways by including only: A) primiparous women, B) women with no prior CS, C) emergency category 2 CS and D) women with a pre pregnancy BMI between 18.5 and 24.99.
In the third sensitivity analysis, the population was stratified into women with presumed long labors and all other labors based on the indication for emergency CS as: i) “failure to progress in labor” or ii) all other indications.
Statistical methods
Risk factors for DFE and consequences of DFE on neonatal and maternal outcomes as well as sensitivity analyses were explored in crude and multiple adjusted logistic regression analyses providing ORs with 95 % confidence intervals.
All potential risk factors were transformed into categorical variables. The reference group for each risk factor was based on normal distribution within maternal age and based on being the least theoretically plausible for DFE within maternal BMI, gestational age, fetal weight, fetal descent into the pelvis, membrane rupture, oxytocin augmentation, cervical dilation, and placental position.
We used SPSS software version 25(Statistical Package of Social Sciences) for all statistical analyses.
Ethics statement
The study was reported to the Danish Patient Safety Authority(3–3013-1732/1) and approved. Data was reported to the Danish Data Protection Agency(NOH-2015–040. I-Suite: 04287).
URL: https://stps.dk/.
Results
In total, 2,892 emergency CSs were assessed, of which 560 were excluded for the following reasons: twin births(n = 134), emergency CS performed with general anesthesia(n = 433) or missing information about type of anesthesia(n = 11), resulting in 2,332 participants in descriptive and crude analyses(Table 1). Furthermore, 241 cases were excluded from the main multiple adjusted analysis due to missing information on risk factors included in this study(total n = 2,091).
Risk factors for a difficult fetal extraction
In the multiple adjusted analysis, the risk of DFE remained significantly higher for top-up epidural compared to spinal anesthesia(aOR:1.37[95 %CI 1.04–1.81]); maternal BMI 25.00–29.99(aOR:1.41[95 %CI 1.05–1.89]) compared to a BMI between 18.5 and 24.99; deeper fetal descent to the ischial spine(aOR:2.53[95 %CI 1.89–3.39]) and pelvic floor(aOR:3.11[95 %CI 1.32–7.33]) compared to the pelvic entrance; and anterior placental position(aOR:1.37[95 %CI 1.06–1.77]) compared to posterior placental location(Table 2).
For results from the crude analyses see Table 2.
Sensitivity analysis
In the first sensitivity analysis with a restricted definition of the outcome(n = 2,332). In this population 12.7 % of the cases had DFE, and the multiple adjusted risk remained increased when administering top-up epidural anesthesia(OR:1.39[95 %CI 1.03–1.86]), with deep fetal descent to the ischial spine(OR:2.73[95 %CI 2.01–3.72]) or pelvic floor(OR:3.88[95 %CI 1.64–9.17]) and in case of anterior placental position(OR:1.43[95 %CI 1.09–1.88]).
In the second sensitivity analysis top-up epidural remained a risk factor for DFE in all four sub-populations(primiparous women(n = 1,411), no prior CS(n = 1,749), emergency category 2 CS(n = 950) and pre-pregnancy normal weight(n = 1,271)) in the crude analyses and showed tendencies in the multiple adjusted analyses. Similar patterns were found for maternal BMI, fetal descent and placental position (Table 3).
Table 3Second sensitivity analyses exploring risk factors for difficult fetal extraction in four different populations.
