The role of prophylactic antibiotic therapy for preterm labour and preterm prelabour rupture of the membranes.
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Amniocentesis↗
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Feeding readiness in preterm infants: the relationship between preterm behavioral state and feeding readiness behaviors and efficiency during transition from gavage to oral feeding.
PURPOSE: The purpose of this secondary analysis was to assess whether alert behavioral states were associated with an increased number of feeding readiness behaviors (FRBs) and whether the number of FRBs were associated with subsequent feeding efficiency in healthy premature infants born between 29 to 35 weeks gestation. STUDY DESIGN AND METHODS: The data were collected as part of a larger study designed to compare the frequency of FRBs and feeding efficiency between control and experimental groups. Data from 21 stable premature infants were included in this secondary analysis. Infants were videotaped immediately prior to each of the first three oral feedings, from which infant behavioral state (IBS) and FRBs were assessed. Feeding efficiency was determined by calculating the ratio of feeding intake to feeding duration. RESULTS: IBS was not a significant predictor of the number of FRBs. The number of FRBs was predictive of feeding efficiency (p <.05). Group assignment was a marginally significant predictor of feeding efficiency (p < .10). Infant sex (p < .05), birthweight (p < .01), gestational age at birth (p <.01), and gestational age at entry (p < .05) were identified as significant predictors of the number of FRBs. Group assignment was marginally significant (p < .10). CLINICAL IMPLICATIONS: Feeding efficiency may be predicted by the increased number of FRBs immediately prior to feeding. An infant's attributes (sex, birth-weight, and gestational age) may relate to feeding efficiency and should be assessed when instituting oral feeding. Assessment of FRBs can be easily incorporated into routine clinical practice.
Attention↗
The next steps forward in reducing the impact of preterm birth. Proceedings of the 2nd International Preterm Labour Congress. 2-4 September 2004, Montreux, Switzerland.
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Female↗
Is preterm milk tailored to the needs of a preterm infant?
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Dietary Proteins↗
Nutrition and feeding of preterm infants. Committee on Nutrition of the Preterm Infant, European Society of Paediatric Gastroenterology and Nutrition.
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Enteral Nutrition↗
Mortality in very preterm and very low birth weight infants according to place of birth and level of care: results of a national collaborative survey of preterm and very low birth weight infants in The Netherlands.
As part of a collaborative project in the Netherlands in 1983, for which data were collected on 1,338 newborn infants (less than 32 weeks' gestation and/or less than 1,500 g birth weight), all infants were assigned to one of three levels of care according to hospital of birth. Considerable centralization was achieved by antenatal and neonatal transport. Although the uncorrected mortality rates were similar, the mortality odds (adjusted for four and 22 potential confounding perinatal factors, respectively) were significantly higher in level 1 and level 2 hospitals compared with level 3 hospitals (tertiary perinatal care centers). By extending the facilities for full perinatal intensive care in level 3 centers and thus providing optimal care for all such infants, the overall mortality rate is expected to decrease further.
Female↗
What is the role of preterm breast milk supplementation in the host defenses of preterm infants? Science vs. fiction.
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Antibody Formation↗
Current understanding of genetic factors in preterm birth.
Several lines of evidence support a genetic predisposition to spontaneous preterm labour and preterm birth. Firstly, a leading risk factor for spontaneous preterm labour and preterm birth is a personal or family history. If a woman previously delivered preterm, her subsequent babies are also more likely to be born preterm. Women who experienced an early preterm birth (<32 completed weeks) in their first pregnancy have the highest rate of recurrent preterm birth in subsequent pregnancies. Spontaneous preterm labour and preterm birth in subsequent pregnancies tend to recur at equivalent gestational ages. If a woman herself was born preterm, she is also at an increased risk of spontaneous preterm labour and preterm birth, with the risks being highest for those women who themselves were born most preterm. This predisposition does not apply to men who were born preterm. Racial predispositions to preterm birth have also been observed. Black women suffer twice the rate of preterm birth compared with Caucasians, even when confounding social and economic variables are controlled. It is well established that upper genital tract infection and/or inflammation is seen in association with spontaneous preterm labour and preterm birth. Previous investigations have focussed primarily on an infectious aetiology for this finding. However, an alternative hypothesis has emerged, which suggests that this finding may represent an abnormal inflammatory response. The frequent association of spontaneous preterm labour and preterm birth with histological infection/inflammation and elevated body fluid concentrations of inflammatory cytokines has focussed investigations on single gene polymorphisms of these cytokines in both mother and fetus. The polymorphisms tumour necrosis factor-alpha-308 (TNF-alpha-308), interleukin-1beta (IL-1beta) + 3953/3954 and IL-6-174 have been most consistently associated with spontaneous preterm labour and preterm birth. Toll-like receptors (TLRs) are important components of the innate immune systems, which have also been linked to spontaneous preterm labour and preterm birth. Both maternal and fetal polymorphisms of the TLR-4 gene have been associated with spontaneous preterm labour and preterm birth in certain populations, but in others no apparent link has been observed. These findings confirm a clear genetic predisposition to spontaneous preterm labour and preterm birth and raise hopes that patient-specific therapies may be developed in the future.
