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AHRQ Evidence reports and summaries AHRQ Evidence Reports, Numbers 1-60 53. Management of Prolonged Pregnancy Evidence Report/Technology Assessment Number 53 Prepared for: Contract No. 290-97-0014 Prepared by: AHRQ Publication No. 02-E018 May 2002 On December 6, 1999, under Public Law 106-129, the Agency for Health Care Policy and Research (AHCPR) was reauthorized and renamed the Agency for Healthcare Research and Quality (AHRQ). The law authorizes AHRQ to continue its research on the cost, quality, and outcomes of health care, and expands its role to improve patient safety and address medical errors. This report may be used, in whole or in part, as the basis for development of clinical practice guidelines and other quality enhancement tools, or a basis for reimbursement and coverage policies. AHRQ or U.S. Department of Health and Human Services endorsement of such derivative products may not be stated or implied. This document is in the public domain and may be used and reprinted without permission except those copyrighted materials noted for which further reproduction is prohibited without the specific permission of copyrightholders. Suggested citation:Myers ER, Blumrick R, Christian AL, et al. Management of prolonged pregnancy. Evidence Report/Technology Assessment No. 53 (Prepared by Duke Evidence-based Practice Center, Durham, NC, under Contract No. 290-97-0014). AHRQ Publication No. 02-E018. Rockville, MD: Agency for Healthcare Research and Quality. May 2002. PrefaceThe Agency for Healthcare Research and Quality (AHRQ, formerly the Agency for Health Care Policy and Research, AHCPR), through its Evidence-based Practice Centers (EPCs), sponsors the development of evidence reports and technology assessments to assist public- and private-sector organizations in their efforts to improve the quality of health care in the United States. The reports and assessments provide organizations with comprehensive, science-based information on common, costly medical conditions and new health care technologies. The EPCs systematicallyreview the relevant scientific literature on topics assigned to them by AHRQ and conduct additional analyses when appropriate prior to developing their reports and assessments. To bring the broadest range of experts into the development of evidence reports and health technology assessments, AHRQ encourages the EPCs to form partnerships and enter into collaborations with other medical and research organizations. The EPCs work with these partner organizations to ensure that the evidence reports and technology assessments they produce will become building blocks for health care quality improvement projects throughout the Nation. The reports undergo peer review prior to their release. AHRQ expects that the EPCevidence reports and technology assessments will inform individual health plans, providers, and purchasers as well as the health care system as a whole by providing important information to help improve health care quality. We welcome written comments on this evidence report. Theymay be sent to: Director, Center for Practice and Technology Assessment, Agency for Healthcare Research and Quality, 6010 Executive Blvd., Suite 300, Rockville, MD 20852.
Objective. Approximately 18 percent of pregnancies in the United States extend beyond 41 weeks gestation, 7 percent beyond 42 weeks. Risks of adverse perinatal and maternal outcomes increase with increasing gestational age beyond term. This report assesses the literature on the benefits, risks, and costs of different strategies for managing prolonged pregnancy in order to avoid adverse perinatal and maternal outcomes. Search Strategy.Published literature on the management of prolonged pregnancy was identified in MEDLINE, CINAHL, EMBASE, HealthSTAR, the Cochrane Database of Systematic Reviews, and the Database of Abstracts of Reviews of Effectiveness for the years 1980 through 2001. MeSH terms included "pregnancy, prolonged" and "post$ pregnan$.tw". Selection Criteria.Study designs considered included randomized controlled trials, cohort studies, and large (n > 20) case series with or without controls. Studies were included if the study population included women with prolonged pregnancy and data were provided that were relevant to one or more of the key research questions. Studies were excluded from formal abstraction if they did not report on original research, the patient population did not include women with prolonged pregnancy, the study design was a single case report or small case series, or a 2-by-2 table could not be constructed (for studies of test characteristics). Data Collection and Analysis.Paired reviewers independently screened each abstract and article and performed the data abstraction. Included studies were graded for internal and external validity. Supplemental data were collected from the Nationwide Inpatient Sample. Main Results.Although there is no direct evidence that antepartum testing reduces perinatal mortality in prolonged gestation, retrospective data suggest that morbidity may be reduced. Selection of appropriate outcomes for evaluating antepartum testing is difficult since mortality and morbidity are rare, and commonly used surrogate markers have substantial weaknesses. All currently used tests and combinations of tests have better specificity than sensitivity but good negative predictive values. There are no definitive data supporting the superiority of any particular testing method. Most studies of interventions for the induction of labor do not report results specifically for women induced because of prolonged pregnancy or its complications. In general, agents that result in more efficient induction of labor also have higher rates of fetal heart rate pattern changes associated with frequent uterine contractions. Pooled analysis of randomized trials of planned induction versus expectant management with antepartum testing