Revealed Versus Concealed Cerebroplacental Ratio

This is a multicenter, open-label randomized trial with groups in parallel. Singleton pregnancies are recruited after routine second trimester scan (19+0 to 22+6 weeks of gestation) and randomly allocated at that moment to revealed or concealed strategy. A routine scan will be booked at 36-37 weeks. For a reduction of the stillbirth rate of 3‰ (from 5‰ to 2‰), assuming a type I error of 5% and aiming for a power of 80% a total of 11,582 subjects (5791 per arm) were projected. The participating centers sum up 12,000 deliveries a year. It is not possible to blind participants, obstetricians, or outcome assessors to the study group.

General hypothesis: A proportion of fetuses with "normal" growth as per current standards have placental insufficiency and restriction of their growth potential. These fetuses exhibit biophysical changes expressed by abnormal cerebroplacental ratio. A combination of this marker with fetal biometry for the detection of fetuses affected by fetal growth restriction could identify a group of babies on which labor induction once term is reached may prevent the occurrence of adverse outcomes.

Specific hypothesis

• The cerebroplacental ratio has predictive value in late pregnancy for placental insufficiency.
• The cerebroplacental ratio could improve the effectiveness of late pregnancy screening for the prediction placental insufficiency-related complications.

Inclusion criteria

• Viable singleton non-malformed fetus
• Available first-trimester US dating
• Maternal age at recruitment ≥18 years
• No adverse medical or obstetrical history at booking
• Capacity to give informed consent

Exclusion criteria

• Abnormal karyotype
• Structural abnormalities
• Congenital infections