Differences in intrapartum obstetric care provided to women at low risk by family physicians and obstetricians.

To determine differences in practice style and to examine maternal and neonatal outcomes, we reviewed the hospital charts of 1115 women admitted by family physicians and 1250 women admitted by obstetricians who gave birth at one of three teaching hospitals in Toronto between April 1985 and March 1986. All the women in the two groups were categorized retrospectively as being at low risk at the onset of labour on the basis of their prenatal records and their admission histories and physical examination results. There were higher proportions of younger women and women of lower socioeconomic status in the family physician group than in the obstetrician group (p less than 0.001). The rates of interventions, including artificial rupture of the membranes, induction, augmentation, low forceps plus vacuum extraction, episiotomy and epidural anesthesia, were all higher in the obstetrician group. The mean birth weight and the cesarean section rate were the same in the two groups. Differences in labour and delivery outcomes between the two groups, including a higher rate of spontaneous vaginal delivery for the family physicians, reflected a more "expectant" practice style by family doctors. However, there were no significant differences in the rates of maternal or neonatal complications. A practice style characterized by a higher rate of interventions was not associated with improved maternal or newborn outcome in this low-risk setting.     

Prenatal risk assessment and obstetric care in a small rural hospital: comparison with guidelines.

An assessment was made of the potential usefulness in a small rural hospital of the guidelines for prenatal risk assessment and management of the Newfoundland and Labrador Prenatal Record, a form similar to that in use in other provinces. A retrospective chart review was done for 266 pregnancies followed at the Baie Verte Peninsula Health Centre prior to the introduction of the guidelines. The pattern of practice was to request consultation and to transfer patients for delivery less often than was suggested by the guidelines; only 32% of patients at risk were assessed by an obstetrician. By the time of delivery only 39% of the patients were at no predictable risk according to the guidelines. Nevertheless, neonatal morbidity was present in this group (4% of the infants had an Apgar score of 6 or less at 1 or 5 minutes), though less often than in those at risk (18% of the infants had a low Apgar score). However, the group at no predictable risk required nonelective intervention in 40% of cases, approximately the same rate as that for the group at risk. It is necessary for some small hospitals to have the facilities and the trained staff to handle the problems that occur even in low-risk patients. To maintain the delivery rate necessary to retain skills, the guidelines may help family practitioners and consulting obstetricians to select some patients at risk who can be managed in small hospitals.     

Clinical characteristics and outcomes of hospitalized older patients with distinct risk profiles for functional decline: a prospective cohort study

Background

The aim of this research was to study the clinical characteristics and mortality and disability outcomes of patients who present distinct risk profiles for functional decline at admission.

Methods

Multicenter, prospective cohort study conducted between 2006 and 2009 in three hospitals in the Netherlands in consecutive patients of ≥65 years, acutely admitted and hospitalized for at least 48 hours. Nineteen geriatric conditions were assessed at hospital admission, and mortality and functional decline were assessed until twelve months after admission. Patients were divided into risk categories for functional decline (low, intermediate or high risk) according to the Identification of Seniors at Risk-Hospitalized Patients.

Results

A total of 639 patients were included, with a mean age of 78 years. Overall, 27%, 33% and 40% of the patients were at low, intermediate or high risk, respectively, for functional decline. Low-risk patients had fewer geriatric conditions (mean 2.2 [standard deviation [SD] 1.3]) compared with those at intermediate (mean 3.8 [SD 2.1]) or high risk (mean 5.1 [SD 1.8]) (p<0.001). Twelve months after admission, 39% of the low-risk group had an adverse outcome, compared with 50% in the intermediate risk group and 69% in the high risk group (p<0.001).

Conclusion

By using a simple risk assessment instrument at hospital admission, patients at low, intermediate or high risk for functional decline could be identified, with distinct clinical characteristics and outcomes. This approach should be tested in clinical practice and research and might help appropriately tailor patient care.     

Association between statin therapy and outcomes in critically ill patients: a nested cohort study

Background

The effect of statin therapy on mortality in critically ill patients is controversial, with some studies suggesting a benefit and others suggesting no benefit or even potential harm. The objective of this study was to evaluate the association between statin therapy during intensive care unit (ICU) admission and all-cause mortality in critically ill patients.

