Maternal placental abnormality and the risk of sudden infant death syndrome.
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To determine whether placental abnormality (placental abruption or placental previa) during pregnancy predisposes an infant to a high risk of sudden infant death syndrome (SIDS), the authors conducted a population-based case-control study using 1989-1991 California linked birth and death certificate data. They identified 2,107 SIDS cases, 96% of whom were diagnosed through autopsy. Ten controls were randomly selected for each case from the same linked birth-death certificate data, matched to the case on year of birth. About 1.4% of mothers of cases and 0.7% of mothers of controls had either placental abruption or placenta previa during the index pregnancy. After adjustment for potential confounders, placental abnormality during pregnancy was associated with a twofold increase in the risk of SIDS in offspring (odds ratio = 2.1, 95% confidence interval 1.3-3.1). The individual effects of placental abruption and placenta previa on the risk of SIDS did not differ significantly. An impaired fetal development due to placental abnormality may predispose an infant to a high risk of SIDS. (+info)
Placenta previa: preponderance of male sex at birth.
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To determine the relation between placenta previa and male sex at birth, the authors conducted two types of analysis: 1) a historical cohort analysis of singleton live births in New Jersey hospitals during 1989-1992 (N = 447,963); and 2) a meta-analysis of previously published studies on the subject. For the cohort analysis, subject mother-infant dyads were identified from linked birth certificate and maternal and infant hospital claims data. The infant's sex for mothers with an International Classification of Diseases, Ninth Revision, Clinical Modification, code of 641.0-641.1 for placenta previa (n = 2,685) was compared with infant's sex for mothers without placenta previa (n = 445,270). For the meta-analysis, seven published articles were located and summary effects were calculated using both fixed-effect and random-effects models. In the present cohort study, the male:female ratio at birth was significantly higher in women with placenta previa (1.19) than in those without placenta previa (1.05) (p<0.001). The association of placenta previa with male sex persisted when the analysis was either stratified or adjusted for the effects of maternal age, maternal parity, maternal smoking during the index pregnancy, race/ethnicity, the infant's gestational age, and the infant's birth weight. The meta-analytic results from the fixed-effect and random-effects models showed a 14% excess of placenta previa when women were carrying a viable male fetus as compared with a viable female fetus during pregnancy. The results were the same regardless of whether the present cohort study was included in the meta-analysis. In conclusion, the evidence obtained from these analyses strongly argues for an association between placenta previa and male sex at birth. The mechanism for this association remains to be determined. (+info)
Prenatal diagnosis of placenta previa accreta by transabdominal color Doppler ultrasound.
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OBJECTIVE: The aim of this study was to evaluate the efficacy of transabdominal color Doppler ultrasound in diagnosing placenta previa accreta. DESIGN: Eighty patients with persistent placenta previa underwent transabdominal B-mode and color Doppler ultrasound evaluation in the second and third trimesters because they had a high risk of placenta accreta. Color Doppler imaging criteria used included diffuse intraparenchymal placental lacunar flow; focal intraparenchymal placental lacunar flow; bladder-uterine serosa interphase hypervascularity; prominent subplacental venous complex; and loss of subplacental Doppler vascular signals. The color Doppler images were interpreted prospectively for signs of placenta previa accreta according to the exhibited color Doppler sonographic features. RESULTS: Sixteen of the 80 patients exhibited characteristic color Doppler imaging patterns highly specific for placenta accreta according to the preceding criteria, and 14 of these had histopathological proof of placenta accreta. Two patients had false-positive color Doppler imaging evidence mistaken for interphase hypervascularity caused by bladder varices. Thirteen patients underwent hysterectomy in the group suspicious for accreta. Of the 64 patients with negative color Doppler imaging results, three had placenta accreta, while two required cesarean hysterectomy; the remaining patient underwent uterine artery ligation for bleeding from the lower uterine segment. The sensitivity of color Doppler imaging in the diagnosis of placenta previa accreta was 82.4% (14/17) and the specificity was 96.8% (61/63). The positive and negative predictive values were 87.5% (14/16) and 95.3% (61/64), respectively. CONCLUSIONS: Variable vascular morphological patterns of placenta previa accreta were exhibited and categorized by transabdominal color Doppler sonography in the antenatal period. The identification of these specific vascular patterns had a positive impact on the peripartum clinical management of the affected patients. (+info)
Caesarean section for placenta praevia: a retrospective study of anaesthetic management.
