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Hormonal Changes in Pregnancy

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During pregnancy, the body undergoes several changes, and these changes are due to hormones. Read this article to learn about hormonal changes during pregnancy.

Written by

Dr. Asna Fatma

Medically reviewed by

Dr. Manwani Saloni Dilip

Published At September 30, 2022
Reviewed AtNovember 22, 2022

Introduction:

Pregnancy is a period characterized by sharp changes in the levels of several hormones. From the first trimester to the last trimester, the level of human chorionic gonadotropin, estrogen, progesterone, human placental lactogen, etc changes invariably. Each of these hormones plays a vital role in supporting the pregnancy, helping in the development of the baby, growth of several organs of the baby, milk production during lactation, etc.

What Are Hormones?

Hormones are chemical messengers secreted by certain glands into the bloodstream, where they are carried to other organs and tissues. Hormones are responsible for maintaining and regulating several functions of the body like growth and development, metabolism, sexual growth, functioning, maintaining a normal body temperature, etc. The hormones play a vital role in pregnancy.

How do Hormonal Changes Occur During Pregnancy?

The hormones play a crucial role in pregnancy, and a correct balance of hormones is important for a successful pregnancy. These chemicals affect the body as well as the mind during the term and cause various changes. From morning sickness to heartburn, various signs and symptoms occur as a result of hormonal changes that occur during the pregnancy.

What Changes Happen During Pregnancy in Each Trimester?

The body of the expecting mother undergoes many changes during the pregnancy. The body shows different changes in different trimesters. The following changes occur during pregnancy in each trimester:

  • First Trimester: In the early stage of pregnancy, after the egg is fertilized and gets implanted into the womb, human chorionic gonadotropin (hCG) is released from the womb. This hormone brings about changes in the body to support pregnancy. The hCG can be detected in the urine after a week of fertilization. During the first trimester, the expecting mother feels doozy because the body will go into a drive to grow the developing embryo. Estrogen and progesterone hormones rise dramatically in level. Thyroid hormones also increase to help in the baby’s neurological and bone development.

  • Second Trimester: During the second trimester, the estrogen and progesterone levels continue to increase to help the baby grow. Melanocyte-stimulating hormone (MSH) is also increased, which causes pigmentation during pregnancy. Cortisol levels also increase, which helps in the baby’s growth, metabolism, and regulation of blood sugar levels. The human placental lactogen hormone is also secreted from the placenta during the second trimester.

  • Third Trimester: During the third trimester, at around 32 weeks, the estrogen and progesterone hormones peak. Prolactin, a hormone responsible for lactation, also begins to secrete during the third trimester. Prolactin levels increase around ten times around the end of the pregnancy as compared to the beginning of the pregnancy. Oxytocin hormone is also released during the third trimester. This hormone is thought to be responsible for contractions during labor.

Which Hormone Plays a Role in Pregnancy?

Hormones that play a major role in pregnancy, from fertilization to implantation and baby’s growth to lactation, are mentioned below:

  • Human chorionic gonadotropin (hCG).

  • Human placental lactogen.

  • Progesterone.

  • Estrogen.

  • Cortisol.

  • Relaxin.

  • Oxytocin.

  • Prolactin.

What Is the Role of the Human Chorionic Hormone During Pregnancy?

  • The human chorionic gonadotropin (hCG) hormone is probably the most significant hormone during pregnancy that is released by the placenta.

  • This hormone is only produced during pregnancy, and then its level rapidly rises during pregnancy.

  • The hCG hormone can be detected in the blood and urine during the first trimester, and it may be associated with nausea and vomiting, known as morning sickness during pregnancy.

  • The hCG helps in preparing the body for the baby, and it also directs the ovaries to stop the production line of maturing an egg every month.

  • The hCG levels rise approximately a week after ovulation and peak after sixty days. During the first two weeks of pregnancy, the hCG level doubles every two weeks.

  • Beta hCG concentration can be measured in the over-the-counter pregnancy kit to test for pregnancy.

What Is the Role of Progesterone During Pregnancy?

  • Progesterone is produced by the corpus luteum, and the corpus luteum continues to produce progesterone until ten weeks, and then its production is done by the placenta thereafter.

