Horon IL, Cheng D. Enhanced Surveillance for Pregnancy-Associated Mortality—Maryland, 1993-1998. JAMA. 2001;285(11):1455-1459. doi:10.1001/jama.285.11.1455
Author Affiliations: Vital Statistics Administration (Dr Horon) and Center for Maternal and Child Health (Dr Cheng), Maryland Department of Health and Mental Hygiene, Baltimore.
Context Deaths occurring among women who are pregnant or who have had a recent
pregnancy have a devastating impact on the family and community. It is important
to understand the magnitude and causes of pregnancy-associated mortality so
that comprehensive strategies can be formulated to prevent such deaths.
Objective To ascertain the number and causes of pregnancy-associated deaths using
enhanced surveillance techniques.
Design, Setting, and Subjects Retrospective, cross-sectional analysis of death certificate data of
reproductive-age women, live birth and fetal death records, and medical examiner
records in Maryland during 1993-1998.
Main Outcome Measure Number of pregnancy-associated deaths, defined as death from any cause
during pregnancy or within 1 year of delivery or pregnancy termination, by
source of data and cause of death.
Results A total of 247 pregnancy-associated deaths were ascertained. Twenty-seven
percent (n = 67) were identified through cause-of-death information obtained
from death certificates, 70% (n = 174) through linkage of death records with
birth and fetal death records, and 47% (n = 116) through review of medical
examiner records. Homicide was the leading cause of pregnancy-associated death
(n = 50; 20%), and cardiovascular disorders were the second-leading cause
(n = 48; 19%).
Conclusions In this Maryland sample, comprehensive identification of pregnancy-associated
deaths was accomplished only after collecting information from multiple sources
and including all deaths occurring up to 1 year after delivery or pregnacy
termination. This enhanced pregnancy mortality surveillance led to the disturbing
finding that a pregnant or recently pregnant woman is more likely to be a
victim of homicide than to die of any other cause. By broadening pregnancy
mortality to include all possible causes, previously neglected factors may
assume increased importance in prenatal and postpartum care.
Complete and accurate identification of all deaths associated with pregnancy
is a critical first step in the prevention of such deaths. Only by having
a clear understanding of the magnitude of pregnancy-associated mortality can
comprehensive prevention strategies be formulated to prevent these unanticipated
deaths among primarily young, healthy women.
Death statistics compiled through the National Vital Statistics System
by the National Center for Health Statistics, Centers for Disease Control
and Prevention, are a major source of data on deaths occurring during pregnancy
and in the postpartum period. Original death certificates from which state
and national vital statistics are derived are filed in and maintained by individual
states. Causes of death on death certificates are reported by attending physicians
or, under certain circumstances such as death from external trauma or unexplained
death, by medical examiners or coroners.
The National Center for Health Statistics is required to use the World
Health Organization (WHO) definition of a maternal death for preparation and
presentation of mortality data. According to the WHO definition, a maternal
death is "the death of a woman while pregnant or within 42 days of termination
of pregnancy, irrespective of the duration and the site of the pregnancy,
from any cause related to or aggravated by the pregnancy or its management
but not from accidental or incidental causes."1
This definition includes deaths assigned to the cause "complication of pregnancy,
childbirth, and the puerperium" (International Classification
of Diseases, Ninth Revision [ICD-9] codes 630-676).
Death records are an important source of data on pregnancy mortality
because they are routinely collected by the states and are comparable over
time and across the nation. However, there are several limitations to using
these data to identify all deaths associated with pregnancy. First, the cause-of-death
information provided on these records is sometimes not accurate. Previous
studies have shown that physicians completing death records following a maternal
death fail to report that the woman was pregnant or had a recent pregnancy
in 50% or more of these cases,2- 4
resulting in the misclassification of the underlying cause of death. Since
these deaths cannot be identified as maternal deaths through routine surveillance
methods, they are not included in the calculation of maternal mortality rates.
An additional limitation of using death records alone for comprehensive
identification of all deaths associated with pregnancy is that the WHO definition
of a maternal death limits the temporal and causal scope of pregnancy mortality.
As defined by WHO, a maternal death does not include deaths occurring more
than 42 days following termination of pregnancy or deaths resulting from causes
other than direct complications of pregnancy, labor, and the puerperium.
