Embryo Development Quiz

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Questions and Answers

What is the primary function of the trophoblast during embryo development?

To absorb nutrients from the fallopian tube

To provide structure to the morula

To form the outer layer of the placenta

To surround the embryo and facilitate nutrition and hormone secretion (correct)

What occurs during the cleavage stage of early embryo development?

The morula forms before the blastocyst

Cells undergo mitotic division without growth (correct)

Cells grow larger while dividing

Only one type of cell is produced

Which hormone primarily opposes estrogen during the early stages of embryo development?

Oxytocin

Testosterone

Luteinizing hormone

Progesterone (correct)

What defines the totipotency of cells in the morula?

They can develop into an entire individual Signup and view all the answers

What is the first structure formed after the blastocyst stage?

The inner cell mass Signup and view all the answers

When does the window of implantation occur in the menstrual cycle?

Days 14-21 Signup and view all the answers

What is the primary function of the placenta?

To facilitate nutrient, gas, and waste exchange between maternal and foetal circulations Signup and view all the answers

Why is a higher surface area to volume ratio beneficial for cleavage stage cells?

It enhances nutrient/oxygen uptake and waste disposal Signup and view all the answers

Which cells form the outer layer of the blastocyst and are essential for providing nutrients to the embryo?

Trophoblast Signup and view all the answers

What role does the corpus luteum play after ovulation concerning embryo development?

It releases hormones that support early pregnancy Signup and view all the answers

What role do chorionic villi play in placental function?

They increase surface area for contact with maternal blood Signup and view all the answers

Which part of the endometrium is involved in forming the placenta?

Decidua basalis Signup and view all the answers

What structure connects the decidua basalis to the placental anchoring villi?

Cytotrophoblastic shell Signup and view all the answers

What triggers the foetal pituitary gland to produce ACTH during pregnancy?

Increasing amounts of CRH from the placenta Signup and view all the answers

What is the primary effect of cortisol during the prepartum surge?

Promotion of foetal organ differentiation Signup and view all the answers

Which of the following is a key feature of cortisol's impact on lung development?

Promotes surfactant production Signup and view all the answers

Which hormone is primarily responsible for maintaining uterine quiescence throughout most of pregnancy?

Progesterone Signup and view all the answers

What percentage of pregnancies worldwide are affected by preterm birth?

11.1% Signup and view all the answers

What phenomenon occurs during the transformation of the uterus leading up to parturition?

Activation of contractile and excitable phenotypes Signup and view all the answers

What long-term risk is associated with being born preterm?

Elevated cancer risks Signup and view all the answers

During which stage of pregnancy does foetal cortisol production begin to rise significantly?

Late third trimester Signup and view all the answers

What initiates the receptivity of implantation in the endometrium?

Surge in progesterone levels Signup and view all the answers

Which cells are responsible for adhering the blastocyst to the endometrium?

Trophoblast cells Signup and view all the answers

What is a primary consequence of implantation failure?

Ectopic pregnancy Signup and view all the answers

What characterizes the primary chorionic villi during placentation?

Expansion into cytotrophoblast structures Signup and view all the answers

What potential problem can arise from deferred implantation?

Placenta previa Signup and view all the answers

What function does the placenta serve after the first few weeks of embryo development?

Supporting fetal growth and waste removal Signup and view all the answers

What happens to the cytotrophoblast cells during placentation?

They form a multinucleated syncytiotrophoblast Signup and view all the answers

What is the role of proteolytic enzymes secreted by trophoblast cells?

To erode endometrial tissue Signup and view all the answers

What can cause scarring of the uterus, which affects implantation?

Pelvic inflammatory disease Signup and view all the answers

What is one of the roles of the amniotic fluid during pregnancy?

Facilitating fetal movement Signup and view all the answers

What structure forms a network for maternal blood flow during early placentation?

Lacunae Signup and view all the answers

What is the result of shallow invasion of the trophoblast?

