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- Triggers of Hot Flashes
Pregnancy is a dynamic process that is dependent on significant, maternal physiological changes to provide for the baby (fetus) to grow and develop. A common side effect that results from these changes includes hot flashes. Hot flashes during pregnancy are completely normal, you can expect them even after the baby is born.
More than 30% of pregnant women experience increased body temperature as their bodies undergo many adjustments.1 You may literally feel like you have ‘a bun in the oven.’ This scenario can be surprising and concerning, especially if they are frequent and last more than a minute or two. Some might want to call it a pregnancy ‘glow,’ but regardless of what you call it, hot flashes when pregnant are due to a cascade of body adjustments that are necessary to accomplish the remarkable feat of creating human life.
The biggest reason that pregnant women experience hot flashes is the sudden change of estrogen and progesterone hormone levels throughout pregnancy. Estrogen and progesterone levels are increased and released at varying levels during pregnancy and drop very quickly after the delivery of the baby. Because estrogen and progesterone levels drop after birth, hot flashes can, and often do, continue postpartum especially if you are breastfeeding.1
The sometimes rapid changes in estrogen and progesterone can actually mimic some of the symptoms women experience during menopause.2 Hot flashes are one of the symptoms of menopause that commonly develop during pregnancy. Sweating, warmer skin, and even the occasional night sweat can be expected.3 Increased metabolism, at about 300 more calories per day, can also lead to hot flashes.4 So yes, this kind of situation is normal.
There are a few physiologic changes during pregnancy that are pretty obvious: enlargement of the uterus and the breasts. When a woman is not pregnant, her uterus is typically about the size of a pear, but with pregnancy, it grows to accommodate the baby and swells to bigger than a newborn baby. The fetus itself releases body heat as it grows, and can act as an internal heater.4 Once the baby is born, the uterus gradually shrinks back again to a pear size.
The breasts swell in anticipation of breastfeeding and become capable of producing large quantities of breast milk. The increased work necessary to produce breast milk further increases metabolism, about 500 additional calories per day, and will lead to further body heat changes.
Less obvious changes in the body of a pregnant woman can lead to increased body temperature including blood volume and the constitution of the blood. By the third trimester, a woman’s total blood volume has increased by about 45% above prepregnancy levels, the red blood cell production is up to 40% greater, and the heart rate increases.5
These changes in blood volume and the cardiac system during pregnancy have been shown to raise the metabolism, contributing to the spikes in body temperature in pregnancy.6
The increased blood volume in pregnancy is necessary for delivering oxygen and nutrition to the fetus but also affects the mother’s blood vessels, especially the vessels near the surface of the skin. The more blood flows to the skin, the more it flushes (or glows), and the warmer the mother can feel.4
Another change that contributes to this situation is weight gain. Weight gain is normal in pregnancy, in fact, a 20-pound weight gain is considered healthy for women that start pregnancy at a normal weight. Increased body mass index (BMI) is a known risk factor for hot flashes. As the baby, placenta, uterus, and mom all grow during pregnancy, hot flashes become more common.
In a 2013 study, 35% of women experienced hot flashes during pregnancy and 29% of women reported hot flashes after delivery.3 Hot flashes peak at 30 weeks of pregnancy but were reported throughout pregnancy by some women. After delivery, hot flashes continued to increase for 2 weeks and then declined as the hormone levels returned to normal pre-pregnancy state. For some women, pregnancy can almost be a taste of what menopause will be like.
This kind of situation can be difficult to treat. It is not safe to give hormones during pregnancy as they can affect the baby. Hormone therapy is also not safe after delivery because it can affect breast milk. Falling estrogen levels, and to a lesser extent falling progesterone levels, is the signal that initiates breast milk production. It is these same falling hormone levels that are thought to be the mechanism of hot flashes. Replacing these hormones immediately after delivery of the baby can blunt the signals needed to establish a milk supply.
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Triggers of Hot Flashes
Anxiety and stress
While feeling warmer, and experiencing hot flashes, can be normal during pregnancy, you may want to check with your doctor if you are experiencing night sweats with other symptoms. See your doctor immediately if you have:
A fever higher than 101F
Fortunately, for the menopausal woman, these considerations are not present. Women experiencing hot flashes due to menopause have excellent treatment options in the form of hormone replacement therapy. Although hormone replacement therapy is not safe for hot flashes during pregnancy, replacing falling hormones in menopause is both safe and effective. Start your free visit and talk to Winona physicians to discuss your treatment options.
“This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.”
Thurston, Rebecca, et. al., Prospective Evaluation of Hot Flashes during Pregnancy and Postpartum, Fertil Steril. 2013 Dec; 100(6): 1667-1672
Hayes M, Larson L (2012).“Chapter 220. Overview of Physiologic Changes of Pregnancy” Principles and Practice of Hospital Medicine. The McGraw-Hill Companies. ISBN 978-0071603898