Risk Of Spontaneous Preterm Labor Research Articles

Impact of isolated fetal congenital heart disease on pregnancy and perinatal outcomes.

The aim of the present study was to evaluate the obstetric complications associated with isolated fetal congenital heart disease (CHD) by comparing pregnancies with and without this condition. In this retrospective matched comparative study at Siriraj Hospital, Thailand, we included 233 postnatally confirmed fetal CHD cases and 466 unaffected fetuses. Controls were selected at a 2:1 ratio, ensuring that they matched the cases in terms of maternal age, parity, and history of preterm deliveries. Fetal CHD was significantly associated with an increased risk of spontaneous preterm labor (30% vs 9.7%; adjusted odds ratio [aOR] 2.42; 95% confidence interval [CI]: 1.35-4.36; P = 0.003), delivery before 34 gestational weeks (11.6% vs 0.6%; aOR 12.33; 95% CI: 3.32-45.78; P < 0.001), and pre-eclampsia (11.6% vs 2.8%; aOR 2.19; 95% CI: 1.01-4.76; P = 0.047). Newborns with CHD were significantly more likely to be small for gestational age (10.7% vs 5.2%; aOR 2.09; 95% CI: 1.11-3.94; P = 0.022). Intriguingly, a prenatal diagnosis of CHD was associated with a reduced risk of preterm delivery in affected pregnancies (P = 0.002). Pregnancies affected by isolated fetal CHD demonstrated a higher propensity for several adverse outcomes. These findings underscore the importance of prenatal CHD detection and tailored perinatal care to potentially improve both pregnancy outcomes and neonatal health.

Beyond stillbirth: association of intrahepatic cholestasis of pregnancy severity and adverse outcomes

Intrahepatic cholestasis of pregnancy is associated with adverse pregnancy outcomes, including sudden fetal cardiac arrhythmias, resulting in stillbirth. This association has been correlated with the total bile acid levels, which are a marker for disease severity. Studies are yet to determine if intrahepatic cholestasis of pregnancy severity is also associated with increased rates of other adverse neonatal outcomes. This study aimed to determine whether pregnancies complicated by intrahepatic cholestasis of pregnancy show a bile acid severity-based relationship with other adverse obstetrical outcomes beyond stillbirth alone. This was a retrospective cohort study of singleton, nonanomalous gestations complicated by intrahepatic cholestasis of pregnancy at the Elmhurst Hospital Center from 2005 to 2019. Severity was defined by the peak total bile acid levels (μmol/L): mild (10-19), low moderate (20-39), high moderate (40-99), and severe (>100). We examined the rates of spontaneous preterm labor, fetal growth restriction, preterm prelabor rupture of membranes, iatrogenic preterm birth, meconium-stained amniotic fluid, cesarean delivery for nonreassuring fetal heart tracing, umbilical artery pH, neonatal intensive care unit admission, and neonatal birthweight. The chi-square, Fisher exact, Student t, Mann-Whitney, and multivariate regression tests were used to determine the association of intrahepatic cholestasis of pregnancy severity and adverse neonatal outcomes. In all analyses, mild severity was used as the base comparator. A P value of <.05 and 95% confidence interval not crossing 1.00 indicated statistical significance. Of the 1202 pregnancies complicated by intrahepatic cholestasis of pregnancy, 306 (25.5%) were mild, 449 were low moderate (37.4%), 327 were high moderate (27.2%), and 120 were severe (10.0%). After adjusting for confounders, progressive intrahepatic cholestasis of pregnancy severity was associated with an increased risk of spontaneous preterm labor (low moderate adjusted odds ratio, 1.60; 95% confidence interval, 0.76-3.38; high moderate adjusted odds ratio, 3.49; 95% confidence interval, 1.69-7.22; severe adjusted odds ratio, 6.58; 95% confidence interval, 2.97-14.55), iatrogenic preterm birth (low moderate adjusted odds ratio, 1.54; 95% confidence interval, 0.95-2.52; high moderate adjusted odds ratio, 3.11; 95% confidence interval, 1.91-5.06; severe adjusted odds ratio, 4.94; 95% confidence interval, 2.81-8.71), and meconium-stained amniotic fluid (low moderate adjusted odds ratio, 1.33; 95% confidence interval, 0.75-2.36; high moderate adjusted odds ratio, 2.63; 95% confidence interval, 1.48-4.65; severe adjusted odds ratio, 3.91; 95% confidence interval, 1.98-7.69). There was no significant association between intrahepatic cholestasis of pregnancy severity and other adverse outcomes. The findings suggest that intrahepatic cholestasis of pregnancy disease severity is associated with an increased risk of spontaneous preterm labor, iatrogenic preterm birth, and meconium-stained amniotic fluid. These findings provide valuable insight toward patient anticipatory counseling.

