Temporal changes in rates and reasons for medical induction of term labor, 1980-1996

Prelabour rupture of the membranes at term: antibiotic overuse in Italy

BACKGROUND

The proper management of women with premature rupture of membrane (PROM) and not spontaneously entering in labour remains controversial. The aim of this study was to identify the current management for women with PROM at term according to the Group B Streptococcus (GBS) status across different Italian hospitals.

METHODS

Anonymous online survey evaluating: the current practice of women with PROM in terms of management (expectant management vs. induction of labour) and antibiotic prophylaxis according to GBS status.

RESULTS

In case of negative GBS status, the 82.4% of respondents wait until 24 hours before labour induction. Antibiotics are administered for prophylaxis in 35.3%, 27.5% and 2% at 18, 12 and 24 hours respectively. The remaining 35.3% of respondents are divided between those using antibiotics only with signs of infections or according to different risk factors (i.e. meconium-stained amniotic fluid or suspected infection). Neonates born from a mother with negative GBS status almost never (90.2%) receive prophylactic antibiotics. In case of positive GBS status, induction is started as soon as possible by 49.1% of respondents; the remnants choose to wait 6 (15.7%), 12 (17.6%), 18 (3.9%) and 24 (13.7%) hours. Antibiotics are administered as soon as possible by 78.4% of clinicians. In the neonates, 51% of neonatologist administer antibiotics upon clinical indications (suspected sepsis); 15.7% use antibiotics routinely or with a short interval between maternal antibiotics and delivery (17.6%).

CONCLUSIONS

The management after PROM is highly heterogeneous with an inappropriate extension of antibiotic prophylaxis in cases with negative GBS status.

Optimal timing of labor induction after prelabor rupture of membranes at term: a secondary analysis of the TERMPROM study

BACKGROUND

In the case of prelabor rupture of membranes at term, the risk for neonatal and maternal infectious morbidity increases progressively with time from prelabor rupture of membranes. Although most studies identified a benefit associated with early induction within the first 24 hours following term prelabor rupture of membranes, there is currently no precise data regarding how early should induction be scheduled.

OBJECTIVE

This study aimed to identify the optimal timing of labor induction among women with term prelabor rupture of membranes by comparing the maternal and neonatal outcomes associated with labor induction with those of expectant management at any given 1-hour interval following prelabor rupture of membranes.

STUDY DESIGN

This was a secondary analysis of data from the TERMPROM trial, an international, multicenter, randomized clinical trial on immediate delivery vs expectant management of women with prelaor rupture of membranes at term (≥37+0/7 weeks' gestation). We considered all participants as a single cohort of women with term prelabor rupture of membranes, irrespective of the original randomized study group allocation. For each given 1-hour time interval within the first 36 hours following prelabor rupture of membranes, we compared the outcomes of subjects for whom labor induction was initiated during this interval with those of subjects managed expectantly at the same time interval. The primary neonatal outcome was a composite of neonatal infection and admission to the neonatal intensive care unit. The primary maternal outcomes included maternal infection (clinical chorioamnionitis or postpartum fever) and cesarean delivery.

RESULTS

Of the 4742 subjects who met the study criteria, 2622 underwent labor induction, and 2120 experienced a spontaneous onset of labor. The rates of the neonatal composite outcome, neonatal admission to intensive care unit, and maternal infection increased progressively with time after prelabor rupture of membranes. The risk for these outcomes was lower among women who underwent induction when compared with those managed expectantly within the first 15 to 20 hours after prelabor rupture of membranes without affecting the risk for cesarean delivery. In addition, women who underwent labor induction within the first 30 to 36 hours had a shorter prelabor rupture of membranes to delivery time and a shorter total maternal hospital stay when compared with those managed expectantly at the same time interval. Among women managed expectantly, less than two-thirds (64%; 1365/2120) experienced a spontaneous onset of labor within the first 24 hours following prelabor rupture of membranes.

CONCLUSION

These findings suggest that immediate labor induction seems to be the optimal management strategy to minimize neonatal and maternal morbidity in the setting of prelabor rupture of membranes at term gestations. In cases for which immediate induction is not feasible, labor induction remains the preferred option over expectant management if performed within the first 15 to 20 hours after prelabor rupture of membranes.

Labour induction in twin pregnancies

Medically-indicated deliveries are common in twin pregnancies given the increased risk of various obstetric complications in twin compared to singleton pregnancies, mainly hypertensive disorders of pregnancy and foetal growth restriction. Due to the unique characteristics of twin pregnancies, the success rates and safety of labour induction may be different than in singleton pregnancies. However, while there are abundant data regarding induction of labour in singleton pregnancies, the efficacy and safety of labour induction in twin pregnancies have been far less studied. In the current manuscript we summarize available data on various aspects of labour induction in twin pregnancies including incidence, success rate, prognostic factors, safety and methods for labour induction in twins. This information may assist healthcare providers in counselling patients with twin pregnancies when labour induction is indicated.

Maternal exposure to ambient fine particulate matter and risk of premature rupture of membranes in Wuhan, Central China: a cohort study

BACKGROUND

The associations between maternal exposure to ambient PM2.5 during pregnancy and the risk of premature rupture of membranes (PROM) and preterm premature rupture of membranes (PPROM) are controversial. And no relevant study has been conducted in Asia. This study aimed to determine the association between maternal exposure to ambient PM2.5 during pregnancy and the risk of (P)PROM.

METHODS

A cohort study including all singleton births in a hospital located in Central China from January 2015 through December 2017 was conducted. Multivariable logistic regression models, stratified analysis, generalized additive model, and two-piece-wise linear regression were conducted to evaluate how exposure to ambient PM2.5 during pregnancy is associated with the risks of PROM and PPROM.

RESULTS

A total of 4364 participants were included in the final analysis, where 11.71 and 2.34% of births were complicated by PROM and PPROM, respectively. The level of PM2.5 exhibited a degree of seasonal variation, and its median concentrations were 63.7, 59.3, 55.8, and 61.8 μg/m3 for the first trimester, second trimester, third trimester, and the whole duration of pregnancy, respectively. After adjustment for potential confounders, PROM was positively associated with PM2.5 exposure (per 10 μg/m3) [Odds Ratio (OR) = 1.14, 95% Confidence Interval (CI), 1.02-1.26 for the first trimester; OR = 1.09, 95% CI, 1.00-1.18 for the second trimester; OR = 1.13, 95% CI, 1.03-1.24 for the third trimester; OR = 1.35, 95% CI, 1.12-1.63 for the whole pregnancy]. PPROM had positive relationship with PM2.5 exposure (per 10 μg/m3) (OR = 1.17, 95% CI, 0.94-1.45 for first trimester; OR = 1.11, 95% CI, 0.92-1.33 for second trimester; OR = 1.19, 95% CI, 0.99-1.44 for third trimester; OR = 1.53, 95% CI, 1.03-2.27 for the whole pregnancy) Positive trends between the acute exposure window (mean concentration of PM2.5 in the last week and day of pregnancy) and risks of PROM and PPROM were also observed.

CONCLUSIONS

Exposure to ambient PM2.5 during pregnancy was associated with the risk of PROM and PPROM.

