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Journal ArticleDOI

639: Temporal trends in chorioamnionitis by maternal race/ethnicity and gestational age: 1991-2008

01 Jan 2011-American Journal of Obstetrics and Gynecology (Elsevier)-Vol. 204, Iss: 1
Topics: Chorioamnionitis (60%), Gestational age (54%)

Summary (1 min read)

1. Introduction

  • Chorioamnionitis, an infection and inflammation of the maternal and fetal interface, is arguably the most important cause of pretermbirth and infantmorbidity.
  • It has been estimated that about 10 percent of all pregnancies are complicated by chorioamnionitis [1, 2].
  • Prevalence varies with race/ethnicity and is higher in non-Whites than Whites [12].
  • The most common route of infection is ascending microbial invasion of the amniotic cavity from upper genital tract [13, 14].
  • There is a gap in knowledge about the recent trends in chorioamnionitis diagnosis rate and the modifying role of maternal race/ethnicity.

2. Materials and Methods

  • The cohort for this study is comprised of all women with a singleton birth at ≥20 weeks gestation who delivered in a KPSC hospital from 1995 to 2010.
  • Pregnancies resulting in preterm births or low birthweight were oversampled to ensure adequate number of subjects with chorioamnionitis.
  • These findings support the validity of the diagnosis codes in their study.
  • The authors decided to exclude women of “other” race/ethnicity from all analyses due to the small number of such women (11,345; 2%).

3. Results

  • Women with chorioamnionitis tend to be younger than those without chorioamnionitis.
  • In order to assess the effect of induction of labor on the rate of chorioamnionitis, the authors repeated the analysis after stratifying the data by indication of labor subtypes (indicated, elective, and spontaneous).

4. Discussion

  • The rate of chorioamnionitis among women with singleton pregnancies delivered in the KPSC hospitals increased by 79% between 1995-1996 and 2009-2010.
  • The authors data further showed disparity in rate of chorioamnionitis by maternal race/ethnicity, which is not explained by maternal sociodemographic, behavioral, and perinatal factors.
  • In addition to increasing neonatalmorbidity, term chorioamnionitis increases maternal morbidity as well.
  • The coding of behavioral risk factors such as smoking during pregnancy may not always be reliable and, additionally, these behaviorsmay be underreported; thus the potential for residual confounding remains.

5. Conclusions

  • Thefindings of this study demonstrated significant variations in the temporal trends of chorioamnionitis by race/ethnicity.
  • Chorioamnionitis diagnosis rates increased for women of all race/ethnic groups, both at preterm and term gestation.
  • The preponderance of chorioamnionitis at term gestation among Hispanic and Asian/Pacific Islander women appears responsible for the observed disparity in chorioamnionitis.

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UC Irvine Previously Published Works
Title
Temporal trends in chorioamnionitis by maternal race/ethnicity and gestational age
(1995-2010).
Permalink
https://escholarship.org/uc/item/5sr1n69t
Authors
Fassett, Michael J
Wing, Deborah A
Getahun, Darios
Publication Date
2013
DOI
10.1155/2013/906467
Peer reviewed
eScholarship.org Powered by the California Digital Library
University of California

