OBI 814 - RD3 - Exam 2

• A pregnant woman's body undergoes dramatic hormone-induced changes to allow for fetal growth.

Conception to Early Embryo Development

• Fertilization happens when the first sperm binds to the egg membrane.
• The sperm head enters the egg, resulting in a cortical reaction to block polyspermy.
• Meiotic completion occurs, leading to a zygote and activation of egg enzymes.
• Early cleavage, from the zygote to the morula stage, occurs in the fallopian tube.
• The blastocyst travels to the uterine cavity, hatches, and invades the endometrium about a week before the next cycle.
• A blastocyst consists of trophoblasts (extraembryonic cells) and an inner cell mass (embryonic stem cells).
• Trophoblasts secrete human chorionic gonadotropin (hCG) to support the corpus luteum in steroid secretion during the first trimester and later form part of the placenta.

Hormone changes during pregnancy weeks 1 and 2

• During the first two weeks HCG secretion continues.
• Estrogen and progesterone secretion from the corpus luteum are supported.
• Morphological changes in the embryoblast produce a bilaminar embryonic disc composed of epiblast and hypoblast.
• The embryonic disc gives rise to germ layers that form tissues and organs of the embryo.

The Placenta

• Construction begins from extraembryonic structures: amniotic cavity, amnion, umbilical vesicle connecting stalk, and chorionic sac.

Week 3

• Gastrulation occurs, generating three germ layers: ectoderm, endoderm, and mesoderm.

Hormones of Maternal Pregnancy

• Includes human chorionic gonadotropin, progesterone, hPL, estrogen, and relaxin.
• Possible Pregnancy Complications:
• Hemodynamics issues (anemia, hypertension).
• Mood swings (anxiety, depression).
• Hyperemesis gravidarum (morning sickness), infections, and being overweight.
• Endocrine gland dysfunction (diabetes, hypothyroidism).

hCG (Human Chorionic Gonadotropin)

• Maintains the function of the corpus luteum (CL) during the first trimester.
• The CL secretes estrogen and progesterone.
• hCG is secreted by trophoblasts of the implanted blastocyst and continues to be secreted when they become a part of the placenta.
• hCG is used to diagnose pregnancy and some cancers.
• There is immunomodulation at the maternal-fetal interface.
• T-cell activation is reduced.
• Immuno-suppression is induced through Treg.
• There is an increase in uterine NK cells.

Progesterone

• It is essential for maintaining the quiescent endometrium.
• Progesterone comes from the CL (1st trimester) and the placenta (2nd-3rd trimesters).
• Decreases contractions of smooth muscle and immune responses (immunomodulatory).
• Progesterone antagonist: a medical abortifacient (e.g., mifepristone).

Estrogen

• It stimulates uterine growth to accommodate the growing fetus and breast development.
• An estrogen is required for progesterone action.
• Estrogen stimulates smooth muscle contraction.
• Estriol synthesis requires a contribution from fetal organs.
• Estriol in the mothers blood shows fetal health.

Maternal Blood Volume

• Maternal blood volume is associated with high plasma levels of building blocks for fetal growth (glucose, amino acids, fat).
• Umbilical arteries carry fetal blood high in wastes and CO2.
• Umbilical veins carry fetal blood high in nutrients and O2.

Exchange of Nutrients

• Nutrients comes from the mother
• Exchange of these nutrients occurs through syncytiotrophoblasts.
• Passive Diffusion: gases, fat-soluble vitamins, fatty acids, steroids.
• Facilitated Diffusion: glucose.
• Active Transport: amino acids, water-soluble vitamins, Ca++, Fe, I- Endocytosis for phospholipids, globulin, lipoproteins (e.g., LDL, HDL).
• Fetal Circulation:
  • Shunts bypass the lungs and liver, which do not work fully until after birth.
  • These shunts direct oxygenated blood to bypass certain body parts (lungs and liver) that are not fully developed while the fetus is still in the womb

Supine Hypotension

• A pregnant woman is prone to supine hypotension in the dental chair.
• Hypotension is caused by supine position due to aortocaval compression by the vertebrae during later pregnancy (20th week gestation and beyond).
• Presents as pallor, tachycardia, sweating, nausea, hypotension, and dizziness.
• Tilt the body 15 degrees to the left by placing rolled towels under the right side of the spinal board to avoid supine hypotension.

