Таблица и Калькулятор Частоты Сердцебиения Плода

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.

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.

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.

Ограничения

• 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.

Частые вопросы

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.

Источники

1. Sholapurkar SL et al. Fetal Heart Rate Tracing: Assessment and Clinical Interpretation. StatPearls, NCBI Bookshelf.
2. MedlinePlus. Fetal health and development.
3. American College of Obstetricians and Gynecologists. How Your Fetus Grows During Pregnancy.
4. MedlinePlus. Prenatal care.