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PubMed2006

Exposures to air pollutants during pregnancy and preterm delivery.

The association between preterm delivery (PTD) and exposure to air pollutants has recently become a major concern. We investigated this relationship in Incheon, Republic of Korea, using spatial and temporal modeling to better infer individual exposures. The birth cohort consisted of 52,113 singleton births in 2001-2002, and data included residential address, gestational age, sex, birth date and order, and parental age and education. We used a geographic information system and kriging methods to construct spatial and temporal exposure models. Associations between exposure and PTD were evaluated using univariate and multivariate log-binomial regressions. Given the gestational age, birth date, and the mother's residential address, we estimated each mother's potential exposure to air pollutants during critical periods of the pregnancy. The adjusted risk ratios for PTD in the highest quartiles of the first trimester exposure were 1.26 [95% confidence interval (CI), 1.11-1.44] for carbon monoxide, 1.27 (95% CI, 1.04-1.56) for particulate matter with aerodynamic diameter < or = 10 microm, 1.24 (95% CI, 1.09-1.41) for nitrogen dioxide, and 1.21 (95% CI, 1.04-1.42) for sulfur dioxide. The relationships between PTD and exposures to CO, NO2, and SO2 were dose dependent (p < 0.001, p < 0.02, p < 0.02, respectively) . In addition, the results of our study indicated a significant association between air pollution and PTD during the third trimester of pregnancy. In conclusion, our study showed that relatively low concentrations of air pollution under current air quality standards during pregnancy may contribute to an increased risk of PTD. A biologic mechanism through increased prostaglandin levels that are triggered by inflammatory mediators during exposure periods is discussed.

Air Pollutants↗
PubMed2005

Race, genes and preterm delivery.

High rates of preterm delivery (PTD) among African Americans are the leading cause of excess infant mortality among African Americans. Failure to fully explain racial disparity in PTD has led to speculation that genetic factors might contribute to this disparity. Current evidence suggests that genetic factors contribute to PTD, but this does not imply that genetic factors contribute to racial disparity in PTD. Environmental factors clearly contribute to PTD. Many of these factors acting over a women's life prior to pregnancy disproportionately affect African Americans and contribute significantly to racial disparity in PTD. Thus, inferring genetic contribution to racial disparity in PTD by attempting to control for environmental factors measured at a single point in time is flawed. There is emerging evidence of gene-environment interactions for PTD, some of which disproportionately affect African Americans. There is also evidence of racial differences in the prevalence of polymorphisms potentially related to PTD. However, to date there is no direct evidence that these differences contribute significantly to racial disparity in PTD. Given the complexity of polygenic conditions such as PTD, the possibility of any single gene contributing substantially to racial disparity in PTD seems remote.

Black or African American↗
PubMed2005

The value of cervical length and plasma proMMP-9 levels for the prediction of preterm delivery in pregnant women presenting with threatened preterm labor.

OBJECTIVE: To assess the value of plasma proMMP-9 levels in predicting the progress of threatened preterm labor to true preterm labor and delivery within 7 days of presentation, along with the ultrasonographic measurement of cervical length. STUDY DESIGN: The study included sixty two pregnant women presented in the 2nd Department of Obstetrics and Gynecology of University of Athens at Aretaieion Hospital with threatened preterm labor. On subjects' presentation, cervical length was evaluated with transvaginal ultrasonography, plasma proMMP-9 levels were measured with the use of a solid phase enzyme immunoassay, and maternal characteristics (smoking, history of preterm delivery and parity) as well as the use of tocolytics were recorded. Subjects were followed up for premature delivery within 7 days. ROC analysis for plasma proMMP-9 levels was performed and logistic regression analysis was used for the evaluation of the prognostic effect of the parameters. RESULTS: The only significant predictors for establishment of true preterm labor and delivery within 7 days of presentation were cervical length (with cutoff value 15 mm: odds ratio=0.022, 95% CI=0.002-0.243, p=0.002) and plasma proMMP-9 (with cutoff value 67.15 ng/ml: odds ratio=0.035, 95% CI=0.003-0.388, p=0.006). The combination of the adopted proMMP-9 and cervical length cutoff values was characterized by a sensitivity of 90.9% and a specificity of 98.3% for predicting the progress to true preterm labor and delivery. CONCLUSION: Plasma proMMP-9 levels could possibly serve as a predictive factor for the progress of threatened preterm labor to true preterm labor and delivery within 7 days of presentation, along with the ultrasonographic evaluation of cervical length.

