Trends in major risk factors for anal sphincter lacerations: a 10-year study.

OBJECTIVES: (1) To identify independent risk factors for anal sphincter laceration, (2) to determine the trend in rates of anal sphincter laceration over a 10-year period, and (3) to examine the impact of temporal trends in risk factors on anal sphincter laceration rates. METHODS: Population-based data were obtained from the Nova Scotia Atlee Perinatal Database, on 91 206 women who had a singleton vaginal live birth > or =500 g for the years 1988 to 1997. Risk factors for anal sphincter laceration were identified using stepwise logistic regression. A multivariate model was used to study temporal changes in laceration rates after controlling for changes in parity, episiotomy rates, operative vaginal deliveries, birth weight, prolonged second stage of labour, and other determinants. RESULTS: Nulliparity (relative risk [RR] = 6.97), occiput posterior position (RR = 2.44), non-vertex presentations (RR = 2.27), second stage > or =120 min (RR range = 1.47-2.02), delivery by an obstetrician (RR = 1.30), and birth weight > or =3000 g (RR range = 1.43-6.63) increased the risk of laceration. Instrument-assisted delivery involved risks that ranged from a 2-fold increase for a vacuum-assisted delivery (RR = 2.15) to a greater than 5-fold increase for a forceps delivery after an unsuccessful vacuum extraction (RR = 5.69). Episiotomy, particularly midline incisions, increased the risk of laceration (RR = 2.57). The risk of a sphincter laceration increased 2-fold from 1988 to 1997, despite controlling for risk factors. CONCLUSIONS: Sufficient evidence exists about the risk factors for anal sphincter laceration to permit modification of management of labour and delivery to minimize the risk of anal sphincter laceration. Increased awareness of the clinical importance of recognition and repair of anal sphincter laceration may explain the rising incidence.

Double-blind comparison of carbetocin versus oxytocin in prevention of uterine atony after cesarean section.

OBJECTIVE: The goal of this study was to compare carbetocin, a long-acting oxytocin analog, with oxytocin in the prevention of uterine atony after cesarean section. STUDY DESIGN: We enrolled 694 patients undergoing elective cesarean section in a Canadian multicenter, double-blind, randomized clinical trial. We compared the effect of a single 100 microg dose of carbetocin with that of a standard 8-hour infusion of oxytocin. The primary outcome was the proportion of patients requiring additional oxytocic intervention for uterine atony. A variable sample size, sequential design was used. RESULTS: The overall oxytocic intervention rate was 7.4%. The odds of treatment failure requiring oxytocic intervention was 2.03 (95% confidence interval 1.1 to 2.8) times higher in the oxytocin group compared with the carbetocin group, respectively, 32 of 318 (10.1%) versus 15 of 317 (4.7%), P <.05. CONCLUSIONS: Carbetocin, a new drug for the prevention of uterine atony, appears to be more effective than a continuous infusion of oxytocin and has a similar safety profile.

Relationship between pregnancy-induced hypertension and placenta previa: a population-based study.

