Obstetric emergency

Dr. Miada Mahmoud

Rady

Lecture 1

Physiology of conception and physiological

changes during pregnancy

Lecture outlines

1. Physiology of conception : ovulation ,

fertilization and implantation.

2. Function of the placenta.

3. Umbilical cord

4. Gestational period

Physiology of conception

It starts with ovulation.

Ovulation : expulsion of the ova into

peritoneal cavity.

Expelled ovum is picked up by the fimbria of

the fallopian tube.

Then the ovum gets fertilized by male sperm in

the Outer Third Of The Fallopian Tube.

Fertilization to Implantation

Fertilization : is fusion of genetic material

from sperm and ovum into a single nucleus to

form zygote.

Cell continuously divides as it moves down

the fallopian tube to the uterus where it

become Implanted.

Physiology of conception

Implantation : adherence of the Blastocytes stage

into the endometrium , it takes place around 6 day

post conception.

Implantation of ovum triggers the formation of the

placenta .

placenta is fully formed by the 4th week of

gestation , before that corpus luteum supports the

pregnancy.

Physiology of conception

Function of the placenta

1. Serves to maintain fetus by supplying

oxygen and nutrients and removing carbon

dioxide and wastes

2. Serves as a protective barrier against most

microorganisms

3. Serves to maintain pregnancy via

secretion of hormones.

Umbilical cord

• It is vascular connection between fetus and mother:

• It contains :

1. One umbilical vein : carries blood rich in

nutrients and oxygen to the fetus from the

placenta.

2. Two umbilical arteries : carry carbon dioxide

and wastes away from the fetus to the placenta.

Amniotic sac

It is fluid filled sac that surrounds the growing embryo .

Function of amniotic sac and fluid:

1. Serves as shock absorber for fetus;

2. Helps regulate fetal temperature;

3. Prevents adhesions between skin of fetus and other

tissues.

4. Fetal cells slough off into this fluid and may be

removed during a procedure called an amniocentesis.

Gestational period

Normally 38 weeks in average from date of

conception.

but in practice it is calculated from the first

day of the pregnant woman’s last menstrual

period and it is estimated to be about 40

weeks ( as ovulation is about 2 weeks before

the menstruation).

Summary

1. During the menstrual cycle one follicle releases

an ovum which, if it becomes fertilized,

develops into an embryo, and then a fetus.

2. The fallopian tubes transport the ovum from the

ovary to the uterus. Once an egg is fertilized, it

implants in the endometrium.

3. The fetus is enclosed in the amniotic sac.

4. The gestational period normally lasts 38 weeks.

Maternal Physiological changes during pregnancy

Lecture topics

1. Causes .

2. Changes in the uterus .

3. Fundal level .

4. Respiratory System Changes.

5. Cardiovascular System Changes .

6. Gastrointestinal system changes .

7. Urinary System Changes.

8. Skin changes.

Causes

1. Altered hormone levels.

2. Mechanical effects of enlarging uterus.

3. Increased uterine blood supply.

4. Increasing metabolic demands on the maternal

system .

Changes in the uterus

• During pregnancy the uterus becomes bigger :

1. Before pregnancy, the uterus : Weighs

about 2 g and Has a fluid capacity of about

10 mL .

2. At the end of the pregnancy, the uterus:

Weighs as much as (1 kg) and Has the

capacity to hold about 5,000 mL.

Fundal level

• Fundal level : it gives a rough estimate about the

gestational age .

• Measured in centimeters vertically from the top of the

pubic bone to the top of the fundus.

• If the measurement is different than expected, it could

indicate:

1. Uterine growth problems or breech position (shorter).

2. Possibility of twins (longer).

Respiratory System Changes

1. Increase in oxygen demand so tidal

volume and oxygen consumption .

2. Slight increase in respiratory rate.

3. Diaphragm pushed upward by growing

uterus .

Cardiovascular System Changes

1. Maternal blood volume increases by 50% :

To meet fetus demand .

To adequately perfuse maternal organs .

To compensate for expected blood loss

during labor.

2. Cardiac output and heart rate increases.

Cardiovascular System Changes

The heart workload increases significantly during

both gestation and labor , So if the woman has heart

disease or other cardiac compromise, this can result in:

i. Ventricular failure

ii. Pulmonary edema

iii. Congestive heart failure

iv. Pain and pressure of labor can result in cardiac

arrest.

Gastrointestinal system changes

1. Nausea & vomiting are common in

1st trimester.

2. Bloating and constipation common.

3. Delayed gastric emptying (due to

slowed peristalsis).

Body Weight Changes

There is an average weight gain of about

12.3 kg due to :

1. Increased blood volume , intracellular and

extracellular fluid

2. Increased breast tissue .

3. Increased proteins and fat deposits.

4. Uterine , placental and fetal growth.

Distribution Of

Weight Gain

Urinary System Changes

1. Kidneys increase in size and volume.

2. Ureters increase in diameter.

Both leads to :

I. Increased urinary frequency

II. Increased chance of urinary tract infection

if bladder is not emptied frequently.

Skin changes

1. Increased hair and nail growth along with

changes in texture.

2. “Pregnancy mask”: brown and yellowish color

changes to the face

3. Darkened skin around the areola, axilla, and

genitalia

4. Linea nigra: a dark line of pigment down the

abdominal midline

Summary

1. Physiologic changes during pregnancy

can alter a woman’s response to trauma

and create or exacerbate medical

conditions.

2. Physiological changes of pregnancy affect

various body organs and system .

Review questions

Regarding cardiovascular changes during pregnancy state

what is true and what is false and correct false:

a. Cardiac out put decreases during pregnancy.

b. Labour can lead to heart failure in women with preexisting

heart disease.

c. Maternal blood volume increases by 50%.

d. The heart workload decreases significantly during both

gestation and labor

Review questions

Enumerate the possible complication of

pregnancy and labour in women with pre-

existing heart disease?