History Of Previous Preterm Delivery Research Articles

Can a “snapshot” sagittal view of the cervix by transvaginal ultrasonography predict active preterm labor?

OBJECTIVE: Our purpose was to test the hypothesis that wedging of the cervical internal os determined by transvaginal ultrasonography is associated with premature labor and delivery. STUDY DESIGN: Seventy patients admitted to the hospital for threatened preterm labor were evaluated by transvaginal ultrasonography before institution of therapy. Bivariate and logistic regression analyses were performed to determine the variables that made a significant contribution to the prediction of preterm delivery. RESULTS: Preterm delivery was significantly associated with the presence of cervical wedging, as noted on cervical scan, and with short cervical length. A history of previous preterm delivery was of marginal significance as a predictor of preterm delivery ( p = 0.09). Preterm delivery was not significantly correlated with age, previous voluntary termination of pregnancy, gestational age at the time of study, previous normal spontaneous vaginal delivery, or tocolytic therapy. Use of wedging as a diagnostic test for the prediction of preterm delivery yielded a sensitivity of 100%, a specificity of 74.5%, a positive predictive value of 59.4%, and a negative predictive value of 100%. CONCLUSION: The presence of wedging and shorter cervical length was suggestive of true preterm labor requiring aggressive management. A transvaginal ultrasonographic “snapshot” view of the cervix seems to be a more reliable method to evaluate the cervix in patients with threatened premature labor than are uterine contractions alone. (A M J O BSTET G YNECOL 1996;174:990-5.)

Maternal asthma and idiopathic preterm labor.

Previous studies suggest that women with asthma are at increased risk of preterm birth. Moreover, drugs (especially beta-agonists) used to treat asthma are also used to treat preterm labor. The authors carried out a case-control study of 555 women from three hospital centers with idiopathic preterm labor (< 37 weeks), including two overlapping (i.e., non-mutually exclusive) subsamples: cases with early idiopathic preterm labor (< 34 weeks) and cases with idiopathic recurrent preterm labor (< 37 weeks plus a previous history of preterm delivery or second-trimester miscarriage). Controls were matched to cases according to race and smoking history prior to and during pregnancy. All subjects responded in person to questions about atopic, respiratory, obstetric, and sociodemographic histories. Subjects in the early and recurrent preterm labor subsamples were also asked to undergo spirometric testing with methacholine challenge 6-12 weeks after delivery. Cases were significantly more likely to report histories of asthma symptoms and physician-diagnosed asthma (matched odds ratios of 2-3) than controls, particularly those cases with recurrent preterm labor. No significant associations were observed, however, with methacholine responsiveness. These results could not be explained by residual confounding by smoking or other variables, nor by selective recall of asthma symptoms and histories by cases. Women with asthma are at increased risk of idiopathic preterm labor. The fact that no such association was seen with methacholine responsiveness suggests that nonatopic, noncholinergic mechanisms may link bronchial and uterine smooth muscle lability.

Maternal nutrition and spontaneous preterm birth.

Previous studies suggesting that maternal undernutrition increases the risk of preterm birth have suffered from several methodological shortcomings, including use of total gestational weight gain rather than net rate of gain in maternal tissue, inclusion of induced preterm deliveries, and error-prone gestational age measurements based solely on menstrual dates. The authors have attempted to overcome these shortcomings by investigating the potential etiologic roles of prepregnancy body mass index, net rate of maternal weight gain, height, and a number of other potential biological and sociodemographic determinants of spontaneous (i.e., noninduced) preterm birth in a cohort of 13,102 women with early ultrasound-confirmed gestational age who delivered at the Royal Victoria Hospital in Montreal, Quebec, Canada, between January 1, 1980 and March 31, 1989. Total weight gain, but not body mass index, was highly significantly associated with spontaneous preterm birth, averaging 14.6, 12.5, 9.9, and 9.1 kg, in women delivering at 37 or more, less than 37, less than 34, and less than 32 completed weeks, respectively. Although the relation persisted when weight gain was expressed as an overall rate, it disappeared when the analysis was based on net rate; mean net rates of gain were 0.28, 0.29, 0.27, and 0.27 kg/week, respectively. On the basis of multiple logistic regression analyses, significant determinants of birth at less than 37 weeks included maternal short stature; noncompletion of high school; unmarried status; smoking; diabetes; urinary tract infection within 2 weeks of delivery; prepregnancy hypertension; severe pregnancy-induced hypertension; and previous history of preterm delivery, low birth weight, or neonatal death. Most of these factors retained their significance for birth at less than 34 and less than 32 weeks. In fact, the effect of low maternal education was even stronger at these more severe "levels" of preterm birth. The authors conclude that prepregnancy weight-for-height and gestational weight gain are not important determinants of spontaneous preterm birth and that some previous studies have mistaken an effect of shortened gestation for its cause. Other biologic and social determinants, however, indicate priorities for future research and intervention.

Perinatal outcome in triplet versus twin gestations

The present study was conducted to determine whether triplet pregnancies are associated with a significantly worse perinatal outcome than twin pregnancies. Maternal and neonatal outcome was evaluated in 15 triplet and twin pregnancies that were matched for maternal age, race, type of medical insurance, delivery mode, parity, and history of previous preterm delivery. Preterm labor occurred significantly more often in triplet than in twin gestations (80 versus 40%), as did preterm delivery (87 versus 26.7%). Triplets had a significantly lower mean birth weight (1720 versus 2475 g) and gestational age at delivery (33 versus 36.6 weeks). In addition, 53.3% of triplet pregnancies but only 6.7% of twin pregnancies had one or more neonates with intrauterine growth retardation. Discordancy also occurred more frequently in triplets than in twins (66.7 versus 13.3%). The mean averaged neonatal hospital stay was significantly higher in triplets (29 versus 8.5 days), and triplets had a fivefold increased risk of requiring neonatal intensive care as compared with twins. However, there were no significant differences between the groups in maternal morbidity or major neonatal complications such as respiratory distress syndrome or intraventricular hemorrhage. We believe that these data will be useful in counseling patients with respect to the anticipated perinatal outcome of triplet pregnancies.

Prenatal Ultrasound: Are Socially Disadvantaged Groups Afforded Equal Access?

A retrospective cohort study was conducted of the patterns of ultrasound use during pregnancy for all single live births (n = 2542) delivered at a major teaching hospital in one calendar year. Extent of maternal education was inversely correlated with the probability of receiving a prenatal ultrasound examination (p less than 0.001). Clinic patients were more likely to receive prenatal ultrasound examinations than were private patients (p less than 0.001). Blacks were more likely than whites to receive prenatal ultrasound examinations (p less than 0.001). Short duration of prenatal care, inadequate weight gain during pregnancy, and history of previous pre-term delivery were all associated with an increased probability of receiving a prenatal ultrasound examination (p less than 0.001).