Physiology of pregnancy. The perinatal care of the fetus.

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Physiology of pregnancy. The perinatal care of
the fetus.

• Prepared by N. Bahniy

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STAGES OF PRENATAL DEVELOPMENT

• Preembryonic stage - first 2 weeks. Products of
  conception are called as conceptus.
• Embryonic stage - from the third week until the
  end of the eight week. From this period conceptus
  is called embryo.
• Fetal period starts from the beginning of the
  ninth week through the full 41 weeks of
  development. Products of conception are called as
  fetus.

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Preembryonic Stage

• fertilization
• zygote formation
• division of fertilized ovum
• morula formatiom
• formation of free blastocyst
• implantation of the ovum in the uterine wall
• Primitive chorionic villi formation
• Initial folding into layers gastrulation
  beginning.
• Chorion and amnion begin to form during
  this period also.

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A SPERM FERTILIZING AN OVUM
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Formation of free blastocyst
Morula
From inner layer - embryoblast
From outer layer - trophoblast
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Implantation- attachment of the blastocyst on the
7th day into uterine wall called implantation.
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EMBRYONIC STAGE

• Formation of supportive structures - include the
  placenta, umbilical cord, and certain
  extraembryonic membranes.
• The yolk sac forms early and manufactures blood
  cells until the liver takes over at 6 week.
• The allantois forms the part of the yolk sac it
  produces blood cells and eventually forms the
  umbilical arteries and veins.
• During the third week the primitive streak
  appears, and then, other rudiments of organs
  form, including the central nervous system,
  notochord, neural tube, heart, limbs, finger,
  toes, eyes, ears, and nose.

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AN AMBRYO IS ABOUT 5 WEEKS OLD
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"FETUS OF ABOUT EIGHT WEEKS, ENCLOSED IN THE
AMNION," FROM GRAY'S ANATOMY. PART OF THE
PLACENTA IS SHOWN AS THE LOWEST FEATURE IN THIS
IMAGE, AND THE AMNION EXTENDS ABOVE THE FETUS.1
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Critical periods of fetal development

• Implantation
• Morphogenesis and organogenesis
• Placentation

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Growing and differentiation of the structures
during the Fetal Period
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Conceptus structure in the end of pregnancy

• Fetus
• Umbilical cord
• Placenta
• Amniotic Fluid
• Amnion
• Chorion
• Decidua

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Fetal characteristics
Classification Gestational age (weeks of pregnancy Weight, gram Length, cm Signs of maturity
Deep pre-term fetus 12 22 25 500 9 - 25 Absent
Fetus pre-term 22 366 days 500 2500 25 - 46 Absent
Fetus in-term 37 41 gt 2500 (3200-3500) 47 (50-52) Present
Fetus post-term gt 41 gt 2500 47 Present
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Signs of fetal maturity

• Umbilical ring is between pubis and processes
  xyphoideus
• Pink skin
• Well-developed subcutaneous tissue,
• Lanugo in the shoulders and upper part of the
  back
• Length of the hair on the head is 2 cm
• Nails are present till the top of the fingers
• Well-developed ears and nose cartilage
• Testes are present in the scrotum in the boys and
  labia major are covered labia minor in the girls
• Active movements
• Loud cry of the infant

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FETAL HEAD AT TERM
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DIAMETERS OF THE FETAL HEAD AT TERM

• 1. The suboccipitobregmatic (9.5 cm, 32cm), which
  follows from the middle of the large fontanel to
  the undersurface of the occipital bone.
• 2. The suboccipitofrontalis (10cm,33 cm) from
  subocipital fossa to border of the hair.
• 3. The occipitofrontal (12 cm, 34 cm), which
  follows a line extending from a point just above
  the root of the nose to the most prominent
  portion of the occipital bone.
• 4. The occipitomental (12.5-13 cm, 39-41cm),
  from the chin to the most prominent portion of
  the occiput.
• 5.The sublingquobregmatica (9,5 cm, 32 cm).
• 6. The biparietal (9.5 cm), the greatest
  transverse diameter of the head, which extends
  from one parietal boss to the other.
• 7. The bitemporal (8.0 cm), the greatest
  distance between the two temporal sutures.

