Placental abruption: critical analysis of risk factors and perinatal outcomes

The Journal of M aternal- F etal and N eonatal M edicine, 2010; Early Online, 1–5
Placental abruption: critical analysis of risk factors and perinatal outcomes
GALI PARIENTE1, ARNON WIZNITZER1, RUSLAN SERGIENKO2, MOSHE MAZOR1,
GERSHON HOLCBERG1, & EYAL SHEINER1
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1
F aculty of H ealth Sciences, Department of Obstetrics and G ynecology, Soroka University M edical Center, Ben- Gurion University of
the N egev, Beer-Sheva, Israel and 2 F aculty of H ealth Sciences, Department of Epidemiology and H ealth Services E valuation, Soroka
University M edical Center, Ben- Gurion University of the N egev, Beer-Sheva, Israel
(Received 5 F ebruary 2010; accepted 23 July 2010)
Abstract
Objective. To investigate risk factors and pregnancy outcome of patients with placental abruption.
M ethods. A population-based study comparing all pregnancies of women with and without placental abruption
was conducted. Stratified analysis using multiple logistic regression models was performed to control for confounders.
Results. During the study period there were 185,476 deliveries, of which 0.7% (1365) occurred in patients with
placental abruption. The incidence of placental abruption increased between the years 1998 to 2006 from 0.6 to 0.8%.
Placental abruption was more common at earlier gestational age. The following conditions were significantly associated
with placental abruption, using a multivariable analysis with backward elimination: hypertensive disorders, prior cesarean
section, maternal age, and gestational age. Placental abruption was significantly associated with adverse perinatal outcomes
such as Apgar scores 5 7 at 1 and 5 min and perinatal mortality. Patients with placental abruption were more likely to have
cesarean deliveries, as well as cesarean hysterectomy.Using another multivariate analysis, with perinatal mortality as the
outcome variable, controlling for gestational age, hypertensive disorders, etc., placental abruption was noted as an
independent risk factor for perinatal mortality.
Conclusions. Placental abruption is an independent risk factor for perinatal mortality. Since the incidence of placental
abruption has increased during the last decade, risk factors should be carefully evaluated in an attempt to improve
surveillance and outcome.
Keywords: Placental abruption, perinatal mortality, trends, pregnancy outcome
Introduction
Placental abruption is defined as the partial or complete
separation of a normally implanted placenta from the
uterine wall before delivery of the fetus [1]. It is an
important cause of maternal morbidity and perinatal
mortality [1]. Despite its clinical significance, there are no
reliable diagnostic tests or biomarkers to predict or prevent
the occurrence of abruption. The clinical hallmarks of
abruption include painful vaginal bleeding accompanied by
tetanic uterine contractions, uterine hypertonicity, and a
non-reassuring fetal heart rate patterns [2].
Placental abruption complicates roughly 1 in 100 to
200 (0.5–1%) pregnancies [3,4] and evidence from the
United States and Norway indicate that the frequency
is increasing [5,6]. The rate of placental abruption varies
by gestational age at delivery with the rate being 10-fold
higher at very preterm gestations and sharply declining
as pregnancy progresses toward term, with a rate of
abruption of 5.4 and 0.3% at preterm and term
gestations, respectively [7,8].
Despite extensive research, the majority of placental
abruption cases are of unknown cause [9]. A number of
epidemiologic and clinical studies have identified several
predisposing risk factors for this condition. Our group [8]
found the following factors to be independently associated
with the occurrence of placental abruption in term
pregnancies: gestational hypertension, intrauterine growth
restriction (IUGR), nonvertex presentation, hydramnios,
and advanced maternal age. Other risk factors for the
occurrence of placental abruption included multiparity
[10], intrauterine infection [5,11], premature rupture of
membranes (PROM) [9,11–13], and smoking during
pregnancy [14].