The vaginal microbiome and the risk of preterm birth: a systematic review and network meta-analysis

Preterm birth is a major cause of neonatal morbidity and mortality worldwide. Increasing evidence links the vaginal microbiome to the risk of spontaneous preterm labour that leads to preterm birth. The aim of this systematic review and network meta-analysis was to investigate the association between the vaginal microbiome, defined as community state types (CSTs, i.e. dominance of specific lactobacilli spp, or not (low-lactobacilli)), and the risk of preterm birth. Systematic review using PubMed, Web of Science, Embase and Cochrane library was performed. Longitudinal studies using culture-independent methods categorizing the vaginal microbiome in at least three different CSTs to assess the risk of preterm birth were included. A (network) meta-analysis was conducted, presenting pooled odds ratios (OR) and 95% confidence intervals (CI); and weighted proportions and 95% CI. All 17 studies were published between 2014 and 2021 and included 38–539 pregnancies and 8–107 preterm births. Women presenting with “low-lactobacilli” vaginal microbiome were at increased risk (OR 1.69, 95% CI 1.15–2.49) for delivering preterm compared to Lactobacillus crispatus dominant women. Our network meta-analysis supports the microbiome being predictive of preterm birth, where low abundance of lactobacilli is associated with the highest risk, and L. crispatus dominance the lowest.

Maternal serum vitamin D and spontaneous preterm birth

Poor maternal vitamin D status is associated with adverse pregnancy outcomes such as preeclampsia, gestational diabetes. And increased risk of caesarean delivery. The authors conducted a prospective observational study to determine the association between maternal serum vitamin D levels and spontaneous preterm delivery. Pregnant women between 26 and 34 weeks of gestation, with symptoms of preterm labour were recruited. The control group consisted of healthy pregnant women of similar gestation age. The maternal serum vitamin D and calcium levels were measured and all women were followed up until delivery. The patients’ demographics data and their respective perinatal outcomes were collected and analysed. A total of 161 women were recruited for the study. The prevalence of vitamin D deficiency, insufficiency, and sufficiency were 41.3%, 50.9%, and 6.8% respectively (p &lt; 0.001). The mean maternal serum vitamin D for control, threatened preterm labour, and preterm birth group were 26.5 ± 3.8 ng/mL, 17.9 ± 8.0 ng/mL, and 13.5 ± 6.98 ng/mL respectively (p &lt; 0.001). There were no significant differences in the means of serum vitamin D among women with or without antenatal complications, such as gestational diabetes, gestational hypertension or preeclampsia. Vitamin D level was positively correlated with gestational age at delivery (p &lt; 0.001) and newborn weight (p &lt; 0.001). Vitamin D deficiency is associated with increased risk of spontaneous preterm labour, although there is no strong evidence of correlation with other antenatal complications. In view of high prevalence of vitamin D deficiency and insufficiency in this population, routine supplement of vitamin D maybe beneficial in reduction of premature births.

