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.

Changes in the expression of nitric oxide synthase in the human uterine cervix during pregnancy and parturition

Nitric oxide (NO) has been proposed as a mediator of cervical ripening. We investigated the expression, using Western blotting, and localization, using immunohistochemistry, of the nitric oxide synthase (NOS) enzymes, inducible NOS (iNOS), endothelial NOS (eNOS) and neuronal NOS (bNOS) in the human cervix during pregnancy and parturition. Cervical biopsies were obtained from non-pregnant women, women in the first trimester of pregnancy, and pregnant women at term before and after the onset of labour. Each of the NOS isoforms was localized in the cervices of both non-pregnant and pregnant subjects using immunohistochemistry. iNOS expression was significantly greater in early pregnancy compared with the non-pregnant state (P: < 0.005). iNOS expression was up-regulated further in samples obtained in the third trimester compared with the first trimester. bNOS expression was greater in samples from the first trimester of pregnancy than in non-pregnant samples (P: < 0. 005), but showed no additional increase in late pregnancy or with the onset of labour. eNOS expression was increased in samples obtained in the third trimester both before (P: = 0.002) and after the onset of labour (P: < 0.002) when compared with non-pregnant samples. The increased expression of NOS isoforms in late pregnancy supports the hypothesis that NO is involved in the process of cervical ripening.

Second malignancies in cervical cancer patients in the west of Scotland

A retrospective study was carried out to determine the incidence and nature of second primary malignancies in patients treated for cervical cancer in the West of Scotland. A total of 3911 patients treated for a primary cancer of cervix, diagnosed between 1975 and 1992, were identified from the West of Scotland Cancer Registry. The ratio of observed second primary cancers in the study cohort to the number expected to occur if incidence was the same as in the West of Scotland population as a whole was calculated. Of the 3911 women treated, 129 (3.3%) were diagnosed with a second primary malignancy. Tissues within the pelvic radiation field showed no significant excess of second primary tumours. A significant excess (O/E 2.52 [95% c.i. 1.89-3.30]) of second primary malignancy in the lung and pleura was identified even after correction for socio-economic deprivation. Women treated for cervical cancer in the West of Scotland appear to be at more risk of a subsequent cancer due to causes other than the late effects of radiotherapy.

Intrauterine growth restriction with absent end-diastolic flow velocity in the umbilical artery is associated with maldevelopment of the placental terminal villous tree

OBJECTIVE

Our purpose was to evaluate the structure of placental terminal villi and their capillaries in pregnancies complicated by intrauterine growth restriction with absent end-diastolic flow velocity in the umbilical artery.

STUDY DESIGN

Glutaraldehyde-perfusion-fixed villous tissue and a plastic cast of the vessels in at least two cotyledons were prepared from 10 cases with intrauterine growth restriction and 9 gestational age-matched control placentas. The structure and dimensions of 20 terminal capillary loops per cast were determined by scanning electron microscopic examination, and their appearances were correlated with the peripheral villi of the perfusion-fixed villous tissue.

RESULTS

Capillary loops in the growth-restricted cases were sparse in number and significantly longer than in the control cases (218 microns [72] vs 137 microns [30], mean and SD, p < 0.05). They exhibited fewer branches (4.0 [1.9] per loop vs 6.1 [2.2], p < 0.05) and a majority of loops were uncoiled (79% vs 18%, p < 0.05). The villous tissues from the growth-restricted cases demonstrated elongated villi, consistent with the cast findings. The trophoblast surface was wrinkled and in some areas covered by fibrin plaques.

CONCLUSIONS

The terminal villous compartment of the placenta appears to be maldeveloped in preterm intrauterine growth restriction pregnancies where absent end-diastolic flow velocity is demonstrated in the umbilical artery before delivery. These findings are consistent with an increase in fetoplacental vascular impedance at the capillary level and may account for the impaired gas and nutrient transfer in this disorder.

Expression of cell adhesion molecules in placentae from pregnancies complicated by pre-eclampsia and intrauterine growth retardation

Platelets and neutrophils are involved in maternal placental vascular damage in pre-eclampsia. Recruitment of these cells is probably mediated by cell adhesion molecules expressed at the uteroplacental bed. It remains controversial as to whether platelets and neutrophils mediate damage to trophoblast or villous vasculature. The purpose of this study was to determine the expression of cell adhesion molecules in placentae from normal pregnancies and pregnancies complicated by pre-eclampsia and intrauterine growth retardation (IUGR). Immunostaining for platelet endothelial cell adhesion molecule (PECAM) and intercellular adhesion molecule-1 (ICAM-1) was localized mainly to the endothelium of stem villi, intermediate villi, terminal villi and decidual vessels. Scattered staining for ICAM-1 was also evident in the stroma and fetal membranes. The endothelium of stem villi, intermediate villi and terminal villi were all negative for vascular cell adhesion molecule-1 (VCAM-1) and E-Selectin. PECAM, ICAM-1 and ICAM-2 mRNA were all detectable in normal placentae using northern blotting analysis whereas mRNA for E-Selectin and VCAM-1 were both undetectable. There were no differences in cell adhesion molecule immunostaining or mRNA expression in placentae from pregnancies complicated by pre-eclampsia and IUGR inconclusion, expression of cell adhesion molecules in placentae from pre-eclampsia and IUGR are consistent with a normal physiological role in vascular function.

