Keywords
overweight - obesity - labor dystocia - primary cesarean guidelines
Obesity, defined by the Word Health Organization as BMI ≥30 kg/m2 (BMI = weight [kg]/height
[m] squared) is currently the most common medical condition among reproductive aged
(23–39 years old) women.[1]
[2] Obese pregnant women have higher rates of antepartum comorbidities, such as gestational
diabetes or hypertensive disorders, and often experience iatrogenic preterm birth
and increased peripartum complications such as postpartum hemorrhage, thromboembolic
events, and infectious morbidity with increasing weight class.[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21] The odds ratios of cesarean delivery in overweight and obese women are 1.4 and 2.0,
respectively when compared to their normal weight counterparts.[4]
[22] Similarly, neonatal morbidity and mortality is significantly increased with increasing
maternal BMI.[6]
[7]
[8]
[9]
[23]
[24]
[25]
[26] Recent data suggest that prepregnancy BMI is linked to higher neonatal intensive
care admissions, lower Apgar scores, and a relative risk of 1.15 for neonatal death.[8]
[9]
[23]
[24]
[25]
[26] Although these studies demonstrate similar trends in adverse maternal and perinatal
outcomes, they remain limited in their evaluation of the effect of labor duration
on the aforementioned complications.[4]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
Evidence suggests that the length of active labor is longer in overweight and obese
women, even when adjusting for confounding variables such as medical or antenatal
comorbidities, gestational age at delivery, birthweight, and induction.[9]
[10]
[11]
[12] It has been demonstrated that in obese women, the rate of cervical dilation is inversely
associated with maternal weight and that for each 10-kg increase, the rate of dilation
decreased by 0.04 cm/h.[11] Yet other studies have shown that the median length of labor is not associated with
maternal BMI.[4]
[17]
[18]
[19]
[20]
[25]
[27]
[28]
[29] Importantly, these analyses do not address adherence by providers to contemporary
guidelines for management of protracted labor and the prevention of the primary cesarean
delivery.[17]
[21]
[24]
[30] The American College of Obstetricians and Gynecologists support the extension of
duration of labor in obese patients in order to avoid cesarean delivery and associated
complications.[17] However, the increased risk of adverse perinatal outcomes in this patient population
with prolonged labor should be taken into consideration, with the outcomes analyzed
and compared when applied to current practices for the prevention of the primary cesarean
delivery.[17]
[24]
[30] The aim of this study was to evaluate provider labor guideline adherence with BMI
class and to determine differences in maternal and neonatal outcomes with guideline
adherent labor management across BMI weight class.
Materials and Methods
This retrospective cohort study included all low-risk women with a singleton, term
(37 0/7 to 40 6/7 weeks), cephalic, pregnancy admitted in active labor (≥5-cm cervical dilation in
the presence of regular contractions) or undergoing labor induction between April
30, 2014 through April 30, 2017, at Ben Taub Hospital and the Texas Children's Pavilion
for Women after the prevention of the primary cesarean delivery and labor dystocia
guidelines,[21]
[24]
[30] were implemented by the Department of Obstetrics and Gynecology at the Baylor College
of Medicine (Houston, TX) for the management of labor. The protocol includes the support
of evidence-based options for cervical ripening followed by the intrapartum management
of latent labor.[21]
[30]
A failed labor course may be defined in two ways: first, failed induction with rupture
of membranes greater than 18 hours with the use of oxytocin augmentation over 24 hours,
or second, as an arrest disorder, dilation of 6 cm or greater with membrane rupture
and no cervical change for 4 hours or more of adequate contractions, or 6 hours or
more if contractions are inadequate resulting in a cesarean delivery.[21]
[24] In addition, 3 hours without epidural, or 4 hours with epidural in a nulliparous
patient or 2 hours without epidural, or 3 hours with epidural with a multiparous patient
and pushing at complete cervical dilation without a vaginal birth is required before
a cesarean for arrest of descent is determined.[21]
[24]
Patients included in the study were identified using the PeriBank database. PeriBank