Adult↗
PubMed2004

Alcohol consumption during pregnancy and the risk of preterm delivery.

The authors evaluated the association between amount and type of alcohol consumed during pregnancy and the risk of preterm delivery and whether the relation differs among very (<32 completed weeks) and moderate (from 32 to <37 completed weeks) preterm delivery. The study is based on data of 40,892 pregnant women included in the first part of the Danish National Birth Cohort. The women completed a computer-assisted telephone interview between December 12, 1997, and December 31, 2000, and delivered a liveborn singleton. Of these women, 1,880 gave birth preterm. Compared with those who abstained during pregnancy, the relative risks for preterm delivery among women who consumed from four to less than seven drinks and seven or more drinks per week during pregnancy were 1.15 (95% confidence interval: 0.84, 1.57) and 1.77 (95% confidence interval: 0.94, 3.31), respectively. Below these intake levels of alcohol, no increased risk of preterm delivery was found. Among women who consumed seven or more drinks per week, the relative risk of very preterm delivery was 3.26 (95% confidence interval: 0.80, 13.24) compared with that of nondrinkers. There were no differences in the associations between type of beverage and preterm delivery.

Adult↗
PubMed1994

The effect of smoking cessation during pregnancy on preterm delivery and low birthweight.

BACKGROUND: Evidence exists that maternal cigarette smoking is associated with preterm birth. Our purpose was to investigate the relation between maternal smoking cessation at different points during pregnancy and the preterm delivery rate and low birthweight. METHODS: Data from the 1988 National Health Interview Survey were analyzed. The study included women who gave birth to children within 6 years of the 1988 interview date (N = 4876). Preterm delivery and infant low birthweight were the main outcome measures. These measures were compared with maternal smoking status during pregnancy. Logistic regression models were computed to control for maternal age at the time of birth, parity, race, and total family income. RESULTS: Women who did not smoke cigarettes during pregnancy were less likely to give birth prematurely (5.9% vs 8.2%, P = .003) or give birth to a low-birthweight baby (5.5% vs 8.9%, P < .001) than women who smoked at some time during the year before giving birth. A significant association existed between maternal smoking status and both preterm delivery and low birthweight. Compared with those who smoked beyond the first trimester, those who quit smoking within the first trimester had reductions in the proportion of preterm deliveries (6.7% vs 9.1%) and low birthweight infants (7.9% vs 9.6%). CONCLUSIONS: Low birthweight and preterm delivery are reduced in women who stop smoking in the first trimester of pregnancy.

Adolescent↗
PubMed1995

Epidemiology of preterm delivery in two birth cohorts with an interval of 20 years.

The occurrence and determinants of preterm delivery were studied in two population-based birth cohorts from northern Finland. In the first cohort of 1966 there were 11,475 singleton deliveries and in the later cohort of 1985-1986, 8,888. The overall incidence (percentage) of preterm deliveries fell from 9.1 to 4.8, including a reduction from 8.8 to 3.4 for spontaneous preterm deliveries. For iatrogenic ones, however, there was an increase from 0.3 to 1.4. The relative risks, associated with such known maternal determinants as unmarried status, smoking, low educational level, age over 34 years, unwantedness of the pregnancy, and poor earlier obstetric history, had about the same level in these two series. However, despite a favorable change in the distribution of most of these determinants over the 20 years, only a small part of the decrease of the total incidence of preterm delivery could be attributed to these changes, as a consistent and substantial reduction occurred in the incidence of spontaneous preterm birth in all categories of each single determinant. The increase in the proportion of iatrogenic preterm deliveries was accompanied by these being more common at lower than at higher socioeconomic levels in 1985-1986, whereas the social gradient appeared to be reversed in 1966.

Cohort Studies↗
PubMed1995

Racial differences in the patterns of preterm delivery in central North Carolina, USA.