Hindawi Publishing Corporation
International Journal of Reproductive Medicine
Volume , Article ID , pages
http://dx.doi.org/.//
Research Article
Temporal Trends in Chorioamnionitis by Maternal
Race/Ethnicity and Gestational Age (1995–2010)
Michael J. Fassett,
1
Deborah A. Wing,
2
and Darios Getahun
3,4
1
Division of Maternal-Fetal Medicine, Department of Obstetrics-Gynecology, West Los Angeles Kaiser Permanente Southern California
Medical Group, Los Angeles, CA 90034, USA
2
Division of Maternal-Fetal Medicine, Department of Obstetrics-Gynecology, University of California, Irvine, CA 92868, USA
3
Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, CA 91101, USA
4
Department of Obstetrics and Gynecology, University of Medicine and Dentistry New Jersey, New Brunswick, NJ 08901, USA
Correspondence should be addressed to Darios Getahun; darios.t.getahun@kp.org
Received  December ; Accepted March 
Academic Editor: Yuping Wang
Copyright ©  Michael J. Fassett et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
Objective. To characterize trends in chorioamnionitis (CAM) by maternal race/ethnicity and gestational age. Study Design.We
examined trends in CAM from – among singleton births in all Kaiser Permanente Southern California hospitals (𝑛=
471,821). Data were extracted from Perinatal Service System and clinical utilization records. Gestational age- and race/ethnicity-
specic biannual diagnosis rates were estimated using the Poisson regression aer adjusting for potential confounding factors.
Results. Overall diagnosis rates of CAM increased from .% in - to .% in - with a relative increase of %
(% condence intervals [CI] %–%). From - to -, CAM increased among the Whites (.% to .%, 𝑃-value
for trend <.), Blacks (.% to .%, 𝑃-value for trend <.), Hispanics (.% to .%, 𝑃-value for trend <.), and Asian/Pacic
Islanders (.% to .%, 𝑃-value for trend <.). e adjusted relative percentage change in CAM from - to - was
for Whites [preterm % (%–%), term % (%–%)], for Blacks [preterm % (%–%), term % (%–%)], for
Hispanics [preterm % (%–%), term % (%–%)], and for Asian/Pacic Islanders [preterm % (%–%), term %
(%–%)]. Conclusion. e ndings suggest that CAM diagnosis rate has increased for all race/ethnic groups. is increase is
primarily due to increased diagnosis at term gestation.
1. Introduction
Chorioamnionitis, an infection and inammation of the
maternal and fetal interface, is arguably the most important
cause of preterm birth and infant morbidity. Despite advance-
ments in diagnosis and treatment, chorioamnionitis and its
complications remain major public health concern in the
United States. It has been estimated that about  percent of all
pregnancies are complicated by chorioamnionitis [, ]. Doc-
umented immediate and long-term sequelae of chorioam-
nionitis include fetal mortality [], preterm premature rup-
ture of membranes [],neonatalintensivecareadmission
[], bronchopulmonary dysplasia [, ], and cerebral palsy
[]. Most importantly, chorioamnionitis is responsible for
approximately half of all preterm births []. Prevalence
varies with race/ethnicity and is higher in non-Whites than
Whites [].
e most common route of infection is ascending micro-
bial invasion of the amniotic cavity from upper genital tract
[, ]. Inammatory processes at sites remote from the
female genital tracts are also described as important sources
of infection [, ].
ereisagapinknowledgeabouttherecenttrendsin
chorioamnionitis diagnosis rate and the modifying role of
maternal race/ethnicity. is gap coupled with its association
with preterm birth and the known dierential risk of preterm
labor based on race/ethnicity led us to speculate that there
may be dierential temporal trends in chorioamnionitis diag-
nosis rates based on maternal race/ethnicity and gestational
age at delivery.

