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Physiological Changes During Pregnancy

Maternal physiological adaptations during pregnancy

Pregnancy, as one of the most significant events in a woman’s life, could bring many changes in a woman’s life. These changes can be physical, physiological, emotional and psychological. It is important that these changes support the growing fetus in the mother’s womb. The changes happen because a person should adapt well to the state where the baby is developing and growing. Healthy maternal adaptations are required in pregnancy. Therefore, mothers should know their bodies and the changes that may occur to them. In this article, physiological changes in pregnant women will be discussed. Additionally, information about these changes is also covered.

We must know that the changes in the body is ongoing, it occurs all throughout the pregnancy period and even after the baby has been born. It also affects almost every bodily function and structure. In some ways, these changes can expose a mother to a vulnerable state wherein health problems can happen if she is considered to be at high risk. Additionally, some changes in the body can cause discomfort and requires careful assessment by a healthcare professional.

Changes During Pregnancy

What happens when you get pregnant?

We all know that pregnancy means having a baby inside your womb. In this event, different systems and organs of the woman’s body have their different changes.

Reproductive system – Changes to your sex organs:

Changes in breasts

  • Stimulated by the hormones estrogen, progesterone and human placental lactogen, bilateral changes occur.
  • There will be gradual increase in size of breasts.
  • A thin, clear fluid called pre-colostrum is produced at approximately 6 weeks.
  • Thick and yellowish liquid called colostrum is produced during the third trimester.
  • Due to increase blood volume, circulation and vascularity increases.
  • There will be a suppression of lactation until birth (estrogen-progesteron level drops).
  • Elevation of prolactin at birth will start the lactation cycle (producing milk in breast).
  • Breasts will appear full, heavy end enlarged in the second to third trimester.
  • Breasts will be sensitive and/or tender
  • Upon palpation, breasts are nodular.

Changes in Uterus, vagina, perineum

  • Changes are influenced by estrogen and progesterone activity and the growth of the fetus
  • Uterus will enlarged to 500 times than its pre-pregnant state
  • The top muscular area of uterus rises depending on the weeks of pregnancy.
  • Softening of uterus begins at 7 to 8 weeks.
  • Endometrium or the uterine lining becomes very thick and highly vascular. This allows implantation.
  • There will be pelvic congestion because of the increase in uttering vascularity at 6 to 8 weeks.
  • There will be an increase in sexual arousal and orgasms in second trimester.
  • There can be a varicosity formation because of the increase pelvic pressure and inhibit venous returns. This can happen in the third trimester because of the enlarged uterus.
  • Glands in the vagina and cervix produce more mucus
  • The perineum-vulva is softer and more stretchable and vascular.
  • Menstrual cycle and menses do not occur because the hormones FSH and LH are suppressed.
  • Spotting can occur after sexual intercourse or examination.
  • There will be less acidic discharge in the vagina, therefore, there is a increased risk for vaginal infection especially yeart.

Changes in respiratory system or breathing:

  • Diaphragm is moved upward because of the rising fundus.
  • Oxygen demand increases because of increased metabolic rate.
  • Respiration rate slightly increases and volume is deeper.
  • Chest circumference expands.

Changes in circulatory system


  • Blood volume increases 30 to 50% at about 10-12 weeks and peaks at 20-26 weeks.
  • Heart enlarges slightly.
  • Circulation and cardiac output is enhanced in lateral position (right or left)
  • Coagulation is increased.

Blood pressure

  • There will be a decreased 5 to 10 mm Hg systolic and diastolic in first and second trimester. It will return in its baseline during third trimester.
  • Postural hypotension or fall in blood pressure with sudden change from lying to sitting.

Heart rate and pattern

  • Heart rate will increase by 10 to 15 beats per minute during 14 to 20 weeks.

Physiologic anemia due to dilution of blood

  • Hematocrit falls lower than 33%.
  • Hemoglobin falls lower than 11g/dL.
  • Stabilizes by mid-pregnancy.

Changes in energy and nutrition requirements: 

  • Basal metabolic rate increases by 10%.
  • There will be an increased demand for nutrition because of increased metabolism.
  • Weight increases because of fetal growth, placenta and amniotic fluid; due to maternal blood volume, maternal fat deposition, breast and uterine development.
  • Nausea and vomiting can occur because of hormonal changes
  • There is a decreased motility of upper gastrointestinal tract because of increase progesterone level. This can result to pyrosis or heartburn, slower gastric emptying and slower emptying of gallbladder.
  • Morning sickness can occur any time of day, should diminish by second trimester and should not result in nutritional and fluid insufficiency.
  • There will be an increase in appetite and pica or craving for and ingestion of nonnutritive substances.

Changes in elimination processes:

Bowel elimination

  • There will be decreased bowel sounds.
  • Constipation and flatulence is common.
  • Hemorrhoids can occur because of pelvic pressure.

Urinary elimination

  • Increased frequency and urgency of urinary elimination because of decrease in bladder capacity

Changes in integumentary system – Skin

  • There will be an increased production of hormones like melanotrophin, melanocyte stimulating hormone (MSH) that result in deepening of skin pigmentation.
  • Increased secretion of sweat and sebaceous glands
  • Increased in basal body temperature
  • Striae gravidarum or reddish-purple stretch marks on breasts, abdomen, buttocks, and thighs begin to appear in second half of pregnancy.
  • There can be pigmentary changes such as melasma or brownish discoloration of face, linea nigra or darkening of vertical line along middle of abdomen, and darkening of nipples, areola, vulva, moles, freckles and birth marks.

Activity and rest

  • Discomfort in neck, shoulder, back and lower extremities are common because of the changes in other body systems and enlargement of the baby.
  • There will be a waddling gait or awkward movement.
  • Tension headache can occur.


It is true that being pregnant is not easy. Your body change as you progresses with pregnancy. There are changes that bring risk, but most of the changes happen in order to adapt. It is significant that you know the difference between normal changes and changes that require medical attention. If you are a high-risk case, it is required that you consult your doctor regularly because some changes can endanger the baby and the mother.

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