Kristen Bell, the House of Lies star, and actress in the Disney animated film, Frozen (coming out in theatres this November), admits to having re-recorded her lines in the film due to a pregnancy side effect: voice change. Along with her fiancé Dax Shepard, the 33-year old welcomed daughter Lincoln to the world this past March.

“The pregnancy did change my voice. It made it deeper, there were more womanly tones when I did one recording while I was extremely pregnant,” Bell told People magazine. While the blonde beauty raves about how much she loves motherhood, stating that her daughter is “absolutely intoxicating,” the change in her vocal range leaves many wondering: how common is this pregnancy side effect?

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The Voice Change: Pregnancy Side Effect

A deeper voice as a side effect of pregnancy doesn’t affect most women to the same degree it affected Bell. As an actress, Bell heavily relies on her voice to accurately and successfully portray the characters she plays. For Frozen, the actress told People “I had to go back and re-record those lines so they matched. There was something different about my voice.”

Bell speculated that the hormonal changes that usually accompany pregnancy were the cause of the deeper octave.

She may be right, according to Dr. Reena Gupta, laryngologist and director of the Voice and Swallowing Center at Osborne Head & Neck Institute (OHNI) in California. According to Dr. Gupta, the significant rise in estrogen and progesterone changes during pregnancy affects every aspect of a woman’s body. Several changes that could affect a expectant mother’s voice include:

Swelling (edema) of the vocal folds

Pregnancy increases the heaviness of the vocal folds, which in turn can alter your octave range. Women may lose their high notes but in exchange gain low, deeper notes.

“The most important thing is that you not strain to reach those top notes if you’ve lost them because the increasingly fragile blood vessel are more likely to rupture and the swollen vocal folds are more likely to tear,” said Dr. Gupta on her website.

Increased Propensity for Acid Reflux

The esophageal sphincter, responsible for keeping food in the stomach from coming into your larynx can become overly relaxed due to the hormonal changes during pregnancy. As a result, your stomach capacity is lessened as you begin to get fuller at a much quicker pace, This can lead you to have acid reflux.

According to Mayo Clinic, symptoms of acid reflux include:

  • Chest pain
  • Difficulty swallowing (dysphagia)
  • Dry cough
  • Hoarseness or sore throat
  • Regurgitation of food or sour liquid
  • Sensation of a lump in the throat

Decreased Lung Capacity

During pregnancy, the fetus is pushing the diaphragm of the expectant mother’s body. Therefore, the mother may experience vocal fatigue. The inability to maintain your vocal notes for long periods of time is also an effect caused by the decrease in your lung capacity.

Decreased Nasal/Sinus Tone

During pregnancy, every part of your body swells up, and your nose is not an exception to the rule. As a result of the swelling, your nose sinus lose muscle tone and when this occurs, your vocal sounds cannot echo through the nose and your sinuses as effectively as before. This can result in a more unclear, raspy voice.

Altered Posture

Pregnancy alters a woman’s posture because of the changes that occur in the back, pelvis, and chest. During the last trimester, some women cannot even sing, says Gupta. If you push yourself to sing without the ability to do so, you can cause permanent damage to your voice. Findings published in Journal of Voice suggest that most pregnant women during the third trimester do experience abnormal levels of voice changes due to the physiological and body changes that occur during pregnancy.

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Bell's self-diagnosis is correct: hormonal changes in the body during pregnancy do account for shift in vocal range in pregnant mothers.