Tabela e Calculadora de Frequência Cardíaca Fetal
Acompanhe a frequência cardíaca fetal normal por semana de gravidez. Entenda a linha de base, variabilidade e o que esperar durante cada trimestre.
Aviso Legal: Esta ferramenta é apenas para fins informativos e não substitui o aconselhamento médico profissional. Sempre consulte seu provedor de saúde para preocupações sobre a frequência cardíaca fetal.
Entendendo os Padrões de Frequência Cardíaca Fetal
Na Semana 20
Faixa Normal
120-160
BPM
Frequência Cardíaca de Linha de Base
140
BPM avg
Status
Second trimester - heart rate stabilizing
Entendendo os Padrões de Frequência Cardíaca Fetal
O monitoramento da frequência cardíaca fetal (FCF) é uma ferramenta importante para avaliar o bem-estar fetal durante a gravidez. A FCF normal muda durante a gestação.
Frequência Cardíaca de Linha de Base
Linha de base: A frequência cardíaca média durante um período de 10 minutos, excluindo acelerações e desacelerações. A linha de base normal é 110-160 bpm.
Variabilidade da Frequência Cardíaca
Variabilidade: Flutuações na frequência cardíaca de linha de base. A variabilidade normal indica um sistema nervoso fetal saudável e responsivo.
Acelerações
Acelerações: Aumentos temporários na frequência cardíaca de pelo menos 15 bpm acima da linha de base, durando pelo menos 15 segundos. Estes são sinais reconfortantes.
Desacelerações
Desacelerações: Diminuições temporárias na frequência cardíaca. As desacelerações precoces geralmente são benignas, mas as desacelerações variáveis ou tardias podem exigir atenção médica.
Quando Se Preocupar
- Frequência cardíaca consistentemente abaixo de 110 bpm (bradicardia)
- Frequência cardíaca consistentemente acima de 160 bpm (taquicardia)
- Movimentos fetais diminuídos ou ausentes
- Variabilidade de frequência cardíaca ausente ou mínima
- Desacelerações repetitivas
- Quaisquer mudanças repentinas ou significativas nos padrões
- Padrão de movimento fetal reduzido
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.
Limitações
- 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.
Perguntas frequentes
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.