Effect of cell-free fetal DNA on spontaneous preterm labor

Inflammatory phenomenon, including cell-free fetal DNA (cffDNA), is one of the various causes of preterm delivery. Always, there is a trend in the prediction and prevention of preterm labor. Herein, the aim of this study is to assess the value of cffDNA levels in serum of pregnant women for prediction of spontaneous preterm labor. A case–control study with nonrandomized convenience sampling was conducted. One hundred women qualifying for the study were enrolled. The participants were divided into two groups of healthy nulliparous pregnant women (n = 50) and nulliparous pregnant women experiencing preterm labor (n = 50). Then, venous blood was sampled from each participant and its plasma was separated and analyzed. The mean age of women in the experimental group was 22.90 years with the standard deviation of 4.04, while in the control group these two values were 23.78 and 4.37, respectively. In the experimental group, 29 patients (58%), and in the control group, 27 patients (54%) had cffDNA. The mean of the counted DNA in the experimental group was 2080/03 with the standard deviation of 909/792 while the same values for the control group were 1183/26 and 620/720, in the same order. The statistical analysis revealed that this difference was meaningful at P = 0.001. Furthermore, in the experimental group, cffDNA increased with increase in the age and the difference was meaningful. Finally, increasing pregnancy age in the experimental group led to an increase in the number of cffDNA (P = 0.001). The results of this study indicated that the cumulative frequency of preterm labor for women with positive cffDNA was significantly higher. High levels of cells' DNA in the serum of pregnant mothers increase the risk of spontaneous preterm labor. These observations may have implications for preterm labor.

Risk of spontaneous preterm labor in pregnancies achieved by in vitro fertilization and complicated with severe form of ovarian hyperstimulation syndrome: A case control study.

Objectives:The purpose of this study was to examine the potential impact of severe Ovarian hyper stimulation syndrome (OHSS) on the risk of preterm birth. Severe ovarian hyperstimulation syndrome is a serious complication in the methods of in vitro fertilization. The pathophysiology of this process is not clear enough and the treatment is symptomatic. Human chorionic gonadotropin (h-CG) is the most important known cause of this condition. Findings of other authors often do not match when it comes to complications that may occur in pregnancy.Methods:In the Gynecology and Obstetrics Clinic “Narodni Front” a case control study was conducted on 50 female patients with severe forms of OHSS in the period from January 2008 to March 2015. A control group was created based on age and it involved 59 patients with pregnancy achieved with IVF/ICSI during the same period, but in which OHSS did not occur.Results:Patients with the pregnancy complicated by OHSS, had a considerably higher rate of preterm labor, whether this was labor before gestation week 37 (56.0% vs. 30.5%) or before gestation week 34 (34.0% vs. 6.8%); significantly lower weight of newborns, as in the newborns with low body weight <2500g (45.6% vs. 25.0%) and specially in the newborn with very low body weight <1500 grams (19.1% vs. 3.8%), as well as preterm premature rupture of membranes (PPROM), (11.76% vs. 1.59%).Conclusions:Pregnancy achieved by the IVF/ICSI method in which severe form of OHSS has been developed could have an increased risk of preterm birth.

The relationship between lipid profiles in pregnancy and preterm delivery: a systematic review

Background: High-density lipoprotein (HDL), low-density lipoprotein (LDL), triglyceride (TG), and total cholesterol (TC) are associated with maternal hormonal changes which can lead to pregnancy complications. High lipid levels during pregnancy may be accompanied by an increased risk of spontaneous preterm labor. The purpose of this review was to determine the relationship between lipid profiles in pregnancy and preterm delivery.&#x0D; Methods: A systematic search was performed in PubMed, EMBASE, Web of Science, Scopus, and Science Direct databases to find cross-sectional, case-control, and cohort studies on the associations between lipid profiles in pregnancy and preterm delivery. The search results were limited to papers published during 2000-2018. The quality of the selected studies was assessed based on the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist. Finally, a total of 25 eligible high-quality papers were reviewed.&#x0D; Results: A high maternal TG level in the first trimester of pregnancy was identified as a significant risk factor for preterm delivery. Low TG, HDL-cholesterol (HDL-C) and LDL-cholesterol (LDL-C) levels were uniquely associated with an increased risk of preterm delivery. High TC, TG, and LDL-C levels increased the risk of spontaneous preterm labor. A further association was found between high TG and TC levels and an elevated risk of preterm labor before 34 weeks of gestation. The risk of preterm labor before 34 weeks and during the 34th-37th weeks of gestation increased with increasing TG and TC levels. Moreover, overweight women who had a delivery before 34 weeks exhibited significant increases in TC and LDL concentrations during early pregnancy.&#x0D; Conclusion: Lipid metabolism undergoes complicated changes in pregnancy. Lipid levels (LDL, HDL, TC, and TG) above or below the normal range during pregnancy increase the risk of preterm delivery. Considering the significance of maternal lipid metabolism in the incidence of preterm delivery, lipid profile screening in early pregnancy can largely contribute to the prevention of preterm delivery. Further studies are warranted to meticulously examine the effects of lipid profile on preterm delivery.

