Physiologic changes - Pregnancy: Nursing

Chapters:

Watch video only

Introduction0:00–0:19

Physiological changes in pregnancy include all adaptations of the human body that occur in response to a developing fetus.
These changes are essential for fetal survival and are primarily caused by high levels of estrogen and progesterone in the body.First, let’s cover the most important signs and symptoms of pregnancy, which can be subdivided into three main groups: presumptive, probable, and positive.

Subjective and objective signs and symptoms of pregnancy0:19–2:06

Presumptive signs and symptoms include amenorrhea, or the absence of menstruation; increased breast size and breast tenderness; nausea and vomiting; as well as increased urinary frequency; and quickening, meaning the fluttering sensation caused by fetal first movements.
Probable signs of pregnancy include a positive pregnancy test, uterine enlargement, and irregular uterine contractions, which are often referred to as Braxton Hicks contractions.
Other important probable signs include the Goodell’s sign, or the softening of the cervix that occurs after 4 gestational weeks; the Hegar’s sign, which indicates the softening of the lower uterine segment that occurs after 6 gestational weeks; and finally, the Chadwick’s sign, which describes the blue to purple discoloration of vulvar, vaginal, and cervical mucous membranes.
Just like Hegar's sign, Chadwick's sign also appears after 6 weeks of gestation.Another important probable sign is ballottement.
Here, an examiner places a finger inside the vagina and pushes the lower segment of the uterus, indirectly pushing the fetus to go upwards.
Once displaced, the fetus returns to its previous position causing an impact on the uterine wall. This impact can be felt on the examiner’s finger.
Finally, we have positive signs of pregnancy, which include active fetal movements, detection of fetal heart rate, and ultrasound detection of the fetus.Now, let’s look at the physiological changes that impact the cardiovascular system, which must adapt in order to accommodate the needs of an enlarging uterus and a growing fetus.

Cardiovascular system2:06–4:43

Pregnancy is called a high volume state because the maternal circulating blood volume increases by 30–50%, which means that blood volume increases from about five liters, in the average individual, to about seven and a half liters by the third trimester.
The number of red blood cells increases a bit, but there’s a much larger increase in the plasma volume, which is the portion of blood that doesn’t have red blood cells, which eventually dilutes the blood.
As a result, hemoglobin and hematocrit actually go down. This apparent decline in red blood cell levels is called physiological anemia, or pseudoanemia of pregnancy.
Similarly, the number of leukocytes increases, but platelets stay within the normal range. However, there’s an increased synthesis of factors that favor blood clotting.Now, in order to pump all this extra blood to the systemic circulation, cardiac output increases as well, by increasing the number of beats per minute by 10 to 15 bpm, and stroke volume, which refers to the amount of blood pumped with each contraction.
In response to the increased workload, the heart size increases. The high volume state can also alter the client’s heart sounds.
Finally, as the uterus enlarges, it pushes up on the diaphragm, nudging the heart slightly upward and to the left. Now, even though there’s an increased circulating blood volume, blood pressure actually falls because increased progesterone and estrogen levels cause vasodilation of peripheral blood vessels and decreased vascular resistance.
Now, blood pressure changes are actually minimal when a client is standing or sitting. But, if the client is in the supine position, the weight of the uterus and fetus can compress the large blood vessels, such as the inferior vena cava, decreasing venous return to the heart and cardiac output, causing supine hypotension.
More importantly, decreased cardiac output means that the heart pumps less blood into the systemic circulation and the placenta, subsequently causing a deficiency of the uterine circulation that might result in fetal distress.
Clients with supine hypotension usually complain of symptoms such as lightheadedness, dizziness, and nausea when lying on their back.
To correct this, the client should be turned to a lateral recumbent position, or have a pillow or foam wedge placed under their right lower back.
This alleviates the pressure on the vena cava inferior and reestablishes the venous return to the heart.Now, let’s switch gears and move on to respiratory changes.
During pregnancy, oxygen consumption increases by about 15 to 20 percent. The human body adapts to accommodate this by increasing the tidal volume, which is the amount of air inhaled and exhaled per breath, and the respiratory minute volume, which refers to the amount of air inhaled or exhaled per minute.

Respiratory system4:43–5:53

Additionally, high progesterone levels increase the sensitivity of the respiratory center in the medulla oblongata and at the same time, decrease airway resistance.On the other hand, estrogen does not increase respiratory function, instead, it increases the blood flow through the mucous membranes of the upper respiratory tract.
This can result in nasal and sinus stiffness, nosebleeds, and deepening of the voice. Increased blood flow can result in edema of the eustachian tubes and eardrums and cause a sense of fullness in the ears.
Finally, as the uterus enlarges, it pushes the diaphragm up around 4 centimeters, which can make it more difficult for the lungs to expand, causing shortness of breath.
This can cause the client to compensate by hyperventilation. Next up are the gastrointestinal changes.
Let’s start with the mouth, where estrogen increases the blood flow and causes mucosal hyperemia. Hormonal changes also increase the inflammatory response to dental plaques, which can result in severe gingivitis and gingival bleeding.

