Small biparietal diameter in the first trimester and pregnancy outcome
Bibliographic record
Abstract
The biparietal diameter (BPD) should be measured as part of the routine first-trimester ultrasound examination1. Several recent reports have suggested that identification of a small BPD at 11–14 weeks' gestation, adjusted for crown–rump length, may pick up 60–70% of fetuses with spina bifida, with a 5–10% false-positive rate2-4. However, introducing a policy of BPD measurement at an early gestational age, when termination of pregnancy may be considered, may result in unnecessary anxiety in women and health practitioners if a small BPD is noted. The association between small BPD in the first trimester and adverse pregnancy outcome is controversial; the finding has been variously associated with chromosomal anomalies5 and small-for-gestational-age (SGA) newborns. This prompted us to analyze the outcomes of fetuses with small BPD measurements on the first-trimester scan. We performed a retrospective study of women who had undergone routine first-trimester ultrasound examination at Necker Hospital, Paris, between 1 January 2009 and 1 January 2012. Of 6584 patients, 437 (6.6%) were lost to follow-up. Of the remaining 6147 patients with known pregnancy outcomes, 799 (13.0%), 432 (7.0%) and 246 (4.0%) had a fetus with a BPD below the 10th, 5th and 2.5th percentile, respectively. In the subgroup lost to follow-up, 66 fetuses (15.1%) had a BPD below the 10th percentile (P = 0.27). We found a strong association between BPD ≤ 10th percentile and risk of spina bifida (n = 5/9; odds ratio (OR) 8.41 (95% confidence interval (CI) 1.97–37.2), P = 0.0029), using a significance level of P < 0.05. This measurement was not associated with other adverse outcomes, including early miscarriage (n = 1/29; OR, 0.24 (95% CI, 0.01–1.63), P = 0.16), intrauterine fetal death (n = 7/45; OR, 1.57 (95% CI, 0.63–3.75), P = 0.32), fetal and newborn malformations (n = 30/201; OR, 1.18 (95% CI, 0.79–1.75), P = 0.31), abnormal karyotype (n = 8/53; OR, 1.19 (95% CI, 0.52–2.64), P = 0.64), termination of pregnancy (n = 20/124; OR 1.29 (95% CI, 0.77–2.15), P = 0.29), SGA (n = 125/868; OR, 1.15 (95% CI, 0.93–1.42), P = 0.18) or preterm delivery (n = 88/597; OR, 1.18 (95% CI, 0.92–1.50), P = 0.18). There was a similar lack of association between first-trimester BPD and adverse outcomes for measurements below the 5th and 2.5th percentiles (Table S1). Given the low incidence of adverse pregnancy outcomes after 11 weeks, detecting a 50% increase in the composite adverse outcome risk (from 2 to 3%, for example) would require more than 3500 fetuses with BPD measurements under the 10th percentile. However, our study does not support any strong association between a small BPD in the first trimester and adverse pregnancy outcomes, other than for spina bifida. A small BPD at 11–14 weeks' gestation should prompt a careful examination of the fetal spine. In the absence of a neural tube defect, a small first-trimester BPD does not seem to be associated with other adverse outcomes, and patients can be immediately reassured, even if the value is below the 5th or 2.5th percentile. D. Socolov†, B. Deloison‡§, J.P. Bernard‡§, Y. Ville‡§ and L.J. Salomon*‡§ †Grigore T. Popa University of Medicine and Pharmacy, Iasi, Romania and Agence Universitaire de la Francophonie, projet no: 56135FT2A0/U GrPopaIasi-Socolov, ‡Department of Obstetrics and Maternal-Fetal Medicine, GHU Necker-Enfants Malades, AP-HP, University of Paris Descartes, 149, rue de Sevres 75015, Paris, France; §Société Française pour l'Amélioration des Pratiques Echographiques, Paris, France *Correspondence. (e-mail: [email protected]) Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. The following supporting information may be found in the online version of this article: Table S1 Pregnancy outcome of fetuses with small biparietal diameter in the first trimester.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.039 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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 teacher head, 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".