Increased concentrations of cytokines interleukin-6 and interleukin-1 receptor antagonist in plasma of women with preeclampsia: a mechanism for endothelial dysfunction?

OBJECTIVE

To determine if plasma concentrations of defined cytokines are increased in women with preeclampsia, and to correlate any increases with the elevated concentrations of the vascular cell adhesion molecule (VCAM)-1.

METHODS

Twenty primigravidas with preeclampsia were compared to 20 healthy primigravidas. Plasma levels of cytokines, tumor necrosis factor-alpha (TNF alpha), interleukin (IL)-6, IL-8, IL-1 beta, IL-1 receptor antagonist (IL-1ra), granulocyte macrophage-colony-stimulating factor (GM-CSF), and VCAM-1, were measured by enzyme-linked immunosorbent assay.

RESULTS

Concentrations of IL-6 and IL-1ra were significantly higher (P < .01) in preeclamptic women (2.56 and 251.85 pg/mL, respectively) compared to normal pregnant patients (2.06 and 142.00 pg/mL, respectively). There were no significant changes in concentrations of TNF alpha, IL-8, GM-CSF, and IL-1 beta in preeclamptic patients (14.09, 50.52, 125.8, and 2.08 pg/mL, respectively) compared to normal patients (11.96 44.46, 121.3, and 2.01 pg/mL, respectively). Serum concentrations of VCAM-1 were increased in women with preeclampsia (preeclamptic group 841.9 +/- 49.7 ng/mL, control group 560.2 +/- 47.9 ng/mL; t = 3.673, P < .001). Interleukin-6 and IL-1ra concentrations correlated with VCAM-1 concentrations (IL-6: r = 0.539, z = 2.9, P < .005; IL-1ra: r = 0.451, z = 2.428, P < .02).

CONCLUSIONS

Increased cytokine concentrations may contribute to the endothelial damage that occurs with preeclampsia and may explain the mechanism underlying leukocyte activation in this disorder. The increased cytokine concentration may also be responsible for the endothelial adhesion that accompanies preeclampsia.

The contribution of dystocia to the cesarean section rate

OBJECTIVE

Our purpose was to examine the indications for performing cesarean sections in current obstetric practice and to define and measure the true contribution of dystocia ("difficult labor") to the overall cesarean section rate.

STUDY DESIGN

A prospective audit was done of all cesarean sections performed during 1991 at The Queen Mother's Hospital, Glasgow, a teaching hospital and tertiary referral center.

RESULTS

The cesarean section rate for 1991 was 16.3%. Dystocia was the primary indication in 16% of all cesarean sections in 1991 but was actually a contributing factor, directly or indirectly, in the decision to operate in up to 38% of all cesarean sections that year. Seventy-eight percent of patients delivered because of dystocia were in spontaneous labor. We advocate more widespread use of a policy of active management in nulliparous women who labor spontaneously. If dystocia is addressed successfully, then many repeat cesarean sections may also be avoided.

CONCLUSIONS

Improved management of dystocia in nulliparous women, such as the use of a policy of active management of labor, may be the most useful approach to reducing the cesarean section rate in modern obstetric practice.

The cell adhesion molecule, VCAM-1, is selectively elevated in serum in pre-eclampsia: does this indicate the mechanism of leucocyte activation?

OBJECTIVE

To determine whether circulating levels of cell adhesion molecules, markers of endothelial damage and leucocyte activation, were increased in pre-eclampsia.

DESIGN

Serum was prepared from peripheral venous blood and stored at -70 degrees C. The cell adhesion molecules, VCAM-1, E-Selectin and ICAM-1, were measured by ELISA.

SETTING

Department of Obstetrics and Gynaecology, Royal Infirmary, Glasgow.

SUBJECTS

Sixteen primigravid women with pre-eclampsia were recruited for the study. The preeclampsia group were compared with 18 healthy primigravid women with uncomplicated pregnancies.

RESULTS

The pre-eclamptic group had significantly higher serum levels of the cell adhesion molecule VCAM-1 (t = 3.673; P < 0.001). There were no significant differences in the adhesion molecules ICAM-1 or E-Selectin.

CONCLUSIONS

Endothelial damage and dysfunction are common to all the pathological features of pre-eclampsia. This study shows that concentrations of cell adhesion molecules, which indicate leucocyte-endothelial attachment and activation, are elevated in the serum of patients with pre-eclampsia. Such increases in soluble circulating cell adhesion molecules may reflect increased expression of these molecules on the endothelium and thereby explain the mechanism for leucocyte activation in pre-eclampsia.