OBJECTIVE: Our purpose was to investigate, in a large population-based cohort, the hypothesis that the risk of pregnancy-induced hypertension is lower among pregnancies complicated by placenta previa compared with pregnancies occurring in women with fundally implanted placentas. STUDY DESIGN: Data for this retrospective cohort study were derived from the computerized Atlee perinatal database of the Reproductive Care Program, Nova Scotia, Canada. Women who were delivered in the province between 1980 and 1993 were included in the study. Patients with pregnancy-induced hypertension were clinically diagnosed by the presence of elevated blood pressure, proteinuria, or edema. The risk of pregnancy-induced hypertension was compared between women diagnosed with placenta previa and those with a normally implanted placenta, after adjustment for potential confounders through multivariable logistic regression models based on the method of generalized estimating equations. RESULTS: During the 14 years (1980 to 1993), 121,082 singleton pregnancies were registered in the program, 416 (0.4%) of which had a confirmed diagnosis of placenta previa. Women with chronic hypertension had a relative risk of 1.2 (95% confidence interval 0.4 to 3.7) for placenta previa compared with normotensive women. However, the risk of pregnancy-induced hypertension was reduced by half among those with placenta previa (relative risk 0.5, 95% confidence interval 0.3 to 0.7). Adjustments for potential confounders, including maternal age, parity, prepregnancy body weight, prior cesarean delivery, prior spontaneous or induced abortions, and cigarette smoking, had no influence on this association. Analyses on the basis of stratification of women by parity (nulliparous vs multiparous), cigarette smoking (smoker vs nonsmoker), and gestational duration (< 28, 28 to 32, 33 to 36, and > 37 completed weeks) consistently showed reduced risks for pregnancy-induced hypertension among women with placenta previa, indicating that the association was not a result of shortened duration of gestation among women with placenta previa. CONCLUSIONS: The results from this study clearly show a decreased frequency of pregnancy-induced hypertension among those pregnancies with placenta previa. We speculate that the pathophysiologic mechanisms for this finding may be due to altered placental perfusion seen among women diagnosed with placenta previa.

Influence of hypertensive disorders and cigarette smoking on placental abruption and uterine bleeding during pregnancy.

OBJECTIVE: To assess the influence of hypertensive disorders in pregnancy on the subsequent risk of placental abruption and uterine bleeding of unknown aetiology, and to examine the combined effects of hypertensive disorders and cigarette smoking during pregnancy on the risk of uteroplacental bleeding disorders. DESIGN: Retrospective cohort study. SETTING: Data for this study were derived from the Nova Scotia Atlee Perinatal database, Canada, comprising of women who were delivered in the province between 1980 and 1993. POPULATION: 120,666 pregnancies resulting in singleton births, of which 13,360 pregnancies were complicated by pre-eclampsia and/or chronic hypertension. MAIN OUTCOME MEASURES: Risks and relative risks of placental abruption and uterine bleeding of unknown aetiology in pregnancies complicated by chronic hypertension, mild and severe pre-eclampsia, and chronic hypertension with superimposed pre-eclampsia, each compared with normotensive patients. Adjusted relative risks were obtained through the fit of multivariable logistic regression models based on the method of generalised estimating equations. RESULTS: Chronically hypertensive women had no increased risk of abruption (RR 1.4; 95% CI 0.5-3.6), while women whose pregnancies were complicated by severe pre-eclampsia (RR 3.8; 95% CI 2.1-6.9), and chronic hypertension with superimposed pre-eclampsia (RR 2.8; 95% CI 1.2-6.3) showed strong associations with placental abruption. However, none of the hypertensive disorders were associated with uterine bleeding of unknown aetiology. The association between placental abruption and hypertensive disorders varied by parity. Parous women with chronic hypertension and superimposed pre-eclampsia were at greater risk of placental abruption (aRR 3.8; 95% CI 1.9-7.8) than nulliparous women with chronic hypertension and superimposed pre-eclampsia (aRR 1.6; 95% CI 0.5-4.9). The joint effects of smoking and hypertension had a greater effect on the risk of placental abruption than would have been expected based on their individual effects. CONCLUSIONS: The pattern of association between placental abruption and hypertension varied in relation to the specific type of hypertensive disorder. However, uterine bleeding of unknown aetiology was not associated with hypertension. Findings from this study suggest that placental abruption and uterine bleeding of unknown origin are aetiologically distinct obstetric complications with respect to hypertensive disorders during pregnancy.

Influence of gestational age on the time from spontaneous rupture of the chorioamniotic membranes to the onset of labor.

Our goal was to assess the influence of gestational age on the timing of labor onset following spontaneous rupture of the chorioamniotic membranes. The 24,831 patients in the Nova Scotia Atlee perinatal database from 1986 to 1992 whose membranes ruptured prior to labor onset and had live births were analyzed using life-table analysis methods. The probability of labor onset at specified intervals following rupture was markedly lower when rupture occurred earlier in gestation. Pregnancies of < 33 weeks' gestation were less than half as likely as term pregnancies to proceed to labor within 24 hours and pregnancies of 33-36 weeks' gestation were 50-75% as likely as term pregnancies to progress within that period. These data provide clear evidence that the earlier in gestation the rupture occurs, the less likely labor onset is within specified time periods. This pattern supports the contention that preterm rupture of membranes is etiologically distinct from preterm labor.