Placental abruption is associated with a variety of
maternal complications, including disseminated intravascular coagulation, hemorrhagic shock, uterine rupture,
hysterectomy, acute renal failure, and maternal death [15–
20]. Although its rarity, placental abruption contributes
disproportionately to excessively high rates of preterm birth
[21], fetal growth restriction [22], and perinatal mortality
[7,8].
This study was designed to investigate trends over the
years, timing during pregnancy, risk factors and pregnancy outcomes of patients with placental abruption.
We hypothesized that most cases of abruption will
Correspondence: Eyal Sheiner, Department of Obstetrics and Gynecology, Soroka University Medical Center, P. O. Box 151, Beer-Sheva, Israel.
Tel: þ972-54-804-5074. Fax: þ972-8-627-5338. E-mail: [email protected]
Presented in part at the Society of Maternal Fetal Medicine (SMFM) 30th Annual Scientific Meeting, Chicago, USA, 1–6 February 2010.
ISSN 1476-7058 print/ISSN 1476-4954 online ! 2010 Informa UK, Ltd.
DOI: 10.3109/14767058.2010.511346
2
G . Pariente et al.
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occur preterm, that major risk factors for placental
abruption would be maternal age and hypertensive
disorders, and that in an era where women tend to
delay pregnancies later to their reproductive life, the rate
of this critical complication will increase over the years.
We also wanted to investigate whether placental abruption
is an independent risk factor for perinatal mortality or
whether the risk is attributed to other preexisting
conditions. During 20-year period, we were able to
examine a relatively large number of women with
placental abruption who delivered in the southern part
of Israel.
Materials and methods
A population-based study comparing all pregnancies of
women with and without placental abruption was conducted. Deliveries occurred during the years 1988–2008 at
the Soroka University Medical Center. This is the sole
hospital in the Negev, the southern part of Israel, which
serves the entire obstetric population in this region. Data
were collected from the computerized perinatal database
that consists of information recorded directly after delivery
by an obstetrician. Only four skilled medical secretaries
examine the information routinely before entering it into
the database. Coding was done after assessing the medical
prenatal care records, as well as the routine hospital
documents. These procedures assure maximal completeness and accuracy of the database. The following clinical
characteristics were evaluated: ethnicity (i.e. Jewish or
Bedouin Arabs), maternal age, parity, gestational age, birth
weight, small for gestational age (birth weight below the
10th percentile, using local standards), and gender. The
following obstetric risk factors were examined: smoking,
previous cesarean delivery, recurrent abortions (two or
more consecutive pregnancies resulting in spontaneous
abortion), fertility treatments, vasa previa, hypertensive
disorders [23,24], gestational diabetes mellitus [25], and
premature rupture of membranes.
The following labor characteristics and perinatal outcomes were assessed: second trimester bleeding, placenta
accreta, cesarean delivery, Apgar score at 1 and 5 min less
than 7, congenital malformations, perinatal mortality,
postpartum hemorrhage, pathological presentation, IUGR,
cesarean hysterectomy, maternal sepsis, and maternal
packed cell transfusions. The local ethics institutional
review board approved the study.
Statistical analysis was performed with the SPSS
package (SPSS, Chicago, IL). Statistical significance was
calculated by using the X 2 for differences in qualitative
variables and the Student t-test for differences in
continuous variables. A multivariable logistic regression
model, with backward elimination, was constructed to
find independent risk factors associated with placental
abruption. Since we had special interest in the association
between abruption and perinatal mortality, another multivariable model was constructed with perinatal mortality as
the outcome variable. Odds ratios (ORs) and their 95%
confidence intervals (CIs) were computed. A value of
P 5 0.05 was considered statistically significant.
Results
During the study period, there were 184,111 deliveries,
of which 1365 (0.7%) occurred in patients with placental abruption. The incidence of placental abruption
increased between the years 1998 and 2008 from 0.6 to
0.8%.
Placental abruption was more common in elderly
women and in lower gestational age (Table I, Figure 1).