Outcome of misoprostol and oxytocin in induction of labour

BACKGROUND

Induction of labour is the process of initiating the labour by artificial means from 24 weeks of gestation. The main aim of this study is to find out the maternal and foetal outcomes after induction of labour with misoprostol and oxytocin beyond 37 weeks of gestation.

METHODS

This was a hospital-based observational study carried out at Paropakar Maternity and Women's Hospital, Nepal. Misoprostol of 25 µg was inserted in posterior fornix of vagina or oxytocin infusion was started from 2.5 units on whom induction was decided. Maternal and foetal/neonatal outcomes were observed. Collected data were analysed using SPSS and MS Excel.

RESULTS

General induction rate was found to be 7.2%. In this study, post-term pregnancy was found to be the most common reason for induction of labour. Analysis of onset of labour led to the finding that mean onset of labour was much rapid in oxytocin (6.6 h) than misoprostol (13.6 h). However, there is similarity in induction-delivery interval in both groups. Overall, the rate of normal delivery and caesarean section was found to be 64.9% and 33.2%, respectively. Similarly, normal delivery within 12 h was seen in 18.4% of the patients given with misoprostol and 43.5% in oxytocin group. Foetal distress was found as the most common reason for caesarean section. The overall occurrence of maternal complication was found to be similar in misoprostol and oxytocin groups, nausea/vomiting being the most common (36.7%) complication followed by fever (24.1%). Besides this, the most common neonatal complication found in overall cases was meconium stained liquor (49.2%).

CONCLUSION

It was found that misoprostol was used most frequently for induction of labour compared to oxytocin. The onset of labour was found to be rapid in oxytocin than misoprostol. However, the occurrence of side effects was found to be similar in both misoprostol and oxytocin groups.

Planned early birth versus expectant management (waiting) for prelabour rupture of membranes at term (37 weeks or more)

BACKGROUND

Prelabour rupture of membranes (PROM) at term is managed expectantly or by planned early birth. It is not clear if waiting for birth to occur spontaneously is better than intervening, e.g. by inducing labour.

OBJECTIVES

The objective of this review is to assess the effects of planned early birth (immediate intervention or intervention within 24 hours) when compared with expectant management (no planned intervention within 24 hours) for women with term PROM on maternal, fetal and neonatal outcomes.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (9 September 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials of planned early birth compared with expectant management (either in hospital or at home) in women with PROM at 37 weeks' gestation or later.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, extracted the data, and assessed risk of bias of the included studies. Data were checked for accuracy.

MAIN RESULTS

Twenty-three trials involving 8615 women and their babies were included in the update of this review. Ten trials assessed intravenous oxytocin; 12 trials assessed prostaglandins (six trials in the form of vaginal prostaglandin E2 and six as oral, sublingual or vaginal misoprostol); and one trial each assessed Caulophyllum and acupuncture. Overall, three trials were judged to be at low risk of bias, while the other 20 were at unclear or high risk of bias.Primary outcomes: women who had planned early birth were at a reduced risk of maternal infectious morbidity (chorioamnionitis and/or endometritis) than women who had expectant management following term prelabour rupture of membranes (average risk ratio (RR) 0.49; 95% confidence interval (CI) 0.33 to 0.72; eight trials, 6864 women; Tau² = 0.19; I² = 72%; low-quality evidence), and their neonates were less likely to have definite or probable early-onset neonatal sepsis (RR 0.73; 95% CI 0.58 to 0.92; 16 trials, 7314 infants;low-quality evidence). No clear differences between the planned early birth and expectant management groups were seen for the risk of caesarean section (average RR 0.84; 95% CI 0.69 to 1.04; 23 trials, 8576 women; Tau² = 0.10; I² = 55%; low-quality evidence); serious maternal morbidity or mortality (no events; three trials; 425 women; very low-quality evidence); definite early-onset neonatal sepsis (RR 0.57; 95% CI 0.24 to 1.33; six trials, 1303 infants; very low-quality evidence); or perinatal mortality (RR 0.47; 95% CI 0.13 to 1.66; eight trials, 6392 infants; moderate-quality evidence).

SECONDARY OUTCOMES

women who had a planned early birth were at a reduced risk of chorioamnionitis (average RR 0.55; 95% CI 0.37 to 0.82; eight trials, 6874 women; Tau² = 0.19; I² = 73%), and postpartum septicaemia (RR 0.26; 95% CI 0.07 to 0.96; three trials, 263 women), and their neonates were less likely to receive antibiotics (average RR 0.61; 95% CI 0.44 to 0.84; 10 trials, 6427 infants; Tau² = 0.06; I² = 32%). Women in the planned early birth group were more likely to have their labour induced (average RR 3.41; 95% CI 2.87 to 4.06; 12 trials, 6945 women; Tau² = 0.05; I² = 71%), had a shorter time from rupture of membranes to birth (mean difference (MD) -10.10 hours; 95% CI -12.15 to -8.06; nine trials, 1484 women; Tau² = 5.81; I² = 60%), and their neonates had lower birthweights (MD -79.25 g; 95% CI -124.96 to -33.55; five trials, 1043 infants). Women who had a planned early birth had a shorter length of hospitalisation (MD -0.79 days; 95% CI -1.20 to -0.38; two trials, 748 women; Tau² = 0.05; I² = 59%), and their neonates were less likely to be admitted to the neonatal special or intensive care unit (RR 0.75; 95% CI 0.66 to 0.85; eight trials, 6179 infants), and had a shorter duration of hospital (-11.00 hours; 95% CI -21.96 to -0.04; one trial, 182 infants) or special or intensive care unit stay (RR 0.72; 95% CI 0.61 to 0.85; four trials, 5691 infants). Women in the planned early birth group had more positive experiences compared with women in the expectant management group.No clear differences between groups were observed for endometritis; postpartum pyrexia; postpartum antibiotic usage; caesarean for fetal distress; operative vaginal birth; uterine rupture; epidural analgesia; postpartum haemorrhage; adverse effects; cord prolapse; stillbirth; neonatal mortality; pneumonia; Apgar score less than seven at five minutes; use of mechanical ventilation; or abnormality on cerebral ultrasound (no events).None of the trials reported on breastfeeding; postnatal depression; gestational age at birth; meningitis; respiratory distress syndrome; necrotising enterocolitis; neonatal encephalopathy; or disability at childhood follow-up.In subgroup analyses, there were no clear patterns of differential effects for method of induction, parity, use of maternal antibiotic prophylaxis, or digital vaginal examination. Results of the sensitivity analyses based on trial quality were consistent with those of the main analysis, except for definite or probable early-onset neonatal sepsis where no clear difference was observed.