Preeclampsia and preterm birth subtypes in Nova Scotia, 1986 to 1992.

The goal of this study was to evaluate the influence of preeclampsia on preterm delivery, examining whether the association varied among preterm birth subtypes defined by gestational age and precipitating events. A population-based, longitudinal study of the association between mild and severe preeclampsia and preterm birth subtypes was conducted among 59,851 women (resulting in a total of 78,086 pregnancies) delivering singleton live births in the province of Nova Scotia, Canada between 1986 and 1992, utilizing the Nova Scotia Atlee perinatal database. Very preterm (< 33 weeks' gestation) and moderately preterm (33-36 weeks' gestation) births were further classified as occurring due to (1) membrane rupture, (2) medical intervention, and (3) spontaneous onset of labor (before membrane rupture). Mild and severe preeclampsia occurred in 8.7 and 1.7% of pregnancies, respectively, after exclusions of multiple births. After adjustment for confounders by multivariable logistic regression based on the generalized estimating equations, severe preeclampsia was strongly associated with the risk of very preterm birth (RR = 80.8, 95% CI: 54.2-120.6), and moderately preterm birth (RR = 41.8, 95% CI: 34.0-51.4) due to medical intervention. A less dramatically elevated risk of very preterm (RR = 2.1, 95% CI: 1.1-4.0) and moderately preterm (RR = 2.2, 95% CI: 1.7-2.9) birth due to medical intervention was apparent among pregnancies complicated by mild preeclampsia. Very preterm births due to membrane rupture were too rare to examine, but moderately preterm births due to membrane rupture were not associated with preeclampsia. Preeclampsia was associated with an increase in the risk of moderately preterm births due to spontaneous labor (RR = 1.9, 95% CI: 1.3-2.8), but not very preterm births (RR = 1.0, 95% CI: 0.7-1.2). Substantial variability was observed in the association between preeclampsia and preterm birth in relation to the subtypes defined by gestational age and pathway, with strong associations between hypertension and medically induced preterm births. The results indicate a need to separate preterm births into subcategories to properly evaluate the association between preeclampsia and preterm births and interventions to reduce the adverse effects of preeclampsia.

Maternal cigarette smoking as a risk factor for placental abruption, placenta previa, and uterine bleeding in pregnancy.

The authors carried out an epidemiologic study to evaluate the role of maternal cigarette smoking as a potential risk factor for placental abruption, placenta previa, and uterine bleeding of unknown etiology in pregnancy. Data for this prospective cohort study were obtained from women seeking prenatal care at any of the two tertiary, seven regional, or 17 community hospitals in the province of Nova Scotia, Canada, between January 1, 1986, and December 31, 1993. A total of 87,184 pregnancies (among 61,667 women) were registered in the database. Women who smoked during pregnancy (33%) were compared with nonsmokers, and all women were followed until the termination of pregnancy. Placental abruption was indicated in 9.9 per 1,000 pregnancies, while placenta previa and uterine bleeding of unknown etiology were indicated in 3.6 and 58.9 per 1,000 pregnancies, respectively. Women who smoked had a twofold increase in the risk of abruption (relative risk = 2.05, 95% confidence interval (CI) 1.75-2.40) in comparison with nonsmokers, while the relative risk for placenta previa was 1.36 (95% CI 1.04-1.79). However, cigarette smoking was not found to be associated with uterine bleeding of unknown etiology (relative risk = 1.01, 95% CI 0.94-1.08). There was no evidence for an increased risk of uteroplacental bleeding disorders with increasing numbers of cigarettes smoked. All analyses were adjusted for potentially confounding factors through logistic regression models based on the method of generalized estimating equations. The study confirms a positive association between cigarette smoking and placental abruption and a weak association with placenta previa but not with other uterine bleeding. The distinct pattern of results for placental abruption, placenta previa, and uterine bleeding of unknown origin suggests that these three uteroplacental bleeding disorders do not have a common etiology in relation to cigarette smoking.

