First-Trimester Intrauterine Hematoma and Outcome
Gianpaolo Maso, MD, Giuseppina D’Ottavio, MD, Francesco De Seta, MD, Andrea Sartore, MD,
Monica Piccoli, MD, and Giampaolo Mandruzzato, MD
OBJECTIVE: To evaluate the outcome of pregnancies com-
plicated by first-trimester intrauterine hematoma.
METHODS: An analysis was performed on 248 cases. The
pregnancy outcome was correlated with hematoma vol-
ume, gestational age (weeks), and maternal age (years).
RESULTS: One hundred eighty-two cases were eligible for
the study. Clinical complications occurred in 38.5% of the
cases (adverse outcome group). Spontaneous abortion
(14.3%), fetal growth restriction (7.7%), and preterm deliv-
ery (6.6%) were the most frequent clinical conditions ob-
served. Considering the hematoma variables in adverse
and favorable outcome groups, we found a significant
difference only for gestational age at diagnosis. The me-
dian gestational age was significantly lower (P < .02) in the
adverse outcome group (7.27, I and III quartiles 6.22–8.78)
than in the favorable outcome cases (8.62, I and III quar-
tiles 6.70–9.98). Among clinical conditions, the median
gestational age was significantly lower (P ? .02) in preg-
nancies complicated by spontaneous abortion (6.60, I and
III quartiles 5.95–8.36) than in cases not ending in a mis-
carriage (8.50, I and III quartiles 6.70–9.91). The overall
risk of adverse outcome was 2.4 times higher when the
hematoma was diagnosed before 9 weeks (odds ratio 2.37,
95% confidence interval 1.20–4.70). In particular, intra-
uterine hematoma observed before 9 weeks significantly
increases the risk of spontaneous abortion (odds ratio
14.79, 95% confidence interval 1.95–112.09)
CONCLUSION: Intrauterine hematoma can affect the out-
come of pregnancy. The risk of spontaneous abortion is
related to gestational age and is significantly increased if
diagnosed before 9 weeks.
339–44. © 2005 by The American College of Obstetri-
cians and Gynecologists.)
LEVEL OF EVIDENCE: III
(Obstet Gynecol 2005;105:
Intrauterine hematoma is not an uncommon finding at
ultrasound scanning in the early stages of pregnancies.
Pre-existing medical conditions, autoimmune diseases,
and immunological factors have been associated with
is still unknown.1–5Intrauterine or subchorionic hema-
toma is defined as a collection of fluid in the uterine
cavity, and it is believed to result from subchorionic
bleeding caused by a partial detachment of the tropho-
blast from the uterine wall. This condition can be diag-
nosed only by ultrasonography. Mantoni and Pedersen6
first described its sonographic patterns. On ultrasound
examination, it appears as an anechoic area that has a
falciform shape, and it is usually observed behind or
below the gestational sac, separating the chorion from
the inner wall of the uterus. Small echogenic structures
can be found in such areas, and they are believed to be
The reported incidence of intrauterine hematoma has
a wide range, between 0.5%7and 22%,8mainly associ-
ated with vaginal bleeding. The discrepancy in these
rates might be related to different patient populations,
study design, range of gestational ages, and lack of a
standard definition. Moreover, the different approaches
to ultrasound scanning, ie, transabdominal or transvag-
inal, may be a factor in this epidemiological issue.9
The clinical significance of this sonographic finding
remains controversial, and observational studies focus-
ing on this topic reported conflicting results.5Many
authors reported adverse outcome of pregnancy related
to hematoma volume.6,10–13Others observed that the
subchorionic hematoma did not represent a risk factor
for complications of pregnancy.14–16Two large-series,
controlled studies on unselected obstetric populations
have been addressed to clarify this issue, concluding that
this condition is significantly associated with adverse
The aim of our study was to investigate whether the
volume of intrauterine hematoma observed in the first
trimester of a viable pregnancy and 2 other variables
From the Department of Obstetrics and Gynecology, IRCCS Burlo Garofolo,
University of Trieste, Trieste, Italy.
The authors thank Dr.SandroZicari,UniversityofTrieste,forhisassistancewiththe
statistical analysis of data and Drs. Giancarlo Conoscenti and Mariangela Rustico
fortheir contribution in preparing the manuscript.
VOL. 105, NO. 2, FEBRUARY 2005
© 2005 by The American College of Obstetricians and Gynecologists.
Published by Lippincott Williams & Wilkins.
(such as maternal age and gestational age at the time of
the diagnosis) are predictive factors of adverse outcome.