is an Institutional Review Board-approved comprehensive, prospectively recorded, institutional
database and biobank focusing on detailed clinical data and accompanying specimens
collected at delivery and curated at Baylor College of Medicine, Houston, TX. A detailed
description of PeriBank has been previously published.[31] The database was queried for demographic, delivery, maternal, and neonatal outcome
data including, indication for induction, length of labor (all stages), membrane rupture,
oxytocin administration, and indication for cesarean in accordance with the Strengthening
the Reporting of Observational Studies in Epidemiology guidelines (STROBE).[32] The index pregnancy was the most recent pregnancy in the database for each subject
and the BMI closest to delivery was used for analysis for consistency due to variation
in gestational age in presentation for care. Pregnancies complicated by fetal anomalies
and women with a contraindication to a vaginal delivery (malpresentation, abnormal
placentation, and prior myomectomy) were excluded. In addition, women with a BMI <18.5,
pregestational diabetes, hypertensive disorders of pregnancy antepartum stillbirth,
fetal growth restriction (defined as estimated fetal weight below the 10th percentile
for gestational age) prior cesarean delivery and cesarean for nonreassuring fetal
status in this index pregnancy were excluded to minimize factors that may confound
results.
The primary outcome was provider adherence to the published labor dystocia guidelines
across BMI classes. In addition, a comparison of maternal and neonatal outcomes when
labor management was compliant with published guidelines across groups was analyzed.
Maternal variables collected included gestational age at delivery, labor type (scheduled
induction of labor, labor augmentation for patients presenting in labor or spontaneous
labor), mode of delivery, method of anesthesia used, oligohydramnios (defined as maximum
vertical pocket less than 2 cm, or amniotic fluid index less than 5 cm), chorioamnionitis,
endomyometritis, hemorrhage (>1,000 mL blood loss for cesarean delivery and vaginal
delivery), and a composite of adverse maternal outcomes defined as blood transfusion,
hysterectomy, wound infection, wound separation, ileus and delayed postpartum hemorrhage
(>24 hours after delivery).
Neonatal characteristics obtained were newborn weight, Apgar scores, meconium passage
at birth, arterial blood gas, neonatal intensive care unit admission for sepsis evaluation
and a composite of adverse outcomes defined as respiratory distress, transient tachypnea
of the newborn, necrotizing enterocolitis, bronchopulmonary dysplasia, retinopathy,
pulmonary interstitial emphysema, hypertonicity, or use of pressors. BMI classes in
kg/m2 were defined as follows: normal weight 18.5 to <25, overweight 25 to <30, class I
obesity 30 to <35, class II obesity 35 to <40, and class III obesity ≥40.
Protocol adherence was considered if a cesarean delivery occurred for a failed labor
or induction course as previously defined using recorded times for admission, initiation
of active labor, rupture of membranes, oxytocin augmentation, Montevideo units, labor
stages, and delivery as collected in Peribank.[21]
[24] Residents, midwives, obstetrician–gynecologists, and maternal fetal medicine providers
manage labor and delivery units at both sites. All decisions concerning labor dystocia
and cesarean delivery are made with agreement between house staff and faculty.
Descriptive statistics were calculated for all study variables. Women were grouped
according to their BMI class and compared by the Kruskal–Wallis for continuous or
ordinal outcomes and chi-square/Fisher exact test for categorical outcomes. Logistic
regression of guideline adherence was conducted controlling for maternal age, race,
ethnicity, parity, and newborn weight. Subgroup analyses were conducted in women who
underwent induction. In this subgroup, logistic and generalized linear regression
of maternal and neonatal outcomes was used to determine if there was an interaction
between gestational age at delivery and BMI. The regression model controlled for the
potential confounders of age, race, Hispanic ethnicity, parity, and newborn weight.
p < 0.05 was considered significant and no adjustment was made for multiple comparisons.
All analyses were performed in SAS software (9.4 SAS Institute Inc, Cary, NC).