Cytokines↗
Preterm premature rupture of membranes: risks of recurrent complications in the next pregnancy among a population-based sample of gravid women.
OBJECTIVE: The purpose of this study was to ascertain the predictive value of antecedent preterm premature rupture of membranes for recurrent preterm premature rupture of membranes and preterm delivery rates in the next pregnancy compared with background rates among a population-based sample of women at a single institution. STUDY DESIGN: Records of patients with index singleton pregnancies that were complicated by preterm premature rupture of membranes whose next delivery resulted in a delivery at >or=20 weeks at the same institution were reviewed for the incidence and gestational age of recurrent preterm premature rupture of membranes and preterm delivery. All subjects were patients of physicians whose obstetric practices were based at a single institution. Background rates of preterm premature rupture of membranes and preterm delivery in this population were generated from a systematically selected comparison group composed of the two deliveries after each of the study group's second delivery. RESULTS: The rates of recurrent preterm premature rupture of membranes (16.7%) and preterm delivery (34.2%) in the 114 study group patients were substantially greater (odds ratio, 20.6; 95% CI, 4.7-90.2; and odds ratio, 3.6; 95% CI, 2.1-6.4) than noted background rates (0.96% and 12.5%) but considerably less than the recurrence rates of either preterm premature rupture of membranes or preterm delivery that were reported by others. The gestational age of preterm premature rupture of membranes in the index pregnancy affected neither the magnitude of risk nor the gestational age of recurrent preterm premature rupture of membranes or preterm delivery in the subsequent pregnancy. Stratification of outcome measures into three subgroups that were based on the gestational age of index preterm premature rupture of membranes demonstrated no significant differences in the incidence of preterm premature rupture of membranes or preterm delivery. CONCLUSION: After a pregnancy that was complicated by preterm premature rupture of membranes, the risk for recurrent preterm premature rupture of membranes is increased by 20-fold and for recurrent preterm delivery by almost 4-fold. Gestational age of antecedent preterm premature rupture of membranes is predictive of neither risk nor timing of recurrent complications. Estimates of recurrence risks appear to be moderated by limiting analysis to a population-based sample of gravid women when compared with previous studies.
Adult↗
[Risk factors for preterm labor].
OBJECTIVES: Most studies investigating preterm risk factors include medically induced preterm labor due to fetal or maternal complications and do not distinguish preterm labor from preterm premature rupture of membranes. Thus, the objective of this study was to determine the proportion of the three types of preterm birth and identify risk factors for spontaneous preterm labor in a sample of pregnant women who delivered at two level III units. STUDY DESIGN: From January to October 1996, we interviewed 385 women with live preterm newborns and, as controls, 357 mothers of term newborns. Preterm births were classified as preterm labor, preterm premature rupture of membranes and iathrogenic preterm. Independent associations between maternal sociodemographic, constitutional, nutritional and obstetric characteristics and preterm labor were identified using logistic regression analysis. RESULTS: In this sample of preterm births, 29% corresponded to preterm labor, 49% to preterm premature rupture of the membranes and 22% were iathrogenic preterm. The identified risk factors for preterm labor were multiple gestation, no paid work during pregnancy, less than six prenatal care visits, arm circumference less than 26 cm and previous preterm or low birth-weight. Gestational bleeding during the first or third trimester was significantly associated with preterm labor. CONCLUSIONS: As previously recognized, multiple gestation, prior preterm or low birthweight and gestational bleeding are established risk factors for preterm labor. However, prenatal care, maternal work and nutritional status have also been revealed as important issues in preterm risk, deserving special interest since they are susceptible to preventive intervention.
Adult↗
Risk factors for preterm birth subtypes.