Effect of maternal age and parity on the risk of uteroplacental bleeding disorders in pregnancy.

OBJECTIVE: To examine the risk of placental abruption, placenta previa, and uterine bleeding of unknown etiology in relation to advanced maternal age and parity in a large, population-based study. METHODS: Data for this study were derived from the Nova Scotia Atlee perinatal provincial data base, Canada, an ongoing project on human reproduction. Women who delivered between 1980 and 1993 (n = 123,941) in the province of Nova Scotia were included in the study, with the exception of pregnancies resulting in multiple births (n = 2859) and those missing data on maternal age or parity (n = 14). Multivariable logistic regression models based on the method of generalized estimating equations were used to generate odds ratios after adjustment for multiple confounders. RESULTS: The frequency of abruption was increased slightly among younger women (relative risk [RR] 1.3, 95% confidence interval [CI] 1.0-1.7), compared with women ages 25-29 years, but there was no increase with advancing maternal age. In contrast, the risk of placenta previa increased dramatically with advancing maternal age, with women older than 40 years having a nearly ninefold greater risk than women under the age of 20, after adjustment for potential confounders, including parity. Uterine bleeding of unknown etiology was not associated with advanced maternal age, except for a slight increase among women over 40 (RR 1.3, 95% CI 1.0-1.6). The risk of placenta previa and placental abruption was increased with higher parity among younger women only, but uterine bleeding of unknown etiology was more weakly associated with higher parity. In addition, an analysis of the joint effects of age and parity on placental abruption indicated a strong parity effect for women under 30 years, whereas the risk of placenta previa increased with increasing parity up to age 35 years. Uterine bleeding of unknown etiology also indicated a parity effect that was restricted to women under 25 years. CONCLUSION: Multiparity is associated with the risk of placenta previa and, to a lesser extent, placental abruption, but not with other uterine bleeding. Increasing maternal age is associated independently with the risk of placenta previa, but not with either of the other two conditions. Finally, the increased risks of uteroplacental bleeding disorders with advanced parity among the younger women (ie, 20-25 years, parity 3+) may reflect effects of close pregnancy spacing, or confounding by unmeasured factors that characterize women who have many pregnancies at a relatively young age. Overall, the findings suggest that the three uteroplacental bleeding disorders do not share a common etiology in relation to maternal age and parity, and that placenta previa is linked to aging of the uterus and the effects of repeated pregnancies.

Comparison of a trial of labor with an elective second cesarean section.

BACKGROUND: In an attempt to reduce the rate of cesarean section, obstetricians now offer a trial of labor to pregnant women who have had a previous cesarean section. Although a trial of labor is usually successful and is relatively safe, few studies have directly addressed the maternal and perinatal morbidity and mortality associated with this method of delivery. METHODS: We performed a population-based, longitudinal study of 6138 women in Nova Scotia who had previously undergone cesarean section and had delivered a singleton live infant in the period from 1986 through 1992. RESULTS: A total of 3249 women elected a trial of labor, and 2889 women chose to undergo a second cesarean section. There were no maternal deaths. The overall rate of maternal morbidity was 8.1 percent; 1.3 percent had major complications (a need for hysterectomy, uterine rupture, or operative injury) and 6.9 percent had minor complications (puerperal fever, a need for blood transfusion, or abdominal-wound infection). Although the overall rate of maternal complications did not differ significantly between women who chose a trial of labor and the women who elected cesarean section (odds ratio for the trial-of-labor group, 0.9; 95 percent confidence interval, 0.8 to 1.1), major complications were nearly twice as likely among women undergoing a trial of labor (odds ratio, 1.8; 95 percent confidence interval, 1.1 to 3.0). Apgar scores, admission to the neonatal intensive care unit, and perinatal mortality were similar among the infants whose mothers had a trial of labor and those whose mothers underwent elective cesarean section. CONCLUSION: Among pregnant women who have had a cesarean section, major maternal complications are almost twice as likely among those whose deliveries are managed with a trial of labor as among those who undergo an elective second cesarean section.