suggests that planned induction reduces the risk of perinatal death with no increase in other perinatal or maternal morbidity, including cesarean section. At least 500 inductions are needed to prevent one perinatal death. There are virtually no data on patient values and preferences for management options. There also are no published data on potential differences in epidemiology or outcomes of prolonged pregnancy in racial, ethnic, or socioeconomic subgroups and no data allowing comparison of the cost-effectiveness of different strategies for managing prolonged pregnancy. Conclusions.Induction of labor at 41 weeks or beyond results in fewer perinatal deaths compared with antepartum testing, but at least 500 inductions are necessary to prevent one death. There is insufficient evidence to recommend any specific induction agent in this setting. Additional high-quality research is needed. SummaryOverview The estimated date of confinement, or due date, for normal pregnancies is calculated as 38 weeks after conception, or 40 weeks after the first day of the last normal menstrual period (assuming a "normal" 28-day menstrual cycle). Prolonged pregnancy has traditionally been defined as a pregnancy that extends 2 weeks or more beyond the estimated day of confinement, or 42 weeks. Approximately 18 percent of pregnancies in the United States extend beyond 41 weeks, and 7 percent extend beyond 42 weeks. It has long been known that pregnancies extending many weeks beyond the average length are at increased risk for adverse outcomes, both because certain fetal anomalies, such as anencephaly, are associated with prolonged pregnancy, and also because of an increased incidence of stillbirth among otherwise normal infants. The increasing availability of ultrasound has significantly improved the accuracy of pregnancy dating and detection of fetal anomalies, so that extremely long gestations are rare. However, adverse outcomes continue to be associated with prolonged gestation. In some cases, these risks appear to be due to uteroplacental insufficiency, resulting in eventual fetal hypoxia. Data from large registries show that the risk of perinatal death, especially of antepartum stillbirth, increases with advancing gestational age. If risk is calculated based on the number of ongoing pregnancies, gestational-age-specific stillbirth risk reaches a nadir at 37-38 weeks and then begins to increase slowly. Risks increase substantially after 41 weeks; however, the absolute risk is still low (between 1 and 2 per 1,000 ongoing pregnancies between 41 and 43 weeks). Other adverse outcomes associated with uteroplacental insufficiency include meconium aspiration, growth restriction, and intrapartum asphyxia. In other cases, continued growth of the fetus leads to macrosomia, increasing the risk of labor abnormalities, shoulder dystocia, and brachial plexus injuries. Potential maternal risks associated with prolonged gestation, besides the obvious emotional trauma accompanying an unexpected fetal death or serious complication, include potential increased risk of injury to the pelvic floor associated with difficult deliveries of macrosomic infants. Interventions intended to prevent adverse perinatal outcomes, such as induction of labor and cesarean section, may themselves carry iatrogenic risks, such as increased rates of infection, hemorrhage, or other complications. Several strategies currently are used in practice to prevent adverse outcomes associated with advancing gestation. Testing methods developed for reducing perinatal morbidity and mortality in women with high-risk pregnancies because of diabetes, hypertension, or other complications of pregnancy have been applied to women with pregnancies extending beyond 40 weeks. Another strategy, induction of labor at a predefined gestational age, has been proposed and evaluated as a method of reducing perinatal mortality and other adverse outcomes associated with prolonged gestation. However, because the point at which the risk of adverse outcomes outweighs the risks and costs of active interventions is uncertain, controversy remains about the optimal timing and methods for managing increased risks to both fetus and mother associated with prolonged gestation. Investigators at the Duke University Evidence-based Practice Center reviewed the evidence concerning the benefits, risks, and costs of commonly used tests, induction agents, and strategies for reducing the risks associated with prolonged gestation. Because of the inherent uncertainty in estimates of gestational age, variability in the length of otherwise uncomplicated pregnancies, and the lack of clear consensus on when risks of adverse outcomes outweigh risks of intervention, the researchers did not restrict the review to interventions performed only after a specified gestational age. This summary and evidence report were prepared based on the Duke EPC review. The primary target audiences for the summary and evidence report are groups involved in writing guidelines or educational documents on management of prolonged pregnancy for health care professionals. Secondary audiences include health care professionals providing care for pregnant women (obstetricians, family physicians, nurse-midwives, nurses, childbirth educators, etc.); policymakers involved in payment decisions; agencies involved in funding basic, clinical, and health services research; media involved in dissemination and education about health issues; and patients with an interest in reviewing the medical literature concerning management of prolonged pregnancy. Reporting the EvidenceKey Research Questions Four key research questions were addressed:
The following interventions were considered: Testing
1.
Tests to determine risk of stillbirth or compromise related to prolonged gestation, including:
2.
Tests to determine the risk of macrosomia, including estimation of fetal weight (maternal judgment, clinical examination, ultrasound).
