Pregnancy And Lactation Unit 10.1 PDF

Pregnancy and Lactation I: Lactation and fertilization of the ovum Unit 10. 1 Second Semester Second Medicine  Breast development The human breast begins to develop at puberty, stimulated by the estrogens. Estrogens promote the breasts’ mammary glands an...

Pregnancy and Lactation I: Lactation and fertilization of the ovum Unit 10. 1 Second Semester Second Medicine  Breast development The human breast begins to develop at puberty, stimulated by the estrogens. Estrogens promote the breasts’ mammary glands and the deposition of fat. This period is call thelarche.  Breast development Polymastia is a common developmental abnormality of the breast, consisting in more than 2 mammary glands. Supernumerary breast tissue usually develops along the mammary line. 3  Breast development The peak of breasts’ growth occurs during pregnancy, and only then does the glandular tissue become able to produce milk. Lobules’ evolution during life Both type 3 and type 4 lobules are resistant to carcinogens. If a woman does not have pregnancy, she has increased risk for breast cancer. If she has children after age 30-40, she has increased risk, because, for most of her menstrual life, her estrogen has been stimulating immature type 1 and 2 breast lobules.  Lobules’ evolution during life Breastfeeding reduces estrogen exposure, misses menstrual cycles and for even one year, the breast tissue maturity to type 4 lobules. During pregnancy large amounts of estrogens are secreted by the placenta  Estrogen stimulate growth of the ductal system of the breast Estrogens cause: 1) the ductal system of the breasts to grow and branch, 2) the stroma of the breasts increases in quantity, and 3) fat lays down the stroma.  Estrogen stimulate growth of the ductal system of the breast Also four other hormones are involved on this development: Growth hormone, insulin, prolactin and glucocorticoids. Milk secretion from breast requires progesterone.  Progesterone is required for full development of the lobule-alveolar system Progesterone, plus estrogen and growth hormone, prolactin, adrenal glucocorticoids and insulin develop the mature breast lobules, with budding of alveoli and progress of secretory characteristics in the cells of the alveoli, in a similar way of the changes produced on the endometrium of the uterus during the latter half of the female menstrual cycle.  Progesterone is required for full development of the lobule-alveolar system  Prolactin promotes lactaction Estrogen and progesterone during pregnancy: 1. develop the breasts, 2. inhibit the actual secretion of milk. Because of the suppressive effects of estrogen and progesterone, no more than a few milliliters of fluid are secreted until after the baby is born.  Prolactin promotes lactaction prolactin promotes milk secretion. It is secreted by the mother’s anterior pituitary gland, and its concentration in her blood rises steadily from the fifth week of pregnancy until birth of the baby, at which time it has risen to 10 to 20 times the normal nonpregnant level.  Prolactin promotes lactaction Once the baby is born, estrogen and progesterone and placenta secretions disappear. prolactin from the mother’s induces milk secretion and in 1 to 7 days, the breasts begin to secrete milk, which requires an adequate hormonal regulation especially of growth hormone, cortisol, parathyroid hormone, and insulin. These hormones are necessary to provide the amino acids, fatty acids, glucose, and calcium required for milk formation.  Prolactin promotes lactaction After birth of the baby, the basal level of prolactin secretion returns to the non-pregnant level over the next few weeks. If the mother nurses her baby, in each breast feading, nervous signals from the nipples to the hypothalamus cause a 10- to 20-fold surge in prolactin secretion that lasts for about 1 hour.  Prolactin promotes lactaction This mechanisms keeps the mammary glands secreting milk into the alveoli for the subsequent nursing periods. This way milk production can continue for several years if the child continues to suckle, although the rate of milk formation normally decreases considerably after 7 to 9 months. Hypothalamus secretes prolactin inhibitory hormone The hypothalamus inhibits prolactin production. Therefore, it is believed that anterior pituitary secretion of prolactin is controlled by an inhibitory factor formed in the hypothalamus and transported through the hypothalamic- hypophysial portal system to the anterior pituitary gland. This factor is called prolactin inhibitory hormone, that seems to be dopamine. Dopamine is secreted by the arcuate nuclei of the hypothalamus and can decrease prolactin secretion 10-fold.  Other lactotropes The placenta-specific hormone chorionic somatomammotropin is one of the most abundantly produced placental hormones and belongs to the growth hormone/prolactin gene family, and probably has some lactogenic properties. Its production and secretion is due to the Syncytiotrophoblast cells in the human placenta. Other hormone in the same group is the human placental lactogen.  Other lactotropes Human placental lactogen is a placental hormone which appears to have key metabolic functions in pregnancy. Is a peptide of 191 amino acids detectable as early as 6 weeks' gestation and increases across gestation with a peak around 30 weeks. It is similar to growth hormone. It mobilizes free fatty acids from lipids.  Effects of lactogens in mother mood Maternal behavior represents a profound change in a female’s behavior that ensure the healthy development of offspring while maintaining maternal health. Could lactogenic hormones have a role in regulating postpartum mood in women?.  Effects of lactogens in mother mood Prenatal depression in women is associated with low levels of placental lactogen, and postpartum depression has been linked to low placental lactogen levels at term in mothers who give birth to female infants. One cause of low placental lactogen production in women is maternal obesity, a concurrent risk factor for developing postpartum depression and anxiety.  