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A retrospective survey of anaesthesia for Caesarean section (CS) for placenta praevia was performed, covering the period between January 1, 1984 and December 31, 1998. Three hundred and fifty consecutive cases of placenta praevia were identified. Overall a regional technique was used 60% of the time. Five women had a placenta accreta which required Caesarean hysterectomy: one had general anaesthesia (GA) throughout and four initially received a single-shot spinal injection. Of these latter four cases, two were converted to GA during the hysterectomy and two continued with spinal anaesthesia throughout. Two other women (both GA), suffered postoperative thrombotic episodes (one pulmonary embolus and one cerebral thrombosis) but made full recoveries. Control of blood pressure when using regional anaesthesia (RA), even in the presence of considerable haemorrhage, was not a problem. Statistical regression models indicated that RA was associated with a significantly reduced estimated blood loss and reduced need for blood transfusion. This retrospective survey finds no data to support the much quoted aphorism that RA is contraindicated for CS in the presence of placenta praevia. (+info)
Clinical significance of placenta previa detected at early routine transvaginal scan.
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Transvaginal ultrasonography in early pregnancy was used to determine the prevalence of placenta previa and the rate of persistence until delivery. The location of the placenta was registered systematically in 2342 pregnant women who underwent transvaginal ultrasonography at 10 to 16 weeks' gestation as a primary examination. The outcome of pregnancy as well as the presence or absence of placenta previa at delivery was noted in a total of 2158 cases. A receiver operating characteristic curve was generated for the different measurements from the edge of the placenta to the internal cervical os versus placenta previa at delivery. In 105 of the 2158 women screened in the early stages of pregnancy (4.9%) the placenta extended to or over the internal cervical os, and in 34 of 2158 patients (1.6%) the distance to the placental edge beyond the internal cervical os was equal to or greater than 14 mm. Of the eight cases of placenta previa at delivery, six (75%) were identified in our study, and two cases were missed. When a cutoff value of greater than 14 mm is used for the receiver operating characteristic curve the likelihood is 17.6% (95% confidence interval = 6.8 to 34.5) for placenta previa at delivery. Although a high percentage of false-positive results occur owing to the low prevalence at delivery, this screening procedure can identify high-risk patients who should be rescanned later in pregnancy. (+info)
The relevance of placental location at 20-23 gestational weeks for prediction of placenta previa at delivery: evaluation of 8650 cases.
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OBJECTIVE: To determine the correlation between placental position at 20-23 weeks and incidence of birth complications caused by placental position. SUBJECTS AND METHODS: In an ongoing prospective study, placental position was determined by transabdominal sonography as part of anomaly scanning at 20-23 gestational weeks, followed by transvaginal sonography in uncertain or suspicious situations. Examination was performed in 9532 cases; feedback was obtained from 8650 patients (90.7%). RESULTS: Transabdominal sonography was followed by transvaginal scan in 363 of 8650 cases (4.2%). In 8551 cases (98.9%), we found normal placental position, with the placenta not reaching the internal os and a Cesarean section rate of 17.1% (1458/8551). The incidence of 'low placental position', with the placenta reaching the internal os was 0.66% (57/8650), with a Cesarean section rate of 21% (12/57). In 0.49% (42/8650) of cases, the placenta overlapped the internal os at 20-23 weeks; Cesarean section because of placenta previa or bleeding was performed in 28 of 8650 cases (0.32%). Vaginal delivery was possible in 43% of cases (13/30), when the overlap did not exceed 25 mm. If the overlap exceeded 25 mm (12 cases), no vaginal delivery was reported. There was no reported case of placenta previa missed at the 20-23-week scan. CONCLUSION: At 20-23 weeks, a combination of routine transabdominal and indication-based transvaginal location of placental position is a powerful tool in predicting placenta previa at delivery. The advantage of determining placental position at this stage of pregnancy is a low false-positive rate compared to at earlier stages of pregnancy. We conclude that an overlapping placenta at 20-23 weeks has the consequence of a high probability of placenta previa at delivery. An overlap of 25 mm or more at 20-23 weeks seems to be incompatible with later vaginal delivery. (+info)
Diagnosis of low-lying placenta: can migration in the third trimester predict outcome?