In order to assess racial differences in rates of idiopathic preterm labour, preterm premature rupture of membranes, and medically indicated preterm delivery, the authors analysed data on 388 preterm (< 37 completed weeks of gestation) births (7.9% of all births) occurring between 1 September 1988 and 31 August 1989, in three central North Carolina counties. The crude relative risk (RR) of preterm birth among black women compared with white women was 2.6 [95% confidence interval (CI) 2.1, 3.1]. With adjustment for age, gravidity, marital status, education, and county of residence, the estimated relative risk for black women compared with white women was 2.1 (95% CI 1.1, 4.1) for medically indicated preterm delivery, 1.6 (95% CI 1.1, 2.3) for preterm birth as a result of preterm labour, and 1.9 (95% CI 1.2, 3.1) for preterm premature rupture of membranes. Compared with white women, black women were at the highest risk of a preterm birth before 34 weeks of gestation (RR = 2.9; 95% CI 1.8, 4.7). The risk of medically indicated preterm delivery at 36 weeks was considerably higher for black women than for white women (RR = 3.4; 95% CI 1.1, 10.2). For a better understanding and ultimately a reduction of the risk for preterm delivery among black women, investigation of specific aetiological pathways and gestational age groups may be required.

Adolescent↗
PubMedDate not supplied

Is inflammation on Papanicolaou smear a risk factor for preterm delivery?

OBJECTIVE: Inflammation on Papanicolaou (Pap) smear has been associated with a 30-50% incidence of bacterial vaginosis (BV), a recognized risk factor for preterm delivery. We determined whether inflammation on Pap smear is associated with preterm delivery. STUDY DESIGN: 5,348 cases were studied with complete prenatal data including the potential confounder of treatment with antibiotics. Cases were categorized by presence (n = 1,139) or absence (n = 4,209) of inflammation on Pap smear. RESULTS: In the inflammation group the proportion of African Americans was lower (66.9 vs. 74.5%; p < 0.001). There were no significant differences (t test) for maternal age, gravidity, history of preterm delivery, or gestational age at delivery between inflammation and noninflammation groups. Multiple stepwise regression analysis showed that maternal age, history of preterm delivery, and African American race were all significantly positively associated with preterm delivery. Treatment with metronidazole during the pregnancy was significantly negatively associated with preterm delivery. Inflammation on Pap smear, gonorrhea detected during the pregnancy and prenatal treatment with erythromycin were not associated. CONCLUSION: Unlike bacterial vaginosis, inflammation on routine Pap smear does not appear to be a risk for subsequent preterm birth. We are unable to use inflammation on Pap smear as a surrogate for more specific diagnosis of bacterial vaginosis.

Adult↗
PubMed1998

Second trimester calcium-phosphorus-magnesium homeostasis in women with threatened preterm delivery.

OBJECTIVE: The effect of threatened preterm delivery on calcium, phosphorus, magnesium homeostasis in the second trimester of pregnancy was investigated. METHODS: Serum concentrations of total and ionized calcium, inorganic phosphorus, magnesium, total protein, albumin, total estrogens and human placental lactogen were determined in women with threatened preterm delivery at 23-28 weeks of gestation (the studied group) and in women with uncomplicated pregnancy of the same duration (the control group). Additionally activities of total alkaline phosphatase and heat-stable alkaline phosphatase fraction were measured. RESULTS: Patients of the studied group compared to the control group showed decreased concentration of total calcium (2.15 +/- 0.073 vs. 2.25 +/- 0.11 mmol/l, P < 0.001), inorganic phosphorus (1.21 +/- 0.26 vs. 1.34 +/- 0.22 mmol/l, P < 0.01) and magnesium (0.63 +/- 0.053 vs. 0.71 +/- 0.12 mmol/l, P < 0.001), total protein (64.0 +/- 5.4 vs. 68.6 + 1.0 g/l, P < 0.001), albumin (546.3 +/- 55.1 vs. 579.6 +/- 49.3 micromol/l, P < 0.003) and placental lactogen (3664 +/- 1806 vs. 4651 +/- 1858 ng/ml, P < 0.02); they also demonstrated decreased activity of total alkaline phosphatase (42.17 +/- 16.99 vs. 50.66 +/- 6.56 IU/l, P < 0.001) and its heat stable fraction (22.65 +/- 7.89 vs. 31.89 +/- 9.09 IU/l, P < 0.001). Patients of the studied group showed normal values of ionized calcium and total estrogens. CONCLUSIONS: Premature uterine contractility in women in the second trimester is accompanied by lowered serum concentrations of total calcium, inorganic phosphorus, magnesium, total protein and albumin. There is also decreased activity of total alkaline phosphatase, its heat-stable fraction and placental lactogen which may have diagnostic value. Premature uterine contractility in women in the second trimester may be related to the disturbances of calcium-phosphorus-magnesium homeostasis and calcium supplementation should be considered.