Results
There were 13,978 deliveries post implementation of the labor dystocia guidelines
at both delivery sites during the study period. Of these, 949 were missing data on
BMI or had a BMI <18.5 and were excluded, leaving a total of 13,029 deliveries for
analysis (See Flow diagram [Fig. 1]). Guideline adherence decreased with increasing BMI, with 93% adherence among women
of normal weight compared to 89% for class I, 88% for class II, and 81% for class
III obese women (p < 0.0001 adjusted for race, parity, neonatal weight, and maternal age; [Table 1]). Demographic and baseline characteristics of the population treated in accordance
with guidelines are presented in [Table 2]. There was no clinically significant difference in maternal age, race, ethnicity,
and parity across the BMI classes; however, the percentage of Hispanic women increased
with increasing BMI. There were more inductions of labor and cesarean deliveries with
increasing weight class; however, there was no difference in rates of chorioamnionitis,
endomyometritis, hemorrhage, or the maternal composite outcome after adjusting for
parity, maternal age, race, and Hispanic ethnicity (p = 0.98, 0.63, and 0.09, respectively). These results are demonstrated in [Table 3].
Fig. 1 Association between maternal obesity class, adherence to labor guidelines, and perinatal
outcomes. Patients consented and enrolled April 30, 2014 to April 30, 2017.
Table 1
Guideline adherence by BMI category
|
Normal weight BMI ≥18.5 to <25 (N = 1,361)
|
Overweight BMI 25 to <30 (N = 4,799)
|
Class 1 obesity BMI 30 to <35 (N = 4,071)
|
Class 2 obesity BMI 35 to <40 (N = 1,852)
|
Class 3 obesity BMI ≥40 (N = 946)
|
Total (N = 13,029)
|
|
Did not follow guidelines
|
101 (7.4%)
|
435 (9.1%)
|
448 (11.0%)
|
218 (11.8%)
|
184 (19.5%)
|
1,386 (10.6%)
|
|
Followed guidelines
|
1,260 (92.6%)
|
4,364 (90.9%)
|
3,623 (89.0%)
|
1,634 (88.2%)
|
762 (80.6%)
|
1,1643 (89.4%)
|
Note: p ≤0.0001 both unadjusted and adjusted for white race, parity, neonatal weight, and
maternal age; data presented as N(%).
Table 2
Demographics and baseline characteristics (guideline followed)
|
Normal weight
BMI ≥18.5 to <25 (N = 1,260)
|
Overweight BMI 25 to <30 (N = 4,364)
|
Class 1 obesity BMI 30 to <35 (N = 3,623)
|
Class 2 obesity BMI 35 to <40 (N = 1,634)
|
Class 3 obesity
BMI ≥40 (N = 762)