PP.02 Effect of Method and Gestational Age at Termination of Pregnancy on Future Obstetric and Perinatal Outcomes: A Retrospective Cohort Study

Induced abortion (IA) is believed to increase the risk of spontaneous preterm labour. Few studies have investigated the impact of method used (medical versus surgical) or the gestational age at...

Limited Relationship between Cervico-Vaginal Fluid Cytokine Profiles and Cervical Shortening in Women at High Risk of Spontaneous Preterm Birth

ObjectiveTo determine the relationship between high vaginal pro-inflammatory cytokines and cervical shortening in women at high risk of spontaneous preterm labor and to assess the influence of cervical cerclage and vaginal progesterone on this relationship.MethodsThis prospective longitudinal observational study assessed 112 women with at least one previous preterm delivery between 16 and 34 weeks’ gestation. Transvaginal cervical length was measured and cervico-vaginal fluid sampled every two weeks until 28 weeks. If the cervix shortened (<25 mm) before 24 weeks’ gestation, women (cases) were randomly assigned to cerclage or progesterone and sampled weekly. Cytokine concentrations were measured in a subset of cervico-vaginal fluid samples (n = 477 from 78 women) by 11-plex fluid-phase immunoassay.ResultsAll 11 inflammatory cytokines investigated were detected in cervico-vaginal fluid from women at high risk of preterm birth, irrespective of later cervical shortening. At less than 24 weeks’ gestation and prior to intervention, women destined to develop a short cervix (n = 36) exhibited higher cervico-vaginal concentrations than controls (n = 42) of granulocyte-macrophage colony-stimulating factor [(GM-CSF) 16.2 fold increase, confidence interval (CI) 1.8–147; p = 0.01] and monocyte chemotactic protein-1 [(MCP-1) 4.8, CI 1.0–23.0; p = 0.05]. Other cytokines were similar between cases and controls. Progesterone treatment did not suppress cytokine concentrations. Interleukin (IL)-6, IL-8, granulocyte colony-stimulating factor (G-CSF), interferon (IFN)-γ and tumour necrosis factor (TNF)-α concentrations were higher following randomization to cerclage versus progesterone (p<0.05). Cerclage, but not progesterone treatment, was followed by a significant increase in cervical length [mean 11.4 mm, CI 5.0–17.7; p<0.001].ConclusionsAlthough GM-CSF and MCP-1 cervico-vaginal fluid concentrations were raised, the majority of cervico-vaginal cytokines did not increase in association with cervical shortening. Progesterone treatment showed no significant anti-inflammation action on cytokine concentrations. Cerclage insertion was associated with an increase in the majority of inflammatory markers and cervical length.

Periodontal disease and bacterial vaginosis as genetic and environmental markers for the risk of spontaneous preterm labor and preterm birth