Increased risk of pre-eclampsia Signup and view all the answers

Which protein plays a crucial role in the adhesion of trophoblasts to the endometrium?

Selectin Signup and view all the answers

What physiological change is caused by oxytocin during nursing?

Contraction of myoepithelial cells to release milk Signup and view all the answers

What role does prolactin play in lactation?

It promotes milk production in the mammary glands Signup and view all the answers

What initiates the lactation reflex when a baby suckles?

Afferent inputs to hypothalamus from mechanoreceptors in the nipples Signup and view all the answers

What is the main component of colostrum secreted after delivery?

Protein-rich fluid Signup and view all the answers

How does suckling affect ovulation in a breastfeeding mother?

It blocks ovulation through increased prolactin levels Signup and view all the answers

What is the primary reason breast milk is recommended for 6-12 months of breastfeeding?

Breast milk offers antibodies and growth factors crucial for development Signup and view all the answers

What is the primary role of the placenta during pregnancy?

It serves as the organ of exchange between mother and fetus. Signup and view all the answers

What is the function of myoepithelial cells during lactation?

To aid in milk ejection into the ducts Signup and view all the answers

Which hormone is primarily responsible for regulating mammary gland development during pregnancy?

Progesterone Signup and view all the answers

Which of the following substances cannot cross the placenta?

Maternal antibodies Signup and view all the answers

What is the primary function of human chorionic gonadotrophin (HCG) during early pregnancy?

Maintaining pregnancy by stimulating steroid hormone production. Signup and view all the answers

What effect does dopamine have on prolactin release?

It inhibits prolactin release Signup and view all the answers

How does progesterone primarily affect the myometrium during pregnancy?

Prevents contractions to maintain pregnancy. Signup and view all the answers

Why are newborns able to absorb proteins in breast milk more effectively than adults?

Their intestinal epithelium is more permeable to proteins Signup and view all the answers

What effect does progesterone have on maternal metabolism during pregnancy?

Stimulates appetite and fat deposition. Signup and view all the answers

What complications can arise from reduced placental perfusion?

Impeded fetal growth. Signup and view all the answers

Which of the following hormones is NOT produced by the placenta?

Relaxin Signup and view all the answers

What physiological change increases in a mother’s cardiovascular system during pregnancy?

Increased cardiac output. Signup and view all the answers

What is the primary purpose of amniotic fluid during pregnancy?

To cushion the fetus and prevent compression. Signup and view all the answers

What triggers the release of glucocorticoids like cortisol during the later stages of fetal development?

Real or perceived threats stimulating the HPA axis. Signup and view all the answers

What significant risk is associated with preterm birth?

Reduced fetal brain development. Signup and view all the answers

What is the primary action of human placental lactogen (hPL) during pregnancy?

Increases maternal metabolism. Signup and view all the answers

Which of the following hormones is primarily responsible for stimulating lactation?

Prolactin Signup and view all the answers

What anatomical change occurs in the mother's body as pregnancy progresses?

Increased engorgement of blood in reproductive organs. Signup and view all the answers

What event is collectively termed parturition?

The entire process leading up to childbirth Signup and view all the answers

During which stage of labor does the cervix fully dilate to approximately 10 cm?

Dilation stage Signup and view all the answers

What hormonal changes are responsible for the transition of progesterone activity late in pregnancy?

Dominance of progesterone receptor A Signup and view all the answers

What triggers the release of oxytocin during labor?

Pain and uterine distention Signup and view all the answers

How do fetal and maternal circulations interact at the placenta?

They remain completely separate with simple diffusion for low molecular weight substances. Signup and view all the answers

What is the expected APGAR score range for a healthy infant?

8-10 Signup and view all the answers

What role does the enzyme 20 alpha HSD play in late pregnancy?

Reduces progesterone signalling Signup and view all the answers

What is a significant reason for performing a cesarean section?