Effects of lactogens in mother mood Prolactin can be synthesized and released into the cerebrospinal fluid by epithelial cells in the choroid plexus and it is produce in high doses in the hypothalamus during pregnancy. Prolactin binding to its receptors results in dimerization and activation of JAK2 which, in turn, triggers a signaling cascade resulting in effects on gene transcription.  Effects of lactogens in mother mood Latogenic hormones production during pregnancy and lactation seems to regulate functions in the mother and the new born as: pup retrieval, licking nursing, grooming (animal care of the body of its offsprings), increase maternal motivation, reduction of anxiety, building a nest, increment of maternal aggressiveness to protect the baby.  Supression of ovarian cycles after delivery In most nursing mothers, the ovarian cycle (and ovulation) is blocked until a few weeks after cessation of nursing. It is supposed that the nervous signals from the breasts to the hypothalamus that cause prolactin secretion during suckling inhibit secretion of gonadotropin-releasing hormone (GnRH) by the hypothalamus.  Supression of ovarian cycles after delivery GnRH stimulates the formation of the gonadotropic hormones. Its absence blocks ovarian cycle during several months of lactation. When breastfeeding is reduced the pituitary begins to secrete gonadotropic hormones to reinstate the menstruation, even though nursing continues.  Milk ejection and oxytocin Milk needs to be ejected from the alveoli into the ducts before the baby can obtain it. When the baby suckles, sensory impulses are transmitted through somatic nerves from the nipples to the mother’s spinal cord and then to her hypothalamus, where they cause nerve signals that promote oxytocin and prolactin secretion. The oxytocin is carried in the blood to the breasts, in around one minute and stimulates the myoepithelial cells in the outer walls of the alveoli to contract.  Inhibition of milk ejection Many psychogenic factors or generalized sympathetic nervous system stimulation throughout the mother’s body can inhibit oxytocin secretion and consequently depress milk ejection.  Colostrum Colostrum is a form of milk produced by the mammary glands in late pregnancy and the few days after delivery. Human colostrums are thick, sticky and yellowish. It has high concentrations of nutrients and antibodies, but it is small in quantity. Colostrum is high in carbohydrates, protein, specially antibodies, and low in fat. Its maximum rate of production is about 1/100 the subsequent rate of milk production.  Colostrum It has a mild laxative effect, helping the passing of the meconium. This clears excess bilirubin, a waste product of dead red blood cells which is produced in large quantities at birth due to blood volume reduction, and helps prevent jaundice. Colostrum contains large numbers of "secretory immunoglobulin" (IgA) that help protect the mucous membranes in the throat, lungs, and intestines of the infant and leukocytes to protect the infant from harmful microbia.  Colostrum Ingesting colostrum establishes beneficial bacteria in the digestive tract. Yes, bacteria goes from the mother to the baby. Premature babies tend to fare better on human colostrum than commercial infant formulas. Human milk contains growth modulators, that help the premature baby's digestive system adjust to oral feedings. Research indicates that premature babies fed formula tend to vomit more and continue tube feeding longer than those fed human colostrum and breast milk.  Milk composition  Milk production At the height of lactation, 1.5 liters of milk may be formed each day. Milk has around 700 kilocalories per liter, although the composition and caloric content of the milk depends on the mother’s diet and other factors. Large amounts of metabolic substrates are also lost from the mother. This helps to recover the previous weight but also 2 to 3 grams of calcium phosphate may be lost each day; the output of calcium and phosphate by the lactating mammae is often much greater than their intake. Antibodies and other anti-infectious agents in milk Milk also provides important protection against infection. For instance, multiple types of antibodies and other anti- infectious agents; and several types of white blood cells, including both neutrophils and macrophages, some of which are especially lethal to bacteria that could cause deadly infections in newborn babies. Particularly important are antibodies and macrophages that destroy Escherichia coli bacteria.  Nutrition of the neonate The main fuel in a fetus is glucose obtained from its mother’s blood, which is partly stored as glycogen in the liver and muscle. This supply is consume in a few hours, and gluconeogenesis is not available in the newborn. Therefore, the baby’s glucose concentration falls the first day to as low as 30 to 40 mg/dl of plasma, less than half the normal value. But the baby can use its stored fats and proteins for metabolism for the 2 to 3 days before milk is secreted.  Nutrition of the neonate During the first year, can be problems associated with the right hydration of the infant due to its rate of body fluid turnover, that is seven times that of an adult. Specially since the mother’s milk supply requires several days to develop. Ordinarily, the infant’s weight decreases even 20% within the first 2 to 3 days of life, mostly for loss of fluids. Milk is 88% water, but in many Mediterranean countries, women where giving boiled water (the first days with sugar solved) to the babies preventing dehydration.  Brain development and intelligence Some major tracts in the central nervous system finishing their myelination at the end of the first year of life, and thousand of neurons died during this period, allowing to assume that the nervous system is not fully functional at birth. Some functions, such as vision, seem to require several months after birth for total functional development. The complete maturity of the brain is achieved around 21 years after birth.  Brain development and intelligence At birth, the baby brain mass is 26 % of the adult brain mass and 55% at 1 year, but it reaches almost adult proportions by the end of the second year, coinciding with closure of the fontanels and sutures of the skull. After this closure, brain only growths and additional 20% until adulthood.