|
|
Age
|
|
|
|
|
|
|
Mean (SD)
|
27.6 (6.07)
|
29.1 (5.84)
|
29.3 (5.77)
|
29.2 (5.82)
|
29.1 (5.62)
|
|
Race
|
|
|
|
|
|
|
Black
|
157 (12.5%)
|
544 (12.5%)
|
491 (13.6%)
|
247 (15.1%)
|
178 (23.4%)
|
|
Caucasian
|
950 (75.4%)
|
3,449 (79.0%)
|
2,929 (80.8%)
|
1,328 (81.3%)
|
567 (74.4%)
|
|
Asian
|
123 (9.8%)
|
292 (6.7%)
|
139 (3.8%)
|
22 (1.4%)
|
12 (1.8%)
|
|
Alaskan or American Indian
|
1 (0.08%)
|
1 (0.02%)
|
1 (0.03%)
|
1 (0.06%)
|
2 (0.26%)
|
|
Hawaiian or Pacific Islander
|
3 (0.24%)
|
1 (0.02%)
|
1 (0.03%)
|
0
|
2 (0.26%)
|
|
Unknown
|
31 (2.5%)
|
92 (2.1%)
|
72 (2.0%)
|
38 (2.3%)
|
9 (1.2%)
|
|
Ethnicity
|
|
|
|
|
|
|
Hispanic
|
548 (43.5%)
|
2,217 (50.8%)
|
2,236 (61.7%)
|
1,090 (66.7%)
|
476 (62.5%)
|
|
Not Hispanic
|
712 (56.5)
|
2,146 (49.2)
|
1,385 (38.2)
|
544 (33.3)
|
286 (37.5)
|
|
Not disclosed
|
0
|
1 (0.02%)
|
2 (0.06%)
|
0
|
0
|
|
BMI
|
|
|
|
|
|
|
Mean (SD)
|
23.4 (1.20)
|
27.6 (1.40)
|
32.2 (1.42)
|
37.1 (1.39)
|
44.2 (5.70)
|
|
Gravida
|
2 (1–3)
|
2 (1–3)
|
2 (2–4)
|
3 (2-4)
|
|
|
Parity
|
1 (0–1)
|
1 (0–2)
|
1 (0–2)
|
1 (0–2)
|
1 (0–2)
|
|
Marital status
|
|
|
|
|
|
|
Married
|
888 (70.5%)
|
3,082 (70.6%)
|
2,431 (67.1%)
|
1,075
(65.8%)
|
472 (61.9%)
|
|
Single
|
332 (26.4%)
|
1,134 (26.0%)
|
1,064 (29.4%)
|
490 (30.0%)
|
258 (33.9%)
|
|
Not reported
|
20 (1.6%)
|
56 (1.3%)
|
52 (1.4%)
|
30 (1.8%)
|
9 (1.2%)
|
|
GA at 1st prenatal visit
|
11.7 (8.7–16.0)
|
11.4 (8.7–15.9)
|
11.7 (8.7–16.0)
|
11.9 (8.9–15.9)
|
12.0 (9.8–18)
|
|
Number of prenatal visits
|
11 (8–12)
|
11 (9–13)
|
11 (9–13)
|
11 (9–13)
|
11 (8–12)
|
|
HIV
|
2 (0.16%)
|
13 (0.30%)
|
16 (0.44%)
|
3 (0.18%)
|
6 (0.79%)
|
|
Hepatitis B
|
10 (0.79%)
|
23 (0.53%)
|
26 (0.72%)
|
7 (0.43%)
|
6 (0.79%)
|
|
GBS
|
299 (23.7%)
|
926 (21.2%)
|
795 (21.9%)
|
383 (23.4%)
|
217 (28.5%)
|
|
RPR
|
6 (0.48%)
|
14 (0.32%)
|
8 (0.22%)
|
8 (0.49%)
|
8 (1.1%)
|
|
Current smoking
|
9 (0.71%)
|
23 (0.53%)
|
14 (0.39%)
|
11 (0.67%)
|
9 (1.2%)
|
|
Prior alcohol use
|
25 (2.0%)
|
61 (1.4%)
|
39 (1.1%)
|
15 (0.92%)
|
7 (0.92%)
|
|
Substance use
|
0
|
3 (0.07%)
|
2 (0.06%)
|
1 (0.06%)
|
0
|
Abbreviations: BMI, body mass index; GA, gestational age; GBS, group B Streptococcus; HIV, human immunodeficiency virus; RPR, rapid plasma reagin; SD, standard deviation.
Note: Data presented as N(%) mean (SD) or median (interquartile range).
