Pregnancy Lecture

Embryo

Day 15 to 8 Weeks. Period of organogenesis with rapid cell division

Chorion

Fetal side of the placenta, contains the major umbilical blood vessels that branch over the surface of the placenta

Amnion

Embroyo draws the amnion around itsself, forming a fluid filled sac that covers the umbilical cord and the chorion on the fetal surface of the placenta

1st Trimester Amniotic fluid made from

Diffusion of the maternal blood

2nd and Third Trimester Amniotic Fluid Made from

Fetal fluid production from lungs and urine, fluid resorption through fetal swallowing, and flow across membranes which should total 800 mL at term

Functions of Amniotic Fluid

maintains body temperature

source of oral fluid and repository for waste

maintains fluid and electrolyte homeostasis

freedom of movement and symmetrical development

cushions

antibacterial

Intervillous Spaces of placenta

Maternal blood supplies oxygen and nutrients to embryonic capillaries and waste products and carbon dioxide diffuse into the maternal Blood. No direct link between vessels of chorionic villi and the maternal blood in the intervillous spaces, only seperated by one layer of cells.

Placental Function

Endocrine: Progesterone and Estrogen

Metabolic: Respiration, nutrittion, excretion, storage (oxygen and glucose)

Placental Function depends on the maternal blood pressure and supplying circulation

Ductus Venosus

Placenta is the site for gas Exchange. Oxygenated blood enters fetal circulation through the ubilical vein. Half is shunted through ductus venosus to the inferior vena canva

Foramen Ovale

Oxygenated blood is shunted from the right to the left atrium through the formen ovale.Blood in the left atrium flows to the left ventricle and is pumped through ascending aorta to heart, brain, head and upper body

Ductus Arteriosus

Deoxygenated blood from the superior vena cava flows from right atrium to right ventricle to pulmonary artery. Due to vascular resistance blood is shunted through ductus arterious into descending aorta and returns to the placenta for oxygenation.

Ligamentum Venosus and Teres

Umblilical cord clamping fuctionally closes the umbilical arteries, umbilical vein, and ductus venosus and all convert to ligaments in 2-3 months

Ligamentum Arteriosus

Initation of respiration inflats lungs, decreases pulmonary vascular resistance and stimulated increased pulmonary flow. Increased oxygen levels cause the ductus arteriosus to fuctionally close within 24 hours it converts to a ligmament within 3-4 weeks

Fossa Ovalis

Increased pulmonary blood flow to the left atrium promotes the closure of teh foramen ovale, with ocmplete closuring occuring three months

Gravida

A woman who is pregnant

Gravidity

Pregnancy

Primigravida

A woman who is pregnant for the first time

Multigravida

A woman who had 2 or more pregnancies

Parity

The number of pregnancies in which the fetus has reacehd 20 weeks of gestation or more

Nullipara

A woman who has not completed pregnancy to 20 weeks

Primipara

A woman who has completed one pregnancy to 20 weeks

Multipara

A woman who has completed 2+ pregnacies to 20 weeks

Preterm

Greater than 20 weeks but less than 37 weeks

Normal Pregnancy

280 days or 10 months or 40 weeks

1st trimester

1-13 weeks

second trimester

14-26 weeks

3rd trimester

27-40+ weeks

EDB Naegles Rule

LMP -3 Calendar Months +7

Most accurate assessment of EDB is based on US of embryo during

first trimester of pregnancy

Physiologic Adaptation of Pregnancy Attributed to

Hormones of Pregnancy, mechanical pressure of enlargieng uterus and orther tissues

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Ovaries changes to pregnancy

Ovulation is suppressed by estrogen and progesterone. Amenorrhea occurs. Corups lutem is source of hormones for 6-19 weeks. Estrogen and progesteron suppress FSH and LH

Vagina and Vulva changes to pregnancy

Hormones prepare vagina for stretching by thicking mucosa, loosing connective tissue, englarging smooth muscle and strengthening valut length. THe Vaginal mibroiome changes to prevent infetion increased leukorrhea and decreased PH

How does heart rate change during pregnancy?

Heart rate increases by 10–20 beats/min.

How does systolic blood pressure change during pregnancy?