MATERIALS AND METHODS
We reviewed the information from a 7-year period
(1991–1997) collected from our database (tertiary refer-
ral center) on 248 unselected viable pregnancies with a
history of vaginal bleeding/spotting and diagnosis of
intrauterine hematoma. Patients’ informed consent to
participate in the study was obtained in all the cases
before the analysis. The study was exempt from institu-
tional review board approval. All cases were diagnosed
by transvaginal sonography (Acuson XP10 System,
transducer 5–7 MHz; Acuson Corporation, Mountain
View, CA) in the first trimester of pregnancy (6–13
weeks of gestation). Gestational age was calculated on
the basis of the last menstrual period and was corrected
when the crown-rump length measurements were more
as previously described by Mantoni and Pedersen.6The
the maximum transverse, antero-posterior, and longitu-
dinal diameters, multiplying these values by a constant
of 0.523.19The management and follow up of the study
cases were decided on the basis of the clinical and sono-
graphic picture. However, when serial scans were per-
formed, only the hematoma volume and the gestational
age at the first examination were considered for the
analysis. We included in our study only the cases with
calculated hematoma volume and complete follow-up of
pregnancy. Patients who underwent elective abortion
nancies, recurrent miscarriage (defined as a history of 2
or more consecutive first-trimester losses), uterine pa-
thology (myomas), and malformations were excluded.
The outcome of pregnancy was defined as adverse if one
of the following conditions was present:
1. Spontaneous abortion, defined as loss before 20
weeks of gestation;
2. Fetal growth restriction, defined as birth weight of
less than the tenth percentile for gestational age
according to our population norms;
3. Intensive care for threatened preterm delivery,
defined as need of admission and tocolytic therapy;
4. Preterm delivery, defined as delivery before 37
weeks of gestation;
5. Placental abruption, defined as a clinically relevant
event determined by the managing physician; or
6. Fetal distress, defined as abnormal fetal heart
monitoring traces or fetal blood sampling suggestive
Outcome of pregnancy was first evaluated according to
maternal age at the time of diagnosis (years).
In the second part of the study, we tested the results of
Bennett et al,10who found that large intrauterine hema-
toma volume, advanced maternal age (? 35 years), and
early gestational age at diagnosis (? 9 weeks) might
affect adversely the outcome of pregnancy. Our evalua-
tion of the size of the hematoma was different from the
one proposed by Bennett, who defined the size of the
hematoma as the degree of the gestational sac circumfer-
ence elevated by the hematoma. We arbitrarily stratified
the hematoma volumes as small, medium, and large,
according to volume values, respectively, of less than 1
mL, between 1 and 10 mL, and larger than 10 mL.
All statistical evaluations were performed with SPSS
11.5 statistical software (SPSS Inc, Chicago, IL). The
Student t test was used to compare continuous variables
between the groups. When the Kolmogorov-Smirnov
normality test failed (P ? .05), the Mann-Whitney rank
sum test was used. The univariate association between
the variables of the hematoma and the outcome of preg-
nancy was assessed by computing the corresponding
odds ratios (ORs) for prevalence data and, when neces-
sary, by Fisher exact test. The null hypothesis was
rejected with ? equal to 0.05.
One hundred eighty-two cases (73.4%) met the inclusion
criteria for the analysis. The mean maternal age (? stan-
dard deviation ?SD?) was 30.7 years (? 4.8) (range
19.6–44), the median of the hematoma volume at the
diagnosis was 1.36 mL (I quartile 0.48 mL, III quartile
3.38 mL; range 0.002–103.6 mL), and the mean gesta-
tional age (? SD) at diagnosis was 8.2 weeks (? 2.1)
(range 5.3–13.1). Of the cases, 67.6% (123/182) were
diagnosed before 9 weeks of gestation. Clinical compli-
cations occurred in 38.5% of the cases (70/182). Table 1
Table 1. Intrauterine Hematoma and Associated Clinical
Outcome of Pregnancy
Fetal growth restriction
Threatened preterm delivery
340 Maso et al
OBSTETRICS & GYNECOLOGY
observed in our cases: spontaneous abortion (14.3%),
fetal growth restriction (7.7%), and preterm delivery
(6.6%) were the most frequent.
Considering the hematoma volumes, maternal age,
and gestational age at diagnosis in adverse and favorable
groups, we found a significant difference only for gesta-
tional age at diagnosis. The median gestational age was
significantly lower overall in the adverse outcome group
than in the favorable outcome cases (Table 2). When we
separately analyzed every complication, a correlation
was found only between gestational age at diagnosis and
spontaneous abortion: a significantly earlier median ges-
tational age was observed in cases complicated by spon-
taneous abortion (Table 2).
