Chills, experienced as sudden, uncontrollable shivering or a profound sensation of coldness, are a common symptom reported during pregnancy. While many assume pregnancy brings only warmth, fluctuations in body temperature are frequent and usually harmless. Most episodes stem from the body’s normal adaptation to carrying a pregnancy, representing a benign physiological shift. Understanding the difference between a normal, temporary chill and one that signals a medical concern is important for timely intervention.
Physiological Causes: Why Pregnancy Itself Causes Chills
The primary driver of temperature fluctuations during pregnancy is the surge in hormones, particularly progesterone. Progesterone acts on the hypothalamus, which is the brain’s thermoregulatory center, effectively resetting the body’s internal thermostat. This hormonal influence can cause a pregnant person to alternate rapidly between feeling flushed and suddenly experiencing a deep chill, especially during the first trimester.
Pregnancy significantly increases the basal metabolic rate as the body works to support the developing fetus. This heightened metabolic activity generates more heat, but the body must dissipate it, sometimes overcompensating and leading to a temporary drop in skin temperature. These efforts to regulate temperature often manifest as sudden, mild chills or feeling cold.
Shifts in the circulatory system are another contributing factor to transient cold sensations. The body increases blood volume by up to 50% throughout pregnancy, but much of this flow is redirected to the uterus and other vital organs. This necessary redistribution can temporarily reduce circulation to the extremities, such as the hands and feet, resulting in localized feelings of coldness or mild shivering.
Furthermore, increased metabolic demand combined with nausea or appetite changes can lead to episodes of hypoglycemia (low blood sugar). When glucose levels drop, the body releases hormones that trigger responses like sweating and shivering, which can be perceived as a sudden chill. Underlying iron-deficiency anemia, common in pregnancy, also contributes to a persistent cold feeling due to reduced oxygen-carrying capacity.
Warning Signs: When Chills Indicate a Medical Concern
Chills that are frequent, severe, or accompanied by other specific symptoms must be evaluated immediately, as they can indicate an underlying infection or complication. The most significant red flag is the presence of a fever, defined as a temperature of 100.4°F (38°C) or higher, alongside the chills. Chills are the body’s mechanism to rapidly increase temperature in response to an infectious agent, and a fever confirms this immune response.
One of the most common infections signaled by chills and fever is a urinary tract infection (UTI), particularly if the infection has ascended to the kidneys, a condition called pyelonephritis. A kidney infection in pregnancy is a serious concern that may present with chills, fever, pain in the flank or back, and painful or frequent urination. Prompt antibiotic treatment is necessary to prevent complications for both the parent and the fetus.
Chills and fever can also signal influenza or other respiratory infections, which pose a greater risk during pregnancy due to immune system suppression. A sustained high fever can be dangerous, so flu-like symptoms should not be dismissed. Other infections, such as chorioamnionitis (an infection of the amniotic fluid and membranes), also present with maternal fever and chills, often accompanied by uterine tenderness.
Rarely, chills may be associated with conditions like preeclampsia, especially if they coincide with other neurological symptoms. Chills accompanied by a persistent headache, visual disturbances, or sudden swelling warrant immediate medical assessment. Severe, protracted vomiting (hyperemesis gravidarum) can lead to significant dehydration, which may trigger chills due to fluid and electrolyte imbalances. If chills are accompanied by any sign of preterm labor, such as contractions or vaginal bleeding, medical attention is required immediately.
Navigating Chills: What to Do and When to Call the Doctor
For mild, occasional chills without an accompanying fever, simple comfort measures can help manage the symptoms. Wearing clothing in layers allows for easy adjustment to sudden temperature shifts, and keeping hands and feet warm with socks can counteract circulatory changes. To address potential hypoglycemia, consuming small, frequent, nutrient-dense snacks can help maintain stable blood sugar levels throughout the day.
Staying well-hydrated is important, as dehydration can disrupt the body’s ability to regulate temperature effectively. If a chill occurs, resting and drinking warm fluids can often resolve the episode quickly. It is helpful to monitor the frequency and severity of these chills and note any accompanying symptoms to discuss with a healthcare provider during routine appointments.
The decision to contact a doctor should be based on objective signs of potential infection or complication. Call your healthcare provider immediately if chills are followed by a temperature reading of 100.4°F (38°C) or higher. Immediate contact is also necessary if chills occur alongside symptoms such as:
- Burning or pain when urinating.
- Intense abdominal or back pain.
- Foul-smelling vaginal discharge.
- A persistent headache.
These symptoms suggest an underlying issue requiring prompt medical diagnosis and treatment.