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Fetal growth and parturition. Fetal growth Rate of growth in humans –Relatively slow during first 20 weeks –Rapidly increased during week 30-36 –Slows.

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Presentation on theme: "Fetal growth and parturition. Fetal growth Rate of growth in humans –Relatively slow during first 20 weeks –Rapidly increased during week 30-36 –Slows."— Presentation transcript:

1 Fetal growth and parturition

2 Fetal growth Rate of growth in humans –Relatively slow during first 20 weeks –Rapidly increased during week –Slows down until birth –Different from domestic species Majority of growth takes place during the last trimester

3 Accumulation of proteins –Muscle development –Precedes fat deposition Eventually exceeds protein deposition Energy storage Decreased placenta to fetus ratio

4 Rate of growth –Fetal genome –Maternal factors Nutrients –Postnatal health –Postnatal development Placental lactogen –Stimulation of growth

5 Fetal metabolism Nutrients –Maternal source Glucose –Major energy source (50 % of total energy for fetal growth) Amino acids Fatty acids Vitamins Minerals

6 Placenta –Physical barrier Diffusion of very small molecules and lipid-soluble molecules Large molecules and polar molecules –Transport system –Breach in the placenta –Movement of molecules between maternal and fetal circulation Layers of cells between two circulations

7 Importance of fetal adrenal gland

8 Parturition Three stages –First stage Initiation of myometrium contraction Initiated by the fetus –Second stage Expulsion of the fetus –Third stage Expulsion of fetal membrane

9 Parturition First stage –Initiated by fetus –Distress Maximum size that can be maintained –Lack of nutrients –Hypoxia Activation of fetal hypothalamus-pituitary-adrenal axis –Release of ACTH by the fetal pituitary gland

10 Fetal ACTH –Release of cortisol from fetal adrenal gland Fetal cortisol –Removal of “progesterone block” Contraction of myometrium Conversion of progesterone to estradiol –17  -hydroxylase –17-20 lyase –Aromatase

11 Fetal cortisol –Increase production of PGF 2  by the endometrium Further removal of progesterone block –Cause luteolysis Stimulates contraction of myometrium –Synergism with estradiol

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13 Contraction of myometrium –Pushes the fetus toward cervix Activation of the CNS –Secretion of oxytocin from the posterior pituitary gland Oxytocin –Increased contraction of the uterine smooth muscle –Positive feedback More contraction (pushing of fetus), increased oxytocin secretion Entering of the fetus in the cervical canal –End of the first stage

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15 Expulsion of fetus Relaxation of the cervix and pelvic ligaments –Relaxin Secretion stimulated by PGF 2 

16 Role of estradiol on parturition –Increased overall secretory activity Mucus production by cervix and vagina –Removal of cervical plug –Lubrication

17 Rupture of fetal membrane –Loss of amniotic and allantonic fluid Further lubrication Fetus becomes hypoxic –Movement of the fetus Stimulates further contraction of the myometrium –Increased strength of contraction

18 Expulsion of the fetal membrane Shortly after expulsion of the fetus –Dislodging of fetal membrane from the uterus –Vasoconstriction

19 Mammary gland development Cyclic changes in ovarian steroid hormones –Essential for mammary development Estradiol –Development of mammary alveoli (secretory unit) Progesterone –Development of mammary ducts

20 Final stage of mammary gland development –Pregnancy Ovarian/placental steroid hormones –Periparturient period GH and prolactin –Placental lactogen? Glucocorticoids

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22 Lactation Parturition –Metabolic shift Fetal growth to synthesis and secretion of milk –Mobilization of nutrients Storage within the body –Fats Triggered by changes in hormones

23 Lactation and re-initiation of reproductive cycle Lactating women –High prolactin –Low LH and estradiol No ovulation –Lactation-induced anovulation/amenorrhea (infertility) –Women remain anovulatory as long as they breast-feed their babies Increased survivability of the infants

24 Lactational anestrus in the domestic species –Divert nutrients for lactation Ensure the survival of offspring –Lactation stimuli/physical contact between mother and offspring –Animals remain in anestrus (absence of estrus) until nutrient intake exceeds nutrient demand


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