It has a slight decrease or may remain relatively unchanged.

How does diastolic blood pressure change during pregnancy?

It decreases during midpregnancy and returns toward normal levels by the end of pregnancy.

How does maternal blood volume change during pregnancy?

Blood volume increases by about 40–50% (≈1,200–1,600 mL above prepregnancy levels), reaching a plateau around 32 weeks.

How does cardiac output change during pregnancy?

Cardiac output increases by approximately 30–50%.

How does systemic vascular resistance (SVR) change during pregnancy?

SVR decreases by about 30–50% because of vasodilatory effects, including those of progesterone.

What happens to cardiac output when a pregnant patient lies supine?

Cardiac output can decrease by about 25–30% because the uterus compresses major blood vessels, particularly the inferior vena cava.

Why can the supine position be problematic during pregnancy?

Uterine compression of the inferior vena cava reduces venous return to the heart, which can decrease cardiac output and contribute to supine hypotension.

How does the maternal heart physically change during pregnancy?

The heart enlarges slightly and is displaced upward and to the left.

Are systolic ejection murmurs normal during pregnancy?

They can be. Increased blood volume and cardiac output can produce a physiologic systolic ejection murmur.

How does RBC mass change during pregnancy?

RBC mass increases by approximately 20–30%, depending partly on the amount of iron available.

Why do hemoglobin and hematocrit decrease during pregnancy even though RBC mass increases?

Plasma volume increases more than RBC mass, producing hemodilution (physiologic anemia of pregnancy).

What are typical pregnancy-related changes in hemoglobin and hematocrit?

Hemoglobin and hematocrit decrease, commonly to around Hgb 11–13 g/dL and Hct 33% because of hemodilution.

How do WBCs and lymphocytes change during pregnancy?

WBC count increases, while lymphocyte levels remain relatively similar.

Is pregnancy a hypercoagulable or hypocoagulable state?

Pregnancy is a hypercoagulable state.

Why does pregnancy increase the risk of thromboembolic disease?

There is an increase in clotting factors and a decrease in anticoagulant/fibrinolytic activity, making clot formation more likely.

How much does pregnancy increase the risk of thromboembolic disease?

Approximately 5–6 times compared with the nonpregnant state.

Why is hypercoagulability beneficial during pregnancy/postpartum?

It helps limit excessive bleeding after placental separation and delivery, but it also increases the mother's risk for DVT/

How do increased estrogen and progesterone affect the breasts during pregnancy?

Increased estrogen and progesterone cause heightened breast sensitivity, fullness, tingling, and heaviness.

How do the areola and nipples change during pregnancy?

The areola and nipples become more pigmented (darker).

How do the sebaceous glands of the breasts change during pregnancy?

The sebaceous glands become more prominent.

How do breast blood vessels change during pregnancy?

Blood vessels become more visible.

When can colostrum first appear during pregnancy?

Colostrum can appear as early as the end of the first trimester.

Where is prolactin produced?

Prolactin is produced by the anterior pituitary gland.

What does prolactin do during pregnancy?

Prolactin stimulates the production of colostrum.

Why does full lactation not occur during pregnancy despite increased prolactin?

Progesterone inhibits lactation during pregnancy

What happens after progesterone levels decrease following delivery?

The loss of progesterone's inhibitory effect allows prolactin to promote milk production/lactation.

How do estrogen and progesterone affect the uterus during pregnancy?

Increased estrogen and progesterone stimulate uterine growth, causing changes in size, shape, position, vascularity, muscle fibers, fibroelastic tissue, and contractility.

How does uterine vascularity change during pregnancy?

Uterine vascularity increases, with dilation of the blood vessels.

What is uterine hyperplasia during pregnancy?

Hyperplasia = formation of new muscle fibers and fibroelastic tissue.

What is uterine hypertrophy during pregnancy?

Hypertrophy = enlargement of preexisting muscle fibers.

How does uterine weight change during pregnancy?

Uterine weight increases from approximately 40–70 g before pregnancy to 1,200 g at term.

How does uterine volume change during pregnancy?

Uterine volume increases from approximately 10 mL to 5 L at term.

How does uteroplacental blood flow change during pregnancy?