Methods

This was a nested cohort study within two randomised controlled trials conducted in a tertiary care ICU. All 763 patients who participated in the two trials were included in this study. Of these, 107 patients (14%) received statins during their ICU stay. The primary endpoint was all-cause ICU and hospital mortality. Secondary endpoints included the development of sepsis and severe sepsis during the ICU stay, the ICU length of stay, the hospital length of stay, and the duration of mechanical ventilation. Multivariate logistic regression was used to adjust for clinically and statistically relevant variables.

Results

Statin therapy was associated with a reduction in hospital mortality (adjusted odds ratio [aOR] = 0.60, 95% confidence interval [CI] 0.36-0.99). Statin therapy was associated with lower hospital mortality in the following groups: patients >58 years of age (aOR = 0.58, 95% CI 0.35-0.97), those with an acute physiology and chronic health evaluation (APACHE II) score >22 (aOR = 0.54, 95% CI 0.31-0.96), diabetic patients (aOR = 0.52, 95% CI 0.30-0.90), patients on vasopressor therapy (aOR = 0.53, 95% CI 0.29-0.97), those admitted with severe sepsis (aOR = 0.22, 95% CI 0.07-0.66), patients with creatinine ≤100 μmol/L (aOR = 0.14, 95% CI 0.04-0.51), and patients with GCS ≤9 (aOR = 0.34, 95% CI 0.17-0.71). When stratified by statin dose, the mortality reduction was mainly observed with statin equipotent doses ≥40 mg of simvastatin (aOR = 0.53, 95% CI 0.28-1.00). Mortality reduction was observed with simvastatin (aOR = 0.37, 95% CI 0.17-0.81) but not with atorvastatin (aOR = 0.80, 95% CI 0.84-1.46). Statin therapy was not associated with a difference in any of the secondary outcomes.

Conclusion

Statin therapy during ICU stay was associated with a reduction in all-cause hospital mortality. This association was especially noted in high-risk subgroups. This potential benefit needs to be validated in a randomised, controlled trial.     

Prognosis in patients with recent onset low back pain in Australian primary care: inception cohort study

Objective To estimate the one year prognosis and identify prognostic factors in cases of recent onset low back pain managed in primary care.Design Cohort study with one year follow-up.Setting Primary care clinics in Sydney, Australia.Participants An inception cohort of 973 consecutive primary care patients (mean age 43.3, 54.8% men) with non-specific low back pain of less than two weeks’ duration recruited from the clinics of 170 general practitioners, physiotherapists, and chiropractors.Main outcome measures Participants completed a baseline questionnaire and were contacted six weeks, three months, and 12 months after the initial consultation. Recovery was assessed in terms of return to work, return to function, and resolution of pain. The association between potential prognostic factors and time to recovery was modelled with Cox regression.Results The follow-up rate over the 12 months was more than 97%. Half of those who reduced their work status at baseline had returned to previous work status within 14 days (95% confidence interval 11 to 17 days) and 83% had returned to previous work status by three months. Disability (median recovery time 31 days, 25 to 37 days) and pain (median 58 days, 52 to 63 days) took much longer to resolve. Only 72% of participants had completely recovered 12 months after the baseline consultation. Older age, compensation cases, higher pain intensity, longer duration of low back pain before consultation, more days of reduced activity because of lower back pain before consultation, feelings of depression, and a perceived risk of persistence were each associated with a longer time to recovery.Conclusions In this cohort of patients with acute low back pain in primary care, prognosis was not as favourable as claimed in clinical practice guidelines. Recovery was slow for most patients. Nearly a third of patients did not recover from the presenting episode within a year.     

Argininosuccinic aciduria: prenatal studies in a family at risk.

We have monitored two successive pregnancies in a family which we found to be at risk for argininosuccinic aciduria. We measured argininosuccinic acid (ASA) concentrations in amniotic fluid and utilized an indirect assay of ASA lyase activity in cultured amniotic fluid cells. The assay procedure is based on the uptake of 14C from [14C]citrulline and of [3H]leucine into protein. ASA was easily measured in amniotic fluid from the first fetus at risk, whereas none was detectable in control fluids. Amniotic fluid cells cultured from this fetus had only 5.5% of control ASA lyase activity. The pregnancy was terminated, and hepatic ASA lyase activity in the fetus was shown to be about 1.3% of control values. In addition, eight fetal tissues were analyzed for ASA, and all had significant accumulation. ASA was not detected in amniotic fluid from the second fetus at risk, and ASA lyase activity in cultured cells was 80% of control activity. Enzymatic analysis of erythrocyte lysate confirmed the diagnosis of an unaffected child (ASA lyase = 46% of control) and indicated heterozygosity. Thus, we provide further evidence that argininosuccinic aciduria can be diagnosed successfully in utero by indirect assay of ASA lyase activity in cultured amniotic fluid cells. In addition, high amniotic fluid ASA concentrations provide strong adjunctive evidence for such a prenatal determination, and may prove to be sufficient for diagnosis.     