Gastrointestinal changes5:53–7:00

In the esophagus, progesterone decreases the tone of the lower esophageal sphincter, thereby increasing the risk of gastric reflux and heartburn.
Hormonal changes during pregnancy also decrease the tone and motility of the gastrointestinal tract, thereby delaying the emptying of the gastrointestinal content.
Furthermore, a decrease in motility gives the intestines enough time to absorb necessary nutrients from the gastrointestinal lumen.
On the other hand, decreased motility can also cause bloating, abdominal distension, and constipation. Finally, just like the rest of the gastrointestinal tract, the gallbladder is hypotonic, therefore it requires more time to empty.
As a result, the bile becomes thicker, which increases the risk of gallstones.As far as the nutritional needs go, during pregnancy, clients need to increase their caloric intake by around 300 calories per day.
In addition, more protein, calcium, vitamins like folate, and minerals like iron are needed to meet the needs of the growing fetus.
Of note, folate supplementation is especially important for the prevention of neural tube defects in the fetus. Luckily, an extra 400 micrograms of folate per day can be found in various prenatal vitamins, and this is just about enough!

Nutrition7:00–7:32

Ok, now, let’s look at the renal system changes. Increased cardiac output means that there is more blood going through the kidneys, so they work harder to remove both maternal and fetal waste products.
At the same time, the renal threshold for glucose, meaning the blood glucose levels above which glucose is excreted into urine, is lowered, which can sometimes cause glycosuria.

Renal changes7:32–8:42

Overall, these adaptations make the renal pelvises, calyces, and ureters dilate, resulting in physiologic hydronephrosis and hydroureter.
In addition the enlarging uterus itself can compress the bladder in the first trimester causing urinary frequency. This can decrease in the 2nd trimester because the uterus moves up into the abdomen, but it’ll return again in the third trimester when the fetus descends into the pelvis.
Finally, progesterone decreases the urethral and bladder tone, but at the same time, it increases bladder capacity. Increased capacity to store urine, combined with hypomotility of the ureters, results in urinary stasis in the kidneys and increases the risk of urinary tract infections.Now let’s switch gears and have a look at some endocrine changes that occur during pregnancy.
First, the anterior pituitary increases prolactin production, which is a hormone required for normal lactation, while the posterior pituitary increases oxytocin secretion, which is a hormone that stimulates uterine contraction during labor, and milk let down, or milk ejection, during lactation.
The posterior pituitary increases oxytocin secretion, but during the first half of pregnancy, high levels of progesterone block oxytocin effects.

Endocrine changes8:42–11:25

As the pregnancy progresses, the uterus overcomes progesterone effects by increasing the number of oxytocin receptors, eventually increasing the number of uterine contractions near term.
Another gland affected by pregnancy is the thyroid gland, which enlarges and increases the production of thyroid hormones to increase the cellular basal metabolic rate and meet the demands of the pregnancy.
Also, maternal thyroid hormones are important for normal fetal development of the neurologic system during the first 10 to 12 weeks of pregnancy.
Afterward, the fetus starts to produce thyroid hormones on its own. Insulin secretion from the pancreas also increases during pregnancy.
In early pregnancy, maternal insulin sensitivity goes up to match the body’s increased caloric needs. As the pregnancy progresses, an increase in hormones like estrogen and progesterone will cause maternal insulin resistance.
When the mother’s tissue is taking in less glucose, there’s more available for the developing fetus. Finally, adrenal glands increase the production of cortisol, to stimulate gluconeogenesis, and aldosterone, to block the salt-wasting effect of progesterone.Finally, don’t forget that the placenta is also an endocrine organ, which secretes several hormones, including estrogen, progesterone, human chorionic gonadotropin, and human placental lactogen.
Estrogen has various effects throughout the body, but the most important ones include suppression of pituitary FSH and LH secretion, stimulation of uterine growth, increase in uterine blood supply, and promotion of breast development.
Progesterone also suppresses FSH and LH secretion, but at the same time, it also prepares the endometrial layer for implantation, prevents menstruation, and prepares the breasts for lactation.
Human chorionic gonadotropin, or hCG for short enables further production of estrogen and progesterone. Finally, human placental lactogen, or hPL for short, prepares breasts for lactation and helps regulate maternal glucose blood levels, by utilizing free fatty acids for energy.During pregnancy, estrogen and progesterone promote breast development and milk production.
Blood flow also increases to support the growth of breast tissue. Together, these changes can cause symptoms like tingling, fullness, and tenderness of the breasts.
Other important changes include leakage of colostrum and hypertrophy of Montgomery’s tubercles, which are sebaceous glands that lubricate the nipples.Uterine enlargement is a result of hyperplasia and hypertrophy of the uterine smooth muscle cells.

