Maternal Changes During Pregnancy

What occurs to the mammary glands and breasts after delivery and how do hormones regulate this process?

1. After delivery, plasma levels of estrogen and progesterone fall, and milk producing cells undergo terminal differentiation leading to milk produciton. 2. Lactation is mainly regulated by prolactin, but also requires insulin and cortisol. 3. Prolactin stimulates the synthesis of milk proteins and lactose, increases milk yield, and stimulates reabsorption of sodium from milk. 4. Nipple stimulation is the main stimulus for prolactin secretion during lactation.

What happens to the Progesterone concentration in the maternal plasma over the course of pregnancy and why?

1. At the beginning, there is an increase in progesterone from the corpus luteum. 2. Then the corpus luteum's role is taken over by the placenta. 3. Progesterone increases until birth, and then the concentration drops rapidly after birth.

What is the cellular cause of insulin resistance in pregnant women?

1. Believed to be due to a defect in the transmission in the insulin signal from the insulin receptor to the cellular GLUT4 glucose transport (post-receptor defect). 2. This defect is caused by increased levels of cortisol, human placental lactogen, GH-V, and perhaps progesterone.

What occurs to the blood volume and contents during Pregnancy?

1. Blood volume increases by 50%. 2. Hematocrit decreases slightly (actually increases, but total volume increase more). 3. Plasma electrolyte concentrations remain unchanged. 4. Plasma fibrinogen concentration increases (why pregnant women are at higher risk for blood clots, hypercoagulative state).

What are the functions of Prolactin during Pregnancy?

1. Causes rapid growth and maturation of milk producing cells of the mammary gland. 2. However, lactation does not occur because the onset of milk production is inhibited by high levels of estrogens and progesterones. 3. Simultaneously, prolactin and estrogens cause deposition of adipose tissue in the breasts leading to engorgement of the breasts.

How do the levels of GH, GH-V, and hCS differ in relation to each other?

1. During 1st trimester, only pituitary GH is present in episodic manner. 2. From about 15th-17th week, pituitary GH is replaced by a gradual rise in GH-V/hCG. 3. In the 2nd half of pregnancy, maternal pituitary response to hypoglycemia or increased arginine concentration is diminished.

What are the concentrations of LH and FSH and why does this occur?

1. During pregnancy, LH and FSH are nearly undetectable in maternal plasma and maternal pituitary cells which produce these cells become unresponsive to GnRH stimulation. 2. This is due to strong negative feedback suppression by high levels of estrogen, progesterone, and inhibin from the corpus luteum, then placenta.

What occurs to Aldosterone levels during pregnancy and why does this not have an affect on pregnant women?

1. During pregnancy, plasma concentration of aldosterone rises several fold as a result of increasing Angiotensinogen/Renin. 2. Despite these changes, pregnant women do not exhibit hypokalemia or hypernatremia because elevated plasma progesterone inhibits the actions of aldosterone in the kidneys.

What effect does Pregnancy have on thyroid hormone, and what is responsible for these effects?

1. Estrogens increase concentration of TBG which leads to an initial decrease in free T4/T3. 2. Normally functioning feedback regulation increases thyroid hormone release. 3. Restoration of normal concentrations of free T4/T3 is achieved at the expense of an elevated total T4/T3. 4. Thus, healthy pregnant women remain euthyroid.

What are the hormones with growth hormone-like biological actions and how are they released?

1. GH from maternal pituitary, GH-V and hCS from placenta. 2. Normal GH from maternal pituitary is released in an episodic fashion. 3. GH-V and hCS are secreted in a continuous fashion, without fluctuations.

What does increased GH-V cause and how does this affect pituitary GH?

1. GH-V is responsible for the continuously rising IGF-1 levels during pregnancy. 2. High GH-V and IGF-1 in maternal plasma inhibit pituitary GH via negative feedback on the hypothalamus and the pituitary.

What occurs to the Cardiovascular System during Pregnancy and what causes it?

1. Heart rate gradually increases by 20%. 2. Stroke volume increases to a maximum at 19 weeks and then plateaus. 3. Cardiac output increases rapidly by 20%, then gradually increases 10%. 4. Blood pressure gradually decreases 10% at 34 weeks then increases to pre-pregnancy values by birth. 5. Peripheral venous distention progressively increases to term. 6. Peripheral vascular resistance progressively decreases; restoration near term. 7. Caused by progesterone which is a vascular dilator of smooth muscle.

