MCQs on Physiological Changes in Pregnancy

During pregnancy, renal blood flow increases, leading to an increase in glomerular filtration rate (GFR), which helps meet the increased demands for waste removal.

Due to the effects of progesterone causing vasodilation, systemic vascular resistance decreases, and blood pressure generally drops, especially in the second trimester.

The heart rate actually increases during pregnancy to accommodate the increased blood volume and demands of the growing fetus.

During the first two trimesters of pregnancy, maternal circulating blood volume increase by 40%. This is driven by placental estrogen, which drives increases in the levels of angiotensin II and aldosterone. Aldosterone promotes sodium and water retention which leads to an increase in maternal circulating blood volume.

Calcium is required during pregnancy for many processes, including fetal tooth and skeletal development, digestion, cell adhesion, coagulation, intracellular proteolysis and NO synthesis. Iodide is utilized for thyroid hormone synthesis and in areas where dietary iodide is deficient, the incidence of neonates born with abnormal neural development is increased. Iron is a component of hemoglobin, myoglobin and cytochromes; maternal iron requirements in pregnancy nearly double.

Explanation: Blood volume increases significantly during pregnancy to support the growing fetus and placenta.

The heart rate increases during pregnancy to accommodate the increased blood volume and demands of the growing fetus.

Progesterone relaxes smooth muscles throughout the body, which contributes to decreased gastrointestinal motility, vascular relaxation, and uterine quiescence.

Progesterone causes the relaxation of smooth muscles, including the lower esophageal sphincter, leading to an increased risk of gastroesophageal reflux disease (GERD).

Pregnancy leads to an increase in minute ventilation, which is the total volume of air moved in and out of the lungs per minute. This compensates for the increased oxygen demands of the body and fetus, due to hormonal changes and physical pressure on the lungs from the growing uterus.

Diastolic blood pressure tends to decrease during pregnancy due to systemic vasodilation caused by increased progesterone levels. However, systolic blood pressure usually remains unchanged or may increase slightly.

The maternal vascular volume increases that characterize pregnancy outpace the ability of the maternal system to increase hemoglobin and total red blood cell mass. Therefore, although both red blood cell mass

Prolactin, which is produced by the anterior pituitary gland, stimulates milk production in the breasts during pregnancy. However, high progesterone levels prevent milk secretion until after delivery.

Renal glomerular filtration increases rather than decreases during pregnancy. Consider that during pregnancy the maternal circulating blood volume increases and along with that comes an increase in the renal blood flow simply because of the increased volume. An increase in renal blood flow correlates with an increase in the glomerular filtration rate. Filtration increases by as much as 50% by mid-pregnancy. Vasodilatation and increased tidal volume are normal maternal physiologic adaptations to pregnancy. The increased production of POM-C by the pregnant woman results in an increase in circulating melanocyte stimulating hormone (MSH). This, in turn, commonly causes maternal cholasma (darkening of the skin of the cheeks) and darkening of the linea alba.

The increased glomerular filtration rate (GFR) results in increased urine production as the kidneys work to filter out metabolic waste products more efficiently.

Oxytocin and prostaglandins induce contractions and cause the cervix to dilate during phase 2 of labor. Cervical dilatation and uterine contractions allow the fetus, membranes and placenta to be expelled from the uterus. Phase 1 of labor occurs as the uterus becomes activated near the end of a normal pregnancy. At this time, contraction-associated proteins are upregulated as the uterus becomes optimally prepared for the contractions that occur during phase 2. Phase 3 of labor follows parturition and is called involution. It involves sustained contraction of the uterus to promote hemostasis and nearly reduces the uterus to its prepregnancy size. Phase 4 of labor describes the time period covering the first few hours after parturition. It involves the return of maternal hemodynamics back to prepregnant states.

Progesterone is the primary hormone responsible for maintaining pregnancy. It helps to relax the uterus, prevent contractions, and prepare the body for labor.

PGs do affect myometrial sensitivity to oxytocin by upregulating the number of oxytocin receptors present on myometrial cells. Oxytocin binding to these myometrial receptors causes an influx of intracellular calcium and contraction of myometrial cells. The remaining answer choices are true and illustrate the role PGs have during labor.

Pregnancy-induced plasma volume expansion leads to a dilution of red blood cells, resulting in a relative decrease in hemoglobin concentration (physiological anemia of pregnancy).

