Physiological Changes in Pregnancy

A woman certainly undergoes a lot of changes during pregnancy. Some gain changes permanently, others have changes that are very subtle. These changes, however, are welcomed by mothers with open arms because they are signs that a new life is being formed inside of her.

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The Diagnosis of Pregnancy

Before a pregnancy is confirmed, the woman might see small and big changes in her body that could help in determining if she is already pregnant.                              

Presumptive Signs

Presumptive signs are signs that are least indicative of a pregnancy. These changes can only be felt by the woman but cannot be documented by the healthcare provider.


  • Breast changes (swollen), nausea and vomiting, amenorrhea, frequent urination, fatigue, uterine enlargement, quickening, linea nigra, melasma, and striae gravidarum are the presumptive signs of pregnancy.
  • However, these signs may also denote other conditions that the body is undergoing.

Probable Signs

Probable signs of pregnancy are objective and can be seen primarily by the healthcare provider. These can be taken through laboratory tests and home pregnancy tests by detect the presence of human chorionic gonadotropin in the blood or in the urine.

  • Chadwick’s sign or a change in the color of the vagina from pink to violet is a probable sign of pregnancy.
  • Goodell’s sign is a probable sign that depicts a softening of the cervix.
  • Hegar’s sign is the softening of the lower uterine segment.
  • Ballottement is described as the rise of the fetus felt through the abdominal wall when the uterine segment is tapped on a bimanual examination.
  • An evidence of a gestational sac found during ultrasound is another probable sign.
  • Braxton-Hicks contractions are periodic uterine tightening and contractions.
  • The fetal outline can also be now palpated by the examiner through the abdomen.

Positive Signs

There are only three positive signs of pregnancy that are documented by the health care providers.


  • Evidence of a fetal outline on ultrasound.
  • With the use of a Doppler, an audible fetal heart rate is another positive sign.
  • The last is fetal movement felt by the healthcare provider.

Reproductive System Changes

The system that will greatly feel the changes is the reproductive system. It includes the ovaries, uterus, and vagina.

  • On the first trimester in the ovaries, the corpus luteum starts to become active. By the second trimester, it begins to fade until the third trimester where it has already disappeared.
  • The uterus increases in growth starting from the first trimester. On the second trimester, the placenta is forming estrogen and progesterone.
  • The vagina undergoes changes during the first trimester wherein a whitish discharge is present. From the second until the third trimester, the whitish discharge increases in amount.
  • Amenorrhea also occurs, or the absence of menstruation.
  • The cervix undergoes a more vascular and edematous appearance owing to the increased level of estrogen.

Breast Changes

  • Breast changes start from the first trimester as the woman feels tenderness and fullness of her breasts.
  • As the pregnancy progresses, the breast size increases a size or two, as the mammary alveoli and fat deposits increase in size.
  • The areola of the nipples become darker and its diameter increases.
  • The vascularity of the breast also increases, as evidenced by the prominent blue veins over the surface.
  • The Montgomery’s tubercles or the sebaceous glands of the areola protrudes and enlarges.

Systemic Changes

After the changes that occurred mainly in the reproductive system of a pregnant woman, systemic changes will also start to occur in different body systems.


Integumentary System

  • The stretching of the abdomen causes rupture of the small segments of the connective layer of the skin.
  • Striae gravidarum or pinkish to reddish marks on the sides of the abdominal wall are the result of the rupture.
  • Linea nigra is a narrow, brown line that runs from the symphysis pubis to the umbilicus and separates the abdomen into right and left hemispheres.
  • Melasma or chloasma (mask of pregnancy) refers to the darkened areas on the cheeks or the nose that may appear during pregnancy.
  • Telangiectasis is red, branching spots that can be seen on the thighs. It is also called as vascular spiders.
  • Palmar erythema also occurs because of the increase in the estrogen level of the pregnant woman.

Respiratory System

  • A pregnant woman usually experiences stuffiness or marked congestion because of the increasing estrogen levels.
  • Shortness of breath is also a common discomfort of pregnancy as the pregnant uterus pushes the diaphragm upward.
  • The total oxygen consumption of a pregnant woman increases by 20%.

Cardiovascular System

  • The blood pressure of the pregnant woman decreases in the second trimester and then returns to its prepregnancy level on the third trimester.
  • The cardiac output increases 25% to 50%.
  • Plasma volume also increases up to 3600 mL, marking the condition called pseudoanemia early in the pregnancy.
  • Heart rate also increases to 80 to 90 beats per minute.
  • The blood volume increases up to 5,250 mL during pregnancy.