| Including only primiparous women | ||||
|---|---|---|---|---|
| n = 1411 | ||||
| Delivery difficulties n (%) | Crude OR (95% CI) | Adjusted OR (95% CI) | ||
| Yes (n = 247) | No (n = 1164) | n = 1411 | n = 1256 | |
| Maternal pre-pregnancy BMI (kg/m2) | ||||
| ≤18.49 | 4 (1.6) | 43 (3.7) | 0.54 (0.19–1.53) | 0.31 (0.07–1.33) |
| 18.50–24.99 | 114 (46.2) | 662 (56.9) | 1 | 1 |
| 25.00–29.99 | 68 (27.5) | 275 (23.6) | 1.44 (1.03–2.00) | 1.42 (0.99–2.05) |
| 30.00–34.99 | 26 (10.5) | 108 (9.3) | 1.40 (0.87–2.24) | 1.48 (0.89–2.48) |
| 35.00–39.99 | 10 (4.1) | 54 (4.6) | 1.08 (0.53–2.17) | 0.89 (0.41–1.93) |
| ≥40.00 | 5 (2.0) | 22 (1.9) | 1.32 (0.49–3.56) | 1.40 (0.50–3.91) |
| Missing | 0 (0.0) | 0 (0.0) | ||
| Fetal descent into the pelvis | ||||
| Pelvic entrance | 142 (57.5) | 927 (79.6) | 1 | 1 |
| Ischial spine | 80 (32.4) | 221 (19.0) | 2.39 (1.75–3.27) | 2.52 (1.77–3.58) |
| Pelvic floor | 8 (3.2) | 16 (1.4) | 3.61 (1.39–7.87) | 3.79 (1.44–10.0) |
| Missing | 17 (6.9) | 0 (0.0) | ||
| Placental location in the uterus | ||||
| Posterior | 79 (32.0) | 522 (86.9) | 1 | 1 |
| Anterior | 120 (48.6) | 504 (80.8) | 1.57 (1.16–2.14) | 1.59 (1.15–2.20) |
| Fundus | 5 (2.0) | 35 (87.5) | 0.94 (0.36–2.48) | 1.29 (0.47–3.54) |
| Praevia/partial praevia | 0 (0.0) | 9 (100) | - | - |
| Missing | 43 (17.4) | 64 (5.5) | ||
| Type of anesthesia at time of fetal extraction | ||||
| Epidural | 114 (46.2) | 418 (80.5) | 1.45 (1.09–1.93) | 1.34 (0.96–1.88) |
| Spinal | 133 (53.8) | 746 (85.6) | 1 | 1 |
| Missing | 0 (0.0) | 0 (0.0) | ||
| Including only women with no prior caesarean section | ||||
| n = 1749 | ||||
| Delivery difficulties n (%) | Crude OR (95% CI) | Adjusted OR (95% CI) | ||
| Yes (n = 260) | No (n = 1489) | n = 1749 | n = 1561 | |
| Maternal pre-pregnancy BMI (kg/m2) | ||||
| ≤18.49 | 6 (2.3) | 51 (3.4) | 0.75 (0.32–1.79) | 0.60 (0.20–1.75) |
| 18.50–24.99 | 129 (49.6) | 826 (55.5) | 1 | 1 |
| 25.00–29.99 | 74 (28.5) | 358 (24.0) | 1.32 (0.97–1.81) | 1.35 (0.96–1.91) |
| 30.00–34.99 | 29 (11.2) | 142 (9.5) | 1.31 (0.84–2.03) | 1.40 (0.87–2.26) |
| 35.00–39.99 | 12 (4.6) | 63 (4.2) | 1.22 (0.64–2.32) | 1.06 (0.53–2.15) |
| ≥40.00 | 7 (2.7) | 25 (16.8) | 1.79 (0.76–4.23) | 1.64 (0.64–4.21) |
| Missing | 3 (1.2) | 24 (1.6) | ||
| Fetal descent into the pelvis | ||||
| Pelvic entrance | 164 (63.1) | 1204(80.9) | 1 | 1 |
| Ischial spine | 86 (33.1) | 256(17.2) | 2.47 (1.84–3.31) | 2.51 (1.80–3.50) |
| Pelvic floor | 8 (3.1) | 18 (1.2) | 3.26 (1.40–7.62) | 3.31 (1.30–8.46) |
| Missing | 2 (0.8) | 11 (0.7) | ||
| Placental location in the uterus | ||||
| Posterior | 88 (33.8) | 649 (43.6) | 1 | 1 |
| Anterior | 138 (53.1) | 645 (43.3) | 1.58 (1.18–2.12) | 1.62 (1.20–2.19) |
| Fundus | 8 (3.1) | 42 (2.8) | 1.41 (0.64–3.09) | 1.96 (0.87–4.44) |