Table 3
Maternal outcomes (guideline followed)
|
Normal weight BMI ≥18.5 to <25 (N = 1,260)
|
Overweight BMI 25 to <30 (N = 4,364)
|
Class 1 obesity BMI 30 to <35 (N = 3,623)
|
Class 2 obesity BMI 35 to <40 (N = 1,634)
|
Class 3 obesity BMI ≥40 (N = 762)
|
p-Value
|
|
GA at delivery
|
|
|
|
|
|
|
|
Mean (SD)
|
39.3 (1.09)
|
39.5 (1.07)
|
39.5 (1.12)
|
39.4 (1.09)
|
39.4 (1.09)
|
0.001
|
|
Type of labor
|
|
|
|
|
|
< 0.001
|
|
Spontaneous/Augmented
|
1,013 (80.4%)
|
3,433 (78.7%)
|
2,775 (76.6%)
|
1,223 (74.9%)
|
521 (68.4%)
|
|
|
Induced/No labor
|
244 (19.4%)
|
922 (21.1%)
|
839 (23.2%)
|
407 (24.9%)
|
241 (31.6%)
|
|
|
Missing
|
3 (0.24%)
|
9 (0.21%)
|
9 (0.25%)
|
4 (0.24%)
|
0
|
|
|
Delivery route
|
|
|
|
|
|
0.007
|
|
Vaginal
|
1,211 (96.1%)
|
4,228 (96.9%)
|
3,508 (96.8%)
|
1,589 (97.3%)
|
731 (95.9%)
|
|
|
Operative assisted vaginal
|
45 (3.6%)
|
117 (2.7%)
|
93 (2.6%)
|
39 (2.4%)
|
18 (2.4%)
|
|
|
Cesarean
|
4 (0.32%)
|
19 (0.44%)
|
22 (0.61%)
|
6 (0.37%)
|
13 (1.7%)
|
|
|
Oligohydramnios
|
29 (2.3%)
|
101 (2.3%)
|
75 (2.1%)
|
42 (2.6%)
|
27 (3.5%)
|
0.18
|
|
Anesthesia
|
1,077 (85.5%)
|
3,726 (85.4%)
|
3,136 (86.6%)
|
1,427 (87.3%)
|
663 (87.0%)
|
0.24
|
|
Regional
|
885 (70.2%)
|
3,009 (69.0%)
|
2,556 (70.6%)
|
1,209 (74.0%)
|
568 (74.5%)
|
|
|
General
|
7 (0.56%)
|
22 (0.50%)
|
10 (0.28%)
|
8 (0.49%)
|
8 (1.1%)
|
|
|
Other
|
593 (47.1%)
|
2,100 (48.1%)
|
1,844 (50.9%)
|
788 (48.2%)
|
390 (51.2%)
|
|
|
Chorioamnionitis
|
54 (4.3%)
|
178 (4.1%)
|
146 (4.0%)
|
69 (4.2%)
|
29 (3.8%)
|
0.98
|
|
Endomyometritis
|
5 (0.40%)
|
10 (0.23%)
|
13 (0.36%)
|
5 (0.31%)
|
4 (0.52%)
|
0.63
|
|
Hemorrhage
|
40 (3.2%)
|
125 (2.9%)
|
108 (3.0%)
|
47 (2.9%)
|
19 (2.5%)
|
0.93
|
|
Composite[a]
|
14 (1.1%)
|
38 (0.87%)
|
22 (0.61%)
|
12 (0.73%)
|
1 (0.13%)
|
0.09
|
|
Blood transfusion
|
11 (0.87%)
|
31 (0.71%)
|
19 (0.52%)
|
9 (0.55%)
|
0
|
|
|
Hysterectomy from atony
|
0
|
1 (0.02%)
|
4 (0.11%)
|
0
|
0
|
|
|
Accreta hysterectomy
|
0
|
0
|
2 (0.06%)
|
0
|
0
|
|
|
Wound infection
|
1 (0.08%)
|
0
|
0
|
0
|
0
|
|
|
Wound separation
|
0
|
0
|
0
|
0
|
0
|
|
|
Ileus
|
1 (0.08%)
|
0
|
0
|
0
|
0
|
|
|
Delayed postpartum hemorrhage
|
3 (0.24%)
|
11 (0.25%)
|
6 (0.17%)
|
3 (0.18%)
|
1 (0.13%)
|
|
Abbreviations: BMI, body mass index; SD, standard deviation.
Note: Data presented as N(%) or mean (SD) except where indicated.
a Blood transfusion, hysterectomy from atony, accreta hysterectomy, wound infection,
wound separation, ileus, delayed postpartum hemorrhage p-value for categorical variables from chi-squared test and for continuous variables
from Kruskal–Wallis test across BMI categories.