Using the cutoff values for the intrauterine hematoma
variables according to Bennett et al,10modifying the eval-
considering the hematoma volumes. There was an in-
creased rate of adverse pregnancy outcome for cases diag-
nosed at maternal age over 35 years, but this finding was
not statistically significant (P ? .052, Table 3). On the
contrary, when we considered the gestational age at diag-
nosis, the overall risk of adverse outcome was 2.4 times
higher in cases observed before 9 weeks (Table 3).
Once again, when we considered separately every
single complication, we only observed a statistically sig-
nificant correlation between spontaneous abortion and
gestational age at diagnosis. Spontaneous abortion oc-
curred in 20.3% of the cases diagnosed before 9 weeks,
diagnosed after this gestational age was only 1.7%.
To avoid potential bias, adjusted odds ratios for out-
come of pregnancy and spontaneous abortion were cal-
culated with a logistic regression model including the
hematoma volume, maternal age, and gestational age at
diagnosis. The results were comparable to univariate
analysis (crude odds ratios).
Table 2. Outcome of Pregnancy and Characteristics of Intrauterine Hematoma
MA at diagnosis (y)
Mean ? SD
IUH volume (mL)
GA at diagnosis (wk)
MA, maternal age; SD, standard deviation; IUH, intrauterine hematoma; GA, gestational age
* Student t test: P ? .05.
†Mann-Whitney rank sum test.
31.0 ? 5.4
30.6 ? 4.4
.56*32.3 ? 5.8
30.5 ? 4.6
Table 3. Association Between Adverse Pregnancy Outcome and Subchorionic Hematoma Variables
OR (95% CI) OR (95% CI)*
OR (95% CI)OR (95% CI)*
(n ? 70)
(n ? 112)
(n ? 26)
(n ? 156)
Small (? 1 mL)
Medium (1.0–10 mL)
Large (? 10 mL)
MA at diagnosis
? 35 y
? 35 y
GA at diagnosis
? 9 wk
? 9 wk
OR, odds ratio; CI, confidence interval; IUH, intrauterine hematoma; MA, maternal age; GA, gestational age.
Data are presented as n (% of total cases in each subgroup).
* Adjusted odds ratios obtained with logistic regression model including IUH volume, maternal age, and gestational age at diagnosis.
0.91 (0.46–1.80) 0.88 (0.41–1.86)
1.02 (0.33–3.10) 1.01 (0.30–3.03)
1.95 (0.88–4.29) 1.89 (0.89–4.03)
Referent 17 (11.7)
2.31 (0.88–6.06) 2.42 (0.89–6.51)
2.37 (1.20–4.70) 2.22 (1.13–4.40)
14.79 (1.95–112.09) 18.29 (2.36–41.46)
VOL. 105, NO. 2, FEBRUARY 2005
Maso et al
bleeding), clinical and sonographic features of intrauter-
ine hematoma (gestational age at the time of diagnosis,
maternal age at diagnosis, size/volume of the hema-
toma), and the outcome of pregnancy has been differ-
ently and separately investigated in the majority of the
studies, with conflicting results being reported.14–18
Only Ball et al,17in their large case-control study, eval-
uated the prognostic significance of clinical bleeding and
intrauterine hematoma variables, drawing no definitive
Our observational study on symptomatic cases af-
fected by this condition was unique in investigating
together the subchorionic hematoma variables to ad-
dress whether the maternal age and characteristics re-
time of diagnosis, volume of the hematoma) might be
age and gestational age at the time of diagnosis are
possible prognostic factors in pregnancies complicated
by subchorionic hematoma. It is nevertheless important
to consider that both advanced maternal age and early
gestational ages, independently of the presence of the
intrauterine hematoma, are known to be significantly
associated with an increased risk of spontaneous abor-
tion, mainly related to chromosomal or structural fetal
anomalies.20Therefore, these variables might be consid-
ered risk factors per se, independently of the presence or
absence of hematoma.
Dealing with subchorionic hematoma and maternal
age, Bennett et al10observed that the spontaneous abor-
tion rate was approximately twice as high for women
7.3%, respectively). Our results demonstrated a correla-
tion between adverse outcome/spontaneous abortion
rate and advanced maternal age, but this did not reach
statistical significance, probably because of the low
power of the study.
considered in the studies dealing with this topic. Our
results are similar to those observed in the retrospective
study by Bennett et al10of 516 cases complicated by
subchorionic hematoma and focusing on spontaneous
abortion risk. In our experience, using the same gesta-
tional-age cutoff, we observed that the risk of spontane-
ous abortion is nearly 15 times greater for cases diag-
nosed before 9 weeks of gestation than for those
observed after this period. This observation can be help-
complicated by intrauterine hematoma, bearing in mind
that a diagnosis made before 9 weeks gives a 20% likeli-
hood of miscarriage, whereas this possibility is far more
remote (less than 2%) when the hematoma is diagnosed
after this cutoff gestational age.
