Demographic,clinical and microbiological characteristics of maternity patients: A Canadian clinical cohort study

OBJECTIVE:

To determine the demographic, clinical and microbiological characteristics of a representative Canadian obstetrical population.

DESIGN:

A one-year cohort study of all maternity patients who were followed to delivery, using detailed patient questionnaires containing more than 60 demographic and clinical variables, and three microbiological evaluations during gestation - first trimester, 26 to 30 weeks, and labour and delivery. Outcome measurements included birth weight and gestational age.

SETTING:

Labour and delivery suites of all office obstetrical practices affiliated with a single hospital.

POPULATION STUDIED:

A consecutive sample of pregnant women in the study practices during one year were eligible for enrolment; 2237 consecutive patients were approached for consent, 2047 enrolled and 1811 completed the study through delivery.

RESULTS:

The average patient was white, married and 29 years of age. Slightly more than half of the patients had postsecondary education, but 10% fell below the national poverty line for income. Frequency of factors linked to adverse pregnancy outcomes included cigarette smoking (19%), alcohol ingestion (18%), previously having had a premature infant (7%), and maternal diabetes (2%). Overall prevalence of genital microbes variously implicated in prematurity was 37% for ureaplasma, 11% for group B streptococcus and 4% for Mycoplasma hominis. Prevalence of bacterial vaginosis was 14%. The median gestational age for the cohort was 39 weeks, with 7% of infants born less than 37 weeks'' gestation. Mean birth weight was 3415 g.

CONCLUSIONS:

The present clinical cohort represents demographic and medical characteristics of the Canadian obstetrical population. The birth outcomes are consistent with national data. This database provides valuable information about a general obstetrical population that is managed by a universal health care system.Key Words: Genital tract infections, Prematurity, Risk factorsPremature birth (PB), defined as occurring at less than 37 weeks'' gestation, is the leading cause of perinatal mortality and morbidity in the industrialized world (1,2). Despite this recognition and advances in perinatal care, the prevalence of PB in the developed world has increased in recent years (3-6). The medical and economic impact of PB is appreciated specifically in the perinatal and/or neonatal periods, but also continues throughout life. Many factors, including socioeconomic, reproductive and medical conditions have been implicated in the etiology of PB (5,7). Infections have been increasingly recognized as important risk factors for PB (8-11). In some cases, such as with bacterial vaginosis, the stage of gestation during which infection occurs appears to be important in pregnancy outcome (12,13). However, results from several studies have been inconsistent and confounding risk factors have often not been assessed (10,14,15). Antibiotic treatment trials designed to eradicate infections to decrease the incidence of PB have yielded inconsistent results (14,16-21). The majority of studies on PB, carefully conducted and sometimes including large numbers of patients, have involved high risk obstetrical populations, and the results may not necessarily be extrapolated to general populations (1). The purpose of the present study was to evaluate a general obstetrical cohort population and to ultimately assess genital infections at various stages of pregnancy, including labour, in conjunction with other potential risk factors related to PB or low birth weight (less than 2500 g).