Neonatal outcomes are shown in [Table 4]. Newborn birthweight increased significantly with increasing maternal BMI and newborns
of women with class III obesity had higher rates of meconium passage at birth (p < 0.001). However, a composite of neonatal outcomes was not different with increasing
maternal BMI (p = 0.65). When analyzing the subgroup of women who underwent induction (n = 2,658), there was no difference in the number of women induced at different gestational
ages across BMI classes (p = 0.92) and the relationships between BMI class and chorioamnionitis, endomyometritis,
and sepsis were not different across the gestational age categories (p-value is for interaction term, p = 0.60, 0.30, 0.70, respectively) when adjusting for age, race, ethnicity, parity,
and birthweight, despite increasing cesarean rates. When comparing gestational age
37 to 38 to 39 to 40 weeks, there remained no differences in other adverse maternal
or neonatal outcomes (p = 0.58, 0.51). Maternal and neonatal composite outcomes did not differ across BMI
categories at separate gestational ages at induction as well (p = 0.98, 0.90, respectively).
Table 4
Neonatal outcomes (guideline followed)
|
Normal weight BMI ≥18.5 to <25 (N = 1,260)
|
Overweight BMI 25 to <30 (N = 4,364)
|
Class 1 obesity BMI 30 to <35 (N = 3,623)
|
Class 2 obesity
BMI 35 to <40 (N = 1,634)
|
Class 3 obesity BMI ≥40 (N = 762)
|
p-Value
|
|
Birthweight (g)
|
|
|
|
|
|
|
|
Mean (SD)
|
3,194.2 (373.00)
|
3,323.5 (398.28)
|
3,397.3 (400.58)
|
3,466.8 (425.27)
|
3,475.3 (446.52)
|
< 0.001
|
|
Gender
|
|
|
|
|
|
0.87
|
|
Male
|
613 (48.7%)
|
2,130 (48.8%)
|
1,757 (48.5%)
|
818 (50.1%)
|
374 (49.1%)
|
|
|
Female
|
647 (51.4%)
|
2,233 (51.2%)
|
1,866 (51.5%)
|
815 (49.9%)
|
388 (50.9%)
|
|
|
Apgar 1
|
8 (8-9)
|
8 (8-9)
|
8 (8-9)
|
8 (8-9)
|
8 (8-9)
|
0.01
|
|
Apgar 5
|
9 (9-9)
|
9 (9-9)
|
9 (9-9)
|
9 (9-9)
|
9 (9-9)
|
0.65
|
|
Arterial Ph
|
|
|
|
|
|
0.91
|
|
Mean (SD)
|
7.27 (0.07)
|
7.27 (0.07)
|
7.27 (0.00)
|
7.27 (0.07)
|
7.27 (0.07)
|
|
|
Meconium
|
127 (10.1%)
|
471 (10.8%)
|
446 (12.3%)
|
227 (13.9%)
|
118 (15.4%)
|
< 0.001
|
|
Ventilator support (d)
|
0
|
0
|
0
|
0
|
0
|
0.21
|
|
Newborn sepsis/NICU admit
|
|
|
|
|
|
|
|
Suspect
|
33 (2.6%)
|
191 (4.4%)
|
135 (3.7%)
|
70 (4.3%)
|
29 (3.8%)
|
|
|
Proven
|
3 (0.24%)
|
5 (0.11%)
|
4 (0.11%)
|
1 (0.06%)
|
0
|
0.55
|
|
Composite outcome[a]
|
14 (1.1%)
|
66 (1.5%)
|
50 (1.4%)
|
27 (1.7%)
|
14 (1.8%)
|
0.65
|
|
NEC
|
1 (0.08%)
|
1 (0.02%)
|
1 (0.03%)
|
0
|
0
|
|
|
TTN
|
4 (0.32%)
|
32 (0.73%)
|
24 (0.66%)
|
7 (0.43%)
|
7 (0.92%)
|
|
|
BDP
|
0
|
1 (0.02%)
|
1 (0.03%)
|
1 (0.06%)
|
0
|
|
|
RDP
|
7
|
38 (0.87%)
|
23 (0.63%)
|
18 (1.1%)
|
10 (1.3%)
|
|
|
Presser use
|
4 (0.32%)
|
7 (0.16%)
|
4 (0.11%)
|
3 (0.18%)
|
0
|
|
|
PIE
|
0
|
0
|
1 (0.03%)
|
0
|
0
|
|
|
Hypertonicity
|
1 (0.08%)
|
0
|
2 (0.06%)
|
0
|
0
|
|
Abbreviations: BDP, bronchopulmonary dysplasia; BMI, body mass index; NEC, necrotizing
enterocolitis; NICU, neonatal intensive care unit; PIE, pulmonary interstitial emphysema;
RDP, respiratory distress; TTN, transient tachypnea of the newborn.