Change in social status and risk of low birth weight in Denmark: population based cohort study.

OBJECTIVE: To estimate the risk of having a low birthweight infant associated with changes in social, environmental, and genetic factors. DESIGN: Population based, historical cohort study using the Danish medical birth registry and Statistic Denmark''s fertility database. SUBJECTS: All women who had a low birthweight infant (< 2500 g) (index birth) and a subsequent liveborn infant (outcome birth) in Denmark between 1980 and 1992 (exposed cohort, n = 11,069) and a random sample of the population who gave birth to an infant weighing > or = 2500 g and to a subsequent liveborn infant (unexposed cohort, n = 10,211). MAIN OUTCOME MEASURES: Risk of having a low birthweight infant in the outcome birth as a function of changes in male partner, area of residence, type of job, and social status between the two births. RESULTS: Women in the exposed cohort showed a high risk (18.5%) of having a subsequent low birthweight infant while women in the unexposed cohort had a risk of 2.8%. After adjustment for initial social status, a decline in social status increased the absolute risk of having a low birthweight infant by about 5% in both cohorts, though this was significant only in the unexposed cohort. Change of male partner did not modify the risk of low birth weight in either cohort. CONCLUSION: Having had a low birthweight infant and a decline in social status are strong risk factors for having a low birthweight infant subsequently.     

Incidence of neurologic death among patients with brain injury: a cohort study in a Canadian health region

Background:

Hospital mortality has decreased over time for critically ill patients with various forms of brain injury. We hypothesized that the proportion of patients who progress to neurologic death may have also decreased.

Methods:

We performed a prospective cohort study involving consecutive adult patients with traumatic brain injury, subarachnoid hemorrhage, intracerebral hemorrhage or anoxic brain injury admitted to regional intensive care units in southern Alberta over a 10.5-year period. We used multivariable logistic regression to adjust for patient age and score on the Glasgow Coma Scale at admission, and to assess whether the proportion of patients who progress to neurologic death has changed over time.

Results:

The cohort consisted of 2788 patients. The proportion of patients who progressed to neurologic death was 8.1% at the start of the study period, and the adjusted odds of progressing to neurologic death decreased over the study period (odds ratio [OR] per yr 0.92, 95% confidence interval [CI] 0.87–0.98, p = 0.006). This change was most pronounced among patients with traumatic brain injury (OR per yr 0.87, 95% CI 0.78–0.96, p = 0.005); there was no change among patients with anoxic injury (OR per yr 0.96, 95% CI 0.85–1.09, p = 0.6). A review of the medical records suggests that missed cases of neurologic death were rare (≤ 0.5% of deaths).

Interpretation:

The proportion of patients with brain injury who progress to neurologic death has decreased over time, especially among those with head trauma. This finding may reflect positive developments in the prevention and care of brain injury. However, organ donation after neurologic death represents the major source of organs for transplantation. Thus, these findings may help explain the relatively stagnant rates of deceased organ donation in some regions of Canada, which in turn has important implications for the care of patients with end-stage organ failure.Mortality has decreased among critically ill patients with various forms of brain injury in Canada and around the world.^1–10 There have also been changes in the incidence of stroke and the rate of admission to hospital for traumatic brain injury, especially among younger people and those whose injuries are related to motor vehicle or bicycle crashes.^5,6,10–13Some countries have noted a possible decline in the total number of patients with neurologic death.^14,15 Neurologic death (“brain death”) may occur when patients with brain injury experience progressive cerebral edema, complicated by transtentorial herniation. It is defined by the irreversible cessation of cerebral and brainstem functions, including respiration.¹⁶ Circulation and gas exchange persist only because of the use of mechanical ventilation. National guidelines exist for the diagnosis of neurologic death.^17,18 We hypothesized that the proportion of patients with acute brain injury who progress to neurologic death may have decreased over time.     

A cohort study of breast cancer risk in breast reduction patients.