Gastrointestinal System

  • Nausea and vomiting is one of the first signs of pregnancy that a woman feels.
  • Slower intestinal peristalsis occurs during the second trimester of the pregnancy which causes heartburn, flatulence, and constipation.
  • Hemorrhoids also occur from the increased pressure of the uterus on the veins in the lower extremities.

Urinary System

  • The total body water of a pregnant woman increases up to 7.5 L for a more effective placental exchange.
  • Even when the woman has an increased urine output, her potassium levels are still adequate due to progesterone, which is potassium-sparing.
  • The bladder capacity increases to accommodate 1,000 mL of urine during pregnancy.
  • On the first trimester, the frequency of urination already increases. By the last two weeks of pregnancy it reaches up to 10 to 12 times per day. 

Skeletal System

  • By the 32nd week of pregnancy, the symphysis pubis widens for 3 to 4 mm.
  • The center of gravity of a pregnant woman changes, and to make up for it she tends to stand straighter and taller than usual and with the abdomen forward and the shoulders thrown back, the ‘pride of pregnancy’ or commonly ‘lordosis’ occurs.

Endocrine System

  • A slight enlargement in the thyroid and parathyroid gland increases the basal metabolic rate of a pregnant woman and for better consumption of calcium and vitamin D.
  • Thyroid hormone production increases.
  • The insulin produced from the pancreas decreases early in the pregnancy, thereby increasing glucose available for the fetus.
  • Increase in insulin occurs in the first trimester because estrogen, progesterone and HPL have insulin antagonistic properties.
  • FSH and LH decreases causing anovulation.
  • As the breasts are prepared for lactation, prolactin increases in production.
  • The increase in melanocyte-stimulating hormones causes increase in skin pigment.
  • The human growth hormone increase to aid the fetus in growing.
  • Estrogen and progesterone aids in uterine and breast enlargement.
  • Human placental lactogen increases glucose levels to supplement the growing fetus.
  • Relaxin increases to soften the cervix and collagen of joints.

The changes in the physiologic status of a pregnant woman are just one of the many phases of changes that occur during pregnancy. Most of these are normal, but when the pregnant woman experiences an excessive manifestation of these signs, it would be best to consult your healthcare provider.

Pregnancy and Birth in the US Infographic

Physiological Changes in Pregnancy

A woman certainly undergoes a lot of changes during pregnancy. Some gain changes permanently, others have changes that are very subtle. These changes, however, are welcomed by mothers with open arms because they are signs that a new life is being formed inside of her.

The Diagnosis of Pregnancy

Before a pregnancy is confirmed, the woman might see small and big changes in her body that could help in determining if she is already pregnant.                              

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Physiological Changes in Pregnancy
For as low as $13/Page
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Presumptive Signs

Presumptive signs are signs that are least indicative of a pregnancy. These changes can only be felt by the woman but cannot be documented by the healthcare provider.

  • Breast changes (swollen), nausea and vomiting, amenorrhea, frequent urination, fatigue, uterine enlargement, quickening, linea nigra, melasma, and striae gravidarum are the presumptive signs of pregnancy.
  • However, these signs may also denote other conditions that the body is undergoing.

Probable Signs

Probable signs of pregnancy are objective and can be seen primarily by the healthcare provider. These can be taken through laboratory tests and home pregnancy tests by detect the presence of human chorionic gonadotropin in the blood or in the urine.

  • Chadwick’s sign or a change in the color of the vagina from pink to violet is a probable sign of pregnancy.
  • Goodell’s sign is a probable sign that depicts a softening of the cervix.
  • Hegar’s sign is the softening of the lower uterine segment.
  • Ballottement is described as the rise of the fetus felt through the abdominal wall when the uterine segment is tapped on a bimanual examination.
  • An evidence of a gestational sac found during ultrasound is another probable sign.
  • Braxton-Hicks contractions are periodic uterine tightening and contractions.
  • The fetal outline can also be now palpated by the examiner through the abdomen.

Positive Signs

There are only three positive signs of pregnancy that are documented by the health care providers.

  • Evidence of a fetal outline on ultrasound.
  • With the use of a Doppler, an audible fetal heart rate is another positive sign.
  • The last is fetal movement felt by the healthcare provider.

Reproductive System Changes

The system that will greatly feel the changes is the reproductive system. It includes the ovaries, uterus, and vagina.