AUTHORS' CONCLUSIONS

There is low quality evidence to suggest that planned early birth (with induction methods such as oxytocin or prostaglandins) reduces the risk of maternal infectious morbidity compared with expectant management for PROM at 37 weeks' gestation or later, without an apparent increased risk of caesarean section. Evidence was mainly downgraded due to the majority of studies contributing data having some serious design limitations, and for most outcomes estimates were imprecise.Although the 23 included trials in this review involved a large number of women and babies, the quality of the trials and evidence was not high overall, and there was limited reporting for a number of important outcomes. Thus further evidence assessing the benefits or harms of planned early birth compared with expectant management, considering maternal, fetal, neonatal and longer-term childhood outcomes, and the use of health services, would be valuable. Any future trials should be adequately designed and powered to evaluate the effects on short- and long-term outcomes. Standardisation of outcomes and their definitions, including for the assessment of maternal and neonatal infection, would be beneficial.

The association between temporal changes in the use of obstetrical intervention and small-for-gestational age live births

BACKGROUND

The literature attributes secular declines in small-for-gestational age (SGA) live births to changes in maternal smoking and other maternal characteristics. However, there are reasons to believe that the observed reductions in SGA may be a consequence of early delivery following obstetric intervention.

METHODS

We examined temporal trends in obstetrical intervention and SGA among singleton live births in the United States from 1990 to 2010. The modified Kitagawa decomposition, based on the fetuses-at-risk approach, was used to assess the relative contribution of changes in the gestational age distribution and gestational age-specific SGA to overall changes in SGA. Reductions in SGA rates due to a left shift in the gestational age distribution were assumed to primarily reflect increased obstetrical intervention, whereas decreases in overall SGA due to decreases in gestational-age-specific SGA rates were assumed to reflect declines in risk factors.

RESULTS

Temporal trends in SGA followed a non-linear pattern, with substantial declines from 10.1% in 1990-92 to 8.9% in 2002-04, followed by a small increase to 9.1% in 2008-10. Rates of maternal smoking steadily decreased throughout the same time period and changes in SGA rates were more consistent with changes in the gestational age distribution. The modified Kitagawa decomposition analysis also attributed the initial decline in SGA rates to changes in the gestational age distribution.

CONCLUSIONS

Complex temporal pattern in SGA rates cannot be explained by the linear pattern of changes in factors like maternal smoking. Changes in the gestational age distribution are more consistent with the observed secular trends in SGA rates.

Risk factors for cesarean delivery after induction of labor in nulliparous women with an unfavorable cervix at or beyond 41 weeks of gestation

AIMS

To investigate risk factors for cesarean section (CS) following labor induction in nulliparas with an unfavorable cervix at or beyond 41 weeks of gestation.

METHODS

In this retrospective cohort study, a total of 276 nulliparas with an unfavorable cervix (Bishop score ≤6) who underwent labor induction for prolonged pregnancies were included out of a total of 646 patients who delivered ≥41 weeks (2002-2011).

RESULTS

82 (29.7%) patients of the 276 delivered by CS. The patients who underwent CS had less cervical dilatation and a lower Bishop score on admission than those patients who delivered vaginally (0.76 ± 0.47 vs. 0.92 ± 0.58 cm, p = 0.03 and 1.16 ± 1.25 vs. 1.51 ± 1.34, p = 0.04, respectively). Neonatal birth weight and biparietal diameter (BPD) were significantly smaller in the vaginal delivery group (3,414.93 ± 361.37 vs. 3,534.81 ± 383.05 g, p = 0.01 and 9.43 ± 0.35 vs. 9.65 ± 0.42 cm, p < 0.01). After multiple logistic regression analysis, maternal height, BPD, and early rupture of membranes (ROM) were independently related with CS. Early ROM was defined as spontaneous ROM that occurred before the onset of the active phase of labor.

CONCLUSION

Maternal height, BPD, and early ROM were risk factors for CS following labor induction in nulliparas at or beyond 41 weeks of gestation.

Induction of labor: a comparative study of intravaginal misoprostol and dinoprostone

OBJECTIVE

To compare the efficacy and safety of intravaginal misoprostol and dinoprostone for elective induction of labor in nulliparous women with an unfavorable cervix.

MATERIALS AND METHODS

A quasi-experimental study was conducted in Bahawal Victoria Hospital, Bahawalpur, Pakistan, from July 1, 2005 to August 31, 2006. A total of 120 primigravid women with gestational ages of > 40 weeks to < 42 weeks were divided into two groups. Group A (n = 60) was given 50 microg of misoprostol and Group B (n = 60) was given 3 mg of dinoprostone every 6 hours, for a maximum of three doses.

RESULTS

The induction to onset of significant uterine contractions and delivery intervals were lower in Group A than in Group B (6.1 vs. 7.2 hours; p = 0.16; and 8.2 vs. 11.0 hours; p = 0.007, respectively). Group A had a lower cesarean section rate than Group B (7% vs. 30%; p = 0.003), but a higher rate of uterine hyperstimulation (10% vs. 3%; p = 0.16), tachysystole (17% vs. 3%; p = 0.02), and neonatal admissions to the intensive care unit within 24 hours of delivery (4 vs. 3; p = 0.71) and after 24 hours (2 vs. 1; p = 0.56) than Group B.

CONCLUSION

Vaginal misoprostol is more effective than dinoprostone for the elective induction of labor beyond 40 weeks of gestation, but is associated with more uterine hyperstimulation, tachysystole, and neonatal intensive care unit admissions.

The influence of obstetric intervention on trends in twin stillbirths: United States, 1989–99

OBJECTIVE

Although twin stillbirth rates have declined substantially over the past two decades, the contribution of changes in obstetric interventions to reducing twin stillbirths has not been quantified.

METHODS

We carried out a retrospective cohort study of twin live births and stillbirths in the United States between 1989 and 1999 (n=1,102,212). Changes in the rate of stillbirth (> or =22 weeks) before and after adjustment for changes in labor induction, Cesarean delivery and sociodemographic factors were estimated through ecological logistic regression analysis. This analysis was based on aggregating data by each state within the United States.

RESULTS

Between 1989 and 1999, rates of labor induction and Cesarean delivery among twin live births increased by 138% (from 5.8% to 13.8%) and 15% (from 48.3% to 55.6%), respectively. These changes were accompanied by a 43% decline in the stillbirth rate between 1989 and 1999 (from 24.4 to 13.9 per 1000 fetuses at risk). After excluding births weighing < 500 g, rates of labor induction among twins at 22-27 weeks', 28-33 weeks' and > or =34 weeks' gestation increased by 95%, 131% and 127%, respectively, between 1989 and 1999. Cesarean delivery rates also increased by 55%, 29% and 2% in these same gestational age categories. The 48% (relative risk (RR) 0.52, 95% confidence interval (CI) 0.49-0.55) decline in stillbirth rate between 1989-91 and 1997-99 was reduced to a 25% (RR 0.75, 95% CI 0.72-0.79) decline after adjustment for changes in labor induction and Cesarean delivery. The decline in the rate of twin stillbirths was larger at later gestational ages (at > or =32 and > or =34 weeks) where the largest absolute increases in labor induction rates were observed.

CONCLUSIONS

The use of Cesarean delivery and especially labor induction for twin pregnancies has increased substantially in the United States over the last decade and these changes have been associated with a large decline in the rate of stillbirth among twins.

Outcomes of elective labour induction and elective caesarean section in low-risk pregnancies between 37 and 41 weeks' gestation

OBJECTIVE

To compare maternal and neonatal outcomes after elective induction of labour and elective Caesarean section with outcomes after spontaneous labour in women with low-risk, full-term pregnancies.