To address these issues, the term "pregnancy-associated death" was introduced
by the Centers for Disease Control and Prevention, in collaboration with the
Maternal Mortality Special Interest Group of the American College of Obstetricians
and Gynecologists, to define a death from any cause during pregnancy or within
1 calendar year of delivery or pregnancy termination, regardless of the duration
or anatomical site of the pregnancy.5 Pregnancy-associated
deaths include not only deaths commonly associated with pregnancy such as
hemorrhage, pregnancy-induced hypertension, and embolism—which are captured
in the WHO definition—but also deaths not traditionally considered to
be related to pregnancy such as accidents, homicide, and suicide. The term
also includes deaths occurring 43 to 365 days following termination of pregnancy.
Since cause-of-death information on death certificates cannot identify deaths
from nonmaternal causes or deaths occurring 43 or more days following termination
of pregnancy as associated with pregnancy, additional sources of data must
be used for complete ascertainment of all pregnancy-associated deaths.
Previous studies on pregnancy-associated deaths have relied largely
on linkage of records2,6- 8
or the use of a check box on the death certificate9
to identify pregnancy-associated deaths. Only 1 study (Allen et al10) in New York City used death certificates, linkage
of records, and review of autopsy reports to identify pregnancy-associated
deaths. However, this study did not include all pregnancy-associated deaths
since only records for deaths occurring within 6 months of termination of
pregnancy were collected, and medical examiner records for only certain causes
of death were reviewed.
This article, based on Maryland resident data for the years 1993-1998,
presents more comprehensive data on pregnancy-associated deaths since it includes
all deaths occurring during pregnancy or within a year of termination of pregnancy.
In addition, medical examiner records for all women of reproductive age who
died during the study period, regardless of cause of death, were reviewed
to identify pregnancy-associated deaths.
Data for this analysis were collected from the following 3 sources:
(1) review of death certificates to identify those records on which a complication
of pregnancy, childbirth, or the puerperium (ICD-9
codes 630-676) was listed as an underlying or contributing cause of death;
(2) linkage of death certificates of reproductive-age women with corresponding
live birth and fetal death records to identify a pregnancy within the year
preceding death; and (3) review of medical examiner records for evidence of
Vital records data were obtained from the Vital Statistics Administration
of the Maryland Department of Health and Mental Hygiene. Identification of
pregnancy-associated deaths through linkage of vital records was accomplished
by matching death certificates for all women of reproductive age against live
birth and fetal death records to identify pregnancies occurring in the year
preceding death. Successful linkage of records was achieved by matching either
mother's Social Security number or mother's name and date of birth on the
death record with corresponding information on live birth and fetal death
records. All linked records were manually reviewed to ensure accurate matching
Medical examiner records, which include autopsy reports and police records,
were reviewed for all 4195 women aged 10 to 50 years whose deaths were investigated
by the medical examiner during the study period. Maryland law mandates that
the medical examiner investigate all deaths that occur by violence, suicide,
casualty, unexpectedly, or in any suspicious or unusual manner. Death certificates
were obtained for 116 women for whom medical examiner records indicated evidence
With the exception of 1 death to a 14-year-old adolescent, all deaths
identified through medical examiner records occurred among women who were
within the traditional reproductive age group of 15 to 44 years. All deaths
identified through death certificates and record linkage were among women
between the ages of 15 and 44 years.
All death records that did not identify a maternal cause as the underlying
cause of death (n = 184) were reviewed by trained nosologists to determine
the underlying cause of death that would have been assigned if a history of
pregnancy had been reported on the death certificate. Nosologists were provided
with information on pregnancy outcome and, if available, the date of delivery,
date of pregnancy termination, or gestational age. Revised underlying cause-of-death
information was used to categorize data by cause of death.
A total of 247 pregnancy-associated deaths occurring between 1993 and
1998 were identified from the 3 data sources. Sixty-seven pregnancy-associated
deaths (27.1%) were identified through cause-of-death information obtained
from death certificates. Sixty-two of these records listed pregnancy complications
as the underlying cause of death; the remaining 5 certificates listed pregnancy
complications as a contributing, but not underlying, cause of death. Linkage
of records identified 174 (70.4%) of all pregnancy-associated deaths and review
of medical examiner records resulted in the identification of 116 (47.0%)
deaths (Table 1).
Sixty-five percent (n = 160) of pregnancy-associated deaths were identified
through a single surveillance method. One hundred two (41.3%) were identified
only through linkage of records, 45 (18.2%) only through review of medical
examiner records, and 13 (5.3%) only through cause-of-death information provided
on death certificates. Thirty-five percent of pregnancy-associated deaths
were identified through more than 1 data source (n = 87).
