Physiology Of Pregnancy Flashcards
What is the big picture of pregnancy?
Ovulation occurs about 14th day & fertilization about 24 to 48 hours later
• hCG is secreted soon after fertilization into Maternal circulation
• Implantation begins 5 to 6 days post fertilization
• Human pregnancy lasts about 280 days or 40 weeks from the last menstrual perio
What are the 3 main hormones of pregnancy?
- HCG surge maintains menstruation
- Estrogens stimulate uterine growth and breast development
- Progesterone facilitates implantation and suppresses endometrial contractions
What is HCG?
Large glycoprotein has a long 1⁄2 life. Secreted by syncytial cells of trophoblast into maternal circulation
• Can be measured in urine ~ 9 days after fertilization. It prevents the involution of corpus luteum
• Plasma hCG doubles every 2 days & peaks around the 13th week
• hCG has been implicated in morning sickness
• Main role is luteal uninterrupted levels of progesterone required for maintenance of pregnancy
What are the roles of HCG?
Male fetus
• Stimulates testosterone production
• Promotes descent of testes
HCG Supports corpus Luteum which
• Estrogens and Progesterone • Relaxin
- relaxes pelvic ligaments
Events in early pregnancy in mom
Up to 6 weeks-corpus Luteum—> progesterone
6-12 weeks- placenta develops
More than 12 weeks-placenta- corpus Luteum involuted about this time—> progesterone
What is the placenta?
A specialized organ for exchange between maternal and fetal blood
• The fetal placenta comprises 60 to 70 villous trees that increase interface surface area.
• The space between fetal and maternal placenta is filled with ~500 mL of maternal blood. Blood flows in an unregulated manner at relatively high pressure (~70 mm Hg) from eroded spiral arteries and washes over the fetal villous trees
What are the roles of the placenta?
Gas exchange
Nutrients Waste Exchange
Hormone
- synthesis, transports, and degrades
Role of Placenta
-barrier
- immunologic organ
Only IgG can pass through which confers passive immunity to fetus
What is the role of progesterone?
Mother: Maintains pregnancy - supports endometrial lining - forms a cervical plug - required for breast development - makes uterus < excitable as it expands Inhibits lactation during pregnancy
Fetus
Important precursor for synthesis of adrenocortical hormones by fetal adrenal corte
What is the role of estrogen in the mother and the fetus?
Mother
- Prepares body for parturition - inhibits milk production
- Development of breast
- Initiation of labor ???
- ↑ levels of all binding globulins
Fetus:
- placenta has strong aromatase activity which convert androgens to estrogens which prevents masculinization of female fetus
What is the role of human placental lactogen (hPL)?
Growth Hormone Effects ??? - On breast
Decreases maternal Insulin sensitivity
More glucose available For fetus
Releases FFA stores & inhibits uptake of glucose in the mother
- CRH & CRH binding protein are synthesized by placenta & secreted into both maternal & fetal circulation
- CRH concentration rises exponentially in maternal plasma near term
What are the physical endocrine changes in pregnancy?
Increase of anterior pituitary size 50%
-Pituitary lactotrophs undergo hyperplasia & hypertrophy
This increases TSH, ACTH, PRL
Decreases FSH, LH
- are suppressed to almost undetectable
- gonadotrophs are unresponsive to GnRH challenge 1
week postpartum
How does the thyroid gland change in pregnancy for the mother?
TSH, hCG, hCT(human chorionic thyrotropin hormone secreted by placenta)—> increases thyroid gland size by 50%—> increases T3 &T4 Patient is euthyroid as elevated levels of TBG
Increased parathyroid gland size —> increased PTH for calcium for fetus and calcium for milk after birth
How Do Insulin, cortisol and aldosterone changes in pregnancy?
In response to high levels of glucose in the mother —> pancreas—> increases insulin—> but insulin resistance in tissues causes more glucose for fetus
In response to high levels of CRH & ACTH —> adrenal gland increase in cortisol(only moderate rise in cortisol levels due to increased CBG levels) & aldosterone
Aldosterone increases cardiac output
Cortisol aids in
AAs for fetus
Stretch marks
Insulin resistance
Weight gain & hyperphagia
What are the maternal physiological changes?
During gestation, the uterus continuously enlarges, filling first the pelvic and then the abdominal cavity, displacing and compressing a number of structures
- Weight gain due to fat deposition and fetus & amniotic fluid
- Nausea & vomiting @1st trimester. Skin pigmentation and stretch mark
- Increased GFR by 40%
- Renal artery compression (Hypertension)
- Increased nutritional requirements – vit K, Fe, folate Ca2
What hematological and cardiological changes in the mother?
- Blood volume ↑ by 50% in 2nd trimester
- Hematocrit ↓ slightly
- Clotting Factors (fibrinogen) ↑:Protects from hemorrhage during parturition
Increase CO leads to ↑ Blood flow to fetus
- compensates for blood loss during birth of the baby
What is the fetus?
Anterior pituitary hormones get released into fetus by ~ 20 weeks of gestation
• ACTH important for adrenal development
• By third trimester all feedback mechanisms working
• Fetal gonadotropins necessary for development of gonads and genitalia
• ADH and oxytocin released by week 18. Oxytocin may have role in parturition
• Fetal insulin, HCG influence development and growth of fetus.