Prevalence of lower genital tract infections in pregnancy.

A descriptive profile of 106 pregnant women with various forms of cervicitis and vaginitis is provided. Fifty women attending individual physicians' private offices are compared with 56 clinic patients: 34 attending a university prenatal teaching clinic and 22 attending a pregnancy termination unit. Univariate analysis showed that single women were significantly more likely to be infected by mycoplasmas, yeasts, trichomonads, and Gardnerella vaginalis than were married women. Teenagers were more frequently infected by Mycoplasma hominis, yeasts, and Trichomonas vaginalis than were women older than 20 years. After stepwise logistic regression analysis, the most significant predictor of infection with M. hominis, Ureaplasma urealyticum, or yeasts was being a clinic patient; for G. vaginalis, the most significant variable was being unmarried. These data suggest that teenaged and single women who are pregnant will benefit most from routine screening for vaginitis/cervicitis-producing microorganisms.

Deceased co-twin as a cause of false positive amniotic fluid AFP and AChE.

A pregnancy was terminated because of persistently elevated amniotic fluid AFP (+10 S.D.) and an AChE band of low intensity on gel electrophoresis. No fetal anomalies were detected by ultrasonographic examination. Autopsy revealed an apparently normal fetus of about 20 weeks gestation. Attached to the placenta was a small sac containing a fetus papyraceus co-twin of about 8-9 weeks gestation. The small deceased co-twin and its gestational sac were not detected prenatally despite multiple ultrasonographic examinations. The difficulty in the interpretation of apparently conflicting results is emphasized.

Amniotic fluid phosphatidylglycerol and phosphatidylcholine phosphorus as predictors of fetal lung maturity.

The contents of phosphatidylglycerol and phosphatidylcholine phosphorus in amniotic fluid (10,000 X g pellets) were studied as predictors of fetal lung maturity. The presence of phosphatidylglycerol predicted the absence of neonatal respiratory distress syndrome with 99% probability. When phosphatidylglycerol was absent, phosphatidylcholine phosphorus was a reliable predictor if measured 3 to 7 days before delivery. The probability that respiratory distress syndrome would not occur was 94% when phosphatidylcholine phosphorus was greater than 6. When measurement was performed within 2 days of delivery, the probability that respiratory distress syndrome would not occur fell to 69%. As measured in amniotic fluid, phosphatidylglycerol and phosphatidylcholine phosphorus are reliable antenatal predictors of fetal pulmonary maturity and, therefore, are useful in the management of a number of obstetric conditions.

The effect of vaginal administration of various doses of prostaglandin E2 gel on cervical ripening and induction of labor.

Eighty patients with a Bishop score of less than or equal to 4 were randomly administered vaginal triacetin gel containing placebo or prostaglandin E2 in 1, 2, and 3 mg doses. Twelve to sixteen hours later, those not in labor underwent oxytocin induction. Increasing doses of prostaglandin were effective in ripening the cervix, and the higher doses were associated with significant success in inducing labor.

Characteristics of glucose-stimulated breathing movements in human fetuses with intrauterine growth retardation.

The characteristics of fetal breathing movements were analyzed in 13 fetuses who were intrauterine growth retarded and in a comparison group of 13 well-grown fetuses. The numbers of minutes of breathing activity per hour were similar for the two groups; the increase (p less than 0.05) after maternally administered glucose was due to longer (p less than 0.05) and more frequent (p less than 0.05) breathing episodes, and was mainly deep breathing. The deep breathing rate increased significantly (p less than 0.05) after glucose. The two groups exhibited similar low occurrences of shallow breathing (less than 5 minutes per hour) throughout the experiments. No significant differences could be demonstrated between intrauterine growth-retarded and well-grown fetuses with respect to the amount, rate, and pattern of breathing activity during fasting or after oral administration of glucose to the mother.