One hundred eighty-two (73.7%) of the 247 pregnancy-associated deaths
identified in this study followed a live birth, 5 (2.0%) followed a fetal
death, 1 followed a therapeutic abortion, and 53 (21.4%) occurred among women
who were pregnant at the time of death. Of the 53 deaths that occurred among
pregnant women, 7 were the result of ruptured ectopic pregnancies and 1 resulted
from a molar pregnancy (Table 1).
Eighty-four (34.0%) deaths occurred within 42 days of delivery or termination
of pregnancy, and 103 (41.7%) deaths occurred 43 to 365 days following delivery
or termination of pregnancy. The time of death was unknown for 7 women (Table 2).
The leading cause of pregnancy-associated death was homicide (n = 50).
All homicides were identified through record linkage or review of medical
examiner records rather than from death certificates, as would be expected
since homicide is not a maternal cause of death. Deaths from cardiovascular
disorders, the second leading cause of death (n = 48), were identified through
all 3 data sources, although no single source was able to identify all deaths.
Of the 26 deaths from cardiovascular disorders that occurred during pregnancy
or within 42 days of delivery and should therefore have been classified as
maternal deaths, only 8 were identified through death certificates. A substantial
proportion of deaths from other maternal causes, including embolism and infection,
could not be identified from death certificates since the physicians filling
out the certificates failed to report that the women were pregnant or had
recent pregnancies (Table 2).
All maternal deaths, by definition, occurred during pregnancy or within
42 days of delivery or termination of pregnancy. This included most deaths
from embolism, hemorrhage, and hypertensive disorders of pregnancy as well
as a substantial proportion of deaths resulting from cardiovascular disorders
and infection. Homicide was responsible for the majority of deaths during
pregnancy (23 [43.4%]) and during the 43- to 365-day period following delivery
or termination of pregnancy (24 [23.3%]), but accounted for only a small proportion
of deaths occurring within 42 days of pregnancy (3 [3.6%]), when obstetric
causes were responsible for most pregnancy-associated deaths. Cardiovascular
disorders (n = 21) were the leading cause of death in the 42-day period following
delivery or termination of pregnancy and the second leading cause of death
(n = 18), following homicide, in the late postpartum period (Table 2).
Homicide, the leading cause of pregnancy-associated death, was responsible
for 20.2% of all pregnancy-associated deaths. By comparison, homicide was
the fifth leading cause of death among Maryland women aged 14 to 44 years
who had not had a pregnancy in the year preceding death and was responsible
for 457 (6.4%) of total deaths among this group (z
= 7.737, P<.001). The pregnant group was younger
and included a higher percentage of African American women than the nonpregnant
group, factors that are associated with higher rates of homicide independent
of pregnancy. However, these factors did not explain the higher proportion
of homicide deaths in the pregnant group. While adjustment for race and maternal
age increased the proportion of deaths due to homicide to 11.2% among women
who had not been pregnant in the year preceding death, the adjusted figure
was still significantly lower than the figure of 20.2% among women who had
been pregnant (z = 4.349, P<.001).
The use of multiple data sources substantially enhances pregnancy mortality
surveillance because no single source can identify all pregnancy-associated
deaths. Death certificates are designed to collect only a small subset of
pregnancy-associated deaths. Even these deaths are frequently not included
in maternal mortality statistics because physicians completing death certificates
fail to provide the information needed to correctly classify a maternal death.
Analysis of data in this report indicated that 30 (34.5%) of the 87 deaths
meeting the WHO definition of a maternal death could not be identified through
cause-of-death information reported by physicians on the death certificate.
Data linkage is an additional tool for identifying pregnancy-associated deaths,
but it is limited to those deaths with a reported outcome, such as a live
birth or fetal death. Medical examiner records are the most useful source
for identifying pregnancy-associated deaths among women who have not delivered
at the time of death.
Data linkage and review of medical examiner records contribute substantially
to identification of pregnancy-associated mortality. In Maryland, this led
to the disturbing finding that a pregnant or recently pregnant woman is more
likely to be a victim of homicide than to die of any other cause. Other reports
have identified homicide as a cause of pregnancy-associated death.7,11,12 However, none of these
studies reported on pregnancy-associated deaths from other causes as well,
and therefore could not provide a ranking of deaths by cause.