Surgical reduction of the female breast (reduction mammaplasty) is very common in plastic surgery. The purpose of this study was to determine whether women who have undergone breast reduction surgery are at the same, greater, or lesser risk of developing breast cancer than women who have not undergone breast reduction surgery. This study incorporates a population-based, non-concurrent cohort linkage methodology. The Canadian Institute for Health Information hospital records were used to identify all Ontario women who had undergone breast reduction surgery in Ontario between 1979 and 1992. Three computerized probabilistic record linkages were performed. The first linkage was between a file of the 28,042 Ontario women who had undergone bilateral breast reduction surgery between April 1, 1979, and December 31, 1992, and a file of incident cancer cases among Ontario women for the calendar period 1979 to 1993. Follow-up of the cohort was undertaken starting from the date of breast reduction surgery, and vital status was ascertained as of December 31, 1993, by record linkage with the Ontario Mortality Database maintained at the Ontario Cancer Registry. The incidence of cancer in the Ontario breast reduction cohort was compared with the cancer incidence of the general Ontario population after appropriate adjustments for age and calendar time period. The expected number of cancers was calculated using the "PERSON YEARS" computer program. Within the cohort, followed for an average of 6.5 years after bilateral breast reduction surgery, 101 breast cancers were observed and 165.8 were expected, for a standardized incidence ratio of 0.61 (0.50 to 0.74, 95 percent confidence interval). This effect was independent of patient age at breast reduction. This study demonstrates that there is no increased risk of breast cancer after bilateral breast reduction surgery and, in fact, a significant decreased risk existed in women followed for an average of 6.5 years.     

The risk for depression in patients with ankylosing spondylitis: a population-based cohort study

Introduction

Depression is frequent in ankylosing spondylitis (AS) patients. However, epidemiological data about the potential increase in risk are lacking. This study compares the rate of doctor-diagnosed depression in a well defined cohort of AS patients to the general population seeking care.

Methods

The Skåne Healthcare Register comprises healthcare data of each resident in Region Skåne, Sweden (population 1.2 million), including ICD-10 diagnoses. Using physician coded consultation data from years 1999 to 2011, we calculated depression consultation rates for all AS patients. We obtained standardized depression-rate ratios by dividing the observed depression rate in AS patients by the expected rate based on the corresponding age- and sex-specific rates of depression in the general population seeking care. A ratio >1 equals a higher rate of depression among AS patients.

Results

The AS cohort consisted of 1738 subjects (65% men) with a mean age of 54 years. The reference population consisted of 967,012 subjects. During the 13-year observation period 10% (n = 172) of the AS cohort had a doctor-diagnosed depression compared to 6% (n = 105) to be expected. The standardized estimate of depression-rate ratio was 1.81 (95% confidence interval 1.44 to 2.24) in women men and 1.49 (1.20 to 1.89) in men.

Conclusions

The rate of doctor-diagnosed depression is increased about 80% in female and 50% in male AS patients. Future challenges are to timely identify and treat the AS patients who suffer from depression.     

Survival outcome of care by specialist surgeons in breast cancer: a study of 3786 patients in the west of Scotland.

OBJECTIVE--To compare survival outcome for patients with breast cancer cared for by specialist and non-specialist surgeons in a geographically defined area. DESIGN--Retrospective study of all female patients aged under 75 years in the area treated between 1980 and June 1988 (before breast screening began). Patients were identified from the cancer registry and from pathology records of all hospitals in the area. Specialist surgeons were identified by one author. All other surgeons caring for patients from the area were considered non-specialists. SETTING--A geographically defined population in urban west of Scotland. SUBJECTS--3786 patients with histologically verified breast cancer operated on between 1 January 1980 and 30 June 1988 and followed to 31 December 1993. MAIN OUTCOME MEASURES--Five and 10 year survival rates for specialists and non-specialists; relative hazard ratios derived from Cox''s proportional hazards model adjusted for prognostic factors--age, socioeconomic status, tumour size, and nodal involvement. RESULTS--The five year survival rate was 9% higher and the 10 year survival 8% higher for patients cared for by specialist surgeons. A reduction in risk of dying of 16% (95% confidence interval 6% to 25%) was found after adjustment for age, tumour size, socioeconomic status, and nodal involvement. The benefit of specialist care was apparent for all age groups, for small and large tumours, and for tumours that did and did not affect the nodes and was consistent across all socioeconomic categories. CONCLUSIONS--Survival differences of the magnitude demonstrated have implications for the provision of services for the treatment of women with breast cancer. There is a need to improve equity in the treatment of breast cancer.     