Accordingly, abruption was associated with lower birth
weight as compared to pregnancies without placental
abruption (Figure 2).
Obstetric risk factors are presented in Table II. There
were higher rates of hypertensive disorders, previous
cesarean delivery, infertility treatment, habitual abortions,
and PROM among parturients with placental abruption as
compared with the comparison group. No significant
differences were noted between the groups regarding
smoking.
Placental abruption was significantly associated with
adverse perinatal outcomes such as congenital malformations, vasa previa, Apgar scores at 1 and 5 min less than 7,
and perinatal mortality (Table III). Patients with placental
abruption were more likely to have sepsis, cesarean
deliveries, and cesarean hysterectomies (Table III). Using
a multivariate analysis with backward elimination, the
following conditions were significantly associated with
placental abruption (Table IV): advanced maternal age,
lower gestational age, prior cesarean delivery, and hypertensive disorders. Gestational age was entered to the
multiple logistic regression model as a continuous variable.
The risk is presented for every week . Likewise, maternal
age was entered to the model as a continuous variable, and
the risk was calculated for every year. The other risk factors
were dichotomous (i.e. yes/no hypertensive disorders, etc).
Using another multivariate logistic regression model, with
perinatal mortality as the outcome variable, controlling for
gestational age, hypertensive disorders and congenital
malformations placental abruption was noted as an
independent risk factor for perinatal mortality (weighted
OR: 2.7; 95% CI: 2.2–3.3; P 5 0.001; data not shown in a
table).
Table I. Clinical characteristics of women with and without
placental abruption.
Maternal age
5 20 years
20–29 years
30–34 years
More than 35 years
Ethnicity
Jewish
Bedouin
Gestational age
5 36 weeks
37–41 weeks
More than 42 weeks
Birth weight
500–1500 g
1500–2500 g
2500–4000 g
4000–5000 g
Gender
Male
Female
Placental
abruption
(n ¼ 1365)
No placental
abruption
(n ¼ 184,111)
3.2%
47.7%
25.7%
23.4%
4.1%
55.7%
23.6%
16.5%
50.%
49.2%
54.%
46.%
56.%
42.2%
1.8%
7.5%
87.8%
4.7%
5 0.001
23.7%
31.2%
43.3%
1.3%
1.1%
6.5%
87.7%
4.6%
5 0.001
53.8%
46.2%
51.2%
48.8%
0.063
P value
5 0.001
0.191
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Placental abruption
Figure 1. Incidence of placental abruption by gestational age.
Figure 2. Percent of placental abruption by birth weight.
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Table II. Obstetric risk factors of patients with or without placental abruption.
Risk factor
Placental abruption
(n ¼ 1365)
No placental abruption
(n ¼ 184,111)
OR
95% CI
P value
1.2%
4.1%
19.4%
8.9%
15.3%
8.6%
7.3%
1.3%
1.9%
11.6%
5.4%
5.9%
6.8%
6.8%
0.927
2.25
1.84
1.72
2.86
1.29
1.09
0.5–1.4
1.72–2.95
1.61–2.11
1.42–2.07
2.46–3.32
1.07–1.56
0.89–1.33
0.758
5 0.001
5 0.001
5 0.001
5 0.001
0.007
0.401
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Smoking
Infertility treatment
Prior cesarean delivery
Habitual abortions
Hypertensive disorders
PROM
Diabetes mellitus
Table III. Pregnancy and labor complications and outcomes associated with placental abruption.