Reproductive changes11:25–12:58

By 20 weeks of gestation, the uterus reaches the level of the umbilicus, and by 36 weeks, it rises to the xiphoid process.
At the same time, the number and size of blood vessels increase to provide nutritional support to the enlarging uterus. During the first two trimesters, the uterus is usually calm, with irregular, brief contractions, called Braxton-Hicks contractions, or false labor pains.
Once the third trimester starts, the uterus becomes active. These frequent uterine contractions can cause discomfort.
Now, let’s zoom in and take a look at the cervix. The cervix increases in diameter and becomes hyperemic and more elastic.
Endocervical glands start secreting a thick mucus that forms a plug and blocks the cervical canal. This plug prevents bacteria from entering the uterus, keeping the fetal membranes and fetus safe.
Similarly, the vagina increases the production of white, thick, and acidic secretions.Next, let’s quickly look at physiologic skin changes during pregnancy, including hyperpigmentation, cutaneous vascular changes, and striae gravidarum.
Hyperpigmentation occurs because hormones like estrogen, progesterone and melanocyte-stimulating hormones make the melanocytes produce more melanin.
On the face, this results in brownish patches of the skin typically located on the forehead, bridge of the nose, and cheeks.
This condition is called melasma, or the mask of pregnancy. On the other hand, the overactivity of melanocytes on the abdomen darkens the normally unseen stripe of fibrous tissue called the linea alba.

Skin changes12:58–14:12

As a result, the linea alba transforms and becomes the linea nigra. Finally, during pregnancy, the preexisting hyperpigmentations of the skin, such as moles, freckles, and areolae, also become darker.
Next up are cutaneous vascular changes, which are caused by estrogen and include palmar erythema, and telangiectasia, or vascular spiders.
Finally, striae gravidarum are purple to red stretch marks that usually appear on the upper arms, breasts, abdomen, and thighs.Finally, there are musculoskeletal changes, which primarily include postural and abdominal wall changes.
First, let’s go over postural changes. During pregnancy, a client usually gains 25 to 35 pounds and this extra weight, along with a forward shift in the center of gravity, can cause lordosis and lower back pain.
Additionally, progesterone and relaxin loosen ligaments around the sacroiliac joints and the symphysis pubis in preparation for fetal passage through the birth canal.
This results in a waddling gait, which can cause walking difficulties and increase the risk of falling. On the other hand, the most important change of the abdominal wall is called diastasis recti.

Musculoskeletal changes14:12–15:03

Diastasis recti occurs when the uterus puts direct pressure on the rectus abdominis muscles and causes them to separate.Alright, as a quick recap… Physiologic changes in pregnancy include all adaptations of the human body that occur in response to a developing fetus.
The cardiovascular system adapts by increasing the circulating blood volume and cardiac output, at the same time slightly decreasing the systemic vascular resistance.
The respiratory system increases oxygen consumption, while the gastrointestinal system reduces motility. Kidneys increase the workload to remove maternal and fetal waste products, thereby increasing the urine output and urinary frequency.
The endocrine system adapts and increases the production of estrogen, progesterone, prolactin, and oxytocin, as well as human chorionic gonadotropin, and human placental lactogen.
The reproductive system prepares the breast for future lactation, while the uterus enlarges to accommodate the growth of the developing fetus.

Review15:03–16:12

Finally, the most common skin changes include hyperpigmentation, cutaneous vascular changes, and striae gravidarum; while musculoskeletal changes include postural and abdominal wall adaptations.
the same time. Slightly decreasing the systemic, vascular resistance, the respiratory system increases oxygen consumption, while the gastrointestinal system produces motility kidneys, increase the workload to remove maternal and Fetal, waste products.
Thereby increasing the urine output and urinary frequency. The endocrine system adapts and increases the production of estrogen progesterone prolactin and oxytocin as well as human chorionic gonadotropin and human placental lactogen, the reproductive system, prepares the breast for future lactation while the uterus enlarges to accommodate the growth of the developing fetus.
Finally at the most common skin changes include hyperpigmentation cutaneous. Vascular changes and Striker gravidarum.
Well, musculoskeletal changes include postural and abdominal wall at a patient's.