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Biparietal diameter at 11-13 weeks' gestation in fetuses with open spina bifida
A Khalil1, A Coates, A Papageorghiou
1Fetal Medicine Unit, Academic Department of Obstetrics and Gynaecology, St George's Hospital Medical School, London, UK.
Insights
Reduced biparietal diameter (BPD) in early pregnancy is associated with open spina bifida. This finding may aid in developing early screening tests for this condition.
Area of Science:
- Prenatal diagnosis
- Fetal medicine
- Obstetrics
Background:
- Open spina bifida is a serious birth defect.
- Early detection of fetal anomalies is crucial for timely intervention.
- The biparietal diameter (BPD) is a standard biometric measurement in fetal ultrasound.
Purpose of the Study:
- To investigate the association between reduced biparietal diameter (BPD) in the first trimester (11-13 weeks' gestation) and open spina bifida.
- To evaluate the predictive value of first-trimester BPD for open spina bifida.
Main Methods:
- Retrospective study of 27 fetuses with isolated open spina bifida and 7775 controls.
- BPD measurements at 11-13 weeks' gestation were analyzed as multiples of the median (MoM).
- Logistic regression and ROC curve analysis were used to assess predictive performance and associated maternal factors.
Main Results:
- 44.4% of fetuses with open spina bifida had a BPD below the 5th centile in the first trimester.
- Median BPD MoM was significantly lower in affected fetuses compared to controls (0.930 vs 0.998, P < 0.0001).
- First-trimester BPD screening achieved a 55.6% detection rate with an 11.6% false-positive rate.
Conclusions:
- Fetuses with open spina bifida exhibit a smaller biparietal diameter (BPD) during the first trimester.
- First-trimester BPD measurement shows potential as an early screening tool for open spina bifida.
- Combining BPD with maternal factors (age, BMI) and alpha-fetoprotein may enhance screening efficacy.
Objective:
To ascertain the reported association between reduced biparietal diameter (BPD) at 11-13 weeks' gestation and open spina bifida and to investigate its predictive value in a single-center study.
Methods:
This was a retrospective study of fetuses in which BPD was measured at 11-13 weeks' gestation, including 27 fetuses with isolated open spina bifida subsequently diagnosed at 16-24 weeks and 7775 unaffected controls. BPD values were converted into multiples of the expected median (MoM) after adjustment for crown-rump length and maternal characteristics. Multivariable logistic regression analysis was used to determine the maternal characteristics significantly associated with spina bifida. The performance of screening was determined by receiver-operating characteristics curve analysis. BPD values at 11-13 weeks' gestation were compared with those measured in the second trimester using Z-scores.
Results:
BPD values at 11-13 weeks' gestation were below the 5(th) centile in 44.4% of cases of open spina bifida. In these fetuses, the median BPD MoM value was significantly smaller than that in the control group (0.930 vs 0.998 MoM; P < 0.0001). Multivariable logistic regression analysis showed a significant contribution from maternal age (P = 0.008) and BMI (P = 0.028) to the association between BPD MoM and spina bifida. The detection rate using BPD measurements in the first trimester was 55.6% with a false-positive rate of 11.6%. In fetuses with open spina bifida, the BPD Z-scores were significantly lower at 16-24 weeks compared to those recorded at 11-13 weeks (median, -1.71 (range, -3.98 to -0.20) vs -1.30 (-3.75 to 2.61); P = 0.006).
Conclusion:
Fetuses with open spina bifida have a smaller BPD in the first trimester. This observation may be useful in early screening. It is likely that a combination of maternal characteristics such as age and BMI, fetal BPD and maternal serum alpha-fetoprotein measured in the first trimester would provide a clinically useful screening test for open spina bifida.