3. Tests to estimate likely success of induction of labor, including:
The researchers did not attempt to systematically review the basic and clinical research on the physiology of normal parturition, the role of routine ultrasound in early pregnancy, or interventions performed during labor and delivery to reduce the risks of adverse outcomes of conditions associated with, but not unique to, prolonged pregnancy (such as oligohydramnios or meconium-stained amniotic fluid). Patient Population and SettingsThe primary patient population considered in the review was pregnant women with a single fetus in the vertex position, approaching or past the estimated date of confinement, without any other medical or obstetrical complications (including prior cesarean section), where the only potential factor increasing the risk of an adverse perinatal or maternal outcome was advancing gestational age. The researchers also examined the potential interaction of this risk with age and race/ethnicity. The principal practice settings considered were hospitals, freestanding birthing centers, patients' homes, and prenatal clinics or other facilities where ambulatory prenatal care is delivered. Outcomes ConsideredOutcomes considered varied depending on the study and the question being addressed, but the researchers focused primarily on clinically relevant outcomes. Data recorded included anatomic outcomes (changes in cervical dilation or Bishop score); perinatal and maternal mortality; surrogate markers of fetal compromise (nonreassuring changes in fetal heart rate patterns, meconium); mode of delivery (cesarean, vaginal, operative vaginal); other interventions (need for labor augmentation, need for labor induction); adverse outcomes (complications of vaginal and cesarean delivery, complications of interventions); and use of resources (time to delivery, length of stay, medication, and labor costs). MethodologyLiterature Sources Used The primary sources of literature were the following databases (with search years shown in parentheses) MEDLINE (1980-December 2000), HealthSTAR (1980-December 2000), CINAHL (1983-December 2000), Cochrane Database of Systematic Reviews (CDSR) (Issue 4, 2000; Issue 1, 2001; and Issue 2, 2001), Database of Abstracts of Reviews of Effectiveness (DARE), and EMBASE (1980-Jan 2000). Searches of these databases were supplemented by secondary searches of reference lists in all included articles, especially Cochrane review articles, scanning of current issues of journals not yet indexed in the computerized bibliographic databases, and suggestions from an advisory panel. The initial searches were performed in MEDLINE and then duplicated in other databases. All searches were limited to English-language articles published since 1980 involving human subjects. The cut-off threshold of 1980 was based on the lack of general availability of ultrasound prior to that date. It was judged that trials conducted and published prior to 1980 would be problematic both in terms of the accuracy of diagnosis and comparability with current testing and management strategies. Primary MeSH terms used in all searches included "pregnancy, prolonged/" and "post$ pregnan$.tw." Screening of ArticlesThe searches yielded 701 English-language articles. Abstracts from these articles were reviewed against the inclusion/exclusion criteria by six physician investigators, with assistance from one senior medical student. A team of two investigators reviewed each abstract; when no abstract was available, the title, source, and MeSH words were reviewed. At this stage, articles were included if requested by one member of the team. At the full-text screening stage, two investigators independently reviewed each article, and disagreements were resolved through discussion. Each screened article was coded according to three topic areas: (a) testing: two or more tests were compared in terms of accuracy or agreement of test results, or the test result was correlated with some health outcome; (b) management: the article addressed the relative effectiveness of planned induction versus expectant management or the relative effectiveness of an induction agent; and (c) testing and management: some combination of the above. Included study designs were determined by the article's topic area. Study designs for articles on testing or testing and management included randomized controlled trials, cohort studies, and large case series (at least 20 subjects). The only study design included for management articles was the randomized controlled trial. Studies of these types were included if they met the following criteria:
Exclusion criteria included:
Teams of two investigators performed the data abstraction for eligible articles identified at the full-text screening stage. For each included article, one physician completed the data abstraction form, and the other served as an "over-reader." The information from the data abstraction form -- including details on study characteristics, patient population, outcomes, and quality measures -- was then summarized into evidence tables. Data abstraction assignments were made based on clinical and research interests and expertise. Criteria for Evaluating the Quality of ArticlesUsing criteria developed for prior evidence reports, the researchers evaluated each article for the presence or absence of factors influencing internal and external validity. These criteria were:
The researchers also examined discharge data from the Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample maintained by the Agency for Healthcare Research and Quality. This database contains administrative discharge data from over 1,000 hospitals in 22 States (at the time of the review), representing a stratified sample of 20 percent of U.S. hospitals. The researchers used these data to provide supplemental information on differences in the epidemiology and outcomes of prolonged pregnancy between ethnic and socioeconomic groups. Using ICD-9 codes, they divided all deliveries into "preterm" (644.2x), prolonged (645.x), and "term" (all other delivery codes). The researchers examined differences in outcomes between coded ethnic groups (white, black, Hispanic, Asian/Pacific Islander, American Indian, and other) and by insurance status (Medicare, Medicaid, private/health maintenance organization, self-pay/no insurance, "no charge," and "other") within these categories. FindingsThe principal findings of the report are summarized here.
Future research on the management of prolonged pregnancy should include the following:
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