Uteroplacental blood flow increases approximately 10× as the uterus increases in size.

How much maternal blood is contained within the uterine vascular system during pregnancy?

Approximately 1/6 of the maternal blood volume is within the uterine vascular system.

What is the uteroplacental blood flow rate during pregnancy?

Approximately 450–650 mL/min.

What factors decrease uterine blood flow during pregnancy?

Low maternal arterial blood pressure, uterine contractions (UCs), and the supine position decrease uterine blood flow.

Why can the supine position decrease uterine blood flow?

The uterus can compress the vena cava → decrease venous return/cardiac output → decrease uteroplacental blood flow.

What maternal position improves uterine blood flow?

Side-lying, especially left lateral, improves uterine blood flow by preventing vena cava compression.

What happens to the glands near the cervical os during pregnancy?

Glands near the cervical os proliferate and become more friable.

What is the mucus plug (operculum)?

The mucus plug (operculum) is thick mucus that fills the cervical canal after conception.

What produces the mucus plug during pregnancy?

Endocervical glands produce the thick mucus that forms the mucus plug.

What is the purpose of the mucus plug during pregnancy?

The mucus plug helps prevent ascending infection from entering the uterus.

Why are Pap tests important during pregnancy?

Pap tests are an important component of prenatal care for appropriate cervical cancer screen

How does basal metabolic rate change during pregnancy?

Basal metabolic rate increases during pregnancy, increasing maternal oxygen demands and consumption.

How does maternal oxygen consumption change during pregnancy?

Maternal O₂ consumption increases by 20–40%.

How does the diaphragm change during pregnancy?

The diaphragm rises up to 4 cm due to the enlarging uterus.

How does progesterone affect the rib cage during pregnancy?

Progesterone relaxes the rib cage, allowing increased chest expansion.

How does tidal volume change during pregnancy?

Tidal volume increases by approximately 40%.

What is tidal volume?

Tidal volume is the amount of air exchanged during normal inspiration and expiration.

What hormone contributes to the increased tidal volume during pregnancy?

Progesterone contributes to increased tidal volume and ventilation.

How does pregnancy affect ventilation?

Pregnancy causes chronic mild hyperventilation.

How does PaCO₂ change during pregnancy?

Maternal PaCO₂ decreases due to increased ventilation.

How does PaO₂ change during pregnancy?

Maternal PaO₂ increases.

How does maternal pH change during pregnancy?

Maternal pH increases slightly, producing a mild respiratory alkalosis.

Why does mild respiratory alkalosis occur during pregnancy?

Increased ventilation causes more CO₂ to be exhaled → ↓ PaCO₂ → slight ↑ pH → mild respiratory alkalosis.

What is the benefit of maternal respiratory alkalosis to the fetus?

It facilitates CO₂ transfer from fetus → mother and O₂ transfer from mother → fetus.

Is dyspnea normal during pregnancy?

Pregnancy-related dyspnea is common, but physiologic dyspnea must be differentiated from pathologic dyspnea.

Why can nasal congestion occur during pregnancy?

Increased blood volume and capillary engorgement can cause upper respiratory tract congestion.

Why are nosebleeds (epistaxis) more common during pregnancy?

Increased blood volume and capillary engorgement make the nasal mucosa more vascular, increasing the likelihood of noseble

What causes nausea and vomiting (morning sickness) during pregnancy?

Morning sickness is likely related to high levels of human chorionic gonadotropin (hCG) and other hormonal changes.

When does morning sickness typically begin, peak, and resolve?

It typically begins around 4–6 weeks, peaks around 9 weeks, and usually resolves by about 12 weeks.

Can nausea and vomiting occur only in the morning during pregnancy?

No. Although called "morning sickness," nausea and vomiting can occur at any time of the day.

What changes in eating behavior may occur during pregnancy?

Pregnancy can cause changes in taste, food intake, and pica.

What is pica?

Pica is the craving or consumption of nonfood substances.

Why can bleeding gums occur during pregnancy?

Estrogen and increased vascularity of the gums make them more likely to bleed.

How does progesterone affect the gastrointestinal tract during pregnancy?

Progesterone decreases smooth-muscle motility in the esophagus, stomach, and intestines.