  • On the first trimester in the ovaries, the corpus luteum starts to become active. By the second trimester, it begins to fade until the third trimester where it has already disappeared.
  • The uterus increases in growth starting from the first trimester. On the second trimester, the placenta is forming estrogen and progesterone.
  • The vagina undergoes changes during the first trimester wherein a whitish discharge is present. From the second until the third trimester, the whitish discharge increases in amount.
  • Amenorrhea also occurs, or the absence of menstruation.
  • The cervix undergoes a more vascular and edematous appearance owing to the increased level of estrogen.

Breast Changes

  • Breast changes start from the first trimester as the woman feels tenderness and fullness of her breasts.
  • As the pregnancy progresses, the breast size increases a size or two, as the mammary alveoli and fat deposits increase in size.
  • The areola of the nipples become darker and its diameter increases.
  • The vascularity of the breast also increases, as evidenced by the prominent blue veins over the surface.
  • The Montgomery’s tubercles or the sebaceous glands of the areola protrudes and enlarges.

Systemic Changes

After the changes that occurred mainly in the reproductive system of a pregnant woman, systemic changes will also start to occur in different body systems.

Integumentary System

  • The stretching of the abdomen causes rupture of the small segments of the connective layer of the skin.
  • Striae gravidarum or pinkish to reddish marks on the sides of the abdominal wall are the result of the rupture.
  • Linea nigra is a narrow, brown line that runs from the symphysis pubis to the umbilicus and separates the abdomen into right and left hemispheres.
  • Melasma or chloasma (mask of pregnancy) refers to the darkened areas on the cheeks or the nose that may appear during pregnancy.
  • Telangiectasis is red, branching spots that can be seen on the thighs. It is also called as vascular spiders.
  • Palmar erythema also occurs because of the increase in the estrogen level of the pregnant woman.

Respiratory System

  • A pregnant woman usually experiences stuffiness or marked congestion because of the increasing estrogen levels.
  • Shortness of breath is also a common discomfort of pregnancy as the pregnant uterus pushes the diaphragm upward.
  • The total oxygen consumption of a pregnant woman increases by 20%.

Cardiovascular System

  • The blood pressure of the pregnant woman decreases in the second trimester and then returns to its prepregnancy level on the third trimester.
  • The cardiac output increases 25% to 50%.
  • Plasma volume also increases up to 3600 mL, marking the condition called pseudoanemia early in the pregnancy.
  • Heart rate also increases to 80 to 90 beats per minute.
  • The blood volume increases up to 5,250 mL during pregnancy.

Gastrointestinal System

  • Nausea and vomiting is one of the first signs of pregnancy that a woman feels.
  • Slower intestinal peristalsis occurs during the second trimester of the pregnancy which causes heartburn, flatulence, and constipation.
  • Hemorrhoids also occur from the increased pressure of the uterus on the veins in the lower extremities.

Urinary System

  • The total body water of a pregnant woman increases up to 7.5 L for a more effective placental exchange.
  • Even when the woman has an increased urine output, her potassium levels are still adequate due to progesterone, which is potassium-sparing.
  • The bladder capacity increases to accommodate 1,000 mL of urine during pregnancy.
  • On the first trimester, the frequency of urination already increases. By the last two weeks of pregnancy it reaches up to 10 to 12 times per day. 

Skeletal System

  • By the 32nd week of pregnancy, the symphysis pubis widens for 3 to 4 mm.
  • The center of gravity of a pregnant woman changes, and to make up for it she tends to stand straighter and taller than usual and with the abdomen forward and the shoulders thrown back, the ‘pride of pregnancy’ or commonly ‘lordosis’ occurs.

Endocrine System

  • A slight enlargement in the thyroid and parathyroid gland increases the basal metabolic rate of a pregnant woman and for better consumption of calcium and vitamin D.
  • Thyroid hormone production increases.
  • The insulin produced from the pancreas decreases early in the pregnancy, thereby increasing glucose available for the fetus.
  • Increase in insulin occurs in the first trimester because estrogen, progesterone and HPL have insulin antagonistic properties.
  • FSH and LH decreases causing anovulation.
  • As the breasts are prepared for lactation, prolactin increases in production.
  • The increase in melanocyte-stimulating hormones causes increase in skin pigment.
  • The human growth hormone increase to aid the fetus in growing.
  • Estrogen and progesterone aids in uterine and breast enlargement.
  • Human placental lactogen increases glucose levels to supplement the growing fetus.
  • Relaxin increases to soften the cervix and collagen of joints.

The changes in the physiologic status of a pregnant woman are just one of the many phases of changes that occur during pregnancy. Most of these are normal, but when the pregnant woman experiences an excessive manifestation of these signs, it would be best to consult your healthcare provider.