To assess epidemiologic risk factors for preterm birth subcategories in an urban population, we undertook a study of 31,107 singleton livebirths that took place at Mount Sinai Hospital in New York City between 1986 and 1994. We subdivided the preterm births into preterm premature rupture of the membranes, preterm labor, and medically induced births. We obtained information regarding the preterm subtypes and their epidemiologic risk factors from a computerized perinatal database. Adjusted odds ratios showed an increased risk for all three preterm birth subtypes in women who were black (1.9 for preterm premature rupture of membranes, 2.1 for preterm labor, and 1.7 for medically induced births) or Hispanic (1.7 for preterm premature rupture of membranes, 1.9 for preterm labor, and 1.6 for medically induced births), those who had had a previous preterm birth (3.2 for preterm premature rupture of membranes, 4.5 for preterm labor, and 3.3 for medically induced births), those who began prenatal care after the first trimester ( 1.4 for preterm premature rupture of membranes, 1.3 for preterm labor, and 1.3 for medically induced births), women who had been exposed to diethylstilbestrol in utero (3.1 for preterm premature rupture of membranes, 4.1 for preterm labor, and 3.7 for medically induced births), patients with preexisting diabetes mellitus (2.2 for preterm premature rupture of membranes, 2.4 for preterm labor, and 9.5 for medically induced births), and those with antepartum bleeding (2.8 for preterm premature rupture of membranes, 3.6 for preterm labor, and 3.7 for medically induced births). Other sociodemographic, constitutional, life-style, and obstetrical characteristics differed across the groups. Variation in some of the risk factors among the preterm subtypes implies that epidemiologic assessment of the more specific outcomes would be advisable.
Adolescent↗
Classification and heterogeneity of preterm birth.
Three main conditions explain preterm birth: medically indicated (iatrogenic) preterm birth (25%; 18.7-35.2%), preterm premature rupture of membranes (PPROM) (25%; 7.1-51.2%) and spontaneous (idiopathic) preterm birth (50%; 23.2-64.1%). The majority of multiple pregnancies (10% of all preterm births) are delivered preterm (50% for medical reasons). Although medical indications relate more to feto-maternal conditions, PPROM to infections and idiopathic preterm birth to lifestyle, these risk factors are identified in any category, emphasising that preterm birth has a multifactorial origin. Still, several incidences of preterm birth are not completely explained with a plausible cause for PPROM or spontaneous preterm labour suggesting that other causes have yet to be identified. In addition, preterm birth is associated with unrecognised severe congenital anomalies. Variability within the main categories may be explained by the studied population, ethnic group, social class and preventive interventions towards reducing spontaneous preterm birth where the proportion of medically-indicated preterm birth is increased. Despite being retrospective a classification according to gestational age at birth is important for neonatal prognosis. Preterm birth is stratified into mild preterm (32-36 weeks), very preterm (28-31 weeks) and extremely preterm (<28 weeks) with increasing neonatal mortality and morbidity. Recent studies suggested that infection was mostly responsible for extreme preterm birth, while stress and lifestyle accounted for mild preterm birth, and a mixture of both conditions contributed to very preterm birth.
Female↗
Cardiovascular malformations among preterm infants.
OBJECTIVE: Preterm birth and cardiovascular malformations are the 2 most common causes of neonatal and infant death, but there are no published population-based reports on the relationship between them. We undertook this study to determine the prevalence and spectrum of cardiovascular malformations in a preterm population, the prevalence of prematurity among infants with cardiovascular malformations, and the influence of prematurity and cardiovascular malformations on outcomes. METHODS: We based the study on the population of the former Northern Health Region of England. We identified all live-born infants with cardiovascular malformations diagnosed in the first 1 year of life from the regional pediatric cardiology database, which includes the gestational age and details of the diagnosis. We limited ascertainment to malformations diagnosed by the age of 12 months. Infants with isolated patent ductus arteriosus or atrial septal defect were excluded, to avoid ascertainment bias. Infants with ventricular septal defect were classified according to whether they required surgery in the first 1 year. There are no population data on gestational ages for all births in our population for the era of this study; therefore, we used data published in the literature for populations similar to our own to predict that 0.4% of live births occur at <28 weeks of gestation, 0.9% at 28 to 31 weeks, and 6% at 32 to 36 weeks. Overall, 7.3% of live-born infants are preterm. RESULTS: Of 521619 live-born infants in 1987-2001, 2964 had cardiovascular malformations (prevalence: 5.7 cases per 1000 live births). Cardiovascular malformations were present at 5.1 cases per 1000 term infants and 12.5 cases per 1000 preterm infants. The odds ratio (OR) for a cardiovascular malformation in prematurity was 2.4 (95% confidence interval [CI]: 2.2-2.7). We found that 474 infants (16%) with cardiovascular malformations were born at <37 weeks of gestation, giving an OR for prematurity among infants with a cardiovascular malformation of 2.4 (95% CI: 2.2-2.7). More infants were born preterm with diagnoses of pulmonary atresia with ventricular septal defect (23%), complete atrioventricular septal defect (22%), and coarctation of the aorta, tetralogy of Fallot, and pulmonary valve stenosis (each 20%). Fewer were born preterm with diagnoses of pulmonary atresia and intact ventricular septum (7%), transposition of the great arteries (8%), and single ventricle (9%). We found that 18% of infants with ventricular septal defect requiring surgery were preterm, compared with 13% in the nonsurgical group. Preterm infants with ventricular septal defect required surgery in 30% of cases, compared with 23% of term infants with ventricular septal defect. These figures show that the excess of cardiovascular malformations among preterm infants cannot be explained by greater ascertainment of minor ventricular septal defects. In our denominator population, 646 live-born infants were recognized as having trisomy 21, and gestational age data were available for 609. Of these, 149 (25%; 95% CI: 21-28%) were preterm. Approximately two thirds of infants with complete atrioventricular septal defect have trisomy 21. Complete atrioventricular septal defect was no more common among preterm infants with trisomy 21 (16%) than among term infants with trisomy 21. However, the increased incidence of prematurity among infants with trisomy 21 probably explains some of the excess of preterm births among infants with complete atrioventricular septal defect. Only 4 (11%) of 38 infants with 22q11 deletion were born preterm. None of those infants had pulmonary atresia with ventricular septal defect; therefore, 22q11 deletion does not explain the excess of preterm births in pulmonary atresia with ventricular septal defect. The OR for death in the first 1 year in the presence of a cardiovascular malformation was 4.4 (95% CI: 3.1-5.5) overall; ORs were 1.8 at <28 weeks of gestation, 3.7 at 28 to 31 weeks, 11.0 at 32 to 36 weeks, and 35.6 at term. CONCLUSIONS: This study showed that preterm infants have more than twice as many cardiovascular malformations as do infants born at term and that 16% of all infants with cardiovascular malformations are preterm. It also showed, not surprisingly, that there is an increased mortality rate among infants born preterm with a cardiovascular malformation. The additional effect of cardiovascular malformations on mortality rates is most marked for term and near-term infants, for whom mortality rates are otherwise low. The excess of cardiovascular malformations among preterm infants is intriguing but not easy to explain. Previous studies of birth weight among infants with cardiovascular malformations reported a significant increase in the likelihood of being small for gestational age among infants with tetralogy of Fallot, complete atrioventricular septal defect, hypoplastic left heart, or large ventricular septal defect. There is an obvious relationship between birth weight and gestational age, and those studies also showed an increased prevalence of prematurity among infants with tetralogy of Fallot, pulmonary stenosis, aortic stenosis, coarctation of the aorta, complete atrioventricular septal defect, or ventricular septal defect. There is also a high prevalence of cardiovascular malformations among late stillbirths, with major differences in the number and spectrum of cardiovascular malformations, compared with those seen in postnatal life. In particular, there is a greater incidence of coarctation of the aorta, double-inlet left ventricle, hypoplastic left heart, truncus arteriosus, double-outlet right ventricle, and atrioventricular septal defect among stillbirths. This spectrum of malformations is similar to that in our study and to those in other reports. Whether the increased prevalence of cardiovascular malformations among preterm infants and the increase in stillbirths suggest clues to the cause is difficult to say. The influence of preterm birth should be taken into account in risk assessment and risk stratification for surgical repair.
Heart Defects, Congenital↗
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.
Adult↗
The influence of gestational age and smoking habits on the risk of subsequent preterm deliveries.
BACKGROUND: Previous preterm delivery and maternal smoking are associated with increased risks of preterm delivery. It is not known whether gestational age at the time of a preterm delivery is correlated with gestational age in successive preterm deliveries and whether changes in smoking habits influence the subsequent risk of preterm delivery. METHODS: We studied the associations among smoking habits, previous very preterm or moderately preterm delivery (before 32 weeks and at 32 to 36 weeks, respectively), and the risk of a subsequent very preterm or moderately preterm delivery in a population-based cohort of 243,858 women in Sweden between 1983 and 1993. The results were adjusted for covariates known to be associated with preterm delivery. RESULTS: The odds ratios for very or moderately preterm delivery in a subsequent pregnancy among women with a previous very preterm delivery, as compared with women who had a previous term delivery, were 12.4 (95 percent confidence interval, 9.1 to 17.0) and 7.1 (95 percent confidence interval, 6.0 to 8.4), respectively. Among women with a previous moderately preterm delivery, the corresponding odds ratios were 2.3 (95 percent confidence interval, 1.9 to 3.0) and 5.9 (95 percent confidence interval, 5.5 to 6.3), respectively. The odds ratios for a very preterm second delivery among the women who smoked 1 to 9 cigarettes per day and those who smoked 10 or more cigarettes per day, as compared with nonsmokers, were 1.4 (95 percent confidence interval, 1.1 to 1.7) and 1.6 (95 percent confidence interval, 1.3 to 2.0), respectively. The corresponding odds ratios for moderate preterm delivery were 1.3 (95% confidence interval, 1.2 to 1.4) and 1.5 (95 percent confidence interval, 1.4 to 1.6). The women who quit smoking between pregnancies were not at increased risk for very or moderately preterm delivery, whereas the women who started to smoke in the second pregnancy had the same risk as those who continued to smoke. CONCLUSIONS: The risk of a very preterm delivery in successive pregnancies is increased primarily among women with a previous very preterm delivery. Changes in smoking habits influence the risk of preterm delivery as well.
