Instruments for chorionic villus sampling for prenatal diagnosis
Bibliographic record
Abstract
BACKGROUND: Chorionic villus sampling (CVS) is the method of choice for obtaining fetal tissue for prenatal diagnosis before 15 weeks of pregnancy. CVS can be performed using either transabdominal or transcervical approach. The type of instrument used could have a significant impact on the success rate of the procedure. An ability to manoeuvre the instrument within the uterine cavity without puncturing the gestational sac, and to see the tip of the instrument on ultrasound scanning are particularly important. OBJECTIVES: The objective of this review was to assess the effects of instruments used to obtain chorionic tissue in early pregnancy by transabdominal or transcervical route (chorionic villus sampling). The outcomes of interest were technical difficulties during the procedure, quality and quantity of obtained tissue, maternal adverse effects, pregnancy outcome and cost-effectiveness. SEARCH STRATEGY: The Cochrane Pregnancy and Childbirth Group trials register was searched. Date of last search: November 2002. SELECTION CRITERIA: Randomised trials comparing different instruments (forceps, cannula, needle) for chorionic villus sampling using either transabdominal or transcervical approach. DATA COLLECTION AND ANALYSIS: Eligibility and trial quality were assessed by two reviewers. MAIN RESULTS: There were no trials comparing instruments for transabdominal CVS. Forceps and cannula were evaluated in five transcervical CVS trials involving 472 women. When a cannula was used, operators obtained an inadequate sample (less than 5 mg) more often (relative risk (RR) 4.21, 95% confidence interval (CI) 2.15 to 8.25). Compared with forceps, cannulae had to be re-inserted more often (RR 2.98, 95% CI 1.62 to 5.47). Also, inserting a cannula was more painful (RR 1.93, 95% CI 1.11 to 3.37). One study reported the cost of the procedures and found CVS with cannula to be more expensive (weighted mean difference $183.7, 95% confidence interval 152.62 to 214.78). When different types of cannulae were compared, Portex cannula was more likely to result in an inadequate sample and a difficult or painful procedure when compared with either the silver or aluminum cannula respectively. REVIEWER'S CONCLUSIONS: Although there is some evidence to support the use of small forceps for transcervical chorionic villus sampling, the evidence is not strong enough to support change in practice for clinicians who have become familiar with aspiration cannulae.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.010 | 0.036 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.008 | 0.006 |
| Bibliometrics | 0.005 | 0.005 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.014 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".