Calcium↗
PubMed1998

Tocolysis of preterm contractions does not improve preterm delivery rate or perinatal outcomes.

To determine whether hospital admission and parenteral tocolysis of patients with threatened preterm labor results in a decreased preterm delivery rate and improved perinatal outcome, we performed a prospective cohort study comparing tocolytic treatment versus no tocolytic treatment. Women between 20 and 37 weeks' gestation who presented with at least eight uterine contractions per hour and a cervical examination <2 cm dilated, <80% effaced, and no cervical change over a 2-hr period were entered into the study. Exclusion criteria included cervical change, multiple gestation, chorioamnionitis, rupture of membranes, placenta previa or abruption, undiagnosed vaginal bleeding, and prior tocolytic therapy in the current pregnancy. Seventy-five patients were admitted to the hospital for tocolysis (tocolysis cohort) and 81 were observed and discharged to home (observation cohort). There was no significant difference in mean gestational age at delivery, mean birth weight, or in preterm delivery rate between the two cohorts. Four of the eight women in the observation cohort who delivered preterm had a history of preterm delivery. We conclude that discharging women with preterm contractions without objective evidence of labor does not result in an increase in preterm births. More importantly, tocolysis did not decrease the preterm delivery rate in this cohort.

Adult↗
PubMed1990

Intrauterine growth retardation and preterm delivery: prenatal risk factors in an indigent population.

Prenatally ascertained risk factors for low birth weight were evaluated in a population of 17,000 indigent women for their specific effect on intrauterine growth retardation and on the rate of preterm delivery. In a univariate analysis, intrauterine growth retardation occurred more frequently in women who were black, single, primiparous, less than 17 or greater than 30 years old, short, thin, had a previous preterm delivery, consumed alcohol, took drugs, or gained limited weight. Preterm delivery occurred significantly more frequently in women who were black, single, thin, less than 17 or greater than 30 years old, had less than a twelfth grade education, or gained limited weight. In logistic regression analyses, race, parity, maternal age, a history of preterm delivery, smoking, short stature, low weight, and low weight gain remained significant risk factors of intrauterine growth retardation. Of these factors, smoking, short stature, low weight, and low weight gain showed the greatest correlation. Factors significantly related to preterm delivery included black race, single marital status, younger or older ages, previous preterm delivery, smoking, low weight, and very low or high weight gain. A previous preterm delivery and very low maternal weight had the greatest correlation. Identification of specific risk factors of both intrauterine growth retardation and preterm delivery should aid in the development of strategies to reduce the prevalence of these conditions.

Adult↗
PubMed1992

Pregnancy with an intrauterine device in situ and preterm delivery.

We determined the prevalence of preterm delivery in a population of women who conceived with an IUD in situ and compared the results with those in a group of women without any contraceptive method. The study group consisted of 16 women who conceived with a copper IUD in situ. The control group comprised 48 women matched for age, gravidity and parity. The prevalence of preterm delivery was significantly higher in the study group than in the control group (18.7% (3/16) vs 2% (1/48)), respectively. (P = 0.045, Fisher's exact test.)

Adult↗
PubMed1983

Physical activity and the risk of spontaneous preterm delivery.

An epidemiologic case-control study exploring possible risk factors for preterm delivery was undertaken at Yale-New Haven Hospital during 1977. The study groups consisted of 175 mothers of singleton preterm infants and 313 mothers of singleton term infants. Analysis of questionnaire responses provided no evidence that employment, housework, child care and leisure-time physical activity during pregnancy increased the risk of preterm delivery. Women who participated in sports or physical fitness exercises during pregnancy were found to have a significantly decreased risk of preterm delivery as compared to those who were not similarly active; this finding suggests that certain forms of moderate physical activity may actually protect against preterm delivery.