If the increase in insulin secretion in the second half of pregnancy is insufficient, what occurs to the pregnant women?

1. If the increases secretion of insulin is insufficient to overcome insulin resistance, gestational diabetes mellitus develops. 2. Gestational diabetes mellitus affects 4-6% of pregnant women.

Why do pregnant women not experience signs of hypercortisolism (Cushing's Syndrome)?

1. In spite of cortisol concentrations approaching Cushing syndrom levels, most signs of hypercortisolism do not occur because increase plasma progesterone competes with cortisol for the glucocorticoid receptors.

What causes the development of maternal insulin resistance in pregnancy?

1. Increasing concentrations of GH-V and hCS.

What happens when there is poorly treated Type 1 DM and/or Gestational DM during pregnancy?

1. Maternal hyperglycemia results in an increased transport of glucose into the fetus. 2. This increases fetal plasma glucose concentration which results in elevated secretion of insulin from fetal pancreas. 3. High insulin levels act on both insulin and IGF-1 receptors and stimulate protein synthesis and growth which leads to fetal macrosomia, i.e. a birth weight of more than 4kg.

What happens to the hCG concentration in the maternal plasma over the course of pregnancy?

1. Only hormone which does not show a continuous progressive increase as pregnancy continue. 2. The peak is reached at about 60-90 days. 3. Then there is a fall but it remains steady and high for the remainder of pregnancy.

What affect does placental GH-V and/or hCS have on the fetus?

1. Placental GH-V and/or hCS may enter the fetal circulation and may be involved in promoting fetal growth by stimulating fetal production of IGF-1.

What happens to the levels of ACTH during pregnancy and why?

1. Plasma concentration of ACTH from maternal pituitary also increases through pregnancy. 2. This is partly in response to increasing secretion of CRH by the placenta.

How are plasma insulin levels during the first half of pregnancy?

1. Plasma insulin concentrations before and after meals are unchanged compated to non-pregnant state. 2. Sensitivity of maternal tissues to insulin is also unchanged.

What occurs to the levels of free and bound cortisol during pregnancy and why?

1. Plasma total cortisol increases approximately three fold during pregnancy. 2. Plasma free cortisol increases approximately two fold. 3. Increased estrogen levels increase CBG concentrations resulting in a greater increase in plasma total cortisol than in plasma free cortisol.

What occurs to the concentration of prolactin in the maternal plasma during pregnancy and why does this occur?

1. Prolactin increases steadily over the course of pregnancy. 2. High plasma concentrations of estrogens increase the size and number of prolactin cells in the maternal pituitary. 3. Also stimulates the secretory activity of prolactin producing cells.

What are the effects of Pregnancy on the Renal blood flow, Glomerular Filtration Rate, and urinary volume?

1. RBF increases by 25-50% during the 1st trimester, then plateaus, and decreases to normal levels during the 3rd trimester. 2. GFR increases during the 1st half of pregnancy by about 45% and remains elevated at this level to term. 3. Urinary volume does not change during pregnancy.

What occurs to the respiratory system during Pregnancy and what causes it?

1. Respiratory rate is unchanged. 2. Tidal volume increases by 30-40%. 3. Expiratory reserve volume gradually decreases by 40%. 4. Respiratory minute volume (ventilation) increases by 40%. 5. Arterial blood PCO2 is reduced. 6. This is all due to the actions of progesterone.

What are the levels of plasma free cortisol compared to normal levels and what effects can this cause during pregnancy?

1. The elevated free cortisol contributes to the development of insulin resistance of pregnancy, and possibly stretch marks.

What occurs to plasma insulin during the second half of pregnancy and why response does this trigger?

1. The sensitivity of maternal tissues to insulin is diminished (insulin resistance). 2. Maternal pancreatic beta-cells exhibit increased secretion of insulin to compensate for the insulin resistance which results in elevated levels before meals and exagerated hyperinsulinemia after meals.

What happens to the Estrogen concentration in the maternal plasma over the course of pregnancy?

1. There is a steady increase in Estriol, Estradiol, and Estrone.