Breech presentation Signup and view all the answers

Which hormone is primarily involved in the softening of the cervix during labor?

Estrogen Signup and view all the answers

What is a primary function of surfactant in the lungs of a newborn?

To facilitate lung inflation Signup and view all the answers

How long does the placental stage typically last after the infant's birth?

30 minutes Signup and view all the answers

Which hormone significantly increases during pregnancy to promote breast enlargement?

Human placental lactogen Signup and view all the answers

What characterizes the transition period for infants after birth?

Alternating periods of activity and sleep Signup and view all the answers

What condition can occur if placental fragments are not completely removed after delivery?

Postpartum hemorrhage Signup and view all the answers

The decrease in progesterone and estrogen levels during lactogenesis is crucial for what process?

Milk secretion initiation Signup and view all the answers

Study Notes

Embryo Development and Implantation

The conceptus is everything derived from the original zygote. It spends 3-4 days in the fallopian tube, where estrogen and progesterone regulate its movement. Estrogen promotes contraction of the fallopian tube, while progesterone opposes this.
During this time, the conceptus undergoes cleavage, a series of mitotic divisions without cell growth, creating smaller cells with a higher surface area to volume ratio for better nutrient/oxygen uptake and waste disposal.
After 36 hours of fertilization, the conceptus consists of two identical cells (blastomeres). This continues to divide, forming a morula (16 or more cells) after 72 hours. These cells are totipotent - they can develop into an entire individual.
Identical twins occur when dividing cells split into two separate cell masses during cleavage.
By day 3-4, the conceptus has about 100 cells and floats freely in the uterus, gaining nutrients from its surroundings. Connections form between cells and fluid accumulates inside, forming the blastocyst, a hollow sphere.
The blastocyst comprises two distinct cell types: the inner cell mass (gives rise to the developing human) and the trophoblast (surrounds the embryo/fetus and plays a crucial role in nutrition and hormone secretion).
The inner cell mass loses its totipotency as cells differentiate. The inner cell mass is also responsible for some of the membranes around the embryo.

Implantation and Failure

The window of implantation occurs between days 14-21 of the menstrual cycle, corresponding to the period where the uterine lining is prepared by progesterone for blastocyst reception.
Implantation typically occurs around day 21, seven days after ovulation. Progesterone levels surge in the blood, increasing endometrial receptivity.
This surge induces decidualization, a process in which the endometrium undergoes morphological and functional changes to prepare for implantation, including vascular modifications in maternal arteries.
The trophoblast cells are sticky, with adhesion proteins like integrins and selectins, especially in regions overlying the inner cell mass. This allows the blastocyst to attach to the endometrium and initiate implantation.
The blastocyst preferentially implants high in the uterus. If the endometrium isn't mature, the blastocyst may detach and re-implant at a lower level.
Once contact is made, the trophoblast cells proliferate rapidly and secrete proteolytic enzymes, eroding endometrial tissue to allow the blastocyst to burrow into the endometrial layer.
This process also triggers an inflammatory response, further facilitating implantation. Nutrient-rich endometrial cells provide metabolic fuel and raw materials for early embryo development.
Implantation failure occurs in 2/3 of all fertilized zygotes. Additionally, 1/3 of remaining embryos miscarry due to genetic defects, uterine malformations, or unknown factors.
While the exact reasons for implantation failure are unclear, issues with endometrial receptivity, implantation, or decidualization can contribute to infertility.
A blastocyst implanting lower in the uterus (deferred implantation) can lead to placenta previa, intrauterine growth restriction, pre-eclampsia, or miscarriage.
Premature decidualescence can result in preterm birth or fetal death. Shallow trophoblast invasion is linked to pre-eclampsia.

