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Combined screening for open spina bifida at 11-13 weeks using fetal biparietal diameter and maternal serum markers
Jean-Pierre Bernard1, Howard S Cuckle, Maguy A Bernard
1Centre Hospitalier Universitaire Necker-Enfants Malades, Assistance Publique-Hôpitaux de Paris, Université Paris Descartes, and Société Française pour l'Amélioration des Pratiques Echographiques, Paris, France. bernardjeanpierre@me.com
Insights
Early screening for open spina bifida using first-trimester ultrasound biparietal diameter (BPD) and maternal serum markers like alpha-fetoprotein (AFP) can improve detection rates. Combining these markers offers a promising approach for early identification of open spina bifida.
Area of Science:
- Maternal-fetal medicine
- Prenatal screening
- Neural tube defect detection
Background:
- Ultrasound biparietal diameter (BPD) at 11-13 weeks detects 50% of open spina bifida.
- Maternal serum alpha-fetoprotein (AFP) is elevated 3-4 fold at 15-19 weeks in open spina bifida cases.
Purpose of the Study:
- To assess the efficacy of combined first-trimester screening for open spina bifida.
- To evaluate the use of biparietal diameter (BPD), maternal serum AFP, and other serum markers for early detection.
Main Methods:
- Maternal serum AFP, free beta-human chorionic gonadotropin (β-hCG), and pregnancy-associated plasma protein-A (PAPP-A) were measured at 11-13 weeks.
- A multivariate Gaussian model predicted screening performance using BPD and serum marker data.
Main Results:
- Median AFP levels were significantly higher (1.201 MoM) in open spina bifida cases.
- Combined screening with BPD, AFP, and free β-hCG predicted a 58% detection rate at a 5% false-positive rate.
- This combined approach increased detection by 2% compared to BPD and AFP alone.
Conclusions:
- Combining first-trimester BPD, AFP, and free β-hCG enhances open spina bifida detection.
- This integrated screening strategy allows for early identification of approximately two-thirds of open spina bifida cases.
Objective:
Screening at 11-13 weeks with ultrasound biparietal diameter (BPD) can detect half of open spina bifida cases. Maternal serum α-fetoprotein (AFP) levels at 15-19 weeks are increased 3- to 4-fold, in open spina bifida. We assessed whether combined screening using BPD, AFP, and other serum markers at 11-13 weeks would increase detection.
Study Design:
Maternal AFP levels were measured on serum stored at 11-13 weeks in 44 open spina bifida and 182 unaffected pregnancies, and results were expressed in multiples of the median (MoM) for gestational age. All samples had been measured for free β-human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein (PAPP)-A. A multivariate Gaussian model was used to predict screening performance from the serum data and BPD measurements on 80 cases, including 36 previously published.
Results:
The median AFP level in cases was 1.201 MoM, significantly higher than in unaffected pregnancies (P < .01, 1 tail). The median free β-hCG was significantly reduced to 0.820 MoM (P < .02), but the median PAPP-A was similar in cases and controls. Modeling predicted the following: BPD alone would detect 50% of cases for a 5% false-positive rate or 63% for 10%; adding AFP increases detection by 2%; and a combined test with BPD, AFP, and free β-hCG detects 58% for 5% or 70% for 10%.
Conclusion:
Combining AFP and BPD with free β-hCG as part of first-trimester aneuploidy screening would also allow early detection about two-thirds of cases with open spina bifida.