| Praevia/partial praevia | 0 (0.0) | 20 (1.3) | - | - |
| Missing | 26 (0.1) | 143 (9.6) | ||
| Type of anesthesia at time of fetal extraction | ||||
| Epidural | 107 (41.2) | 489 (82.0) | 1.43 (1.09–1.87) | 1.25 (0.91–1.72) |
| Spinal | 153 (58.8) | 1000 (86.7) | 1 | 1 |
| Missing | 0 (0.0) | 0 (0.0) | ||
| Including only emergency category 2 caesarean sections | ||||
| n = 950 | ||||
| Delivery difficulties n (%) | Crude OR (95% CI) | Adjusted OR (95% CI) | ||
| Yes (n = 146) | No (n = 804) | n = 950 | n = 878 | |
| Maternal pre-pregnancy BMI (kg/m2) | ||||
| ≤18.49 | 2 (1.4) | 28 (3.5) | 0.42 (0.97–1.78) | 0.46 (0.10–2.06) |
| 18.50–24.99 | 77 (52.7) | 447 (55.6) | 1 | 1 |
| 25.00–29.99 | 46 (31.5) | 198 (24.6) | 1.35 (0.90–2.06) | 1.54 (0.99–2.41) |
| 30.00–34.99 | 9 (6.2) | 73 (9.1) | 0.72 (0.34–1.49) | 0.94 (0.44–2.03) |
| 35.00–39.99 | 7 (4.8) | 26 (3.2) | 1.56 (0.66–3.73) | 1.42 (0.53–3.84) |
| ≥40.00 | 4 (2.7) | 10 (1.2) | 2.32 (0.71–7.59) | 1.86 (0.38 -9.10) |
| Missing | 1 (0.7) | 22 (2.7) | ||
| Fetal descent into the pelvis | ||||
| Pelvic entrance | 84 (57.5) | 631 (78.5) | 1 | 1 |
| Ischial spine | 54 (37.0) | 153 (19.0) | 2.65 (1.80–3.90) | 2.87 (1.85–4.44) |
| Pelvic floor | 5 (3.4) | 14 (1.7) | 2.68 (0.94–7.64) | 4.06 (1.30–12.70) |
| Missing | 3 (2.1) | 6 (0.7) | ||
| Placental location in the uterus | ||||
| Posterior | 55 (37.7) | 340 (42.3) | 1 | 1 |
| Anterior | 76 (52.1) | 367 (45.6) | 1.28 (0.89 -1.87) | 1.41 (0.94–2.11) |
| Fundus | 5 (3.4) | 21 (2.6) | 1.47 (0.53–4.07) | 1.64 (0.57–4.76) |
| Praevia/partial praevia | 0 (0.0) | 7 (0.9) | - | - |
| Missing | 10 (6.8) | 69 (7.5) | ||
| Type of anesthesia at time of fetal extraction | ||||
| Epidural | 68 (46.6) | 295 (36.7) | 1.50 (1.05–2.15) | 1.40 (0.92–2.13) |
| Spinal | 78 (53.4) | 509 (63.3) | 1 | 1 |
| Missing | 0 (0.0) | 0 (0.0) | ||
| Including only maternal pre pregnancy BMI (kg/m2) between 18.5–24.99* | ||||
| n = 1271 | ||||
| Delivery difficulties n (%) | Crude OR (95% CI) | Adjusted OR (95% CI) | ||
| Yes (n = 174) | No (n = 1097) | n = 1271 | n = 878 | |
| Fetal descent into the pelvis | ||||
| Pelvic entrance | 112 (64.4) | 899 (82.0) | 1 | 1 |
| Ischial spine | 57 (32.8) | 179 (16.3) | 2.55 (1.79–3.64) | 2.58 (1.73–3.84) |
| Pelvic floor | 4 (2.3) | 16 (1.5) | 2.00 (0.66–6.09) | 2.27 (0.73–7.16) |
| Missing | 1 (0.6) | 3 (0.3) | ||
| Placental location in the uterus | ||||
| Posterior | 64 (36.8) | 486 (44.3) | 1 | 1 |
| Anterior | 86 (49.4) | 482 (44.0) | 1.35 (0.96–1.92) | 1.35 (0.94–1.94) |
| Fundus | 6 (3.4) | 34 (3.1) | 1.34 (0.54–3.16) | 1.49 (0.58–3.84) |
| Praevia/partial praevia | 0 (0.0) | 11 (1.0) | - | - |
| Missing | 18 (10.3) | 84 (7.7) | ||
| Type of anesthesia at time of fetal extraction | ||||
| Epidural | 71 (40.8) | 322 (29.4) | 1.66 (1.19–2.31) | 1.39 (0.94–2.04) |