Implantation Failure Causes

Scarring of the uterus (from pelvic inflammatory disease)
Hormonal imbalances (e.g., Polycystic Ovary Syndrome (PCOS), endometriosis)
Non-receptive endometrium (lack of appropriate receptors, PCOS, endometriosis)

Other Implantation Issues

Ectopic pregnancy: The blastocyst implants outside the uterus, usually in the fallopian tubes, but can also occur on the ovary surface or in the abdominal cavity.
Placenta previa: The blastocyst implants near the cervical opening, potentially covering the vaginal opening and increasing the risk of premature separation.

Placenta

The endometrium can only nourish the embryo in the first few weeks due to size limitations. The placenta takes over this function as a crucial organ of exchange for the remaining pregnancy.
The placenta provides all nutrients to the baby and removes fetal waste.
The placenta also performs endocrine functions, regulating fetal growth and maternal adaptations to pregnancy.
Doppler ultrasounds of the placenta assess its growth and that of the baby.
Placental insufficiency can have severe consequences for the fetus or neonate.
Amniotic fluid has a significant role in fetal development.

Placentation

Placentation begins during implantation.
As the blastocyst adheres to the endometrial epithelium, trophoblast cells differentiate into cytotrophoblast and syncytiotrophoblast.
Cytotrophoblast proliferates, and new cells migrate into the syncytiotrophoblast, losing their cell membranes to form a rapidly expanding multinucleated mass.
Cytotrophoblast secretes proteolytic enzymes, allowing the blastocyst to embed into the endometrium.
Lacunae (spaces) form within the syncytiotrophoblast.
As the syncytiotrophoblast erodes endometrial blood vessels and glands, lacunae fill with maternal blood and granular secretions.
These lacunae fuse to form a network that allows maternal blood to flow, establishing early uteroplacental circulation.

Placenta Development

Towards the end of the second week, cytotrophoblast projections expand into the syncytiotrophoblast, forming primary chorionic villi.
Early in the third week, extraembryonic mesoderm grows into the villi, creating a core of loose connective tissue and forming secondary chorionic villi.
By the end of the third week, blood vessels form in the extraembryonic mesoderm of the secondary chorionic villi, transforming them into tertiary chorionic villi.
Cytotrophoblasts from tertiary villi grow towards the decidua basalis and create a cytotrophoblastic shell.
Villi connected to the decidua basalis through this shell are anchoring villi.
Villi from the sides of the stem villi are branch villi, surrounded by the intervillous space and serving as the primary exchange point between mother and fetus.
By the fourth week, fetal blood flow is established. Oxygen-poor blood travels from the fetus to the placenta via paired umbilical arteries, which branch into chorionic villi and divide into capillary networks.
Carbon dioxide and waste products pass from fetal circulation across the placental membrane into the intervillous space (maternal blood).
Oxygen and nutrients travel across the placental membrane to the fetal capillaries.
Oxygenated fetal blood returns through veins to the single umbilical vein, which carries it to the fetus.
Blood returns to maternal circulation through endometrial veins, forced out by the pressure of incoming arterial blood.
The placenta nourishes the fetus throughout development and is delivered shortly after birth.

Placentation Glossary

Placenta: A temporary fetal organ that develops during pregnancy. It facilitates nutrient, gas, and waste exchange between maternal and fetal circulations and produces hormones regulating maternal and fetal physiology.
Trophoblast: Cells forming the outer layer of the blastocyst. They provide nutrients to the embryo and develop into a large part of the placenta.
Cytotrophoblast: A layer of mononucleated cells that invades the syncytiotrophoblast matrix and forms chorionic villi.
Syncytiotrophoblast: A multinucleated epithelial covering of the highly vascular placental villi. It invades the endometrium to establish nutrient circulation between mother and embryo.
Lacunae: Small spaces or gaps in an organ or tissue.
Chorionic villi: Villi sprouting from the chorion, maximizing contact with maternal blood.
Decidua basalis: Part of the endometrium participating in the formation of the placenta alongside the chorion.
Cytotrophoblastic shell: An external layer of cytotrophoblasts from the fetus found on the maternal surface of the placenta.
Anchoring villi: Villi connected to the decidua basalis through the cytotrophoblastic shell.
Branching villi: Villi growing from the sides of stem villi, surrounded by the intervillous space, serving as the main exchange point between mother and fetus.