Note: q-Value for categorical variables from chi-square test and for continuous variables
from Kruskal–Wallis test across BMI categories; Data presented as N(%) Mean (SD) or Median (interquartile range).
a Includes necrotizing enterocolitis (NEC), transient tachypnea of the newborn (TTN),
bronchopulmonary dysplasia (BPD), respiratory distress (RDS), presser use, pulmonary
interstitial emphysema (PIE), hypertonicity.
Discussion
This study demonstrates a decrease in guideline adherence by providers as maternal
weight class increased, with the lowest rate of compliance among women with class
III obesity. This finding may be a result of bias or weight discrimination that undoubtedly
exists in our society and unfortunately, in medicine. In 2018, the American Medical
Association Journal of Medical Ethics published research surveying first year medical
students for their perception of obesity. Over 70% showcased negative attitudes toward
obesity, with 74% reporting that they believe obesity is a result of ignorance.[33]
[34] Negative weight bias has been shown to adversely affect clinical practice and patient
outcomes, including reduced access to surgery for obese patients.[19]
[34]
[35] These preconceived attitudes are often a result of educational deficiencies; however,
can translate to prejudice in care, further perpetuating negative health outcomes
for obese patients.[33]
The secondary aim was to estimate more accurate perinatal risks for this cohort of
women when standardized induction and labor management is applied, an important consideration
given the current guidelines favor an undefined prolongation of labor to avoid complications
for obese patients.[17]
[24] However, standard labor management recommendations for obese women remain elusive
with no definitive data to support particular timelines or acceptable labor curves.[17]
[24]
These induction and mode of delivery results are consistent with prior studies that
have described a sequential increase in induction and cesarean delivery rates with
increasing maternal BMI, approaching a threefold increase in cesarean delivery for
class III obese women.[9]
[10] In this current large dataset, there were no significant differences in adverse
maternal outcomes including chorioamnionitis and endomyometritis with increasing BMI
class when labor management guidelines were followed, regardless of increased rates
of induction and cesarean delivery among obese parturients.[3]
[4]
[9]
[12]
[13]
[14]
[15]
[18]
[19] With standardized labor management and the contribution of contemporary protocols
optimizing postoperative infection risk,[36] our results suggest rates of postoperative infectious morbidity are improved and
comparable across all weight classes.
However, these results should be interpreted with caution given the exclusion of all
comorbidities, including those associated with obesity. Whereas other research has
described a uterine atony-related hemorrhage rate approaching 5% for obese women who
delivered vaginally, atony-related hemorrhage and the maternal composite including
blood transfusion were not increased with increasing BMI in the current study.[3]
[15]
[21]
[37] Among low-risk obese women, even with class III obesity, vaginal delivery approached
95%, similar to other trials evaluating outcomes involving a low-risk obstetrical
cohort undergoing induction.[38]
[39] It is important to note that all cesarean deliveries for nonreassuring fetal status
were excluded from analysis, contributing to the low cesarean delivery rates in this
analysis. These data were intentionally excluded as it may have altered time points
related to labor dystocia, erroneously altering results.