| Spinal | 103 (59.2) | 775 (70.6) | 1 | 1 |
| Missing | 0 (0.0) | 0 (0.0) | ||
1 Factors collected after fetal extraction. Total population n = 2,332.
2 ”Trainee” defined as all surgeons who were not yet fully trained specialists.
3 Values under 0 or above 30 excluded
*BMI = Body Mass Index.
Number of excluded cases due to missing information: maternal age = 1, maternal pre-pregnancy BMI = 41, fetal birth weight = 7, gestational age = 0, fetal descent into the pelvis = 15, rupture of membranes prior to fetal extraction = 0, oxytocin drop prior to fetal extraction = 0, placental location = 200, five-minute Apgar score = 4, umbilical artery pH value = 402.
In the third sensitivity analysis, top-up epidural was associated with higher risk of DFE(aOR 1.53[95 %CI 1.07–2.20]) in the sub-group where emergency CSs were performed on all other indications than “failure to progress in labor”(n = 1,271), and in total 13.2 % of the emergency CS had DFE.
The risk did not significantly increase in the sub-group of emergency CSs performed on the indication “failure to progress in labor”(aOR:1.23[95 %CI 0.85–1.79](n = 922)). This subgroup was, however, the one with the highest incidence of DFE at 18.3 %.
Clinical consequences of difficult fetal extraction
DFE was associated with increased risk of low umbilical artery pH, low Apgar5 and maternal blood loss. This was found in both crude and multiple adjusted analyses (Table 4).
Table 4Clinical consequences of difficult fetal extraction: three maternal and neonatal outcomes after difficult fetal extraction from binary logistic and multinomial regression.
| Crude OR (95%CI) | Adjusted OR (95%CI) | |
|---|---|---|
| Umbilical artery pH valuea | ||
| ≤6.99 | 3.22 (1.35–7.67) | 4.18 (1.61–10.88) |
| 7.00–7.09 | 3.24 (1.90–5.53) | 3.47 (1.97–6.12) |
| ≥7.10 | 1 | 1 |
| Five-minute Apgar scorea | ||
| ≤6 | 2.24 (1.22–4.12) | 2.44 (1.26–4.73) |
| 7–10 | 1 | 1 |
| Maternal blood loss (ml)b | ||
| 0–500 | 1 | 1 |
| 501–1000 | 1.75 (1.35–2.27) | 1.65 (1.27–2.16) |
| 1001–1500 | 3.52 (2.46–5.03) | 3.24 (2.24–4.67) |
| 1501–2000 | 4.46 (2.55–7.78) | 3.94 (2.24–6.94) |
| ≥2001 | 3.21 (1.32–7.77) | 2.76 (1.12–6.82) |
2332 cases were included in the crude analysis.
Number of excluded cases due to missing information in the adjusted logistic regression: 241.
In the adjusted logistic regression, all nine risk factors listed in this table, was included.
* BMI = Body Mass Index.
The multiple adjusted risk of an umbilical artery pH of 7–7.09 was 3.47[95 %CI 1.97–6.12], whereas the risk of an umbilical artery pH < 7.00 was 4.18[95 %CI 1.61–10.88], both compared to a pH ≥ 7.10(n = 1,930).
The multiple adjusted risk of an Apgar5 score < 7 compared to a score ≥ 7 was 2.44[95 %CI 1.26–4.73](n = 2,328).