Placenta

The placenta is the organ of exchange between the mother and fetus.
It's composed of interlocking fetal and maternal tissues.
The outermost layers of the trophoblast (chorion) supply the fetal part of the placenta.
The endometrium underlying the chorion provides the maternal portion.
Chorionic villi, finger-like projections of the trophoblast cells, extend into the endometrium.
The villi contain a rich capillary network, part of the fetal circulatory system.
Enzymes and molecules secreted by the villi alter the endometrium, creating a pool of maternal blood for exchange.
Maternal and fetal blood supplies are separate, with the mother's blood entering through the uterine artery and the fetus receiving circulation through the umbilical vein.
Reduced placental perfusion can impede fetal growth.
Placental issues are responsible for 88% of intrauterine fetal deaths (IUFD).

Placental Functions

The placenta acts as a gut, kidney, and lung for the developing fetus.
It provides substrates for fetal metabolism, disposes of waste products, exchanges respiratory gases, and acts as a partial immunological barrier.
Produces hormones important for pregnancy, including progesterone, estrogen, hCG, hPL, and CRH.
Facilitated diffusion and active transport enable the exchange of molecules like blood gases, water, urea, free fatty acids, ketones, and non-conjugated steroids.
Placental permeability varies, preventing large proteins and blood cells from crossing, but allowing entry of alcohol, nicotine, drugs, and some pathogens.

Extraembryonic Membranes

Chorion encloses the embryonic body and other membranes, contributing to placenta formation.
Amnion is a transparent sac filled with amniotic fluid, protecting the embryo and providing optimal developmental conditions.
Yolk sac decreases in size and importance during early development.
Allantois is a small outpocketing at the base of the umbilical cord in humans.

Amniotic Fluid

Consists primarily of fetal urine, increasing from 10mL at 8 weeks to 450mL at 32 weeks.
Serves as a reservoir for development of anatomical hollow tube structures like lung airways, gut, and renal nephron.
Cushions the fetus from trauma and provides space for muscle development.
Prevents uterine compression of the fetus and promotes normal lung development.
Maintains a constant temperature.

Maternal Adaptations and Pregnancy Hormones

Estrogen and progesterone levels increase progressively throughout pregnancy.
Estrogen stimulates uterine growth, while progesterone prevents premature contractions.
The corpus luteum supplies the majority of estrogen and progesterone in the first two months of pregnancy.
Human Chorionic Gonadotrophin (hCG) maintains the corpus luteum's viability and leads to increased steroid production.
hCG levels rise from the first week until the end of the second month.
After 2-3 months, the placenta takes over estrogen and progesterone production.
hCG levels fall, allowing the corpus luteum to regress.
Progesterone plays a key role in maintaining the pregnancy, relaxing smooth muscle throughout the body and preventing uterine contractions.
The feto-placental unit produces estrogen using androgens from the ovaries, adrenal glands, and fetal adrenal glands.

Maternal Adaptations in Pregnancy

The female reproductive organs become increasingly vascular and engorged.
Breasts enlarge under the influence of estrogen and progesterone.
The uterus undergoes significant enlargement, filling the abdominal cavity and pressing on surrounding organs.
Increased weight gain is mainly due to fetal and placental growth, maternal organ expansion, and blood volume increase.
Progesterone stimulates maternal appetite, leading to increased fat deposition.
hPL, produced by the placenta, mobilizes maternal fat stores and increases glucose production in the liver.
hCT, released by the placenta, increases maternal metabolic rate.
Insulin production rises during pregnancy, but it doesn't cross the placenta.