Objective. The aim of this study was to review the evidence associating periodontal disease, and bacterial vaginosis with preterm birth, and the link with gene polymorphism, as well as the preventions and interventions which might reduce the risk of spontaneous preterm labor and preterm births in women with periodontal disease and/or bacterial vaginosis.Background. Preterm birth accounts for 70% of perinatal mortality, nearly 50% of long term neurological morbidity, and a significant impact on health care costs. There is evidence that spontaneous preterm labor and preterm birth are associated with intrauterine infection due to abnormal genital and/or oral colonization. Periodontal disease and bacterial vaginosis share microbiological similarities, and both conditions are associated with spontaneous preterm labor and preterm birth. In addition, periodontal disease and bacterial vaginosis have been linked through gene polymorphism.Methods. A review of the literature using widely accepted scientific search engines in English language.Results. Studies evaluating antibiotic administration to eradicate periodontal disease and/or bacterial vaginosis responsible organisms, and minimize the risk of preterm births have yielded conflicting results. With respect to bacterial vaginosis, the timing and the choice of antibiotic administration might partly explain the conflicting results. The use of scaling and/or root planning for women with periodontal disease appears to reduce the risk of preterm birth, but routine administration of antibiotics has not demonstrated any impact on preterm birth.Conclusion. Prospective studies evaluating the association of gene polymorphism with preterm birth, and the contribution of periodontal disease and bacterial vaginosis are needed.

12-INFLUENCE OF BODY MASS INDEX ON THE INCIDENCE OF PRETERM LABOUR

Nutritional status of the women has been considered as an important prognostic indicator of pregnancy outcome and risk of preterm birth. Few studies have evaluated the patterns of body mass index in developing regions where malnutrition and poor weight gain as well as maternal obesity have significant influences on the pregnancy outcome. This study aims to show the effect of pregnancy body mass index on the incidence of preterm labour. This is a prospective descriptive study of 200 women attended Basrah Maternity and Child Hospital who were diagnosed with preterm labour were recruited in the study. Patients were classified into categories that were based on their body mass index (BMI) according to the national institute of health guidelines. Rate of spontaneous preterm birth were determined. Women with body mass index /35kg/m2 had 2%of spontaneous preterm labour. Risk of spontaneous preterm labour tend to progressively decrease with increasing body mass index. Thinner women who have preterm delivery tend to deliver at earlier gestational age than women who were obese 42.3% of non obese women deliver before 30 weeks of gestation compared to 25% of the obese, 44% of non obese deliver at gestational age 30-40 weeks compared to 28.25 of the obese. In conclusion, high body mass index is associated with a lower rate of spontaneous preterm birth.

Effect of Older Maternal Age on the Risk of Spontaneous Preterm Labor: A Population-Based Study

To determine if older maternal age (35 years and older) at first birth was an independent risk factor for spontaneous preterm labor, we conducted a retrospective population-based cohort study. Using provincial perinatal data, we developed separate risk models for low- and high-risk women using multivariate logistic regression. We found that older maternal age exerted a direct and independent effect on spontaneous preterm labor for both nulliparous women with no preexisting chronic illnesses or pregnancy complications (low-risk) and nulliparous women who did not have any preexisting chronic illnesses, but developed one or more pregnancy complications (high-risk).

Mid‐trimester amniotic fluid C‐reactive protein, ferritin and lactate dehydrogenase concentrations and subsequent risk of spontaneous preterm labour

Preterm delivery is a serious problem in obstetrics. A pre-existing inflammation in the first half of gestation has been proposed as a possible condition that leads to preterm delivery. Our aim was to compare C-reactive protein (CRP), ferritin and lactate dehydrogenase (LDH) concentrations in mid-trimester amniotic fluid of patients with preterm and term deliveries and to found out their predictive values for preterm delivery. The study was conducted on 90 pregnant women who underwent genetic amniocentesis between the 15th and the 20th weeks of gestation. The samples were carried immediately to the laboratory for cytogenetic and biochemical examination. Non-parametric tests and receiver-operating characteristic curve analysis were used for statistical purpose. This study showed women with preterm delivery at < 37 weeks (n = 17) had a higher median of amniotic fluid LDH concentration than those women who delivered at term (n = 73) (P = 0.003). Amniotic fluid LDH concentration of > 120 IU/L had a sensitivity of 59% and a specificity of 81% in the prediction of spontaneous preterm delivery at < 37 weeks. Maternal serum alpha-fetoprotein levels were higher in patients delivered preterm compared with term deliveries (P = 0.036). Mid-trimester LDH is found to be quite effective in the prediction of preterm delivery. Pre-existing intrauterine inflammatory process early in gestation may be an important risk factor for preterm delivery.