Although we have shown that homicide is responsible for a greater proportion
of deaths among pregnant and postpartum women than among women who have not
been pregnant in the year preceding death, our findings do not address the
issue of whether the homicide rate is higher among pregnant and postpartum
women in general than among women who have not had recent pregnancies. This
highlights a well-recognized limitation of proportional mortality statistics,
ie, that these statistics include only individuals who die, not those at risk
of dying. Therefore, no direct inferences regarding increased homicide rates
for all pregnant women can be made using only proportional mortality statistics.
The question of whether the homicide rate is higher among pregnant and
postpartum women than among women who have not had recent pregnancies could
be answered by comparing mortality rates in the 2 groups. However, a methodology
for computing pregnancy-associated mortality rates and mortality rates for
nonpregnant women has not yet been established because of complexities in
determining the number of pregnant women in a population. Since a woman may
experience more than 1 pregnancy and more than 1 pregnancy outcome (live birth,
fetal loss, or induced abortion) in a given time period, the number of pregnant
women cannot be computed by summing the number of pregnancy outcomes. Even
if the number of pregnant women could be estimated, an additional issue that
would have to be addressed is how to adjust mortality rates to account for
differences in the time period of risk of death in the 2 populations. It is
important that increased efforts be placed on development of appropriate methodologies
for calculating pregnancy-associated mortality rates so that the questions
raised by this article may be addressed.
The findings of this article also suggest that maternal mortality review
committees should investigate homicides occurring during pregnancy and in
the postpartum period to determine potential relationships between these events.
For example, a homicide resulting from domestic violence may be related to
the stress of pregnancy. Similarly, a suicide soon after delivery may result
from postpartum depression. By broadening pregnancy mortality to include all
possible causes, factors previously neglected may assume increased importance
in prenatal and postpartum care.
Despite the use of enhanced surveillance techniques, it is likely that
some pregnancy-associated deaths remain undetected, particularly those occurring
in women who were pregnant at the time of death. Since autopsies are performed
on all homicide victims, it is more likely that pregnancy would be detected
among these women than among women dying from other causes, who are less likely
to be autopsied. Since Maryland law mandates that the medical examiner investigate
deaths among individuals who were in apparent good health at the time of death,
which describes most pregnant women, the majority of deaths among these women
should have been investigated by the medical examiner. Autopsies were in fact
performed more frequently among women with recognized pregnancy-associated
deaths who died from causes other than homicide (123 [62.4%]) than among women
of reproductive age without recognized pregnancies (6696 [30.6%]). However,
it is still possible that some pregnancies remain undetected, which could
have an impact on the total number of pregnancy-associated deaths as well
as on the distribution of deaths by pregnancy outcome, time of death, or cause
Efforts are being made in Maryland to improve the identification of
pregnancy-associated deaths. Recent legislation mandates that health care
professionals and facilities report all pregnancy-associated deaths to the
Maryland Maternal Mortality Review Program. In addition, the Maryland death
certificate was revised in 2001 to include questions about current or recent
pregnancies. Currently, only 17 states and New York City have a pregnancy
check box or ask about pregnancy status on their death certificates. Use of
a pregnancy question by all states on the revised US Standard Certificate
of Death has been recommended to the National Center for Health Statistics
by the Panel to Evaluate the US Standard Certificates and Reports. Such a
change, which would be consistent with a recommendation of the World Health
Assembly in the International Classification of Diseases,
10th Revision (ICD-10),13 would substantially
improve ascertainment of pregnancy on death certificates. If approved by the
US Department of Health and Human Services, states could adopt the pregnancy
question in the 2003 revision of their death certificates. This change should
help to identify deaths that remain difficult to detect, such as deaths that
cannot be identified through linkage of records and deaths among women who
had not delivered that are not reported to the medical examiner. However,
it would be a service, as well as good medical practice, if physicians made
a greater effort to report pregnancy as a factor contributing to death when
Comprehensive identification of pregnancy-associated deaths can only
be accomplished by collecting information from multiple data sources and including
all deaths occurring up to 1 year after pregnancy termination. Through such
enhanced surveillance, the Maryland Department of Health and Mental Hygiene
has shown that the number of pregnancy-associated deaths is substantially
higher and causes of death substantially broader than previously believed.
Enhanced surveillance of pregnancy-associated deaths is necessary to accurately
document the magnitude of pregnancy mortality, identify groups at increased
risk of death, review factors leading to the death, and plan prevention strategies.
It is therefore a critical step in the reduction of pregnancy-associated mortality.