Physiological Changes in Pregnancy

Cardiovascular system: Blood volume increases by 25-40% by the 32nd week, leading to increased cardiac output and blood pressure.
Respiratory system: Increased tidal volume, dyspnoea, hyperventilation, and CO2 production are common in later stages of pregnancy.
Gastrointestinal system: Morning sickness, heartburn, acidity, and constipation may occur due to hormonal changes and physical pressure from the growing uterus.
Urinary system: Increased urine production, frequent urination, increased blood flow to the kidneys, and fluid retention are typical.

Pre-eclampsia

Pre-eclampsia, complicating 8% of deliveries, is characterized by abnormal vasoconstriction of maternal blood vessels and inadequate trophoblast invasion.
Poor placental perfusion results in hypertension, proteinuria, hepatic ischemia, edema, and coagulation system activation.
Careful monitoring and management are crucial for both mother and fetus.

Fetal Development

Fertilized egg undergoes cleavage and implantation, forming the blastocyst.
Development proceeds through distinct stages, with the formation of germ layers, neurulation, and the primitive gut.
By 7 weeks, most major organs have formed, but the fetus is vulnerable to damage.
By 10 weeks, fingers and toes separate, the face and genitals form, and urine production begins.
By 20 weeks, muscles and bones have developed, and fetal movements become noticeable.
After 25 weeks, the nervous system gains control over some functions, and the respiratory system becomes capable of gas exchange.
At 30 weeks, rapid fat accumulation, fetal breathing movements, and fully developed bones occur.
At term, the fetus is 48-51cm long and weighs 2.8 to 4 kg.

Fetal Maturation

After birth, the fetus needs to mature lungs, prepare the gut for feeding, develop urine-concentrating ability, generate heat, change hemoglobin type, and store energy substrates.
Glucocorticoids, such as cortisol, accelerate these functions.
Cortisol production increases in the fetal adrenal cortex towards the end of pregnancy.
The prepartum surge of cortisol promotes organ differentiation and development, slows growth, and triggers the final maturation of key systems, including the lungs.

Parturition

The uterus transforms from a relaxed state to a contractile and excitable phenotype to facilitate birth.
Progesterone maintains uterine quiescence throughout most of pregnancy.
Estrogen, prostaglandins, and oxytocin mediate uterine contractions at birth.

Preterm Birth

Delivery before 37 weeks, affecting 11.1% of pregnancies worldwide.
Leading cause of neonatal death and associated with long-term health complications for the infant.

Labour

Normal human pregnancy lasts approximately 40 weeks.
The transformation of the uterus from relaxed to active involves a complex interaction of hormones and signaling pathways.

Hormonal Influences on Labour

Progesterone promotes uterine quiescence throughout pregnancy.
Estrogen levels rise towards the end of pregnancy, increasing uterine sensitivity to contractions.
Prostaglandins contribute to cervical softening, uterine contractions, and fetal membrane rupture.
Oxytocin stimulates powerful uterine contractions, playing a key role in the final stages of labor.

Lactation

The process of milk production and secretion by the mammary glands.
Hormones like prolactin and oxytocin are crucial regulators of lactation.
Prolactin promotes milk production, while oxytocin facilitates milk ejection (let-down).
Lactation can be influenced by several factors, including breastfeeding frequency, baby's sucking strength, stress levels, and medication use.### Parturition
Parturition refers to the process of childbirth, encompassing all events from the initiation of labor to the delivery of the infant and placenta.
Progesterone's inhibitory effect on uterine contractions is reduced towards the end of pregnancy, making the myometrium more responsive to estrogen, oxytocin, and prostaglandins.

Role of Progesterone Receptors

Progesterone receptor B dominates during most of pregnancy, preventing the expression of gap junction proteins like connexin 43, which are crucial for rhythmic contractions.
Progesterone receptor A dominates towards the end of pregnancy, binding progesterone in the cytoplasm but not transporting it to the nucleus.
The enzyme 20 alpha HSD reduces progesterone signalling, further contributing to the switch in progesterone activity.