METHODS

We extracted birth data from 1996 to 2005 from an obstetrical database. Singleton pregnancies with vertex presentation, anatomically normal, appropriately grown fetuses, and no medical or surgical complications were included. Outcomes after elective induction of labour and elective Caesarean section were compared with the outcomes after spontaneous labour, using chi-square and Student t tests and logistic regression.

RESULTS

A total of 9686 women met the study criteria(3475 nulliparous, 6211 multiparous). The incidence of unplanned Caesarean section was higher in nulliparous women undergoing elective induction than in those with spontaneous labour (P < 0.001). Postpartum complications were more common in nulliparous and multiparous women undergoing elective induction (P < 0.001 and P < 0.01, respectively) and multiparous women undergoing elective Caesarean section, (P < 0.001). Rates of triage in NICU were higher in nulliparous women undergoing elective Caesarean section (P < 0.01), and requirements for neonatal free-flow oxygen administration were higher in nulliparous and multiparous women undergoing elective Caesarean section (P < 0.01 for each). Unplanned Caesarean section was 2.7 times more likely in nulliparous women undergoing elective induction of labour (95% CI 1.74 to 4.28, P < 0.001) and was more common among nulliparous and multiparous women undergoing induction of labour and requiring cervical ripening (P < 0. 001 and P < 0.05, respectively).

CONCLUSION

Elective induction leads to more unplanned Caesarean sections in nulliparous women and to increased postpartum complications for both nulliparous and multiparous women. Elective Caesarean section has increased maternal and neonatal risks.

Factors and outcomes associated with the induction of labour in Latin America

OBJECTIVE

To describe the prevalence of labour induction, together with its risk factors and outcomes in Latin America.

DESIGN

Analysis of the 2005 WHO global survey database.

SETTING

Eight selected Latin American countries.

POPULATION

All women who gave birth during the study period in 120 participating institutions.

METHODS

Bivariate and multivariate analyses.

MAIN OUTCOME MEASURES

Indications for labour induction per country, success rate per method, risk factors for induction, and maternal and perinatal outcomes.

RESULTS

Of the 97,095 deliveries included in the survey, 11,077 (11.4%) were induced, with 74.2% occurring in public institutions, 20.9% in social security hospitals and 4.9% in private institutions. Induction rates ranged from 5.1% in Peru to 20.1% in Cuba. The main indications were premature rupture of membranes (25.3%) and elective induction (28.9%). The success rate of vaginal delivery was very similar for oxytocin (69.9%) and misoprostol (74.8%), with an overall success rate of 70.4%. Induced labour was more common in women over 35 years of age. Maternal complications included higher rates of perineal laceration, need for uterotonic agents, hysterectomy, ICU admission, hospital stay>7 days and increased need for anaesthetic/analgesic procedures. Some adverse perinatal outcomes were also higher: low 5-minute Apgar score, very low birthweight, admission to neonatal ICU and delayed initiation of breastfeeding.

CONCLUSIONS

In Latin America, labour was induced in slightly more than 10% of deliveries; success rates were high irrespective of the method used. Induced labour is, however, associated with poorer maternal and perinatal outcomes than spontaneous labour.

A scoring system for detection of macrosomia and prediction of shoulder dystocia: A disappointment

OBJECTIVE

To develop a scoring system for the detection of a macrosomic fetus (birth weight (BW) >or= 4000 g) and predict shoulder dystocia among large for gestational age fetuses.

STUDY DESIGN

We retrospectively identified all singletons with accurate gestational age (GA) that were large for GA (abdominal circumference (AC) or estimated fetal weight (EFW) >or= 90% for GA) at >or=37 weeks with delivery within three weeks. The scoring system was: 2 points for biparietal diameter, head circumference, AC, or femur length >or=90% for GA, or if the amniotic fluid index (AFI) was >or=24 cm; for biometric parameters <90% or with AFI <24 cm, 0 points. The predictive values for detection of shoulder dystocia were calculated.

RESULTS

Of the 225 cohorts that met the inclusion criteria the rate of macrosomia was 39% and among vaginal deliveries (n = 120) shoulder dystocia occurred in 12% (15/120; 95% confidence interval (CI) 7-20%). The sensitivity of EFW >or=4500 g to identify a newborn with shoulder dystocia was 0% (95% CI 0-21%), positive predictive values 0% (95% CI 0-46%), and likelihood ratio of 0. For a macrosomia score >6, the corresponding values were 20% (4-48%), 25% (5-57%) and 2.3.

CONCLUSION

Though the scoring system can identify macrosomia, it offers no advantage over EFW. The scoring system and EFW are poor predictors of shoulder dystocia.

Water disinfection by-products and pre-labor rupture of membranes

The causes of term pre labor rupture of membranes (term PROM) remain poorly defined. The authors conducted a record-based prevalence study to explore a possible relation between disinfection by-products in drinking water and term PROM in an Australian community with spatially variable trihalomethane and nitrate levels. A multilevel statistical model was used to examine the relation between factors operating at the levels of the individual, district, and water distribution zone and the prevalence of PROM at term among 16,229 women in Perth, Western Australia (2002-2004). Adjusted odds ratios for term PROM increased with increasing tertiles of nitrate exposure (moderate exposure: odds ratio = 1.23, 95% confidence interval: 1.03, 1.52; high exposure: odds ratio = 1.47, 95% confidence interval: 1.20, 1.79), but there was no significant relation with exposure to trihalomethanes. This study raises the possibility that water contaminants may promote the development of PROM at term.

How big is too big? The perinatal consequences of fetal macrosomia

OBJECTIVE

The objective of the study was to examine the birthweight at which risks of perinatal death, neonatal morbidity, and cesarean delivery begin to rise and the causes and timing (antenatal, early or late neonatal, or postneonatal) of these risks.

STUDY DESIGN

This was a cohort study based on 1999-2001 US-linked stillbirth, live birth, and infant death records. Singletons weighing 2500 g or larger born to white non-Hispanic mothers at 37-44 weeks of gestation were selected (n = 5,983,409).

RESULTS

Infants with birthweights from 4000 to 4499 g were not at increased risk of mortality or morbidity vs those at 3500-3999 g, whereas those 4500-4999 g had significantly increased risks of stillbirth, neonatal mortality (especially because of birth asphyxia), birth injury, neonatal asphyxia, meconium aspiration, and cesarean delivery. Births at 5000 g or larger had even higher risks, including risk of sudden infant death syndrome.

CONCLUSION

Birthweight greater than 4500 g, and especially greater than 5000 g, is associated with increased risks of perinatal and infant mortality and morbidity.

Recurrence of spontaneous versus medically indicated preterm birth

OBJECTIVE

Despite the increased tendency of preterm birth to recur, little is known with regard to recurrence risks for spontaneous and medically indicated preterm birth as well as recurrence risks in relation to severity of preterm birth. We examined the recurrence of spontaneous and medically indicated preterm birth.