A prospective cohort study of pregnancy risk factors and birth outcomes in Aboriginal women

Background

Aboriginal women have been identified as having poorer pregnancy outcomes than other Canadian women, but information on risk factors and outcomes has been acquired mostly from retrospective databases. We compared prenatal risk factors and birth outcomes of First Nations and Métis women with those of other participants in a prospective study.

Methods

During the 12-month period from July 1994 to June 1995, we invited expectant mothers in all obstetric practices affiliated with a single teaching hospital in Edmonton to participate. Women were recruited at their first prenatal visit and followed through delivery. Sociodemographic and clinical data were obtained by means of a patient questionnaire, and microbiological data were collected at 3 points during gestation: in the first and second trimesters and during labour. Our primary outcomes of interest were low birth weight (birth weight less than 2500 g), prematurity (birth at less than 37 weeks'' gestation) and macrosomia (birth weight greater than 4000 g).

Results

Of the 2047 women consecutively enrolled, 1811 completed the study through delivery. Aboriginal women accounted for 70 (3.9%) of the subjects who completed the study (45 First Nations women and 25 Métis women). Known risk factors for adverse pregnancy outcome were more common among Aboriginal than among non-Aboriginal women, including previous premature infant (21% v. 11%), smoking during the current pregnancy (41% v. 13%), presence of bacterial vaginosis in midgestation (33% v. 13%) and poor nutrition as measured by meal consumption. Although Aboriginal women were less likely than non-Aboriginal women to have babies of low birth weight (odds ratio [OR] 1.46, 95% confidence interval [CI] 0.52–4.15) or who were born prematurely (OR 1.45, 95% CI 0.57–3.72) and more likely to have babies with macrosomia (OR 2.04, 95% CI 1.03–4.03), these differences were lower and statistically nonsignificant after adjustment for smoking, cervicovaginal infection and income (adjusted OR for low birth weight 0.85, 95% CI 0.19–3.78; for prematurity 0.90, 95% CI 0.21–3.89; and for macrosomia 2.12, 95% CI 0.84-5.36).

Interpretation

After adjustment for potential confounding factors, we found no statistically significant relation between Aboriginal status and birth outcome.It is generally recognized that Aboriginal women experience poorer birth outcomes than other North American women, including higher rates of stillbirth,¹ low-birth-weight infants^1,2,3 and prematurity.^2,3 Although significant efforts have been made to reduce Aboriginal infant mortality rates, these rates remain higher than for other infants in both Canada⁴ and the United States.⁵ Little is known about the reasons for differences in birth outcomes, although social, economic, medical and prenatal care factors have been suggested. Recent publications, based on retrospective analyses of large databases, have confirmed disparities in birth outcomes between Aboriginal and all other groups,^3,6,7 but there is a paucity of prospective data. In addition, although the term “Aboriginal” refers to a heterogeneous population comprising First Nations people, Métis and Inuit, there are few comparisons between specific Aboriginal groups or of Aboriginal groups with the general population.We report here the results of a prospective study in a general obstetric population, comparing birth outcomes and known pregnancy risk factors of Aboriginal women with those of non-Aboriginal Canadian women. In addition to well-recognized socioeconomic and reproductive risk factors, we investigated the prevalence of maternal cervicovaginal infections, which have been increasingly linked to prematurity.^8,9     

Acute kidney injury biomarkers for patients in a coronary care unit: a prospective cohort study

Background

Renal dysfunction is an established predictor of all-cause mortality in intensive care units. This study analyzed the outcomes of coronary care unit (CCU) patients and evaluated several biomarkers of acute kidney injury (AKI), including neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18) and cystatin C (CysC) on the first day of CCU admission.