Women who had an emergency CS with DFE had increased risk of blood loss of 501–1,000 ml, 1,001–1,500 ml, 1,501–2,000 ml and ≥ 2,001 ml, respectively with ORs of 1.65[95 %CI 1.27–2.16], 3.24[95 %CI 2.24–4.67], 3.94[95 %CI 2.24–6.94] and 2.76[95 %CI 1.12–6.82], respectively(n = 2,285).
Discussion
DFE in emergency CS is a fairly common, known and feared obstetric emergency situation.
We identified four different risk factors for DFE: top-up epidural anesthesia, high maternal pre-pregnancy BMI, deep fetal descent and anterior placental position. Furthermore, we found association between and low umbilical artery pH, low Apgar5 and maternal blood loss.
Our finding of top-up epidurals as a risk factor for DFE is new, though theoretically plausible. Studies have found that even though the time interval from arrival at the operating room to incision is shorter using top-up epidural anesthesia [
8
, 28
], it has a less dense motor block [28
, 29
, 30
]. Tight abdominal muscles might cause difficulties delivering the fetus, though this has not been explored. These studies used the same local anesthetics and quantity as recommended in the Danish national guideline [[5]
]. The finding is of clinical relevance as using spinal anesthesia potentially can eliminate insufficient motor block and consequently lower the risk of DFE.OBSTETRISK ANÆSTESIUDVALG, DASAIM. Anæstesi til kejsersnit [Internet]. 2019. Available from: http://www.dasaim.dk/wp-content/uploads/2019/10/Anæstesi-til-kejsersnit-2019.pdf.
We adjusted for theoretically and biologically plausible potential risk factors, except for duration of active labor. Though a 2005 Cochrane review found second stage of labor to be prolonged with a median of only 14 min [
[31]
], the epidural analgesia could indirectly cause an impacted fetal head and thus DFE, leading the cause to be epidural analgesia and not top-up epidural anesthesia.Anim-Somuah M, Smyth RM, Cyna AM, Cuthbert A. Epidural versus non-epidural or no analgesia for pain management in labour. Cochrane Pregnancy and Childbirth Group, editor. Cochrane Database Syst Rev [Internet]. 2018 May 21 [cited 2022 Nov 22];2018(5). Available from: http://doi.wiley.com/10.1002/14651858.CD000331.pub4.
However, in the third sensitivity analysis, an increased risk of DFE when using top-up epidural anesthesia was still present when excluding “long labors” defined by CS indications “failure to progress in labor”. Based on our analyses, it is likely that our theory of weaker motor blockage in top-up epidural anesthesia, is causing DFE.
We found maternal pre-pregnancy BMI between 25 and 29.99 to be a risk factor for DFE, and a BMI above 29.99 showed tendencies. We did not identify any prior studies reporting pre-pregnancy BMI as a risk factor for DFE.
A deeply engaged head in the pelvis as a risk factor for DFE have been explored [
2
, 3
, 4
, 9
]. These studies only included CS with a deeply engaged head and focused solely on different methods of fetal extraction. The strategies include reverse breech extraction, Patwardhan and the push method. In our study, we aimed to assess whether the depth of fetal descent into the pelvis was a risk factor. As expected, we found the risk of DFE increased the more descended the fetal head was. One other study finds fetal descent to be a risk factor for a deeply engaged head and thus DFE [[9]
].The anterior placental position was also found to be a risk factor for DFE. No prior studies researching placental location as a risk factor for DFE were found. Although it is impossible to alter the placental position, this finding suggests knowledge of the placental position prior to emergency CS could be useful for the surgeon to be prepared for a potentially DFE.
Prior studies have found associations between maternal and neonatal morbidity and caesarean delivery of a deeply engaged head [
1
, 2
, 3
, 32
]. We found DFE to be associated with an increased risk of maternal morbidity in terms of maternal blood loss, and increased risk of neonatal morbidity reflected in lower Apgar5 scores and lower umbilical artery pH. These findings are of clinical relevance and stress the importance of future studies on DFE in order to inform the development of evidence-based guidelines on this matter.Strengths and limitations
This study is the first to explore risk factors for DFE in emergency caesarean sections. Selection bias was reduced, as all women undergoing emergency CS were included in the study. Women included in this study live in North Zealand, which is one specific region of Denmark and the external validity of the findings is not known.