  • During the first trimester, the progesterone levels rise exponentially, and then they flatten down to a stable level.

  • Progesterone stimulates the thickening of the lining of the uterus, and it also keeps the uterus muscles relaxed. Progesterone helps the uterus grow and prevents contractions in the uterus; later in the pregnancy, progesterone helps in lactation.

  • Progesterone also helps the mother’s immune system to welcome the foreign deoxyribonucleic acid (DNA) of the baby.

  • The downside of high levels of progesterone is probably low blood pressure because it dilutes the blood vessels, which may cause occasional dizziness. Progesterone may also cause excessive hair growth in the body.

What Is the Role of Estrogen During Pregnancy?

  • Estrogen, just like progesterone, is also produced by the corpus luteum and then by the placenta.

  • Estrogen is the hormone responsible for the development of female sexual characteristics.

  • This pregnancy hormone plays a crucial role in the development of the baby in the womb and initiates the growth of numerous organs and systems in the fetus.

  • Estrogen stimulates the growth and hormone production in the baby’s adrenal glands, which in turn helps in growing the mother’s uterus. Estrogen enables the mother’s uterus to respond to another pregnancy hormone (oxytocin).

  • Towards the end of the first trimester, the estrogen levels peak, and then it plateaus. The downside of elevated estrogen levels is the appearance of spider veins, nausea, vomiting, skin changes, etc.

  • Estrogen is also responsible for increased appetite during pregnancy. Increased estrogen levels are also responsible for the “pregnancy glow” many women experience during their term.

What Is the Role of Relaxin During Pregnancy?

  • Relaxin hormone is again produced by the corpus luteum in pregnant and nonpregnant females. However, during pregnancy, it is also produced by the placenta and decidua when it reaches its highest plasma level.

  • The primary function of relaxin during pregnancy is to relax the ligaments in the pelvis. It also softens and widens the cervix while holding the pelvic bone together. This hormone also relaxes the arteries so that the increased blood volume can be managed without increasing the blood pressure.

  • The downside of excess relaxin is the loosening of ligaments in other parts of the body like shoulders, knees, hips, ankles, etc. This may also cause pain and inflammation in the joints.

  • During pregnancy, the level of relaxin increases almost tenfold as compared to nonpregnant days.

What Is the Role of Oxytocin During Pregnancy?

  • Oxytocin is a neuropeptide that is produced by the hypothalamus and secreted via the posterior pituitary into the bloodstream.

  • The main function of oxytocin is to facilitate the childbirth process. It stimulates the muscles of the uterus to contract and boosts the production of prostaglandins, which increases uterine contractions.

  • In some cases where labor is induced, women are given Pitocin, which is a synthetic form of oxytocin.

  • Oxytocin is also responsible for the “nesting behavior” before the delivery of the baby.

  • After childbirth, oxytocin helps in moving the milk from ducts in the breasts into the nipples.

What Is the Role of Prolactin During Pregnancy?

  • Prolactin is produced by the lactotrophs in the anterior pituitary gland during pregnancy. The number of lactotrophs increases during pregnancy because of the physiologic need of the body to produce milk.

  • The primary function of prolactin is to help in growing the breasts and milk production, and that is why this hormone is also known as the “milk hormone.”

  • The levels of prolactin increase almost ten to twenty times during pregnancy as compared to nonpregnant days.

Conclusion:

Hormones are responsible for the several physical and mental changes that occur in an expecting mother’s body. The correct balance of these hormones is essential for a successful pregnancy. The pregnancy-related hormones are primarily produced by the ovaries and the placenta. Hormones like hCG, progesterone, estrogen, prolactin, relaxin, oxytocin, etc., are responsible for different functions in the body during pregnancy. These hormones will collectively facilitate the fertilization, growth of the fetus, uterine contraction, and milk production. From the moment of conception to weeks after birth, these hormones will exponentially increase and decrease in the level to facilitate a healthy and successful pregnancy.

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Dr. Manwani Saloni Dilip
Dr. Manwani Saloni Dilip

Obstetrics and Gynecology

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