Methodology/Principal Findings

Serum and urinary samples collected from 150 patients in the coronary care unit of a tertiary care university hospital between September 2009 and August 2010 were tested for NGAL, IL-18 and CysC. Prospective demographic, clinical and laboratory data were evaluated as predictors of survival in this patient group. The most common cause of CCU admission was acute myocardial infarction (80%). According to Acute Kidney Injury Network criteria, 28.7% (43/150) of CCU patients had AKI of varying severity. Cumulative survival rates at 6-month follow-up following hospital discharge differed significantly (p<0.05) between patients with AKI versus those without AKI. For predicting AKI, serum CysC displayed an excellent areas under the receiver operating characteristic curve (AUROC) (0.895±0.031, p<0.001). The overall 180-day survival rate was 88.7% (133/150). Multiple Cox logistic regression hazard analysis revealed that urinary NGAL, serum IL-18, Acute Physiology, Age and Chronic Health Evaluation II (APACHE II) and sodium on CCU admission day one were independent risk factors for 6-month mortality. In terms of 6-month mortality, urinary NGAL had the best discriminatory power, the best Youden index, and the highest overall correctness of prediction.

Conclusions

Our data showed that serum CysC has the best discriminative power for predicting AKI in CCU patients. However, urinary NGAL and serum IL-18 are associated with short-term mortality in these critically ill patients.     

Outcomes of deliveries by family physicians or obstetricians: a population-based cohort study using an instrumental variable

Background:

Previous research has suggested that obstetric outcomes are similar for deliveries by family physicians and obstetricians, but many of these studies were small, and none of them adjusted for unmeasured selection bias. We compared obstetric outcomes between these provider types using an econometric method designed to adjust for unobserved confounding.

Methods:

We performed a retrospective population-based cohort study of all Canadian (except Quebec) hospital births with delivery by family physicians and obstetricians at more than 20 weeks gestational age, with birth weight greater than 500 g, between Apr. 1, 2006, and Mar. 31, 2009. The primary outcomes were the relative risks of in-hospital perinatal death and a composite of maternal mortality and major morbidity assessed with multivariable logistic regression and instrumental variable–adjusted multivariable regression.

Results:

After exclusions, there were 3600 perinatal deaths and 14 394 cases of maternal morbidity among 799 823 infants and 793 053 mothers at 390 hospitals. For deliveries by family physicians v. obstetricians, the relative risk of perinatal mortality was 0.98 (95% confidence interval [CI] 0.85–1.14) and of maternal morbidity was 0.81 (95% CI 0.70–0.94) according to logistic regression. The respective relative risks were 0.97 (95% CI 0.58–1.64) and 1.13 (95% CI 0.65–1.95) according to instrumental variable methods.

Interpretation:

After adjusting for both observed and unobserved confounders, we found a similar risk of perinatal mortality and adverse maternal outcome for obstetric deliveries by family physicians and obstetricians. Whether there are differences between these groups for other outcomes remains to be seen.Over the past several decades in Canada, obstetric deliveries have increasingly been attended by specialist obstetricians rather than family physicians.¹ Although specialized care is beneficial for high-risk mothers and their infants,^2–4 there are concerns that it might increase risk for women whose deliveries could be safely managed without a specialized approach. Most prior studies have concluded that obstetric outcomes between family physicians and obstetricians are similar, but many of these studies were small, and none of them adjusted for unmeasured factors that might affect both the choice of delivery provider and outcomes.^5–8Obstetric risk is typically divided between providers, with family physicians and obstetricians sharing the lowest-risk patients, obstetricians caring for moderate-risk patients, and sub-specialized perinatologists caring for the highest-risk individuals. Although traditional statistical methods can be used to adjust for observed differences between these groups, they cannot be used to adjust for unobserved differences. For example, the presence of gestational diabetes mellitus is usually noted, but its severity is often not coded in administrative databases. Women with mild diabetes mellitus are usually eligible for delivery by family physicians, but those with severe diabetes (and the attendant increased risk of adverse outcome) are not. There are many prominent examples where traditional analyses of observational data produced results that were subsequently refuted by randomized trials, presumably because of these unmeasured or unknown factors that also affect treatment decisions or outcomes.^4,9–11The instrumental variable method from the field of econometrics is a technique designed to control for unmeasured covariates in regression analyses. Results from instrumental variable–controlled observational analyses of the effect of angiography after myocardial infarction⁹ and of long-acting bronchodilators on asthma control¹² closely approximated those of randomized controlled trials, whereas analyses using traditional statistical methods differed substantially. Instrumental variable analyses of obstetric data have shown that traditional statistical approaches significantly underestimate the mortality benefit of high-volume hospitals for high-risk neonates.⁴ The objective of the current study was to compare perinatal mortality and maternal morbidity and mortality for deliveries by family physicians and obstetricians using instrumental variable methodology.