Urine flows more slowly through the maternal renal collecting system due to dilatation of the ducts. This dilatation is the result of mechanical obstruction by the enlarging uterus along with the relaxing effects of progesterone on smooth muscle. As a result of the increase in overall maternal blood volume during pregnancy, there is an increase in renal blood flow and in the glomerular filtration rate. Increased filtration leads to an increased creatinine clearance. Increased filtration in the maternal kidney combines with dilatation of the collecting ducts to cause a slight increase, not a decrease, in overall kidney size.

Pregnancy induces insulin resistance, which helps to ensure that more glucose is available to the fetus. However, this can sometimes lead to gestational diabetes if insulin production doesn't meet the increased demand.

Explanation: The glomerular filtration rate (GFR) increases during pregnancy to accommodate the increased blood volume and waste products from the fetus.

The increased oxygen consumption during pregnancy is primarily due to the increased metabolic demands of the fetus, the placenta, and the maternal tissues.

Oxytocin is released from the posterior pituitary gland, not the anterior pituitary gland. The posterior pituitary gland also releases ADH. The anterior pituitary gland releases FSH, LH, prolactin, TSH and ACTH. The remaining answer choices are all involved in the induction of labor.

Pregnancy increases the synthesis of clotting factors by the liver, leading to a hypercoagulable state that helps prevent excessive bleeding during delivery but increases the risk of thromboembolism.

Estrogen increases the number of blood vessels in the uterus, improving uterine blood flow. This ensures adequate nutrient and oxygen supply to the fetus.

Stroke volume increases during pregnancy, contributing to an increase in cardiac output to meet the increased circulatory demands of the growing fetus.

During pregnancy, the immune system adapts to tolerate the fetus, which is genetically distinct from the mother. This is essential to prevent rejection of the fetus.

Relaxin is the hormone responsible for increasing the flexibility and relaxation of pelvic ligaments and soft tissues in preparation for childbirth. It helps in softening the cervix and relaxing the pelvic joints to facilitate delivery.

The average human gestation lasts 280 days after the beginning of the menstrual period directly predating conception.

Progesterone relaxes smooth muscle and slows gastric and gallbladder emptying. Due to these changes nausea, vomiting, constipation and heartburn are very common during pregnancy.

During pregnancy, the levels of clotting factors (such as fibrinogen) increase, contributing to a hypercoagulable state. This increases the risk of deep vein thrombosis (DVT) and other thrombotic events.

Pregnancy hormones, especially progesterone, relax the smooth muscles of the gastrointestinal tract, leading to decreased motility. This results in constipation and slower gastric emptying.

Pregnancy can cause increased pigmentation due to hormonal changes, especially the darkening of the linea nigra (line on the abdomen) and the appearance of melasma (dark spots on the face).

Progesterone relaxes the smooth muscle of the uterus to prevent premature uterine contractions and support the growing fetus.

During pregnancy, stroke volume increases due to higher blood volume, leading to a rise in cardiac output, which places a higher workload on the heart to maintain sufficient blood circulation.

As the uterus enlarges, it can compress the urinary tract, leading to urinary stasis. This allows bacteria to proliferate, increasing the risk of urinary tract infections.

Pregnancy leads to increased fat deposition, especially in the second trimester, as the body stores energy reserves for labor and lactation.

The elevated circulating estrogen levels of pregnancy drive increased maternal hepatic production of many proteins. One of these is TBG. While increased TBG binds free T3 and T4, maternal feedback mechanisms cause an increase in T3 and T4 synthesis by the thyroid gland so that total T3 and T4 levels increase but free T3 and T4 levels remain fairly stable.

Renal plasma flow increases during pregnancy to accommodate the increased metabolic demands of the body and fetus. This helps maintain fluid balance and renal function.

Higher levels of estrogen stimulate melanocytes, leading to an increase in melanin production and causing darkening of the skin, especially in areas such as the face and abdomen.

The maternal immune system is altered during pregnancy. There are likely many factors involved in these alterations and most believe these changes occur to protect the fetal allograft from rejection. Classic placental transplantation antigens are absent. Cellular immunity is generally somewhat suppressed and this is partly responsible for the increased susceptibility of the mother to the severity of particular viral infections, including infection by varicella virus. Maternal IgG is actively transported across the placenta after the early second trimester of pregnancy. Maternal IgM, IgA, IgD and IgE do not cross the placenta.

Pregnancy leads to increased vascular compliance due to the effects of progesterone, which relaxes smooth muscles in blood vessels, helping to accommodate the increased blood volume.

The respiratory rate increases during pregnancy to accommodate the increased oxygen demand of the mother and fetus.

Hormones like relaxin cause increased laxity and flexibility of the pelvic joints and ligaments to accommodate the growing fetus and prepare for delivery.