Overreporting DFE is very unlikely since observations were made based on a clinical setting where personnel and patients were not aware, they were being observed. Therefore, no information bias on the risk factors for DFE are expected, specifically regarding top-up epidural anesthesia compared to spinal anesthesia. Whereas concerning consequences from DFE information bias may occur as surgeons might be more likely to describe details in CS with surgical and neonatal complications. We acknowledge that junior doctors might report DFE more often than senior doctors. However junior doctors and obstetricians reported DFE almost equally as frequent with 15.7 % and 15.5 % respectively, indicating that junior doctors at North Zealand hospital are not more likely to report DFE extraction than obstetricians, therefor we did not include surgical experience as a risk factor.
This study is the first to suggest a definition of DFE based on taking extraordinary measures in regard to the fetal extraction. Theoretically DFE would take longer time than an emergency CS without DFE, and in our descriptive statistics it is easy to see that no matter the emergency category the mean time from skin incision to delivery was almost twice as long as long in the emergency CS we defined as having DFE. This indicates a strong validity in our definition of DFE. However, a universal consensus of the definition of DFE is needed.
Almost all data was collected manually, and even though the data was corrected for typing errors, there are bound to be some mistakes in the data collected. Nonetheless, it is a non-differential misclassification.
An important strength is that all the sensitivity analyses support the findings from the primary analyses.
Finally, our large sample size is considered one of the main strengths.
We recommend prospective future studies with a predefined definition of DFE, including the same risk factors as well as a measurement of the depth of the anesthesia.
Conclusion
DFE in emergency CS was associated with four risk factors: top-up epidural anesthesia, elevated maternal BMI, deep fetal descent to the ischial spine and pelvic floor, and anterior placental position.
Further, DFE was associated with poor neonatal and maternal outcomes defined as low umbilical cord pH, low Apgar5 and maternal blood loss.
There is a need for additional research on this obstetric emergency situation and fetal extraction difficulties need to be formally categorized and coded.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
We have no acknowledgements.
References
- Maternal and neonatal outcomes associated with delivery techniques for impacted fetal head at cesarean section: a systematic review and meta-analysis.J Perinat Med. 2022; 50: 446-456
Waterfall H, Grivell RM, Dodd JM. Techniques for assisting difficult delivery at caesarean section. Cochrane Pregnancy and Childbirth Group, editor. Cochrane Database Syst Rev [Internet]. 2016 Jan 31 [cited 2022 Nov 22];2016(1). Available from: http://doi.wiley.com/10.1002/14651858.CD004944.pub3.
Delivery of the impacted head of the fetus at caesarean section after prolonged obstructed labour: a randomised comparative study of two methods. J Obstet Gynaecol. 2002 Jan;22(4):375–8.
- A meta-analysis of reverse breech extraction to deliver a deeply impacted head during cesarean delivery.Int J Gynecol Obstet. 2014; 124: 99-105
OBSTETRISK ANÆSTESIUDVALG, DASAIM. Anæstesi til kejsersnit [Internet]. 2019. Available from: http://www.dasaim.dk/wp-content/uploads/2019/10/Anæstesi-til-kejsersnit-2019.pdf.
