Anatomical & Physiological Changes in Pregnancy Flashcards
2 main reasons for maternal changes
- To provide suitable environment for nutrition, growth & development of the fetus.
- To protect & prepare the mother for parturition (childbirth) & support/nurture of a newborn baby.
Size of uterus in non-pregnant women
40 - 100g
Size of uterus of a pregnant woman at 20wks
300 - 400g
Size of uterus of a pregnant woman at term (>37 wks)
800 - 1000g
Define involution & how long is it completed?
Involution in pregnancy means the shrinkage of the uterus after birth & this takes 2 months to be completed.
Explain the growth of the myometrium during pregnancy
Smooth muscle cells increase both in size (hypertrophy) & in number (hyperplasia). It is also stretched from the growing conceptus/fetus.
The wall of the uterus consists of?
3 concentric layers:
- Endometrium
- Myometrium
- Perimetrium / serosa
The myometrium is formed from how many layers?
3 intertwining layers of smooth muscle
Regions of the uterus
- Fundus
- Body
- Isthmus
- Cervix
Parts of the cervix
- Cervical canal
- Internal os
- External os
What is the principal role of the cervix?
To retain the conceptus
Explain the 4 changes of the cervix during pregnancy
- Increased vascularity
- Hypertrophy of cervical glands producing an appearance of cervical erosion.
- Increase mucous secretory tissue - antibacterial mucus plug
- Reduced collagen & increased glycosaminoglycan & water in 3rd trimester leading to changes consistent with cervical ripening.
What is the isthmus?
Junctional zone between the cervix & body of uterus
Explain the change of the isthmus in pregnancy
By the 28th-week gestation contractions produce stretching & thinning of the isthmus, which results in lower uterine segment formation.
The uterus changes in _____, ______, ______, ______ throughtout pregnancy.
size, shape, position, consistency
Explain the changes in the body of the uterus - corpus uteri
- Early pregnancy = pear shape
- 2nd / 3rd trimester = globular & ovoid
- uterine cavity = 4ml - 4000ml at term
Myometrium remains ______ until the onset of labor.
quiescent (inactive)
Explain the changes that happen to the vessels supplying the uterus.
- undergo massive hypertrophy
- uterine arteries dilate to 1.5 x non-pregnant state
- spiral arterioles 30x pre-pregnant diameter
- uterine blood flow increases from 50 ml/min (10wks) to 500-600 ml/min (at term).
What is the lining of the vagina?
Stratified squamous epithelium
The stratified squamous epithelium layer of the vagina consists of 3 layers. Name them.
- Basal layer
- Functional layer
- Cornified layer
Explain the changes that occur in the vagina during pregnancy.
The lining of the vagina hypertrophies & pH level lowers from 3.5 to 4 to help clear the vagina of bacterial infection.
How does pH level in the vagina lower?
Glycogen synthesized by high estrogen levels are broken down by lactobacilli to lactic acid lowering pH to 3.5 - 4
State the changes that happens in the musculoskeletal system
- Increase in lumbar lordosis due to enlarged uterus
- Foward flexion of the neck & downward movement of the shoulders to compensate for change in center of gravity.
- Sacroiliac joints & pubic symphysis widen
- Fluid retention may cause compression of nerves in fascial sheaths e.g. median nerve in carpel tunnel syndrome.
Musculoskeletal system is affected by?
Maternal weight gain & hormonal influence
State the characteristic skin changes that is due to Melanocyte-stimulating hormone (MSH) in pregnancy.
(Face, Nipples & Abdominal wall)
Face - chloasma / Melasma (mask of pregnancy)
Nipples - areola (dark circles of skin - dark pigmentation)
Anterior abdominal wall - linea alba becomes linea nigra (dark line)
Striae gravidarum (stretch marks) - seen on the abdominal wall, lateral aspect of thighs & breasts.
What are the 1st signs/symptoms of pregnancy shown on the breasts?
- breast tenderness & increase in size
- enlarged nipples
- increased vascularity & pigmentation of areola (dark circles around the nipples - dark pigmentation)
- prominent montgomery tubercles (hypertrophic sebaceous glands) = small bumps around the areola
Average weight gain over pregnancy is?
Aprox 12.5kg
Most of weight gain in all systems arise from _________- with mean total increase of ______.
water retention, 8.5L
High weight gain is associated with?
Edema & fluid retention
Low weight gain is associated with?
- reduced amniotic fluid volume
- small placenta size
- impaired fetal growth & adverse outcome
What are the effects of progesterone on the alimentary system?
