Fetal assessment, prenatal screening and counselling

Overview & Definition

Most pregnancies are low risk, and most antenatal screening results come back reassuring. The difficulty is that the small number of abnormal or inconclusive results land in the middle of a working antenatal service and demand counselling, decisions and follow-through that families remember for the rest of their lives. Fetal assessment is the set of tests that estimates fetal risk, surveys fetal structure, monitors growth and placental function, and checks fetal wellbeing near term. [4] [8]

The single most important distinction in the whole topic is screening versus diagnosis. Screening estimates a probability. Diagnostic testing confirms or excludes a condition. First-trimester combined screening, cell-free DNA screening and the mid-trimester scan are screens — they tell you whether the chance of a problem is raised. Chorionic villus sampling and amniocentesis are diagnostic — they tell you what the chromosomes actually are. Blurring that line is the most common and most dangerous counselling error. [1] [16]

Antenatal screening fits classic screening principles when the condition is important, an accepted intervention exists, a suitable test is available, and the system can deliver confirmation and care rather than just a result. A positive screen that goes nowhere is not a programme. [6]

[1] [18]

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