STUDY DESIGN

A population-based, retrospective cohort study of births in Missouri (1989 to 1997) was carried out with analyses restricted to women who delivered their first 2 consecutive singleton live births (n = 154,809). Women who experienced spontaneous onset of labor and subsequently delivered preterm (less than 35 weeks) were classified as spontaneous preterm birth. Medically indicated preterm birth included women who delivered preterm through a labor induction or a prelabor cesarean delivery. Risk and odds ratio of preterm birth recurrence were derived from fitting multivariate conditional logistic regression models after adjusting for potential confounders.

RESULTS

If the first pregnancy resulted in a spontaneous preterm birth, then affected women were more likely to deliver preterm spontaneously (adjusted odds ratio 3.6, 95% confidence interval 3.2, 4.0) and also as a medically indicated preterm birth (odds ratio 2.5, 95% confidence interval 2.1, 3.0) in the second birth. Similarly, if the first pregnancy resulted in a medically indicated preterm birth, affected women were 10.6-fold (95% confidence interval 10.1, 12.4) more likely to deliver preterm because of medical indications in the second pregnancy as well as preterm spontaneously (odds ratio 1.6, 95% confidence interval 1.3, 2.1). The greatest risk of recurrence of preterm birth in the second pregnancy tended to occur around the same gestational age as preterm birth in the first pregnancy, regardless of the clinical subtype.

CONCLUSION

The observation that spontaneous preterm birth is not only associated with increased recurrence of spontaneous but also medically indicated preterm birth and vice versa, suggests that the 2 clinical subtypes may share common etiologies.

Outcomes of Pregnancy Beyond 37 Weeks of Gestation

OBJECTIVE

The aim of the study was to evaluate pregnancy outcomes by weeks of gestation. A second aim was to assess the outcomes in groups with spontaneous or induced labor.

METHODS

This was a prospective cohort study of singleton pregnancies delivered after 37 weeks of pregnancy covering a well defined region in Norway from 1990 to 2001 (N = 27,514). Linear regression, chi 2 tests, and multivariable logistic regression analysis were used.

RESULTS

Maternal complications varied with gestational age, and were lowest at 39 weeks and highest postterm (cesarean delivery 12.3-21.6%, operative vaginal delivery 10.7-15.4%, maternal hemorrhage 9.7-14.6%). Poor neonatal outcome varied with gestational age only for spontaneous labors (Apgar at 5 minutes less than 7 1.0-2.3%, pH less than 7.10 3.4-5.2%), whereas induction of labor was a risk factor for delivery complications (odds ratio 1.3-2.8), independent of gestational weeks.

CONCLUSION

Poor pregnancy outcomes vary with gestational age. Postterm pregnancy and induced labor are prognostic factors for poor outcome.

Changes in the gestational age distribution among U.S. singleton births: impact on rates of late preterm birth, 1992 to 2002

There is mounting evidence that infants born late preterm (34-36 weeks) are at greater risk for morbidity than term infants. This article examines the changing epidemiology of gestational length among singleton births in the United States, from 1992 to 2002. Analyzing gestational age by mode of delivery, the distribution of spontaneous births shifted to the left, with 39 weeks becoming the most common length of gestation in 2002, compared with 40 weeks in 1992 (P < 0.001). Deliveries at > or =40 weeks gestation markedly decreased, accompanied by an increase in those at 34 to 39 weeks (P < 0.001). Singleton births with PROM or medical interventions had similar trends. Changes in the distribution of all singleton births differed by race/ethnicity, with non-Hispanic white infants having the largest increase in late preterm births. These observations, in addition to emerging evidence of increased morbidity, suggest the need for investigation of optimal obstetric and neonatal management of these late preterm infants.

Planned early birth versus expectant management (waiting) for prelabour rupture of membranes at term (37 weeks or more)

BACKGROUND

Prelabour rupture of membranes at term is managed expectantly or by elective birth, but it is not clear if waiting for birth to occur spontaneously is better than intervening.

OBJECTIVES

To assess the effects of planned early birth versus expectant management for women with term prelabour rupture of membranes on fetal, infant and maternal wellbeing.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (November 2004), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 4, 2004), MEDLINE (1966 to November 2004) and EMBASE (1974 to November 2004).

SELECTION CRITERIA

Randomised or quasi-randomised trials of planned early birth compared with expectant management in women with prelabour rupture of membranes at 37 weeks' gestation or more.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied eligibility criteria, assessed trial quality and extracted data. A random-effects model was used.

MAIN RESULTS

Twelve trials (total of 6814 women) were included. Planned management was generally induction with oxytocin or prostaglandin, with one trial using homoeopathic caulophyllum. Overall, no differences were detected for mode of birth between planned and expectant groups: relative risk (RR) of caesarean section 0.94, 95% confidence interval (CI) 0.82 to 1.08 (12 trials, 6814 women); RR of operative vaginal birth 0.98, 95% 0.84 to 1.16 (7 trials, 5511 women). Significantly fewer women in the planned compared with expectant management groups had chorioamnionitis (RR 0.74, 95% CI 0.56 to 0.97; 9 trials, 6611 women) or endometritis (RR 0.30, 95% CI 0.12 to 0.74; 4 trials, 445 women). No difference was seen for neonatal infection (RR 0.83, 95% CI 0.61 to 1.12; 9 trials, 6406 infants). However, fewer infants under planned management went to neonatal intensive or special care compared with expectant management (RR 0.72, 95% CI 0.57 to 0.92, number needed to treat 20; 5 trials, 5679 infants). In a single trial, significantly more women with planned management viewed their care more positively than those expectantly managed (RR of "nothing liked" 0.45, 95% CI 0.37 to 0.54; 5031 women).

AUTHORS' CONCLUSIONS

Planned management (with methods such as oxytocin or prostaglandin) reduces the risk of some maternal infectious morbidity without increasing caesarean sections and operative vaginal births. Fewer infants went to neonatal intensive care under planned management although no differences were seen in neonatal infection rates. Since planned and expectant management may not be very different, women need to have appropriate information to make informed choices.

Suspicion and treatment of the macrosomic fetus: a review

OBJECTIVE

To review the prevalence of and our ability to identify macrosomic (birthweight >4000 g) fetuses. Additionally, based on the current evidence, propose an algorithm for treatment of suspected macrosomia.

STUDY DESIGN

A review.

RESULTS

According to the National Vital Statistics, in the United States, the prevalence of newborns weighing at least 4000 g has decreased by 10% in seven years (10.2% in 1996 and 9.2% in 2002) and 19% for newborns with weights >5000 g (0.16% and 0.13%, respectively). Bayesian calculations indicates that the posttest probability of detecting a macrosomic fetus in an uncomplicated pregnancy is variable, ranging from 15% to 79% with sonographic estimates of birth weight, and 40 to 52% with clinical estimates. Among diabetic patients the post-test probability of identifying a newborn weighing >4000 g clinically and sonographically is over 60%. Among uncomplicated pregnancies, there is sufficient evidence that suspected macrosomia is not an indication for induction or for primary cesarean delivery. For pregnancies complicated by diabetes, with a prior cesarean delivery or shoulder dystocia, delivery of a macrosomic fetus increases the rate of complications, but there is insufficient evidence about the threshold of estimated fetal weight that should prompt cesarean delivery.