- lower esophageal sphincter (LES) relaxation = increases GERD
- slow gastric emptying (contents of stomach are moved into the duodenum)
- decreased motility in small & large bowel = constipation = hemorrhoids (due to constipation & increased abdominal pressure)
Changes in the Alimentary system during pregnancy
- Reduced gastric secretion
- Gall bladder increases in size & empties more slowly (this increase likelihood of gallstones)
How much weight is gained up to 18wks in pregnancy?
0.3 kg/wk
How much weight is gained up to 18wks in pregnancy?
0.3 kg/wk
How much weight is gained up to 18wks in pregnancy?
0.3 kg/wk
How much weight is gained between 18 - 28wks in pregnancy?
0.5 kg/wk
How much weight is gained 28wks until term?
0.4 kg/wk
Renal parenchymal volume increase by _____ by ____ trimester with marked _______ of calyces, renal pelvis & ureters.
70%, 3rd, dilatation
Renal changes occur in what trimester? & under influence of what?
Occurs in 1st trimester under progesterone influence.
Define vesico-ureteric reflux
Abnormal flow of urine from the bladder back up to the ureters.
Vesico-ureteric reflux & ureteric dilatation promotes?
urinary stasis & urinary tract infection (UTI)
Does GFR & renal blood flow increase or decrease in pregnancy? results in?
Increases resulting in physiologic fall in:
- serum creatinine
- uric acid
- BUN = blood urea nitrogen
Glycosuria can be physiologic especially in the ___ trimester, this is due to?
- 3rd trimester
- due to reduced reabsorption of glucose from the proximal tubules.
Explain the respiratory changes seen in pregnancy
- increased O2 consumption to meet increased metabolic requirement.
- elevated diaphragm = appears more barrel-shaped
- increased minute ventilation leads to decreased CO2 = results in mild respiratory alkalosis that helps CO2 diffuse across the placenta from fetal to maternal circulation.
Normal pregnancy is a _________ state.
prothrombotic (hypercoagulable)
Normal pregnancy is a prothrombotic (hypercoagulable) state due to ?
- marked increase in coagulation factors = fibrinogen, factors II, VII, VIII, X & XII.
- reduced fibrinolysis
- increased platelet activity
Coagulation system
involves clot formation via complex interactions between coagulation factors, platelets & vascular endothelium.
Fibrinolytic system
Prevents excessive coagulation by removal of fibrin & clot dissolution.
Platelets - normal range
150,000 - 450, 000 microL
Change in platelet count in pregnancy
Platelet count decreases as pregnancy progresses, but generally remains within normal range = 150, 000 - 450, 000 microL.
HELLP syndrome stands for?
H - Haemolysis
EL - Elevated Liver enzymes
LP - Low Platelets
Mean WBC count range
10,000 - 16,000 cells/microL
WBC changes in pregnancy
(neutrophils, lymphocytes, monocytes, basophil & eosinophil)
Neutrophils = increase & plateaus in 2nd/3rd trimester
Lymphocytes (T & B) = unchanged
Monocyte = generally stable
Basophil = slightly decreases
Eosinophil = slightly increases
Most of increase in cardiac output is distributed to the ______, _______ & ______ to?
- placenta, kidneys & skin
- To:
= provide nutrients to the fetus
= excrete maternal & fetal waste products
= assist maternal temperature control
State the benefits of physiologic anemia in pregnancy
- decreased blood viscosity = reduced resistance to flow which facilitates placental perfusion.
- total intravascular volume increases to approx 50% above non-pregnant valves near term = which provides some reserve against normal blood loss during birth (300 - 500mls for NVD & 600 - 1000mls for c-section)
Increase in plasma volume
- begins at 6 - 12wks
- expands rapidly until 30 - 34wks then plateaus
Increase RBC mass
- increases at 8 - 10wks gestation & steadily rises
- a lesser increase compared to plasma volume
Physiologic anemia
- is due to a greater increase in plasma volume compared to red cell mass.
- more apparent at 30 - 34wks when plasma volume peaks
1st trimester
0 - 13wks + 6 days
2nd trimester
14 - 27wks + 6 days
3rd trimester
28wks - delivery
What happens when a pregnant woman is in a supine position?
Supine position reduces cardiac output & stroke volume due to aortocaval compression.
Explain the cardiovascular changes in 1st trimester (0 - 13wks + 6 days)
- systemic vasodilation beings = systemic vascular resistance drops & nadirs in the mid-second trimester.
- CO rises
Explain the cardiovascular changes in 2nd trimester (14 - 27wks + 6 days)
- SVR plateaus in mid-second trimester
- CO continues to rise
Explain the cardiovascular changes in 3rd trimester (28wks - delivery)
- CO peaks
- HR peaks = average 16bpm above non-pregnant values.
- BP returns to pre-pregnancy levels
Placing women in ____________ position releases pressure on the aorta/vena cava.
left lateral
