high fetal heart rate first trimester

high fetal heart rate first trimester

high fetal heart rate first trimester

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Fetal heart rate in the first and second trimester

A normal fetal heart rate (FHR) usually ranges from 120 to 160 beats per minute (bpm) in the in utero period. It is measurable sonographically from around 6 weeks and the normal range varies during gestation, increasing to around 170 bpm at 10 weeks and decreasing from then to around 130 bpm at term.

Evolution through gestation

Although the myocardium begins to contract rhythmically by 3 weeks after conception (from spontaneously depolarizing myocardial pacemaker cells in the embryonic heart) it is first visible on sonography around 6 weeks of gestation. The FHR is then usually around 100 to 120 beats per minute (bpm).

FHR then increases progressively over the subsequent 2-3 weeks becoming 7:

  • ~110 bpm (mean) by 5-6 weeks
  • ~170 bpm by 9-10 weeks

This is followed by a decrease in FHR becoming on average:

  • ~150 bpm by 14 weeks
  • ~140 bpm by 20 weeks
  • ~130 bpm by term

Although in the healthy fetus the heart rate is usually regular, a beat-to-beat variation of approximately 5 to 15 beats per minute can be allowed.

high fetal heart rate first trimester
high fetal heart rate first trimester

Related pathology

A slow fetal heart rate is termed fetal bradycardia and is usually defined as 1:

  • FHR <100 bpm before 6.3 weeks gestation, or
  • FHR <120 bpm between 6.3 and 7.0 weeks

A rapid fetal heart rate is termed a fetal tachycardia and is usually defined as:

  • FHR >160-180 bpm 5,7
  • FHR around 170 bpm may be classified as borderline fetal tachycardia
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A rapid and irregular fetal heart rate is usually termed a fetal tachyarrhythmia.

high fetal heart rate first trimester
high fetal heart rate first trimester

Normal Fetal Heart Rate During Pregnancy

Though there are many words to describe the moment that you first hear your baby’s heartbeat, most people use words like galloping to describe how the heart rate sounds. While the heart rate in pregnancy is faster than an adult’s heart rate, the truth is that a normal fetal heart rate changes during the stages of pregnancy and throughout the day.1


Throughout Pregnancy

At about five weeks gestation, your baby’s heart begins to beat. At this point, a normal fetal heart rate is about the same as the mother’s: 80 to 85 beats per minute (bpm). From this point, it will increase its rate of about three beats per minute per day during that first month. This is so exact that your doctor or midwife can actually use heart rate to help pinpoint the gestational age of your baby via ultrasound.

By the beginning of the ninth week of pregnancy, the normal fetal heart rate is an average of 175 bpm. At this point, it begins a rapid deceleration to the normal fetal heart rate for mid-pregnancy, about 120–180 bpm. There is also a slowing of the normal fetal heart rate in the last 10 weeks of pregnancy, though the normal fetal heart rate is still about twice the normal adult’s resting heart rate.

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Throughout the Day

Your baby’s normal fetal heart rate will also vary naturally throughout the day and night, just as your own heart rate does. Movement, sleeping, and other activities can cause normal variation. Be sure to talk to your midwife or doctor about any concerns that you have with your baby’s heart rate.

If you are having a non-stress test at the end of pregnancy, you can hear the fluctuations. The heart rate goes up and down within a certain framework of normal. Imagine what it would sound like if you had ongoing audio of your heart rate as you were starting to exercise and then cooling down. Your heart rate would go up and down as well. Your baby has the same reaction.

fetal heart rate
fetal heart rate

Monitoring Baby’s Heart Rate

Some parents may wonder if monitoring the baby’s heart rate from day to day while at home is a smart idea. But the practice has pros and cons.

At Home

Some parents feel better when they can monitor the baby’s heartbeat from home. This use of a doppler in the home is not recommended for most people. The concerns are multi-pronged and include overuse of the doppler listening device and/or misinterpretation, positively or negatively.

There are other ways to listen to your baby’s heartbeat. Talk to your doctor or midwife about how to best monitor your baby if you are concerned.

In Labor

Fetal monitoring in labor can be done by intermittent auscultation, which means listening with a stethoscope, fetoscope, or handheld doppler at various points in labor. Your baby may be monitored intermittently with an external monitoring belt. Or your practitioner may recommend continuous monitoring, either external or internal.2

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Each of these practices has benefits and tradeoffs for you and your baby, depending on your labor and your medical history. Talk to your doctor or midwife for advice on which is best for you. In general, low-risk pregnancies will need less monitoring in labor.

However, during the process of labor, your baby may show signs of needing more intense monitoring or your labor or interventions may require increased monitoring to help boost the safety of procedures. For example, even if you are low risk, if you have a Pitocin induction of labor you will likely have continuous external monitoring.


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