Foetal Influence on Labor

The fetus plays a role in determining its own birth date.
Increasing placental CRH levels and fetal stress lead to the production of ACTH and cortisol, triggering the release of large amounts of estrogens (via DHEA) from the placenta.

Initiation of Labor - Estrogen's Role

Estrogen stimulates the synthesis of gap junction proteins (connexins) in the myometrial smooth muscle, enabling coordinated contractions.
Estrogen promotes collagen breakdown in the cervix, making it softer and more flexible.
Estrogen increases the expression of oxytocin receptors in the myometrium.

Initiation of Labor - Prostaglandins

Prostaglandins (PGF2a and PGE2) secreted by the uterus, act as potent stimulators of uterine muscle contraction.
Prostaglandins contribute to the rhythmic expulsive contractions of true labor and increase cervical compliance.

Oxytocin's Role in Labor

Pain and uterine distention trigger the release of oxytocin from the posterior pituitary.
Oxytocin stimulates uterine muscle contraction in a positive feedback loop, increasing levels throughout labor.
The number of oxytocin receptors in the uterus increases during the final weeks of pregnancy, amplifying the contractile response to oxytocin.

Stages of Labor

Dilation Stage (Stage 1)

Begins with the onset of labor and ends when the cervix is fully dilated by the baby's head.
Characterized by weak but regular contractions, increasing in frequency and intensity over time, lasting for 6-12 hours.
The cervix softens, thins, and dilates to approximately 10 centimeters.
The amniotic sac may rupture and the amniotic fluid flows out of the vagina ("breaking of the water").

Expulsion Stage (Stage 2)

Begins when the infant's head enters the true pelvis (engagement).
Ends with the birth of the infant, lasting for 50 minutes in a first birth and 20 minutes in subsequent births.
Strong contractions occur every 2-3 minutes, lasting for about 1 minute.
The mother bears down to increase abdominal pressure, assisting with delivery.
"Crowning" occurs when the largest dimension of the baby's head distends the vulva.
The umbilical cord is clamped and cut after birth.
Breech presentation (baby's body oriented differently than head downwards) may require a Cesarean section.
Other reasons for a Cesarean section include maternal fatigue or failure to progress during labor.
Australia has high rates of Cesarean sections (32% in 2013), exceeding the OECD average of 25.7%.
The WHO recommends a Cesarean section rate of only 10-15%.

Placental Stage (Stage 3)

The placenta and fetal membranes (afterbirth) are delivered within 30 minutes following the birth of the infant.
Strong uterine contractions compress blood vessels and detach the placenta from the uterine wall.
Removal of all placental fragments helps prevent postpartum bleeding.
Postpartum hemorrhaging can be dangerous for the mother.
Monash University is leading the development of methods for limiting and treating postpartum bleeding, including a heat-stable, powdered oxytocin formulation for inhalation.

Infant Adjustments

Birth is a significant shock for the infant.
The baby is exposed to physical trauma during delivery, transitions from a watery, warm environment, and loses placental support.

Breathing

CO2 buildup in the baby's blood causes central acidosis, stimulating the respiratory control centers in the brain.
The baby's first breath is a huge effort, requiring more energy to inflate the airways and lungs.
Once the lungs are inflated, surfactant production reduces surface tension and breathing becomes easier.
The respiratory rate is rapid (45 breaths per minute) for the first two weeks, gradually declining.

APGAR Score

The infant's physical status is assessed at 1 and 5 minutes after birth using the APGAR score, which measures heart rate, respiration, skin tone, muscle tone, and reflex irritability.
Each observation receives a score of 0-2, with a total APGAR score of 8-10 indicating a healthy baby.

Transition Period

Infants pass through a transitional period for 6-8 hours after birth, with alternating periods of increased activity and sleep.
Vital signs are irregular during activity periods, with the baby gagging frequently as it regurgitates mucus and debris.
The infant stabilizes, waking every 3-4 hours mainly due to hunger.