Finally, one of the features that could more directly
influence the pregnancy outcome is hematoma volume.
Doppler studies revealed a significant relationship be-
tween hematoma enlargement and the reduction of
blood flow velocities in spiral arteries, with a potential
threat to the continuance of the pregnancy by a direct
The results from available studies on hematoma vol-
ume and pregnancy outcome are again controversial.
Many observational reports revealed a significant corre-
lation between “large” hematomas and adverse outcome
of pregnancy,6,10–13while others failed to demonstrate
this association (Jakab A Jr, Juhasz B, Toth Z. Outcome
of the first trimester subchorial hematoma ?abstract?.
Tenth International Congress, The Fetus as a Patient.
Brijuni, Croatia; 1994. p. 54).22–26In our study, the
in adverse outcome and favorable outcome groups (P ?
.49). Moreover, no correlation with pregnancy outcome
has been observed when hematoma volume was arbi-
trarily stratified as “small,” “medium,” and “large.” Our
results differed from those of Bennett et al10who found
that large volumes, defined as a degree larger than the
2/3 of the gestational sac circumference elevated by the
hematoma, increased 2.4-fold the risk of spontaneous
abortion. This difference might be due to our arbitrary
definition of hematoma “size,” giving the “absolute”
value of hematoma, without relating it to the size of the
with pregnancy outcome when the stratified volumes
were matched with every single gestational week6–13
(our unpublished data). These different results might be
also the consequence of our limited sample size or might
be explained by considering that the majority of our
cases showed small hematomas (volumes ? 5 mL were
observed in 87.1% of the cases).
Alternatively, the explanation for these discrepancies
on this variable might be addressed by considering the
physiopathological mechanism of formation of the sub-
chorionic hematoma. In fact, the size might be the final
result of 2 processes: the amount of subchorionic bleed-
ing and the amount of the bleeding through the cervix.
Therefore, the size of the hematoma may not represent a
reliable estimation of the overall severity of the process,
which could ultimately be calculated only by knowing the
total amount of blood collected in the uterus, reabsorbed,
and lost through the cervix. On this basis, therefore, it
might be postulated that the presence and location of a
hematoma, as a sign of the impaired placentation, rather
than its volume, is important for pregnancy outcome.17
342 Maso et al
OBSTETRICS & GYNECOLOGY
As in the majority of the studies on subchorionic
hematomas, our data have mainly focused on the corre-
lation between the characteristics of the hematoma and the
recently been reported in the literature about the risks of
other late complications of pregnancy, such as stillbirth,
abruptio placentae, preterm delivery, intrauterine growth
uterine hematoma is diagnosed (Table 4). Many of these
clinical conditions are a consequence of impaired placenta-
tion, and it might be postulated that the presence of a
subchorionic hematoma in early stages affects the normal
process of trophoblast invasion.29–31
Given the absence of a control group, it is not possible
to estimate in our study the relative risk of pregnancy
complications in patients with intrauterine hematoma.
Moreover, because of our limited sample size, it has not
pregnancy outcomes other than the spontaneous abortion.
Nevertheless, our observational study gave an overall inci-
dence of pregnancy complications in these patients as high
as roughly 40%, without including all the possible clinical
adverse conditions due to a lack of data.
From our results it is not possible to draw definitive
conclusions to all the unanswered questions about the
short- and long-term effects of subchorionic hematoma
in pregnancy. However, our study demonstrated that, in
the presence of this finding and clinical bleeding, the prog-
nosis of pregnancy is significantly related to the gestational
age at the time of diagnosis, whereas the size of the hema-
toma does not seem to have a clinical significance. This
might be useful for caregivers in appropriately counseling
particularly, about the risk of miscarriage.
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IUH, intrauterine hematoma; SA, spontaneous abortion; PTD, preterm delivery; Pl Ab, placental abruption; PM, perinatal mortality; NA, not
* Controlled study.
†Presented at Tenth International Congress, The Fetus as a Patient, Brijuni, Croatia, 1994.
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of Obstetrics and Gynecology, IRCCS Burlo Garofolo, Uni-
versity of Trieste, Via dell’Istria 65/1–34137, Trieste, Italy;
Received May 31, 2004. Received in revised form July 31, 2004.
Accepted October 14, 2004.
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OBSTETRICS & GYNECOLOGY