Maternal anaemia and preterm birth: a prospective cohort study

The role of maternal anaemia in preterm birth remains poorly defined, and the association between anaemia and preterm birth clinical subtypes remain unclear. We examined if maternal anaemia exposure both within and across trimesters during gestation is associated with preterm birth. This was a secondary analysis of data from a population-based prospective cohort study in 13 counties of East China (1993-96). All singleton live births delivered at 20-44 weeks to women with at least one haemoglobin measure during pregnancy were included (n = 160 700). Risk of preterm birth (<37 weeks) was examined by clinical subtypes, namely, preterm premature rupture of membranes (PROM), spontaneous preterm labour and medically indicated preterm birth. Haemoglobin changes across trimesters were assessed as proxy of haemo-dilution and haemo-concentration. Multivariable Cox proportional hazards regression models were fitted. Preterm birth rates of preterm birth were 4.1% for anaemic and 5% for non-anaemic women (P < 0.05). Compared with haemoglobin of 11 g/dl (reference), values <or=5 g/dl in the first trimester were associated with increased risk for preterm PROM [hazard ratio (HR) 3.3, 95% confidence interval (CI) 1.4-7.7], whereas low haemoglobin in the third trimester was associated with reduced risk of spontaneous preterm labour. Haemodilution was associated with reduced risk for preterm birth. Anaemia in early pregnancy was found to be associated with increased risk for preterm PROM, whereas exposure in late pregnancy was associated with reduced risk for spontaneous preterm labour.

Examination of the Association Between Male Gender and Preterm Delivery

There is a small but consistent excess of preterm births of male fetuses. Compared to female fetuses, male fetuses are also at increased risk of congenital malformations, miscarriage, delivery by cesarean section, need for resuscitation and intensive care at birth, death at birth, and development of cerebral palsy early in life. Several possible risk factors for male preterm delivery have been proposed. This retrospective study tested potential risk factors for male preterm births by reviewing a database of all deliveries >23 weeks’ gestation occurring over an 11-year period at a teaching hospital. Demographic, antenatal, intrapartum, and outcome variables for preterm male and female neonates born at 3 different gestational age ranges were compared: extremely preterm (24–28 weeks), severely preterm (29–32 weeks), and moderately preterm (33–36 weeks). Exclusions included pregnancies with major congenital abnormalities, terminations, multiple pregnancies and those with fetuses of indeterminate gender. Odds ratios (OR) with 95% confidence intervals (CIs) for preterm delivery at each of the 3 gestational ages were calculated, using the full-term cohort (37–42 weeks) for comparison. Adjusted OR (aORs) with 95% CIs were calculated using binary logistic regression to test potentially causal factors associated with male sex that might account for the sex difference. Of the 75,725 deliveries examined, 4003 (5.3%) were preterm. Preterm birth occurred more frequently among males in all 3 gestation age ranges (OR, 1.13; 95% CI, 1.06–1.20). The increase in preterm births was due to spontaneous (OR, 1.30; 95% CI, 1.19–1.42) but not iatrogenic (OR, 0.96; 95% CI, 0.87–1.05) preterm deliveries. Preeclampsia was more likely to occur among preterm females (P < 0.001), and male fetuses were 130 grams larger. The increased risk of spontaneous preterm labor among pregnancies with male fetuses remained significant after adjustment for the larger male birth weight and the greater incidence of nulliparity and higher frequency of urinary tract infection and placental abruption among the mothers of male fetuses. These data indicate that the increased risk of preterm birth among males is due to an increased incidence of spontaneous preterm labor. No causal factors have been identified.