Placental abruption
(n ¼ 1365)
No placental abruption
(n ¼ 184,111)
OR
95% CI
P value
0.8%
2.3%
0.8%
14.9%
0.3%
19.1%
0.7%
16.9%
19.4%
44.6%
21.6%
67.7%
0.1%
0.4%
8.1%
0.1%
1.3%
0.5%
1.2%
0.%
5.3%
0.1%
5.0%
1.1%
5.7%
2.5%
12.8%
0.%
0.1%
2.1%
15.9
1.8
1.5
14.3
17.4
4.2
6.99
3.8
20.8
13.3
10.8
14.3
15.8
7.9
4.2
8.4–29.7
1.2–2.6
0.8–2.7
12.2–16.7
6.1–49.5
3.6–4.8
3.69–13.2
3.3–4.4
18.1–23.9
11.9–14.8
9.5–12.4
12.7–16.0
3.6–68.8
3.4–18.1
3.4–5.1
5 0.001
0.001
0.18
5 0.001
5 0.001
5 0.001
5 0.001
5 0.001
5 0.001
5 0.001
5 0.001
5 0.001
5 0.000
5 0.001
5 0.001
Second trimester bleeding
Placenta accreta
Post partum hemorrhage
Maternal blood transfusion
Maternal sepsis
Pathological presentation
Vasa previa
Congenital malformation
Perinatal mortality
Apgar score at 1 min 5 7
Apgar score at 5 min 5 7
Cesarean section
Subtotal hysterectomy
Hysterectomy
IUGR
Table IV. Multiple logistic regression with back ward elimination
of factors associated with placental abruption.
Maternal age (years)
Gestational age (weeks)
Prior cesarean section
Habitual abortions
Hypertensive disorders
Second trimester bleeding
Odds ratio
95% CI
P
1.02
0.77
1.38
1.18
2.0
3.1
1.01–1.03
0.76–0.78
1.2–1.6
0.97–1.45
1.7–2.4
1.5–6.3
5 0.001
5 0.001
5 0.001
0.092
5 0.001
0.02
The initial model included, in addition, fertility treatments and
premature rupture of membranes.
Discussion
The present population-based study includes a large
number of patients with placental abruption (n ¼ 1365),
enabling us to describe independent risk factors associated
with this critical condition. Importantly, the incidence of
placental abruption is increasing over the years. Although
causes of temporal increase could be varied and numerous,
it is likely that the increase in cesarean section rate [26]
may have contributed much to these trends.
In accordance to previous studies, placental abruption
was significantly more common among preterm deliveries.
Disease patterns at term may differ from those occurring at
preterm gestations. Conditions associated with acute
inflammation are more common at preterm pregnancies.
Indeed, Nath et al. [27] confirmed the association of
histologic chorioamnionitis with placental abruption in
both preterm and term pregnancies. In this study PROM
and maternal sepsis were significantly more common
among parturitions with placental abruption, reflecting
acute inflammation associated conditions.
Small-for-gestational age and hypertensive disorders,
reflecting chronic processes associated with vascular
dysfunction, were found to be in strong association with
placental abruption, in accordance to the literature [8].
Ananth et al. [28] has postulated that there are acute and
more often chronic disease processes reflected in the
known associated risk factors for placental abruption.
While the frequency of acute inflammation associated
conditions decline steadily with gestational age, in both
women with and without placental abruption, rates of
chronic processes increase with advancing gestation
steadily up to term, among women with placental abruption, in contrast to women without placental abruption
where the rate began to decline much earlier. Conditions
associated with chronic disease processes are present
throughout the pregnancy, and it should be targeted and
carefully evaluated to recognize pregnancies with risk of
placental abruption.
Our study has several inherent weaknesses because of its
retrospective design. Differences in the severity of the
condition could not be evaluated since we did not have
such data. Nevertheless, during 20-year period, we were
able to examine a large number of women and to state that
Placental abruption
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placental abruption is independently associated with
perinatal mortality. With such large database, it is possible
to find statistically significant findings that are not clinically
significant. For this reason, we have constructed the
multivariate logistic regression model, to define independent risk factors for placental abruption.
In conclusion, placental abruption is an independent risk
factor for perinatal mortality. Since the incidence of
placental abruption has increased during the last decade,
risk factors should be carefully evaluated in an attempt to
improve surveillance and outcome.
Declaration of interest: The authors report no conflicts
of interest. The authors alone are responsible for the
content and writing of the paper.
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