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OBJECTIVES: To investigate the relationship between the rate of migration of a low-lying placenta during the third trimester and the eventual route of delivery. METHODS: All patients with a placenta lying within 3 cm of the internal cervical os or overlapping it on transvaginal ultrasound at > or = 26 weeks' gestation were included in the study. The exact distance between the center of the internal cervical os and the leading edge of the placenta was measured by transvaginal sonography, repeated at approximately 4-week intervals until delivery. RESULTS: The mean rates of migration in patients who had (n = 7) and who did not have (n = 29) Cesarean section for placenta previa were +0.3 mm/week and +5.4 mm/week, respectively (P < 0.0001). When the placental edge was initially > 20 mm from the internal os, migration occurred in all cases and no Cesarean section for placenta previa was performed. For those between -20 mm and +20 mm, sufficient migration to avoid Cesarean section occurred in 88.5% of cases. Beyond a 20 mm overlap, significant placental migration did not occur and all patients required Cesarean section. CONCLUSION: Placental migration may occur progressively throughout the third trimester. The initial position of the placental edge and the subsequent rate of migration can be used to predict the eventual route of delivery. (+info)
Third-trimester transvaginal ultrasonography in placenta previa: does the shape of the lower placental edge predict clinical outcome?
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OBJECTIVE: To evaluate the clinical significance of the shape of the lower placental edge in women with transvaginal sonographic diagnosis of placenta previa. DESIGN: A prospective observational study at a tertiary teaching hospital. POPULATION: A total of 104 women with confirmed transvaginal sonographic diagnosis of placenta previa before 32 weeks' gestation. METHODS: Initial transvaginal sonography was performed at between 28 and 32 weeks' gestation in 138 patients with either strong clinical suspicion or previous abdominal sonographic diagnosis of placenta previa in the early third trimester. The lower placental edge was found to be positioned over the internal cervical os in 33 women (complete previa) and within 3 cm from it in 71 women (low-lying placenta). Patients with low-lying placenta were followed up by serial transvaginal sonographic examinations until delivery; detailed information including the placental location (anterior or posterior), the distance of its edge from the internal cervical os and its thickness were recorded. The clinical outcomes of the 17 who had a thick-edge low-lying placenta were compared with those who had a thin-edge one (54 women). In patients with complete placenta previa, demographic data, the shape of the lower placental edge whenever transvaginal sonography visualized it, and the clinical outcomes were documented. The incidence of major complications in thick-edge or central placenta was compared to that in the thin-edge group. RESULTS: Women having a low-lying placenta with a thick edge had a significantly higher rate of antepartum hemorrhage (P = 0.0002), abdominal delivery (P = 0.02), abnormally adherent placenta (P = 0.012) and low birth weight (P = 0.006) than those in whom the placental edge was thin. Cesarean hysterectomy was required in six patients with complete placenta previa because of severe peripartum hemorrhage; all of them had either central or thick-edge placenta accreta. CONCLUSION: Women with placenta previa are at a relatively higher risk of developing complications if the lower placental edge is thick. Integration of the shape of the lower placental edge into transvaginal sonographic assessment of placenta previa may improve the prediction of mode of delivery and clinical outcome. (+info)