Maternal serum C-reactive protein concentrations in early pregnancy and subsequent risk of preterm delivery

Objective: To examine the relation between maternal early pregnancy serum C-reactive protein (CRP) and preterm delivery (PTD). Design and methods: Women were recruited before 20 weeks gestation and were followed up until delivery. Maternal serum CRP was measured by competitive immunoassay. Logistic regression procedures were used to calculate adjusted odds ratio (OR) and 95% confidence intervals (95%CI). Results: Elevations in CRP concentrations were associated with the risk of PTD overall. After adjusting for confounding, the OR for highest quartile (≥ 7.5 vs. < 2.0 mg/L) of CRP was 2.04 (95%CI: 1.13–3.69). Stratified analyses indicated that elevated CRP was associated with an increased risk of spontaneous preterm labour (OR = 2.15, 95%CI: 0.85–5.42), medically indicated preterm delivery (OR = 3.29, 95%CI: 0.98–11.02), and very preterm delivery (OR = 20.6, 95%CI: 2.53–168.03), but not with preterm premature rupture of membranes (OR = 1.48, 95%CI: 0.56–3.86). Conclusions: Elevated CRP concentrations in early pregnancy are associated with an increased risk of PTD, particularly medically indicated PTD and very PTD.

Risk of preterm delivery in relation to vaginal bleeding in early pregnancy

Objective To examine the relationship between vaginal bleeding during early pregnancy and preterm delivery. Methods Study subjects ( N = 2678) provided information regarding socio-demographic, biomedical, and lifestyle characteristics. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI). Results Any vaginal bleeding in early pregnancy was associated with a 1.57-fold increased risk of preterm delivery (95% CI: 1.16–2.11). Vaginal bleeding was most strongly related with spontaneous preterm labor (OR = 2.10) and weakly associated with preterm premature rupture of membrane (OR = 1.36) and medically induced preterm delivery (OR = 1.32). As compared to women with no bleeding, those who bled during the first and second trimesters had a 6.24-fold increased risk of spontaneous preterm labor; and 2–3-fold increased risk of medically induced preterm delivery and preterm premature rupture of membrane, respectively. Conclusion Vaginal bleeding, particularly bleeding that persists across the first two trimesters, is associated with an increased risk of preterm delivery.

Obstetrician-gynecologists' knowledge of preterm birth frequency and risk factors

Objectives. To assess obstetrician-gynecologists' knowledge of preterm birth, including prevalence, risk factors, and utility of various tests in predicting increased risk.Methods. A questionnaire was mailed to 1193 members of the American College of Obstetricians and Gynecologists.Results. The response rate was 59%. The majority of respondents were familiar with basic preterm birth prevalence rates. However, 21% underestimated the proportion of women with presumptive preterm labor in whom preterm birth will not occur. The majority (55%) overestimated the proportion of preterm births accounted for by multiples. Twelve percent indicated bed rest as a proven method for improving newborn outcome. Respondents were fairly accurate as to which factors produce the biggest increased risk of spontaneous preterm labor or rupture of membranes; however, they tended to overestimate the risk associated with smoking, hypertension, and non-gestational diabetes. They tended to underestimate, or were unsure of, the predictive value of positive fetal fibronectin (fFN) test results or short cervical length.Conclusions. Obstetrician-gynecologists' basic knowledge concerning preterm birth prevalence and risk factors was adequate. However, they tended to overestimate the risk associated with various maternal factors and underestimate the predictive value of various test results.

Maternal Obesity in Early Pregnancy and Risk of Spontaneous and Elective Preterm Deliveries: A Retrospective Cohort Study

We sought to determine the association between maternal body mass index and risk of preterm delivery. We assessed 187,290 women in Scotland and estimated adjusted odds ratios for spontaneous and elective preterm deliveries among overweight, obese, and morbidly obese women relative to normal-weight women. Among nulliparous women, the risk of requiring an elective preterm delivery increased with increasing BMI, whereas the risk of spontaneous preterm labor decreased. Morbidly obese nulliparous women were at increased risk of all-cause preterm deliveries, neonatal death, and delivery of an infant weighing less than 1000 g who survived to 1 year of age (a proxy for severe long-term disability). By contrast, obesity and elective preterm delivery were only weakly associated among multiparous women. Obese nulliparous women are at increased risk of elective preterm deliveries. This in turn leads to an increased risk of perinatal mortality and is likely to lead to increased risks of long-term disability among surviving offspring.

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.