What Causes High Fetal Heart Rate?

A high fetal heart rate (FHR) during pregnancy is generally considered a heart rate above 160 to 170 beats per minute (bpm) during the second trimester and above 160 bpm during the third trimester. It’s important to note that fetal heart rates can vary, and some fluctuation is normal. Fetal heart rate can be influenced by a variety of factors, both physiological and non-physiological. Here are some potential causes of a high fetal heart rate:

  • Physiological Factors:
    • Gestational Age: Fetal heart rate tends to be higher earlier in pregnancy and gradually decreases as the pregnancy progresses.
    • Activity Level: Fetal heart rate can increase temporarily in response to fetal movement.
    • Maternal Activity: Maternal exercise, stress, and other activities can influence fetal heart rate.
    • Fetal Activity: Fetal movements and hiccups can temporarily raise the heart rate.
  • Non-Physiological Factors:
    • Maternal Anxiety or Stress: Elevated maternal stress or anxiety can lead to increased fetal heart rate.
    • Maternal Fever: Maternal fever can affect the fetal heart rate.
    • Medications or Substances: Certain medications or substances can affect fetal heart rate, such as medications that stimulate the mother’s heart rate.
    • Maternal Hyperthyroidism: An overactive thyroid in the mother can sometimes affect fetal heart rate.
    • Infection: Infections affecting the mother can sometimes lead to an elevated fetal heart rate.
    • Fetal Anemia: In some cases, fetal anemia (low red blood cell count) can cause a higher heart rate as the heart works harder to compensate for the decreased oxygen-carrying capacity of the blood.
    • Fetal Arrhythmias: In rare cases, abnormal heart rhythms (arrhythmias) in the fetus can cause a high heart rate.
    • Medications Administered During Labor: Some medications used during labor, such as certain pain relief drugs, can temporarily affect fetal heart rate.

It’s important to note that while a high fetal heart rate can sometimes be a normal variation, it’s always advisable to consult with a healthcare professional, typically an obstetrician or midwife, if you have concerns about your baby’s heart rate during pregnancy. Monitoring and assessment by a medical professional are crucial to ensure the well-being of both the mother and the fetus. They can determine whether further evaluation or testing is needed and provide appropriate guidance based on the specific circumstances.