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DIAMETERS OF THE FETAL BODY AT TERM

• Biacromial distance 12cm, 34-35 cm
• Bisiliacus distance 9cm, 27-28 cm

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DECIDUA - MATERNAL MEMBRANE, immunologically
specialized tissue.provides for embryo-fetal
nutrition.
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Fetal membranes

• Structure
• chorion and amnion
• Amnion
• A double-layered
• translucent membrane
• Become distended
• with fluid

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Amniotic fluid 1000-1500ml at 36th-38th week
(peak)

• Absorb
• Fetal membrane
• Umbilical cord
• Fetal skin
• Fetal drinking
• Source
• Fetal urine
• Fetal lung
• Exudation of amnion and fetal skin
• Functions
• Protection of the fetus
• Protect mother, prevent infection

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Formation of the forebag
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Umbilical Cord

• Structure
• amnion, yolk sac, one vein, two artery and
  Wharton jelly
• Length
• 30-70cm

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Placenta at section

• Fetal and maternal parts.
• Cotyledon
• is a small
• compound of placenta.

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Placental villi

• At term, the placenta contains approximately 12
  m2 of villous surface area for maternofetal
  exchange.

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Placental functions

• Endocrine
• Transfer of nutrients
• Excretory - removal
• of the products of fetal catabolism
• Barrier
• Oxygen-transport

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Placental hormones

• 1. Protein hormones of the placenta
• chorionic gonadotropin (cHG) it is maintain the
  function of the corpus luteum during early
  gestation, promote uterine vascular vasodilation
  and myometrial smooth muscle relaxation, relaxin
  secretion by the corpus luteum, stimulate thyroid
  activity, and some more basic forms also
  stimulate iodine uptake
• human lactogen its actions include lipolisis
  and an increase in the levels of circulating free
  fatty acids, thus providing a source of energy
  for maternal metabolism and fetal nutrition
• 2. Steroid hormones of the placenta estrogens
  progesterone.
• 3. Chorionic adrenocorticotropin and thyrotropin,
  growth hormone variant, parathyroid
  hormone-related protein (PTH-rP), calcitonin, and
  relaxin no significant role has been
  established for this substance in normal human
  pregnancy.
• 4. Hypothalamic-like-releasing hormones of the
  placenta

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Type of human placentation - hemochorioendothelial

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Role of Estrogen in Pregnancy

• Increasing blood flow to the uterus by promoting
  vasodilation.
• Changing the sensitivity of the respiratory
  system to carbon dioxide.
• Softening of the cervix, initiating uterine
  activity, and maintaining labor.
• Developing the breasts in preparation for
  lactation and secretion of prolactin by the
  pituitary gland.

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Role of Progesterone in Pregnancy

• Ready the uterus for implantation.
• Relaxes smooth muscle to prevent spontaneous
  abortion.
• Works to prevent a maternal immunologic response
  to the fetus.
• Relaxes smooth muscle
• to decrease motility improve absorption of
  nutrients.
• Enlarges the ureters bladder to increase
  capacity.
• Plays a role in development of the alveoli
  ductal system to prepare for lactation.

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Physiologic changes
in pregnant woman

• Genital organs
• Uterus
• capacity 5ml-5000ml.weight 50g-1000g
• Hypertrophy of muscle cells
• Endometrium?decidua basal decidua, capsular
  decidua, true decidua
• Contraction Braxton Hicks
• Isthmus uteri 1cm? 7-10cm
• Cervix colored
• Ovary placenta replaces ovary (10th week)
• Vagina dilated and soft, pH?(anti-bacteria)
• Ligaments relaxed

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Physiologic changes in pregnant woman

• Cardiovascular system
• Heart
• move upward, hypertrophy of cardiac muscle
• Cardiac Output
• increase by 30, reach to peak at 32nd
  34th week
• Blood pressure
• early or mid pregnancy Bp?.late pregnancy
  Bp? .Supine hypotensive syndrome

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Physiologic changes in pregnant woman

• Hematology
• Blood volume
• Increase by 30-45 at 32nd 34th (peak)
• Relatively diluted
• Composition
• Red cells
• Hb130?110g/L, HCT38? 31.
• White cells slightly increase
• Coagulating power of blood ?
• Albumin ?,35 g/L

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Physiologic changes in pregnant woman

• The Respiratory system
• R rate slightly ?
• vital capacity no change
• Tidal volume ? 40
• Functional residual capacity?
• O2 consumption ? 20

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Physiologic changes in pregnant woman

• Kidney
• Renal plasma flow (RFP)?35
• Glomerular filtration rate (GFR)? 50
• Ureter
• Dilated (P?)
• Bladder
• Frequent urination

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Physiologic changes in pregnant woman

• Gastrointestinal system
• Gastric emptying time is prolonged? nausea.
• The motility of large bowel is diminished ?
  constipation
• Liver function unchanged

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Physiologic changes in pregnant woman

• Endocrine
• Pituitary (hypertrophy)
• LH/FSH ?
• PRL?
• TSH and ACTH?
• Thyroid
• enlarged (TSH and HCG?)
• thyroxine? and TBG? ? free T3 T4 unchanged

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Thanks for attention