Evaluation of a rapid method for the detection of vaginal group B streptococci in women in labor.

Group B streptococci infection is an important cause of neonatal morbidity and mortality. Effective therapeutic intervention has been prevented to date by our inability to rapidly detect vaginal colonization. Material obtained from the lower vagina of 414 women in labor was cultured, incubated in modified Islam serum starch broth and observed on the ward for the production of orange carotenoid pigment specific for group B streptococci. Subcultures yielded 48 true group B streptococci-positive results. For the Islam broth, the pigment appeared in 2 to 22.5 hours (median, 12.5 hours). The test was shown to have a sensitivity of 96% and a specificity of 100% for group B streptococci. This study demonstrated a simple inexpensive method of detecting vaginal group B streptococci colonization which does not require sophisticated 24-hour laboratory facilities. The method holds promise as a screening test for future intervention studies.

Comparison of natural and synthetic prostaglandin E2 tablets in labour induction.

A multicentre, randomized, double-blind trial compared the efficacy and safety of and tolerance to natural and synthetically produced prostaglandin E2 tablets in the induction of labour in 202 women. The compounds were similarly effective, inducing labour in approximately 66% of patients. The total dose required and the interval between induction and delivery were similar in the two groups, as were the Apgar scores at 1 and 5 minutes and the incidence of maternal and fetal side effects.

The effect of maternal glucose infusion on breathing movements in human fetuses with intrauterine growth retardation.

forty-nine patients with suspected intrauterine growth retardation (IUGR) were studied under rigid experimental conditions to determine baseline fetal breathing movement (FBM) activity and the response to 90-minute maternal glucose infusion, as compared to that of normal control subjects. Patients with IUGR showed a normal amount of FBMs during maternal fasting. All groups exhibited a significant increase in FBMs after glucose was administered. During the final 60 minutes of the glucose infusion, the severe IUGR group (weight for gestational age less than the third percentile) showed less FBM activity (p less than 0.01) than the other study and control groups.

Assessment of fetal lung maturity: relationship of gestational age and pregnancy complications to phosphatidylglycerol levels.

Phosphatidylglycerol (PG) was measured in the pellet fraction of 863 amniotic fluid samples, and charts were reviewed for maternal disease, duration of gestation at collection, and outcome of pregnancy. PG was present at 32 to 34 weeks' gestation in 24.1% of samples; at 35 to 36 weeks, in 52.3%; and at 37 weeks, in 85.4%. Pre-eclamptic toxemia/hypertension, diabetes, premature rupture of membranes, and preterm labor all had earlier appearance of PG than a comparison group. There was no delay in lung maturity in gestational diabetics or Rh isoimmunization. Infants of patients with overt diabetes with PG greater than or equal to 0.5% did not develop respiratory distress syndrome. This value appeared in 30% of diabetic patients by 35 to 36 weeks and in 76.9% by 37 weeks' gestation.

Phosphatidylglycerol determination on amniotic fluid 10,000 x g pellet in the prediction of fetal lung maturity.

Phosphatidylglycerol and the lecithin/sphingomyelin (L/S) ratio were determined, and the shake test was performed, as indicators of fetal lung maturity, in more than 600 patients. A clinical review of the outcome was made in all patients who underwent delivery within 2 days after collection of amniotic fluid. Correlation was made phosphatidylglycerol, shake test, and L/S ratio results. L/S ratio had a false positive rate of 5%, and a false negative rate of 58.1%. The shake test had a false positive rate of 1.1%, and a false negative rate of 63.5%. Phosphatidylglycerol determination had a false positive rate of 1.8%, and a false negative rate of 26.9%. Phosphatidylglycerol determination is an accurate predictor of fetal lung maturity, and predicts lung immaturity more correctly than do the L/S ratio and shake test.