- Augmentation of labour.Best Pract Res Clin Obstet Gynaecol. 2020; 67: 80-89
- The use of O-ring retractors at Caesarean section: a systematic review and meta analysis.Eur J Obstet Gynecol Reprod Biol. 2018; 228: 209-214
- Time between skin incision and delivery during cesarean.Int J Gynecol Obstet. 2013; 121: 82-85
- Impacted fetal head: a retrospective cohort study of emergency caesarean section.Eur J Obstet Gynecol Reprod Biol. 2021; 261: 85-91
- WHO analysis of causes of maternal death: a systematic review.Lancet. 2006; 367: 1066-1074
- Pregnancy-Related Mortality in the United States, 2006–2010.Obstet Gynecol. 2015; 125: 5-12
- Frequency of and factors associated with severe maternal morbidity.Obstet Gynecol. 2014; 123: 804-810
- Anterior placental location influences onset and progress of labor and postpartum outcome.Placenta. 2015; 36: 463-466
- Fosterovervågning under fødslen(II) – Metoder [Internet].Dansk Selskab for Obstetrik og Gynækologi. 2022; (Available from:)
- Pathologic fetal acidemia.Obstet Gynecol. 1991; 78: 1103-1107
- Severe umbilical cord acidemia and neurological outcome in preterm and full-term neonates.Neonatology. 2005; 88: 27-34
- Clustering of perinatal markers of birth asphyxia and outcome at age five years.BJOG Int J Obstet Gynaecol. 1994; 101: 774-781
D. Engle W, R. Laptook A, M. Perlman J. Acute changes in arterial carbon dioxide tension and acid–base status and early neurologic characteristics in term infants following perinatal asphyxia. Resuscitation. 1999 Sep;42(1):11–7.
- Diagnosis of birth asphyxia on the basis of fetal pH, Apgar score, and newborn cerebral dysfunction.Am J Obstet Gynecol. 1989; 161: 825-830
- Neurological evolution of asphyctic full-term newborns with severe umbilical acidosis (pHUA <7.00).Rev Neurol. 2000; 31: 107-113
- Outcomes among term infants when two-hour postnatal pH is compared with pH at delivery.Am J Obstet Gynecol. 2001; 184: 447-450
- The relationship between umbilical cord arterial pH and serious adverse neonatal outcome: analysis of 51 519 consecutive validated samples: umbilical cord arterial pH and serious neonatal outcome.BJOG Int J Obstet Gynaecol. 2012; 119: 824-831
- Acidemia in neonates with a 5-minute Apgar score of 7 or greater – What are the outcomes?.Am J Obstet Gynecol. 2016; 215: 486.e1-486.e6
- Asphyxial complications in the term newborn with severe umbilical acidemia.Am J Obstet Gynecol. 1992; 167: 1506-1512
- Relation between umbilical cord blood pH, base deficit, lactate, 5-minute Apgar score and development of hypoxic ischemic encephalopathy.Acta Obstet Gynecol Scand. 2010; 89: 1263-1269
- Long term outcome after umbilical artery acidaemia at term birth: influence of gender and duration of fetal heart rate abnormalities.BJOG Int J Obstet Gynaecol. 1997; 104: 1123-1127
- Postpartum blødning Forebyggelse og håndtering [Internet].Dansk Selskab for Obstetrik og Gynækologi. 2017; (Available from:)
- Comparing epidural surgical anesthesia and spinal anesthesia following epidural labor analgesia for intrapartum cesarean section: a prospective randomized controlled trial.Korean J Anesthesiol. 2017; 70: 412
- Extension of epidural blockade in labour for emergency Caesarean section using 2% lidocaine with epinephrine and fentanyl, with or without alkalinisation*: Forum.Anaesthesia. 2001; 56: 777-798
Choi J, Germond L, Santos AC. Obstetric Regional Anesthesia [Internet]. NYSORA; Available from: https://www.nysora.com/topics/sub-specialties/obstetric/obstetric-regional-anesthesia/.
Anim-Somuah M, Smyth RM, Cyna AM, Cuthbert A. Epidural versus non-epidural or no analgesia for pain management in labour. Cochrane Pregnancy and Childbirth Group, editor. Cochrane Database Syst Rev [Internet]. 2018 May 21 [cited 2022 Nov 22];2018(5). Available from: http://doi.wiley.com/10.1002/14651858.CD000331.pub4.
- Maternal and neonatal outcome of reverse breech extraction of an impacted fetal head during caesarean section in advanced stage of labour: a retrospective cohort study.BMC Pregn Childbirth. 2019; 19: 98
Article info
Publication history
Published online: February 14, 2023
Accepted:
February 13,
2023
Received in revised form:
February 9,
2023
Received:
December 8,
2022
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