Relaxin

• Involved in parturition/labor and helps relax ligaments in the pelvis.
• Softens and widens the cervix to dilate; increase uterine oxytocin-R.
• Relaxin effects tooth movement.

hPL (human placental lactogen)

• Also called human chorionic somatomammotropin (HCS).
• Mimics the action of prolactin and growth hormone.
• Stimulates mammary cell proliferation.
• Modifies the metabolic state of the mother during pregnancy to facilitate the energy supply of the fetus.
• Implicated in the development of gestational diabetes.

Gestational Diabetes

• Gestational diabetes can come from excessive activities of the Pregnancy-Associated Hormones on the metabolic state.
• Diagnosed in the 2nd-3rd trimesters.
• Risk factors include:
  • Overweight or obese.
  • Physical inactivity.
  • Polycystic ovary syndrome.
  • Genetics.
  • Non-white race.
• Results from beta cell hyperplasia, hyperinsulinemia, insulin resistance (reduced glucose utilization by the mother), and hyperglycemia.

Maternal Diabetes

• Can cause Fetal Macrosomia
• Symptoms in a Pregnant Mother:
  • Large fundal height.
  • Polyhydramnios (excessive amniotic fluid).
• Risks for Parturition/Delivery:
  • Labor might need C-section.
  • Possible uterine rupture.
  • Genital tract injury.
  • Possible post-delivery bleeding.
• Complications of Fetal Development:
  • Macroglossia (large tongue).
  • Dentoalveolar abnormalities (development of long narrow faces and high palates).
  • Developmental enamel defects (tooth formation beginning the 4th week and mineralization beginning around 4 to 6 months of pregnancy).
  • Increased risk of dental caries and obesity in childhood.
• Maternal Hyperglycemia Causes Hyperplasia of Fetal Pancreas and Neonatal HYPOGLYCEMIA:
  • Develops at 5 weeks of age.
  • Secretes insulin by 12 weeks of age.
  • Fetal insulin levels reflect the size of the endocrine pancreas (more β-cells)
• Neonatal HYPOGLYCEMIA:
  • Elevated levels of fetal insulin persist even after birth.
  • Lack of glucose (no maternal supply). Gestational Diabetes is linked to Limited Fetal Growth & Development:
  • Several metabolic risks link maternal GDM to fetal growth and development.
  • There are dysfunctions in glucose, insulin, and lipid pathways.
  • Long-lasting on her offspring (fetus, infant, child, and adult).
  • Several metabolic risks link maternal GDM to fetal growth and development. These
• Metabolic effects occur involving dysfunction in glucose, insulin, and lipid pathways.
• Effects are long-lasting on her offspring/ the lifespan of her offspring (fetus, infant, child, and adult).
• Gestational Diabetes is is associated with a decline of oral health.
• Steroid Hormone-Induced Changes in Oral Cavity are Highly Associated with Detrimental Oral Conditions
• Gestational diabetes mellitus increases the frequency of developmental defects of enamel (DDE) in the offspring.

Pregnancy and Oral Health

• Oral health can be declined due to gestational diates
• Pregnancy Gingivitis:
  • Is an inflammation of the gums (redness, swelling, tenderness).
  • Can arise due to high levels of progesterone.
  • Often develops during the second trimester.
• managing pregnancy to prevent periodontiis
• Occasionally a red vascular lump develops on the gums - pregnancy tumor (pyogenic granuloma).

Extensive Breast Development During Pregnancy

• Prepubertal mammary glands are rudimentary with ducts primarily.
• Pubertal changes are caused by hormones estradiol (E), progesterone (P), cortisol (C), insulin (I), growth hormone (GH), and prolactin.
• Mammary glands are mainly consisted of ducts and a few alveoli.
• Pregnancy increases numbers and size of alveoli due to high E, P, C, I, and hPL. During lactation, alveoli are dilated due to prolactin and oxytocin. After weaning, the gland regresses.

Parturition

• Parturition is induced by coordinated estrogen, oxytocin, and prostaglandin for uterine contraction and dilation & thinning of the cervix (relaxin).
  • Hypothalamus releases oxytocin.
  • The cervix then stretches.
  • The stretch of the cervix (relaxin) tells the hypothalamus to release oxytocin.
  • This causes uterine contractions and further cervical dilation.
• Positive feedback mechanism.

Explore the fascinating journey from conception to early embryo development. Learn about fertilization, cleavage, and the role of trophoblasts. Understand hormone changes during the first two weeks of pregnancy.