International Journal of Reproductive Medicine
2. Materials and Methods
e cohort for this study is comprised of all women with
asingletonbirthat weeks gestation who delivered in
a KPSC hospital from  to . For these women, we
matched the Perinatal Services System (PSS) record, which
contained information from the infants birth certicate
(maternal demographics, behavioral characteristics, compli-
cations of labor and delivery, and fetal/infant birth outcomes
from other sources) with the hospital inpatient and outpatient
physicians encounters records, which included more detailed
information on maternal medical and obstetrical history and
fetal and infant outcomes.
International Classication of Diseases, Ninth Revi-
sion Clinical Modication (ICD--CM) codes “.” and
“.x” were used to identify the clinically diagnosed
chorioamnionitis. We validated the accuracy of the ICD--
CM coding by comparing it with diagnoses abstracted from a
random sample of  medical records. Pregnancies resulting
in preterm births or low birthweight were oversampled to
ensure adequate number of subjects with chorioamnioni-
tis.Aer adjusting for sampling fractions, the estimated sen-
sitivity, specicity and positive and negative predictive values
for chorioamnionitis were %, %, %, and %. ese
ndings support the validity of the diagnosis codes in our
study. Gestational age, expressed in completed weeks, was
based on the clinical estimates of gestational ages contained
in electronic medical records. Maternal race/ethnicity was
based on information from the infant birth certicate and
categorized as non-Hispanic White (White), non-Hispanic
Black (Black), Hispanic, and Asian/Pacic Islander.
Of , pregnancies from  to  we excluded
multiple pregnancies (𝑛 = 15,798), early pregnancy termi-
nations (𝑛 = 5,306), pregnancies delivered at < weeks of
gestation (𝑛 = 1,641), and women with other or missing
race/ethnicity. We decided to exclude women of other”
race/ethnicity from all analyses due to the small number
of such women (,; %). Aer these exclusions, ,
women remained for analysis.
We estimated the overall and race/ethnicity-specic
annual diagnosis rates of chorioamnionitis per  singleton
births using the Poisson regression. For this, the yearly count
of chorioamnionitis diagnosis was the outcome variable and
year of diagnosis was the independent variable, adjusting
for potential confounding factors listed in Table .Wealso
examined time trends by comparing event rates in the earliest
(-) versus most recent (-) periods and quan-
tied their % condence interval (CI). In order to assess
race/ethnicity disparity in the diagnosis of chorioamnionitis,
we compared rates for each of the three racial/ethnic groups
to those of White women. Variables considered as potential
confounders included maternal age (<, –, –,
and  years), education (<, , and  years of com-
pleted schooling), median family household income based
on census tract of residence (<,, ,–,,
,–,, ,–,, and ,), prenatal
care (care initiated in the rst trimester versus late or no
prenatal care), smoking during pregnancy (yes/no), and
parity. Finally, because the recent trends in chorioamnionitis
T : Distribution of maternal characteristics based on chorio-
amnionitis (CAM) status.
No CAM CAM
Characteristics (𝑛 = 452,) (𝑛=19,)
%%
Maternal age (years)
< . .
– . .
– . .
 . .
Race/ethnicity
Non-Hispanic White . .
Non-Hispanic Black . .
Hispanics . .
Asian/Pacic Islanders . .
Maternal education (years)
< . .
 . .
 . .
Missing . .
Household income
∗‡
<, . .
,–, . .
,–, . .
,–, . .
, . .
Late or no prenatal care
. .
Smoking during pregnancy . .
Parity
. .
. .
. .
. .
Inductionoflabor
. .
Dierences between CAM and No-CAM by maternal characteristics were
statistically signicant (𝑃 < .001);
Median household income based on
census tract information.
diagnosis may be modied by the rising trends in induction
of labor, we performed subanalyses aer stratifying the data
by no induction, medically indicated induction, and elective
induction of labor categories. Elective induction of labor was
dened as initiation of labor performed in the absence of
any of the medical or obstetrical indication recommended by
ACOG [].
All analyses were performed using SAS . (SAS institute,
Cary, NCUSA).e study was approved by the Kaiser Per-
manente Southern California (KPSC) Institutional Review
Board.
3. Results
e overall chorioamnionitis rate in women delivering in all
KPSC hospitals has risen from . percent in - to
reach its highest level yet in - of . percent, with a

