Tabla y Calculadora de Frecuencia Cardíaca Fetal
Rastree la frecuencia cardíaca fetal normal por semana de embarazo. Entienda el línea base, variabilidad y qué esperar durante cada trimestre.
Descargo de responsabilidad: Esta herramienta es solo para fines informativos y no reemplaza el consejo médico profesional. Siempre consulte a su proveedor de atención médica para preocupaciones sobre la frecuencia cardíaca fetal.
Entendiendo los Patrones de Frecuencia Cardíaca Fetal
En la Semana 20
Rango Normal
120-160
BPM
Frecuencia Cardíaca de Línea Base
140
BPM avg
Status
Second trimester - heart rate stabilizing
Entendiendo los Patrones de Frecuencia Cardíaca Fetal
El monitoreo de la frecuencia cardíaca fetal (FCF) es una herramienta importante para evaluar el bienestar fetal durante el embarazo. La FCF normal cambia durante la gestación.
Frecuencia Cardíaca de Línea Base
Línea base: La frecuencia cardíaca promedio durante un período de 10 minutos, excluyendo aceleraciones y desaceleraciones. La línea base normal es 110-160 lpm.
Variabilidad de la Frecuencia Cardíaca
Variabilidad: Fluctuaciones en la frecuencia cardíaca de línea base. La variabilidad normal indica un sistema nervioso fetal saludable y receptivo.
Aceleraciones
Aceleraciones: Aumentos temporales en la frecuencia cardíaca de al menos 15 lpm por encima de la línea base, durando al menos 15 segundos. Estos son signos reconfortantes.
Deceleraciones
Deceleraciones: Disminuciones temporales en la frecuencia cardíaca. Las desaceleraciones tempranas suelen ser benignas, pero las desaceleraciones variables o tardías pueden requerir atención médica.
Cuándo Preocuparse
- Frecuencia cardíaca consistentemente por debajo de 110 lpm (bradicardia)
- Frecuencia cardíaca consistentemente por encima de 160 lpm (taquicardia)
- Movimientos fetales disminuidos o ausentes
- Variabilidad de frecuencia cardíaca ausente o mínima
- Deceleraciones repetitivas
- Cualquier cambio repentino o significativo en los patrones
- Patrón de movimiento fetal reducido
Fetal Heart Rate Visualization
Fetal heart rate is one of the few direct windows onto fetal wellbeing, and it is interpreted quite differently depending on when in pregnancy it is measured. In the first trimester it is used to confirm viability and follows a rising then falling curve; from the third trimester onward it is monitored as a pattern over time, where the baseline matters far less than variability and how the rate responds to contractions.
Early pregnancy: the rise and fall
Fetal cardiac activity becomes detectable on transvaginal ultrasound at around six weeks, starting near the maternal rate and then accelerating rapidly as the cardiac conduction system develops. It peaks around nine weeks and then settles towards the range maintained for the rest of pregnancy.
- A persistently slow rate in early pregnancy, particularly under 100 bpm at seven weeks or beyond, is associated with a higher risk of loss and is normally followed with a repeat scan.
- The old idea that heart rate predicts sex has been examined repeatedly and does not hold.
| Gestational age | Typical fetal heart rate (bpm) |
|---|---|
| 6 weeks | 100 to 115 |
| 7 weeks | 120 to 145 |
| 8 weeks | 145 to 170 |
| 9 weeks | 155 to 195 (peak) |
| 10 weeks | 150 to 180 |
| 12 weeks | 145 to 170 |
| 14 weeks onward | 110 to 160 |
Later pregnancy: what monitoring actually assesses
From the third trimester the normal baseline is 110 to 160 beats per minute, but the baseline alone is the least informative part of a trace. Variability, the beat-to-beat fluctuation around the baseline, is the strongest single indicator of an intact fetal autonomic nervous system and adequate oxygenation, and reduced variability is more concerning than a baseline near a limit.
The other components are accelerations, transient rises that are reassuring, and decelerations, whose significance depends on their shape and timing relative to contractions. Early decelerations mirroring a contraction reflect head compression and are benign; variable decelerations suggest cord compression; and late decelerations, beginning after the contraction peak, suggest placental insufficiency and are the pattern that most often prompts intervention.
| Feature | Reassuring | Concerning |
|---|---|---|
| Baseline | 110 to 160 bpm | Under 110 (bradycardia) or over 160 (tachycardia), sustained |
| Variability | Moderate, 6 to 25 bpm | Absent or minimal, under 5 bpm |
| Accelerations | Present | Absent over a prolonged period |
| Decelerations | None, or early only | Late or recurrent variable decelerations |
Why continuous monitoring is debated
Continuous electronic fetal monitoring in labour was introduced on the expectation that it would reduce cerebral palsy and perinatal death. Randomised trials have not shown that benefit for low-risk pregnancies, while consistently showing increases in caesarean and instrumental delivery rates, because the trace has high sensitivity and low specificity for genuine fetal compromise.
This is why intermittent auscultation is recommended for low-risk labour in several national guidelines, with continuous monitoring reserved for pregnancies with identified risk factors. It is a good example of a monitoring technology whose information content is real but whose decision threshold is hard to set.
Limitaciones
- Fetal heart rate patterns have high sensitivity and low specificity for fetal compromise. An abnormal trace much more often reflects a normal fetus than a compromised one.
- Early pregnancy ranges are wide and overlap between gestational ages, and dating itself carries uncertainty, so a single measurement is interpreted alongside dating and other findings.
- Interpretation of a trace requires training and the full clinical context. Isolated numbers from a home doppler cannot be interpreted meaningfully.
- Home dopplers are a recognised hazard for exactly this reason: false reassurance from a detected heartbeat has been implicated in delayed presentation when fetal movements have reduced.
- Maternal fever, medication, dehydration and maternal heart rate being picked up instead of fetal all distort readings.
- Reduced fetal movement should always prompt contact with the maternity unit, regardless of any heart rate a home device reports.
Preguntas frecuentes
What is a normal fetal heart rate?
From about 14 weeks onward, 110 to 160 beats per minute. Earlier in pregnancy the rate rises from around 100 to 115 at six weeks to a peak of 155 to 195 around nine weeks, then settles into the normal range.
Does fetal heart rate predict the baby sex?
No. The idea has been examined repeatedly and does not hold. Heart rate varies with gestational age and fetal activity, not with sex.
What matters most on a monitoring trace?
Variability, the beat-to-beat fluctuation around the baseline. Moderate variability of 6 to 25 bpm is the strongest single indicator of adequate oxygenation, and reduced variability is more concerning than a baseline near a limit.
Which decelerations are worrying?
Late decelerations, which begin after the peak of a contraction and suggest placental insufficiency, and recurrent variable decelerations, which suggest cord compression. Early decelerations that mirror a contraction reflect head compression and are benign.
Should I use a home fetal doppler?
They are generally advised against. Finding a heartbeat can produce false reassurance, and delayed presentation after reduced fetal movements is a recognised harm. Reduced movement warrants contacting the maternity unit regardless of what a home device shows.