Child Care↗
PubMed2004

Prediction of preterm delivery in twin pregnancy: a prospective, observational study of cervical length and fetal fibronectin testing.

OBJECTIVE: To evaluate prospectively cervical length measurements and fetal fibronectin detection as predictors of spontaneous preterm delivery in an unselected population of twin pregnancies. METHODS: Transvaginal ultrasound assessments of cervical length were performed serially at 18, 24, 28 and 32 weeks' gestation. Receiver-operating characteristic curves were generated at each time point to determine the optimal cut-off for cervical length and rate of change in cervical length in the prediction of preterm delivery (< 35 weeks). A bedside assay for the detection of fetal fibronectin in the maternal vaginal secretions was performed prior to cervical length measurements from 24 weeks. Likelihood ratios (LRs) were used to assess the performance of each test. RESULTS: The spontaneous preterm delivery rate was 16.5% in 91 studied twin pregnancies. A cervical length </= 25 mm at 18 weeks (LR+ 9.7, sensitivity 14.3%) and </= 22 mm at 24 weeks (LR+ 9.6, sensitivity 28.6%) were the best predictors of preterm delivery. A shortening of cervical length >/= 2.5 mm per week between 18 and 28 weeks' gestation also predicted preterm delivery (LR+ 10.8, sensitivity 16.7%). There was no relationship between the detection of fetal fibronectin and preterm delivery. CONCLUSIONS: This study confirms the value of transvaginal ultrasound assessment of cervical length as a predictor of preterm delivery in twin pregnancies. However, the poor sensitivity of this test makes it unsuitable as a single predictor of preterm delivery. Fetal fibronectin testing does not identify twin pregnancies destined to deliver prematurely.

Adult↗
PubMed2005

High levels of fetal cell-free DNA in maternal serum: a risk factor for spontaneous preterm delivery.

OBJECTIVE: This study was conducted to determine whether there is a relationship between the concentration of fetal cell-free DNA in maternal serum and the duration of pregnancy in women who are at high risk for preterm delivery because of either preterm labor or preterm premature rupture of the membranes. STUDY DESIGN: Sera were collected and frozen from 71 women with a male fetus. Maternal serum fetal cell-free DNA concentration was measured with the use of real-time polymerase chain reaction amplification of DYS1. Fetal cell-free DNA concentrations were converted to multiples of the median. The following groups were studied: group 1: women with preterm labor and intact membranes who were delivered at > or = 36 weeks of gestation (n = 21); group 2: women with preterm labor who were delivered at <36 weeks of gestation (n = 29); and group 3: women with preterm premature rupture of the membranes in labor (n = 20) or not in labor (n = 1) who were delivered prematurely (<36 weeks of gestation). Kaplan-Meier and Cox regression analyses were used to analyze the relationship between fetal cell-free DNA concentrations and the likelihood of preterm delivery. RESULTS: A cut-off value for fetal cell-free DNA of 1.82 multiples of the median was chosen for analysis. The cumulative rate of early preterm delivery (<30 weeks of gestation) was significantly higher for women with fetal cell-free DNA concentrations of > or = 1.82 multiples of the median than those with fetal cell-free DNA concentrations below this cut-off (45% [95% CI, 36%-74%] vs 18% [95% CI, 11%-25%]; P = .008]. The cumulative rate of preterm delivery (<36 weeks of gestation) was also significantly higher at > or = 1.82 multiples of the median (73% [95% CI, 52%-93%] vs 66% [95% CI, 54%-79%]; P = .02). After adjustment for covariates, Cox analysis showed that fetal cell-free DNA at > or = 1.82 multiples of the mechanisms of disease that are associated with a mean hazard rate of delivery of 1.57 (P = .005). CONCLUSION: High concentrations of fetal cell-free DNA in maternal serum are associated with an increased risk of spontaneous preterm delivery. This observation may have implications for the understanding of the mechanisms of disease that is associated with preterm labor.