International Journal of Reproductive Medicine
T : Chorioamnionitis diagnosis rate per  singleton births by Race/ethnicity in KPSC Hospitals, –.
Period Total births Overall rate (%)
Maternal Race/Ethnicity
White Black Hispanic Asian/PI
-  . . . . .
-  . . . . .
-  . . . . .
-  . . . . .
-  . . . . .
-  . . . . .
-  . . . . .
-  . . . . .
P for trend from  to  <. <. . <. <.
Relative increase % (% CI), - versus -  (, )  (, )  (, )  (, )  (, )
Rates are expressed in percent; Adjustments were made for maternal age, education, median household income, parity, prenatal care, and smoking during
pregnancy; Asian/PI: Asian and Pacic Islanders; CI: condence interval.
T : Chorioamnionitis rate per  singleton births by race/ethnicity at term gestation in KPSC Hospitals, –.
Chorioamnionitis rate at preterm (< wks) and term ( wks) gestations
Period
White Black Hispanic Asian/PI
< wks – wks < wks – wks < wks – wks < wks – wks
-
. . . . . . . .
-
. . . . . . . .
-
. . . . . . . .
-
. . . . . . . .
-
. . . . . . . .
-
. . . . . . . .
-
. . . . . . . .
-
. . . . . . . .
𝑃 for trend
<. <. . <. <. <. <. <.
Relative increase % (%
CI), - versus -
 (, )  (, )  (, )  (, )  (, )  (, )  (, )  (, )
Rates are expressed in percent; Adjustments were made for maternal age, education, median household income, parity, prenatal care, and smoking during
pregnancy; Asian/PI: Asian and Pacic Islanders; CI: condence interval.
relative increase of % (% condence interval (CI) %,
%). Women with chorioamnionitis tend to be younger
than those without chorioamnionitis. Race/ethnicity varied
between women with chorioamnionitis and those with-
out chorioamnionitis; in particular, there were more Hispan-
ics or Asian/Pacic Islanders among women with chorioam-
nionitis (Table ). Women with chorioamnionitis tended to
be nulliparous, had more formal education, and were more
likely to have their labor induced than women without cho-
rioamnionitis.
Table shows the recent trends in chorioamnioni-
tis diagnosis between - and - based on
race/ethnicity adjusted for maternal age, education, median
household income, parity, prenatal care, and smoking during
pregnancy. Chorioamnionitis diagnosis rates have increased
by % (% CI %, %; 𝑃 value for trend <.)
among White women, % (% CI %, %; 𝑃 value
for trend <.) among Hispanic women, and % (% CI
%, %; 𝑃 value for trend <.) among Asian/Pacic
Islander women. e increase in chorioamnionitis diagnosis
was lowest among Black women: % (% CI %, %; 𝑃
value for trend .).
e relative (percent) changes in chorioamnionitis rates
between the earliest and the most recent years based on mat-
ernal race/ethnicity and gestational age categories are shown
in Table . Aer adjusting for maternal age, education, pre-
natal care, smoking, and median household income, we
observed signicant changes in chorioamnionitis rates from
- to - among the Whites (preterm birth %,
% CI %, % and term birth %, % CI %,
%), among Hispanics (preterm birth %, % CI %–
%andtermbirth%,%CI%,%),andamong
Asian/Pacic Islanders (preterm birth %, % CI %, %
andtermbirth%,%CI%,%).Weobserveda
nonsignicant percent change in the diagnosis of chorioam-
nionitis for the Blacks at a preterm birth (%, % CI %,
%) and signicant percent change at term birth (%, %
CI %, %).