Adult↗
Physical load and psychological demand at work during pregnancy and preterm birth.
OBJECTIVES: To evaluate the effect of physical workload and psychological demand on all preterm births, and to determine whether these risk factors have the same effect on different types of preterm birth (moderate versus very preterm birth) and different modes of delivery onset (spontaneous versus indicated preterm birth). METHODS: A case-control study was carried out in two public general hospitals in the Valencia Region, Spain. All preterm births (228) which occurred between 22 and 36 completed weeks of amenorrhea and 348 controls of 37 or more completed weeks of amenorrhea were included. The information was collected by interviewing women within 2 days of their giving birth. Physical workload, psychological demand, weekly working hours and daily time spent commuting between home and work were used as explanatory variables. A polytomous logistic regression was carried out. RESULTS: Exposure to medium or high level physical workload increases the risk of preterm birth, with an adjusted odds ratio (OR) of 1.59 and 2.31, respectively. The risk of moderate preterm birth was greater in women with a medium or high level of physical workload, OR: 1.73 and 2.35, respectively. The same trend was observed for very preterm birth. Physical workload showed a different effect on spontaneous and indicated preterm birth. The exposure to medium and high level physical workload increases the risk of indicated preterm birth, with an OR of 2.74 and 3.88, respectively. The same trend was seen in the case of spontaneous preterm birth. Psychological demands were not associated with preterm birth. CONCLUSIONS: High physical exertion increases the risk of preterm birth in Spain. The magnitude of the effect of physical workload on moderate and very preterm birth is similar, but is higher on indicated preterm birth than on spontaneous preterm birth. Psychological demands show no effect on the risk of preterm birth.
Child↗
Indicated versus spontaneous preterm delivery: An evaluation of neonatal morbidity among infants weighing </=1000 grams at birth.
OBJECTIVE: The aim of the study was to determine whether infants weighing </=1000 g after birth who are born to women who undergo indicated preterm delivery have different neonatal outcomes than do those born as a result of either spontaneous preterm labor or preterm premature rupture of membranes. STUDY DESIGN: In a 1-year observational study (1992-1993) the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network collected outcome data for 799 infants whose birth weights were </=1000 g. Only singleton infants with gestational age >20 weeks who were not produced as the result of an induced abortion were included. Our analysis was further limited to infants without major congenital anomalies who survived >2 days, were deemed potentially viable by the obstetrician, and would have undergone a cesarean delivery for fetal indications (N = 411). The primary reason for delivery was categorized as indicated delivery, spontaneous preterm labor, or spontaneous preterm premature rupture of membranes. Selected neonatal outcomes were evaluated among infants born to women in each of these groups. Logistic regression analyses were used to control for the effects of other potentially confounding variables. RESULTS: A total of 156 of the 411 infants were born to women who underwent an indicated preterm delivery, whereas 160 were born after spontaneous preterm labor and 95 were delivered after preterm premature rupture of membranes. Univariate analyses revealed significantly lower incidences of grade III or IV intraventricular hemorrhage, grade III or IV retinopathy of prematurity, and seizure activity among infants born in an indicated preterm delivery than among those born after spontaneous preterm labor or preterm premature rupture of membranes. However, infants of women who underwent indicated preterm delivery had a more advanced mean gestational age at birth than did those born after spontaneous preterm labor or preterm premature rupture of membranes (28 +/- 2 weeks, 26 +/- 2 weeks, and 26 +/- 1 weeks, respectively, P <.001). Multiple logistic regression analysis was therefore used to control for the disparity in gestational age. Multivariate analyses did not confirm the apparent improvement in neonatal outcome in the indicated delivery group. CONCLUSION: In this population of infants weighing </=1000 g, selected neonatal outcomes did not differ according to birth by indicated preterm delivery, spontaneous preterm labor, or preterm premature rupture of membranes.
Adult↗
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.
Adult↗