CONCLUSION

Due to the inaccuracies, among uncomplicated pregnancies suspicion of macrosomia is not an indication for induction or for primary cesarean delivery.

Trends in preterm birth and perinatal mortality among singletons: United States, 1989 through 2000

OBJECTIVE

Despite the recent increase in preterm birth in the United States, trends in preterm birth subtypes have not been adequately examined. We examined trends in preterm birth among singletons following ruptured membranes, medical indications, and spontaneous preterm birth and evaluated the impact of these trends on perinatal mortality.

METHODS

A population-based, retrospective cohort study comprising 46,375,578 women (16% blacks) who delivered singleton births in the United States, 1989 through 2000, was performed. Rates of preterm birth (< 37 weeks), their subtypes, and associated perinatal mortality (stillbirths at >/= 22 weeks plus neonatal deaths within 28 days), before and after adjustment for potential confounders, were derived from ecological logistic regression models.

RESULTS

Preterm birth rates increased by 14% (95% confidence interval 13-15%) among whites from 8.3% to 9.4% and decreased by 15% (95% confidence interval 14-16%) among blacks from 18.5% to 16.2% between 1989 and 2000. Among whites, preterm birth following ruptured membranes declined by 23%, medically indicated preterm birth increased by 55%, and spontaneous preterm birth increased by 3%. Among blacks, preterm birth following ruptured membranes declined by 37%, medically indicated preterm birth increased by 32%, and spontaneous preterm birth decreased by 27%. The largest decline in perinatal mortality among whites was associated with increases in medically indicated preterm birth, whereas the largest decline in perinatal mortality among blacks was associated with declines in preterm birth following ruptured membranes and spontaneous preterm birth.

CONCLUSION

Temporal trends in preterm birth varied substantially based on underlying subtype and maternal race. The recent increase in medically indicated preterm birth was associated with a favorable reduction in perinatal mortality.

Interrater reliability: completing the methods description in medical records review studies

In medical records review studies, information on the interrater reliability (IRR) of the data is seldom reported. This study assesses the IRR of data collected for a complex medical records review study. Elements selected for determining IRR included "demographic" data that require copying explicit information (e.g., gender, birth date), "free-text" data that require identifying and copying (e.g., chief complaints and diagnoses), and data that require abstractor judgment in determining what to record (e.g., whether heart disease was considered). Rates of agreement were assessed by the greatest number of answers (one to all n) that were the same. The IRR scores improved over time. At 1 month, the reliability for demographic data elements was very good, for free-text data elements was good, but for data elements requiring abstractor judgment was unacceptable (only 3.4 of six answers agreed, on average). All assessments after 6 months showed very good to excellent IRR. This study demonstrates that IRR can be evaluated and summarized, providing important information to the study investigators and to the consumer for assessing the reliability of the data and therefore the validity of the study results and conclusions. IRR information should be required for all large medical records studies.

Emergency cesarean delivery in induction of labor: an evaluation of risk factors

BACKGROUND

Induction of labor has been associated with an increased risk of emergency cesarean delivery. Knowledge of factors that influence the risk of cesarean delivery in women with induced labor is limited.

METHODS

We performed a case-control study, nested within a population-based cohort of women with induced labor at term during 1991-1996 in Uppsala County, Sweden. Cases were women delivered with emergency cesarean delivery, and controls were women vaginally delivered (n = 193, respectively). Using logistic regression, analyses were performed. Odds ratio (OR) with 95% confidence intervals (CI) was used as a measure of relative risk.

RESULTS

Women with a previous cesarean delivery had high risks of cesarean delivery (adjusted OR = 10.10, 95% CI = 3.30-30.92). The risk of cesarean delivery was also increased among nulliparous (adjusted OR = 4.92, 95% CI = 2.81-8.61), short (adjusted OR = 2.20, 95% CI = 1.06-4.59), and obese women (adjusted OR = 2.03, 95% CI = 1.07-3.84). A cervix dilatation less than 1.5 cm doubled the risk of cesarean delivery (adjusted OR = 2.26, 95% CI = 1.09-4.66). Mother's age, epidural analgesia, oxytocin augmentation, gestational age, and birthweight were not significantly associated with risks of cesarean delivery.

CONCLUSIONS

Women with a previous cesarean delivery, nulliparous, short, and obese women with induced labor are at high risk of a cesarean delivery. When there is a need to deliver a woman with a previous cesarean section or a nulliparous woman with other risk factors for cesarean delivery, it may be prudent to consider an elective cesarean section.

Comparison of misoprostol and dinoprostone for elective induction of labour in nulliparous women at full term: a randomized prospective study

BACKGROUND

The objective of this randomized prospective study was to compare the efficacy of 50 mcg vaginal misoprostol and 3 mg dinoprostone, administered every nine hours for a maximum of three doses, for elective induction of labor in a specific cohort of nulliparous women with an unfavorable cervix and more than 40 weeks of gestation.

MATERIAL AND METHODS

One hundred and sixty-three pregnant women with more than 285 days of gestation were recruited and analyzed. The main outcome measures were time from induction to delivery and incidence of vaginal delivery within 12 and 24 hours. Admission rate to the neonatal intensive care unit within 24 hours post delivery was a secondary outcome.

RESULTS

The induction-delivery interval was significantly lower in the misoprostol group than in the dinoprostone group (11.9 h vs. 15.5 h, p < 0.001). With misoprostol, more women delivered within 12 hours (57.5% vs. 32.5%, p < 0.01) and 24 hours (98.7% vs. 91.4%, p < 0.05), spontaneous rupture of the membranes occurred more frequently (38.8% vs. 20.5%, p < 0.05), there was less need for oxytocin augmentation (65.8% vs. 81.5%, p < 0.05) and fewer additional doses were required (7.5% vs. 22%, p < 0.05). Although not statistically significant, a lower Caesarean section (CS) rate was observed with misoprostol (7.5% vs. 13.3%, p > 0.05) but with the disadvantage of higher abnormal fetal heart rate (FHR) tracings (22.5% vs. 12%, p > 0.05). From the misoprostol group more neonates were admitted to the intensive neonatal unit, than from the dinoprostone group (13.5% vs. 4.8%, p > 0.05). One woman had an unexplained stillbirth following the administration of one dose of dinoprostone.

CONCLUSIONS

Vaginal misoprostol, compared with dinoprostone in the regimens used, is more effective in elective inductions of labor beyond 40 weeks of gestation. Nevertheless, this is at the expense of more abnormal FHR tracings and more admissions to the neonatal unit, indicating that the faster approach is not necessarily the better approach to childbirth.

Pregnancy outcome in women with heart disease undergoing induction of labour

OBJECTIVE

To examine the safety and outcome of induction of labour in women with heart disease.

DESIGN

Prospective single-centre comparative study.

SETTING

Major university-based medical centre.

POPULATION/SAMPLE

One hundred and twenty-one pregnant women with heart disease.