International Journal of Reproductive Medicine
0.1
1
10
1995-96
1997-98
1999-00
2001-02
2003-04
2005-06
2007-08
2009-10
Period (years)
Black
Asian/Pacic Islander
Hispanic
Relative risk
(95% CI)
F : Race/ethnic disparity in rates of chorioamnionitis (CAM).
Adjustments were made for maternal age, education, median
household income, parity, prenatal care, smoking during pregnancy,
and induction of labor.
Figure describes the race/ethnicity disparity in the diag-
nosis of chorioamnionitis among studied pregnant popu-
lation,usingWhiteraceasthereference.Hispanicand
Asian/Pacic Islander women have signicantly higher cho-
rioamnionitis rates than White women throughout the entire
study period. However, from  to , the gap in the
diagnosis of chorioamnionitis has narrowed for the Blacks.
During the study period, the rate of induction of labor
has increased by % between - (.%) and -
 (.%) for all singleton births. In order to assess the
eect of induction of labor on the rate of chorioamnionitis, we
repeated the analysis aer stratifying the data by indication
of labor subtypes (indicated, elective, and spontaneous).
Women who had a medically induced labor consistently had
the highest chorioamnionitis diagnosis followed by women
who had elective induction of labor (Figure ).
4. Discussion
e rate of chorioamnionitis among women with singleton
pregnancies delivered in the KPSC hospitals increased by
% between - and -. Our data further
showed disparity in rate of chorioamnionitis by maternal
race/ethnicity, which is not explained by maternal sociode-
mographic,behavioral,andperinatalfactors.ereisastag-
gering increase in the rate of chorioamnionitis at preterm
gestation among all but Black race/ethnicity groups. While
there are temporal trends in chorioamnionitis rates at term
gestation among women from all racial/ethnic groups, there
was signicant heterogeneity in the magnitude. While His-
panic and Asian/Pacic Islander women have signicantly
higher rates of chorioamnionitis diagnosis, Black women
have rates of diagnosis that are comparable to those of their
White counterparts.
0
1
2
3
4
5
6
7
8
9
1995-96
1997-98
1999-00
2001-02
2003-04
2005-06
2007-08
2009-10
Period (years)
Medically indicated IOL
Elective IOL
Overall
No IOL
Chorioamnionitis rate
per 100 births
F : Temporal trends in the rate of chorioamnionitis (CAM)
based on induction of labor subtypes. IOL: induction of labor.
Adjustments were made for maternal age, race/ethnicity, educa-
tion, median household income, parity, prenatal care, and smoking
during pregnancy.
e clinical explanation for our observation in the
increase in chorioamnionitis at term is unclear.We hypoth-
esized that the increasing use of labor induction, as a proxy
for chorioamnionitis risk factors such as longer labors and
frequent cervical exams [, ], was not found to be a
signicant confounding factor.ough Asian/Pacic Islander
women have been shown to have signicantly longer second
stage and rates of prolonged second stage as compared to
White women, the absolute prolongation of approximately
ve minutes does not seem to account for our observed
increase in rates of chorioamnionitis []. Changing intra-
partum antibiotic use aer the Centers for Disease Control
 Perinatal GBS Prevention Guidelines may temporally be
consistent with our observed increase in chorioamnionitis;
however overall rates of early onset neonatal sepsis have
remained unchanged [].
While chorioamnionitis may be thought of as more of
a risk for preterm infants, signicant morbidity has been
reported in term births complicated by chorioamnionitis.
Alexander et al. [] reported on more than  term
infants born to women with chorioamnionitis and reported
signicant association with intubations in the delivery room,
neonatal pneumonia, and neonatal sepsis. Chorioamnionitis
in term infants is a signicant risk factor for development in
cerebral palsy. In a nested cohort study of more than ,
singletons born at weeks or more, chorioamnionitis was
found to contribute to % of cerebral palsy cases, with an
OR of . for developing cerebral palsy aer a diagnosis of
chorioamnionitis []. In addition to increasing neonatal mor-
bidity, term chorioamnionitis increases maternal morbidity
as well.e Maternal-Fetal Medicine Network compared 
womenwithchorioamnionitistowomenwhowere
not. Maternal risks of uterine atony, blood transfusion,
pelvic abscess, thromboembolism, and wound complications

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TL;DR: This study demonstrates the metabolic changes of murine macrophages caused by GBS exposure and shows that PGE2 priming was able to exacerbate lactate production, shown by the rapid and substantial lactate increases seen upon GBS Exposure.
Abstract: Globally, maternal and fetal health is greatly impacted by extraplacental inflammation. Group B Streptococcus (GBS), a leading cause of chorioamnionitis, is thought to take advantage of the uterine environment during pregnancy in order to cause inflammation and infection. In this study, we demonstrate the metabolic changes of murine macrophages caused by GBS exposure. GBS alone prompted a delayed increase in lactate production, highlighting its ability to redirect macrophage metabolism from aerobic to anaerobic respiration. This production of lactate is thought to aid in the development and propagation of GBS throughout the surrounding tissue. Additionally, this study shows that PGE2 priming was able to exacerbate lactate production, shown by the rapid and substantial lactate increases seen upon GBS exposure. These data provide a novel model to study the role of GBS exposure to macrophages with and without PGE2 priming.

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Q1. What are the contributions in "Temporal trends in chorioamnionitis by maternal race/ethnicity and gestational age (1995–2010)" ?

In this paper, the authors found significant variations in the temporal trends of chorioamnionitis by race/ethnicity and gestational age at delivery.