Although neonatal outcomes of obese women were not significantly different from normal
or overweight women, meconium passage was more frequent among the newborns of class
III obese women, and newborn weight increased with maternal BMI class, consistent
with prior studies describing lower Apgar scores and possible transitional challenge
for these newborns, along with an increased risks of macrosomia.[15]
[40]
[41] Any pregnancy complicated with fetal growth restriction or maternal morbidity was
excluded and the remaining fetuses, although not macrosomic, were approximately 300 g
larger when delivered from women with class III obesity. Although newborns of class
III obese women had significantly higher rates of meconium passage at birth, there
were no differences in Apgar scores or umbilical artery blood gas values suggestive
of intrapartum fetal hypoxemia or acidosis across weight class, nor was there any
differences in the composite neonatal outcome.
Current recommendations do not support antenatal surveillance or induction of labor
for obese patients given the paucity of data demonstrating improved pregnancy outcomes
with these interventions in the absence of comorbidities.[3]
[4]
[5]
[8]
[10]
[11]
[12]
[13]
[14]
[15]
[18]
[19]
[20]
[21] This was confirmed with our analysis. When analyzing the cohort of women who underwent
induction in this study, there was no difference in outcomes, including the maternal
and neonatal composites according to weeks' gestation at induction across weight classes
up to 40 6/7 weeks with multivariate analysis to exclude confounders.
The publication and implementation of the labor dystocia guidelines in 2014 standardized
labor management at our institution, allowing for more direct comparisons of outcomes
of women with differing BMI classes, excluding the possible deleterious effects of
prolonged labor or inductions. Although maternal and neonatal outcomes are improved
with standardized protocols utilizing the current guidelines for labor management,
cesarean delivery rates in the United States remain increased. Clinical tools to identify
labor progress with obesity, such as BMI—determined labor partograms, may prove helpful
in reducing cesarean rates in this cohort of women, especially when considering changes
in weight gain or loss. Obese women may benefit from optimized induction or augmentation
protocols related to medication dosage and interval, rather than the standard protocols
currently in use for women of any BMI. All induction agents and methods may need to
be evaluated to find the most effective regimen for obese patients in future studies.
Although this analysis included a large cohort of low-risk obese women, further research
should include a similar analysis for obese women with comorbidities to more accurately
predict risk and counsel patients appropriately.
Strengths and Limitations
Strengths and Limitations
Study limitations include that this analysis was retrospective and derived from a
large departmental database where cases may have been missed or data entered incorrectly.
These data are also limited by the accuracy of times documented in the medical record.
However, only 6.8% of the cases were excluded secondary to incorrect or missing BMI
data. In addition, the Department of Obstetrics and Gynecology at the Baylor College
of Medicine publishes evidence-based guidelines and protocols for induction of labor
based on national guidelines that are available to the team of residents, fellows,
and faculty at both delivery sites.
Although our institution attempts to comply with our evidence-based protocols and
national standards, this may not be generalizable to other institutions, centers,
or populations. Despite the discovered decrease in guideline adherence for labor management
of women with increasing BMI, it is commendable that the compliance rate was overall
quite high within the Baylor-affiliated centers, reflecting dedication to evidence-based
training for physicians. The strengths of our study include the large study cohort
of over 13,000 low-risk deliveries between 2014 and 2017 after the publication and
implementation of the labor dystocia and prevention of the primary cesarean labor
management guidelines were published and evidence-based protocols for induction were
utilized.
Conclusion
This study describes perinatal outcomes of low-risk obese women, after adjusting for
significant confounding variables that may have influenced the results of prior publications
addressing adverse maternal and neonatal outcomes, especially related to labor duration.
The results also demonstrate potential quality gaps surrounding protocol and guideline
adherence for obese patients and possible bias when addressing this vulnerable population.
Weight bias is often based on false presumptions that should be dispelled by truth
and evidence. Data such as these, should be communicated and disseminated, especially
in the setting of medical education.