METHODS

The sample included all women with acquired or congenital heart disease who attended our High-Risk Pregnancy Outpatient Clinic from 1995 to 2001. The files were reviewed for baseline data, cardiac and obstetric history, course of pregnancy and induction of labour and outcome of pregnancy. Findings were compared between women who underwent induction of labour and those who did not. Forty-seven healthy women in whom labour was induced for obstetric reasons served as controls.

MAIN OUTCOME MEASURES

Pregnancy outcome.

RESULTS

Of the 121 women with heart disease, 47 (39%) underwent induction of labour. There was no difference in the caesarean delivery rate after induction of labour between the women with heart disease (21%) and the healthy controls (19%). Although the women with heart disease had a higher rate of maternal and neonatal complications than controls (17%vs 2%, P= 0.015), within the study group, there was no difference in complication rate between the patients who did and did not undergo induction of labour.

CONCLUSION

Induction of labour is a relatively safe procedure in women with cardiac disease. It is not associated with a higher rate of caesarean delivery than in healthy women undergoing induction of labour for obstetric indications, or with more maternal and neonatal complications than in women with a milder form of cardiac disease and spontaneous labour.

To induce or not to induce labor: a macrosomic dilemma

We assessed the effect of labor induction among parturients carrying macrosomic fetuses on the risk of a cesarean section (CS). The study population consisted of consecutive women with singleton fetuses weighing >/=4,000 g, delivered between 1988 and 1999. A comparison was made between parturients who delivered after labor induction and those who delivered without labor induction. The Mantel-Haenszel procedure was used to obtain the weighted odds ratios while controlling for confounding variables. During the study period, 4,755 women delivered macrosomic newborns in our institution. In 20% of the women (n = 951) labor was induced, while 80% of them (n = 3,804) delivered without labor induction. The women who delivered after labor induction were more likely to be nulliparous (18.0 vs. 10.0%; p < 0.001). In addition, these women had significantly higher rates of gestational diabetes (23.3 vs. 10.7%; p < 0.001), hypertensive disorders (10.1 vs. 5.3%; p < 0.001), hydramnios (17.4 vs. 9.9%; p < 0.001), and oligohydramnios (2.1 vs. 0.2%; p < 0.001). The CS rate was significantly higher among the patients who delivered after labor induction as compared with those in whom labor was not induced (17.8 vs. 11.9%; odds ratio 1.6, 95% confidence interval 1.3-1.9, p < 0.001). Stratified analysis using the Mantel-Haenszel technique was performed to control for confounders such as gestational diabetes, hypertensive disorders, previous CS, hydramnios, oligohydramnios, and nulliparity. None of these variables changed the significant association between induction of labor and CS. The induction of labor among women carrying macrosomic fetuses was found to be an independent risk factor for a CS.

Trends in twin neonatal mortality rates in the United States, 1989 through 1999: influence of birth registration and obstetric intervention

OBJECTIVE

We sought to evaluate the contributions of changes in birth registration, labor induction, and cesarean delivery on trends in twin neonatal mortality rates.

STUDY DESIGN

We conducted a population-based, retrospective cohort study of twin live births, using linked birth-infant death data in the United States (1989-1999). Relative risks and 95% confidence intervals that quantified changes in neonatal (0-27 days) mortality rates were derived from ecologic logistic regression models that were fit after aggregation of the data by each state in the United States.

RESULTS

The frequency of live born twins who weighed <500 g increased 72%, from 0.7% in 1989 to 1.2% in 1999, of live born twins who weighed 500 to 749 g and 750 to 999 g increased by 55% and 28%, respectively, between 1989 and 1999. Preterm birth rates increased by 19%, from 46.2% in 1989 to 57.2% in 1999. The rate of labor induction increased from 5.8% to 13.9%, and the cesarean delivery rate increased from 49.8% to 56.3%. Between 1989 to 1991 and 1997 to 1999, the crude neonatal mortality rates among twins who weighed >or=500 g declined by 37% (95% CI, 35%-40%) from 21.5 to 13.6 per 1000 twin live births. Adjustments for preterm labor induction, preterm cesarean delivery, term labor induction, term cesarean delivery, and sociodemographic factors had little influence on neonatal mortality rate trends.

CONCLUSION

Increases in preterm birth because of obstetric intervention among twins have not led to increases in twin neonatal mortality rates in the United States.

A parsimonious explanation for intersecting perinatal mortality curves: understanding the effects of race and of maternal smoking

BACKGROUND: Neonatal mortality rates among black infants are lower than neonatal mortality rates among white infants at birth weights <3000 g, whereas white infants have a survival advantage at higher birth weights. This finding is also observed when birth weight-specific neonatal mortality rates are compared between infants of smokers and non-smokers. We provide a parsimonious explanation for this paradoxical phenomenon. METHODS: We used data on births in the United States in 1997 after excluding those with a birth weight <500 g or a gestational age <22 weeks. Birth weight- and gestational age-specific perinatal mortality rates were calculated per convention (using total live births at each birth weight/gestational age as the denominator) and also using the fetuses at risk of death at each gestational age. RESULTS: Perinatal mortality rates (calculated per convention) were lower among blacks than whites at lower birth weights and at preterm gestational ages, while blacks had higher mortality rates at higher birth weights and later gestational ages. With the fetuses-at-risk approach, mortality curves did not intersect; blacks had higher mortality rates at all gestational ages. Increases in birth rates and (especially) growth-restriction rates presaged gestational age-dependent increases in perinatal mortality. Similar findings were obtained in comparisons of smokers versus nonsmokers. CONCLUSIONS: Formulating perinatal risk based on the fetuses-at-risk approach solves the intersecting perinatal mortality curves paradox; blacks have higher perinatal mortality rates than whites and smokers have higher perinatal mortality rates than nonsmokers at all gestational ages and birth weights.

Small-for-gestational-age births in the United States: an age-period-cohort analysis

BACKGROUND

During the last 2 decades, the rate of low birthweight has increased, as has the rate of preterm delivery, among both whites and blacks. Examination of causes for these secular trends has focused largely on changes in the distributions of maternal age and, less commonly, on birth cohort. Little is known as to how age, period, and birth cohort interact on trends in small births at term.

METHODS

The U.S. natality files were used to assess trends in term (>/=37 weeks gestation) small-for-gestational age (SGA) births for 7 5-year maternal age groups (15-19 through 45-49 years), 6 delivery periods (1975, 1980, 1985, 1990, 1995, and 2000), and 12 5-year maternal birth cohorts (1926-1930 through 1981-1985). SGA births were defined as sex-specific birthweight below the 10th percentile for gestational age based on 1995 livebirths in the United States. Logistic regression models were fit to determine the independent effects of age, delivery period, and birth cohort on term SGA trends, separately for blacks and whites.

RESULTS

Between 1975 and 2000, term SGA births declined by 23% (from 21% to 16%) among blacks and by 27% (from 12% to 9%) among whites. Term SGA births declined with increasing age up to 30-34 years, but increased among older women. Within strata of maternal age, the risk also declined with later maternal birth cohorts, among both blacks and whites. The strongest influence on SGA trends was from maternal age, followed by maternal birth cohort, and lastly by delivery period. In general, for any combination of age, period, and birth cohort, blacks showed 1.5- to 2-fold higher rates of term SGA than whites.