Cross-Sectional Studies↗
PubMed2005

Tocolytic effect of a Rho-kinase inhibitor in a mouse model of lipopolysaccharide-induced preterm delivery.

OBJECTIVE: The small guanosine triphosphatase RhoA/Rho-kinase cascade has been implicated in uterine contraction. Our purpose was to evaluate the tocolytic effect of a Rho-kinase inhibitor, Y-27632, in lipopolysaccharide-induced preterm delivery in mice. STUDY DESIGN: We used an animal model of lipopolysaccharide-induced preterm delivery in C3H/HeN x B6D2F1 pregnant mice. Y-27632 was delivered continuously through an osmotic pump that was implanted into the peritoneal cavity 6 hours before lipopolysaccharide treatment. The primary outcome was the preterm delivery rate. To further study the possible involvement of this cascade in lipopolysaccharide-induced preterm delivery, we determined the effect of lipopolysaccharide and prostaglandin F2alpha on RhoA activation in mouse myometrial cells and uterine smooth muscle tissues. RESULTS: The rate of preterm delivery for lipopolysaccharide-treated animals was 94.4%. The administration of Y-27632 (1 or 10 mg/kg/d) significantly reduced the preterm delivery rate to 61.1% or 15.8%, respectively. The level of guanosine triphosphate-bound RhoA was increased after the addition of lipopolysaccharide or prostaglandin F2alpha. CONCLUSION: The RhoA/Rho-kinase cascade is involved in lipopolysaccharide-induced preterm delivery, which suggests that Rho-kinase could be used as a new therapeutic target for the prevention of preterm labor.

Amides↗
PubMed2001

Enhancement of amniotic cyclooxygenase type 2 activity in women with preterm delivery associated with twins or polyhydramnios.

OBJECTIVE: We tested the hypothesis that preterm delivery in women with twins or polyhydramnios is associated with enhanced expression and activity of cyclooxygenase type 2 in the amnion. STUDY DESIGN: We obtained amniotic tissue samples from women undergoing preterm delivery complicated by either twins or polyhydramnios and also from women undergoing preterm cesarean delivery before or after labor. We measured amniotic prostaglandin E2 content and determined cyclooxygenase type 1 and type 2 expressions. We inhibited cyclooxygenase type 1 and type 2 activities with selective inhibitors. RESULTS: Preterm delivery attributed to twins or polyhydramnios was associated with higher prostaglandin E2 production and enhanced amniotic expression of cyclooxygenase type 2. In contrast, cyclooxygenase type 1 expression was unchanged. Incubation of amniotic samples in vitro with either indomethacin or the selective cyclooxygenase type 2 inhibitor SC-236, but not with the cyclooxygenase type 1 inhibitor SC-560, effectively reduced prostaglandin E2 production. CONCLUSION: Preterm delivery related to multiple gestation or polyhydramnios was associated with enhanced amniotic expression and activity of cyclooxygenase type 2.

Amnion↗
PubMed2004

Cervical immunoglobulin A and altered vaginal flora in pregnant women with threatened preterm delivery.

The aim of our study was to investigate the cervical immunoglobulin A concentration in women with threatened preterm delivery. Immunoglobulin A concentration in the cervical mucus of 80 women with symptoms of preterm delivery was measured using radial immunodiffusion. The results were compared with those of 60 healthy pregnant women. Concentrations of immunoglobulins in maternal serum were also measured. There was no significant difference of cervical immunoglobulin A (IgA) concentration between women with threatened preterm delivery and controls: 53.98 (0.0-189.7) mg/l vs. 61.7 (1.4-400.9; p<0.4) mg/l (median, range). The median of cervical IgA levels in the group of threatened preterm delivery did not differ significantly between patients delivered preterm (n=34) or at term (n=46): 38.3 (0.0-187.9) vs. 65.7 (1.4-189.7; p<0.2) mg/l. Women with a normal vaginal flora showed a significantly higher cervical IgA concentration than those with a pathological colonization: 72.7 (0.0-187.9) vs. 42.5 (0.0-189.7) mg/l. Patients with a pathological vaginal smear and preterm delivery had the lowest IgA levels (35.0; 0.0-187.9 mg/l). Measurement of cervical IgA concentration does not differentiate between women who deliver before or at term.

Adolescent↗