Biparietal diameter at 11-13 weeks' gestation in fetuses with open spina bifida.

Abstract

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.

• Authors: A Khalil, A Coates, A Papageorghiou, A Bhide, B Thilaganathan
• Journal: Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology (Ultrasound Obstet Gynecol) Vol. 42 Issue 4 Pg. 409-15 (Oct 2013) ISSN: 1469-0705 [Electronic] England
• PMID: 23362051 (Publication Type: Journal Article)
• Copyright: Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.

Topics

• Adult
• Case-Control Studies
• Cephalometry (methods)
• Crown-Rump Length
• Female
• Gestational Age
• Humans
• Maternal Age
• Parietal Bone (diagnostic imaging, embryology)
• Pregnancy
• Pregnancy Trimester, First
• ROC Curve
• Retrospective Studies
• Spina Bifida Cystica (diagnostic imaging, embryology)
• Ultrasonography, Prenatal (methods)