CONCLUSIONS

The persistence of strong maternal age effects on risk of term SGA births suggests that the effect of age is at least partly the result of biologic factors. Term SGA trends were generally consistent for blacks and whites, although the magnitude of difference in the risks for combinations of age, period, or mother's birth cohort was higher among blacks than whites.

Secular trends in neonatal macrosomia in Berlin: influences of potential determinants

To investigate the trend in the prevalence of neonatal macrosomia and to evaluate the influences of potential determinants, key features of 206 308 hospital deliveries (97% of all) in Berlin in the years 1993-99, collected by the Berlin Medical Board, were analysed using SPSS 10.0. After exclusion of multiple births and preterm infants, there was a significant increase over 7 years (P < 0.01) in the prevalence of birthweights >or= 4000 g, maternal age >or= 30 years, height of >or= 165 cm, prepregnancy BMI (body mass index) >or= 26 kg/m2 and pregnancy weight gain> 16 kg, but no substantial trend in the prevalence of recognised diabetes or maternal smoking. The adjusted model (OR [95% CI]) for delivering a newborn >or= 4000 g was statistically significant for post-term delivery (2.56 [2.39, 2.75]), women aged >or= 30 years (1.06 [1.02-1.11]), >or= 165 cm tall (1.94 [1.87,2.01]), multiparae (1.98 [1.91, 2.05]), not smoking in pregnancy (2.03 [1.93, 2.14]), prepregnancy BMI >or= 26 compared with < 20 (4.01 [3.77, 4.26]), pregnancy weight gain >or= 16 kg compared with < 10 kg (3.37.[3.22, 3.53]) and for recognised diabetes (1.85.[1.69, 2.04]). It is speculated that this increase in the prevalence of neonatal macrosomia may contribute to the secular trend of overweight and obesity under affluent living conditions.

A parsimonious explanation for intersecting perinatal mortality curves: understanding the effect of plurality and of parity

BACKGROUND: Birth weight- and gestational age-specific perinatal mortality curves intersect when compared across categories of maternal smoking, plurality, race and other factors. No simple explanation exists for this paradoxical observation. METHODS: We used data on all live births, stillbirths and infant deaths in Canada (1991-1997) to compare perinatal mortality rates among singleton and twin births, and among singleton births to nulliparous and parous women. Birth weight- and gestational age-specific perinatal mortality rates were first calculated by dividing the number of perinatal deaths at any given birth weight or gestational age by the number of total births at that birth weight or gestational age (conventional calculation). Gestational age-specific perinatal mortality rates were also calculated using the number of fetuses at risk of perinatal death at any given gestational age. RESULTS: Conventional perinatal mortality rates among twin births were lower than those among singletons at lower birth weights and earlier gestation ages, while the reverse was true at higher birth weights and later gestational ages. When perinatal mortality rates were based on fetuses at risk, however, twin births had consistently higher mortality rates than singletons at all gestational ages. A similar pattern emerged in contrasts of gestational age-specific perinatal mortality among singleton births to nulliparous and parous women. Increases in gestational age-specific rates of growth-restriction with advancing gestational age presaged rising rates of gestational age-specific perinatal mortality in both contrasts. CONCLUSIONS: The proper conceptualization of perinatal risk eliminates the mortality crossover paradox and provides new insights into perinatal health issues.

Risk of cesarean delivery after induction at term in nulliparous women with an unfavorable cervix

OBJECTIVE

The purpose of this study was to evaluate the effect of induction on the route of delivery in nulliparous women laboring at term in a community hospital system.

STUDY DESIGN

From April 1997 to October 1999, there were 7282 deliveries in nulliparous patients who met inclusion criteria. Cesarean delivery rates were calculated for patients in spontaneous labor and for patients who underwent induction.

RESULTS

Among 4635 women (63.7%) in spontaneous labor, the cesarean delivery rate was 11.5% versus 23.7% among the 2647 (36.3%) patients who underwent induction. An important variable that affected the delivery route was the Bishop score at the initiation of the induction. The cesarean delivery rate was 31.5% among patients whose Bishop score was <5 at induction versus 18.1% for patients with a score > or =5(P <.001).

CONCLUSION

The induction of labor in nulliparous patients, especially those women with an unfavorable cervix as measured by Bishop score, is associated with a significantly increased risk of cesarean delivery.

Macrosomic births in the united states: determinants, outcomes, and proposed grades of risk

OBJECTIVE

We describe maternal risk factors for macrosomia and assess birth weight categories to determine predictive thresholds of adverse outcomes.

STUDY DESIGN

We analyzed linked live birth and infant death cohort files from 1995 to 1997 for the United States with the use of selected term (37-44 weeks of gestation) single live births to mothers who were US residents. We compared macrosomic infants (4000-4499 g, 4500-4999 g, and >5000 g infants) with a normosomic control group of infants who weighed 3000 to 3999 g.

RESULTS

Maternal risk factors for macrosomia included nonsmoking, advanced age, married, diabetes mellitus, hypertension, and previous macrosomic infant or pregnancy loss. The risks of labor complications, birth injuries, and newborn morbidity rose with each gradation of macrosomic birth weight. Infant mortality rates increased significantly among infants weighing >5000 g.

CONCLUSION

Although a definition of macrosomia as >4000 g (grade 1) may be useful for the identification of increased risks of labor and newborn complications, >4500 g (grade 2) may be more predictive of neonatal morbidity, and >5000 g (grade 3) may be a better indicator of infant mortality risk.

A Native American community with a 7% cesarean delivery rate: does case mix, ethnicity, or labor management explain the low rate?

PURPOSE

Cesarean delivery rates vary widely across populations. Studying communities with low rates of cesarean delivery may identify practices that can lower the cesarean rate.

METHODS

A population-based historical cohort study included all pregnant women (N = 1132) from 1992 through 1996 in a predominantly Native American region of northwestern New Mexico known to have a high prevalence of gestational diabetes and preeclampsia. The outcomes studied included delivery type (eg, cesarean, operative vaginal, spontaneous vaginal), indication for cesarean delivery, presence of obstetrical risk factors, and use of labor induction or augmentation.

RESULTS

The cesarean delivery rate of the study group (7.3%) was only 35% of the 1996 US rate of 20.7%. Among study participants, the relative risk of a primary cesarean delivery for dystocia was 0.22 (95% CI, 0.14, 0.35). Trial of labor after cesarean delivery was attempted by 93% of study participants compared with 42% of women nationwide in 1994. The cesarean delivery rates for women with diabetes in pregnancy (11.5% versus 35.4%) and preeclampsia (14.8% versus 37.4%) were significantly lower than nationwide rates. Case-mix analysis comparison with a standardized population and comparison of standard (ie, term, singleton, vertex) primiparous women demonstrate that the low rate of cesarean delivery was not because of a lower prevalence of risk factors.

CONCLUSIONS

The community's low rate of cesarean delivery is primarily the result of a decreased use of cesarean delivery for labor dystocia and an almost universal acceptance of trial of labor after cesarean delivery. Cultural attitudes toward childbirth, design of the perinatal system, and genetic factors also may explain the low rate of cesarean delivery.