Fetal Wellbeing Monitoring
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Direct answer
Fetal movements felt by the mother are the oldest and still the first line of fetal surveillance — the Cardiff count-to-ten method asks her to record the time taken to feel 10 movements, and a warning is raised when that takes over 12 hours (or, in the simpler "count to ten in two hours" version, fewer than 10 movements). Formal antepartum testing then layers a non-stress test (NST), whose reactive pattern at and beyond 32 weeks needs at least two accelerations of 15 beats per minute lasting 15 seconds in 20 minutes, with amniotic fluid volume; the biophysical profile scores five components — NST, breathing, gross movements, fetal tone and amniotic fluid volume — at 2 points each, where 8-10 is reassuring, 6 is equivocal and repeat testing or delivery, and 4 or less usually delivers. Doppler velocimetry is the growth-restricted fetus's test; the NST is the post-dates and post-term fetus's test.
What you must remember
- Daily fetal movement count (Cardiff): 10 movements within 12 hours is normal at term; fewer than 10 movements, or a maternal report of reduced movements, triggers same-day assessment — never reassurance alone.
- NST reactive criteria (32 weeks and beyond): two or more accelerations of at least 15 bpm above baseline for at least 15 seconds within 20 minutes (10 x 10 before 32 weeks); a non-reactive NST gets extended, then provoked (vibroacoustic stimulation) before escalation.
- Biophysical profile (BPP): NST plus breathing movements (at least one of 30 seconds), gross body movements (three), tone (flexion-extension), and amniotic fluid (single deepest pocket over 2 cm) — each scored 0 or 2; 8-10 normal, 6 equivocal (repeat in 24 hours or deliver if high risk), 4 or below delivers.
- Modified BPP: NST plus amniotic fluid index — the practical compromise; normal is reassuring for one week in most high-risk protocols.
- Interpretation anchor: the BPP is a composite of acute (NST, breathing, movement, tone — CNS markers) and chronic (fluid — long-term perfusion) markers, so a low score with normal fluid reads acute change, and oligohydramnios alone reads chronic compromise.
- Doppler assignments: umbilical artery Doppler for suspected growth restriction (times delivery); middle cerebral artery peak systolic velocity for fetal anaemia (isoimmunisation, parvovirus); ductus venosus for the very preterm compromised fetus; uterine artery at 20-24 weeks for pre-eclampsia screening.
- Contraction stress test: oxytocin or nipple stimulation to three contractions in 10 minutes — late decelerations after each contraction is positive, meaning uteroplacental insufficiency; rarely used now but examinable.
- Timing of testing: most high-risk pregnancies are tested weekly from about 32-34 weeks; post-dates pregnancies get twice-weekly NST plus fluid from 41 weeks.
Reading a non-stress test from the tracing
Take a 34-week diabetic whose NST strip shows a baseline of 140 with rhythmic variability and two clear accelerations to 158 lasting 20 seconds during fetal movements. Acceleration with movement is intact autonomic coupling — reactive, a healthy fetus with its somatic and sympathetic systems talking to each other; the report reads "reactive NST" and she goes home to count movements daily. Give the same patient a flat baseline with minimal variability and no accelerations across 40 minutes: extend the test, then try vibroacoustic stimulation with the artificial larynx — a healthy sleeping fetus wakes and accelerates; a fetus that fails to respond moves to BPP or, with other risk factors, to admission and delivery planning.
Now escalate to the full BPP on a growth-restricted 35-week fetus: breathing absent, one movement in 30 minutes, tone absent, deepest pocket 1.8 cm, NST non-reactive — total 2 out of 10. Chronic hypoxia has stripped the composite from the top down (breathing goes first, tone last — the biophysical decompensation sequence Manning described), and the answer is delivery. Contrast the same fetus a week earlier with an 8/10 profile but abnormal umbilical Dopplers: the BPP says "currently compensated", the Doppler says "placenta failing" — and Doppler wins the timing argument, which is exactly the reasoning the exam wants you to display.
Examiners love thresholds
The arithmetic marks sit in three numbers: 15 by 15 (acceleration size and duration), 2 cm (deepest pocket for fluid), and 6 versus 4 (BPP decision bands). The recurrent distractor is applying the 15-by-15 rule before 32 weeks — preterm fetuses accelerate less, hence the 10-by-10 rule. And the classic one-liner asks which BPP component reflects chronic rather than acute status: amniotic fluid volume, because fetal urine output falls over days to weeks of hypoperfusion.
Frequently asked questions
What makes a non-stress test reactive?
At and beyond 32 weeks, two or more accelerations of at least 15 beats per minute above baseline, each lasting at least 15 seconds, within 20 minutes.
What are the five components of the biophysical profile?
Non-stress test, fetal breathing movements, gross body movements, fetal tone and amniotic fluid volume, each scored 0 or 2 for a maximum of 10.
What biophysical profile score mandates delivery?
A score of 4 or less generally warrants delivery depending on gestation; 6 is equivocal and is repeated within 24 hours or acted on in high-risk settings.
Which BPP component indicates chronic fetal compromise?
Amniotic fluid volume — reduced urine output from sustained hypoperfusion shrinks fluid over weeks, while the other four markers reflect acute CNS oxygenation.
What does a daily fetal movement count of fewer than 10 movements in 12 hours mean?
Possible fetal compromise requiring same-day formal assessment with cardiotocography — maternal perception of reduced movement is never dismissed.