Probability Of Spontaneous Delivery Research Articles

Cervical length in late second and third trimesters: a mixture model for predicting delivery.

To examine the distribution of cervical length (CL) in the late second and third trimesters of pregnancy and construct survival models for spontaneous delivery. This cross-sectional study included 647 women with a singleton pregnancy who had routine CL measurements taken by transvaginal ultrasonography between 24 and 40 weeks' gestation. Only one measurement per patient was included in the analysis. Exploratory data analysis revealed that the distribution of CL measurements was a mixture of two Gaussian distributions, and subsequently a mixture model was applied to describe the distribution of CL. Changes in CL in relation to gestational age were examined by regression analysis and measurements were converted to Z-scores. Survival analysis was applied to the subgroups identified, to describe the probability of delivery throughout gestation. CL was best described by a mixture model of two subgroups with Gaussian distribution, one including women with a long cervix (73.85% of the study population, mean CL of 28.2 ± 4.45 mm) and the other including women with a short cervix (26.15% of the study population, mean CL of 12.3 ± 5.14 mm). CL was dependent on gestational age (GA), therefore conversion to Z-scores was employed in the analysis. Women with a short cervix had a higher probability for spontaneous delivery (hazard ratio (HR), 1.807; P < 0.001) than did women with a long cervix, after adjustment for GA at the time of measurement (GA HR, 1.115; P < 0.001). In both subgroups, the probability of spontaneous delivery was predicted by the GA and CL Z-scores. Survival models for the prediction of spontaneous delivery were constructed separately for the short-cervix subgroup (GA HR, 1.085; P < 0.001 and CL Z-score HR, 0.819; P = 0.003) and the long-cervix subgroup (GA HR, 1.130; P < 0.001 and CL Z-score HR, 0.864; P = 0.005). CL follows a mixture of two Gaussian distributions, one for a short and one for a long cervix. Late second-trimester/third-trimester CL measurement may be of value in estimating the probability for spontaneous delivery at any given gestational age.

The probability of spontaneous delivery -- possibility and limits of obstetric risk scores

For a sound consultation of pregnant women e. g. regarding the choice of delivery place, a simple, reliable prepartal risk estimation system would be desirable. After exclusion of all "hospital required" risk cases, out of 203,111 records from the Berlin Clinical Perinatal Data 1993 - 1999 176,734 births remained, for which all risks already discernible before delivery (catalogues of the German Maternity Guidelines) were retrospectively valued and weighted by means of a logistic regression analysis on their real importance for the prediction of a spontaneous birth. On the basis of logarithms of the odds ratio for the individual risk factors a point system was developed. There is a clearly higher risk for a surgical delivery in primiparae compared with multiparae. For multiparae 27, for primiparae 26 statistically significant (p < 0.01) risk factors could be identified. After conversion of the odds ratio-values into the point system of the score, for the group of primiparae the cut off value was > 1 point (with a specificity of 0.5 and a sensitivity of 0.5), in the multiparae > 3 points (sensitivity 0.7, specificity 0.7). As for primiparae the resulting prognosis of birth mode (spontaneous vs. surgical birth) using the described score is false at 46 %, in multiparae at 33 %, the prognosis power of the risk score can therefore only be classified as relatively poor. The risk assessment system is therefore not suitable e. g. as aid to decision-making for or against an extra-clinical delivery place where no obstetrical operations are possible.