Pregnancy is a period of adaptation for: • The needs of the fetus • Meeting the stress of pregnancy & labor
↑’s from 7.5 x 5 x 2.5 cm in non-pregnant state to 35 x 25 x 20 cm at term, i.e. the volume 1000x 1 - Size
pyriform– non pregnant stateglobular - 8th week pyriform - 16th week till term 3 -Shape
with ascent from the pelvis, the uterus usually undergoes rotation, with a tilt to the right (dextrorotation) due to presence of the recto-sigmoid colon on the left side. 4 - Position
5 - Consistency: Becomes progressively softer due to: i - ↑vascularity ii - Presence of amniotic fluid
From the 1st trimester onward, the uterus undergoes irregular painless contractions (Braxton Hicks contractions).They may cause some discomfort late in pregnancy & may a/c for false labor pain. 6 -Contractility
7- Capacity ↑ from 4 ml in non-pregnant state to 4000 ml at term
(B) Myometrial changes 1 - Hypertrophy (estrogen effect) rather than hyperplasia (progesterone effect)till 14thweek, then the fetus exerts a direct stretch 2 - Formation of the (L.U.S.) lower uterine segment from the isthmus and lower half inch of the bodyof uterus
Formation of lower uterine segment After 12 wks, the isthmus(0.5cm) starts to expand gradually to form the lower uterine segment, which measures 10 cm in length at term
Upper Uterine Segment • Peritoneum: Firmly-attached • Myometrium:3 layers: outer longitudinal, middle oblique & inner circular • The middle layer forms 8-shaped fibers around blood vessels to control postpartum hemorrhage (living ligatures)
Upper Uterine Segment • Decidua: Well-developed • Membranes: Firmly-attached • Activity: Active, contracts, retracts and becomes thicker during labor.
Lower Uterine Segment • Peritoneum: Loosely attached • Myometrium: 2 layers: outer longitudinal inner circular.
Lower Uterine Segment • Decidua: Poorly developed • Membranes: Loosely attached. • Activity: Passive, dilates, stretches & becomes thinner during labor
The junction b/w/ the upper uterine segment (U.U.S.) (thick) & the lower uterine segment (thin) is called the physiologic contraction ringat the level of the symphysis pubis (not seen/ felt)
(C) Uterine blood vessels 1 - Uterine artery lumen: is doubled & its blood flow ↑ 5x 2 - Myometrial & decidual arteries(spiral arteries)undergo fibrinoid degeneration due to 2 waves of trophoblastic migration & become dilated to form the uteroplacentalarteries • Uterine blood flow ↑’s progressively & reaches about500 ml / min at term
(D) Changes in the cervix 1 - becomes hypertrophied, soft & bluish in color due to edema & ↑ vascularity. 2 - Soon after conception, a thick cervical secretion obstructs the cervical canal forming a mucous plug. 3 - The endocervical epithelium proliferates and/ or gets everted forming cervical ectopy (previously called erosion)
(E) Changes in fallopian tubes & ligaments (round & broad) . Inactive, elongated, marked ↑ in vascularity. .There may be broad ligament varicose veins.
(F) Changes in the vagina The vagina becomes soft, warm, moist with ↑ secretion and violet in color (Chadwick's sign) due to ↑ vascularity
(G) Changes in the vulva • It becomes soft, violet in colour • Edema & varicosities may develop
(H) Changes in the ovaries 1 -Both ovaries are enlarged due to ↑ vascularity & oedema, particularly the ovary which contains the corpus luteum. 2 - Ovulation ceases during pregnancy due to pituitary inhibition by the ↑ levels of estrogen & progesterone
(H) Changes in the ovaries 3 - Corpus luteum continues to grow till 7 - 8 wks, then it stops growing. It becomes inactive & starts degeneration at 12 wks (degeneration is completed after labor)
Corpus luteum secretes 1.estrogen 2.progesterone 3.relaxin
Relaxin is a protein hormone. • Its exact role in pregnancy is unknown. • It may induce softness & effacement of the cervix.
(A) Blood volume The total blood volume ↑’s steadily from early pregnancy to reach a maximum of 35-45 % above the non-pregnant level at 32 wks
Plasma volume ↑’sfrom 2600 ml by ± 45 % (1250 in the 1st pregnancy & 1500 ml in subsequent pregnancies)
Red blood cell mass • ↑’s from 1400 ml (non pregnant) by 33 % (± 450 ml) due to ↑ production resulting from erythropoeitin or action of hCG / HPL • The ↑ is steady till full term.
The ↑ in plasma volume is > ↑ in red blood cell mass (Hb mass) resulting in haemodilution (physiologic anemia) However, the minimal Hb. accepted is10-11 gm%
Value of ↑ blood volume 1 - Meets ↑ demands for uterus, baby, etc. 2 - Protects against supine hypotension syndrome. 3 - Protects against fluid loss in labor.
↑ in the blood volume > the ↑ in red cell mass -- leads to: ↓ blood viscosity which ↓ in peripheral resistance
1 - ↓ Hb% & RBC%: • Erythrocytes ↓ from 4.5 million/ cb.mm to 3.7 million / cb.mm (due to the relative ↑ in plasma volume > red cell mass) Erythrocytecontents:2, 3 - DPG↑’s which competes for 02 binding sites in the Hb molecule, thus releasingmore 02 to the fetus .
Hb concentrations falls from 14 gm / dl to 12 gm / dl.
2 - M.C.H.C: no change 3 - M.C.V: , or no change (depending on the availability of Fe). 4 - Fragilityof R.B.Cs: 5 -Reticulocytes: mild 6 - E.S.R: from 12 to 50 mm / hr 7 – Fibrinogen: from 200 - 400 mg / dl to 400 - 600 mg / dl
8 - White blood cells: (from 7,000 / mm3 to 10,500/ mm3 during pregnancy & up to 16,000/ mm3 during labor) - Lymphocytes: no change. 9 - Platelets: or 10-Total plasma proteins slightly (mainly albumin) resulting in osmotic pressure.
(C) Coagulation system • Platelets or (controversial) • Fibrinogen doubled to 600 mg% • Factor VIII tripled • Factor VII & factor X are doubled • Factor XI & factor XIII slight • Fibrinolytic activity
Therefore pregnancy is a hyper-coagulative state. • All these changes are reversed after labor with RBC production (not destruction) & the excess Fe is stored.
Position: As the diaphragm is elevated progressively during pregnancy the apex is displaced upwards & to the left so that it lies in the 4th intercostalspace outside the midclavicular line.
Pulse rate • The resting pulse rate ↑ by 8 beats/ min (8 wks) & 16 beats / min (full term). - Some episodes of ectopic beats - Water hammer pulse.
Heart sounds • The 1st heart sound becomes louder before mid pregnancy & splitting of this sound may occur due to earlier closer of the mitral valve than the tricuspid valve • The intensity of the second heart sound may ↑ • The 3rd sound becomes louder before mid-pregnancy & persists as such till 1 wk post partum. • The 4th sound may be detectable by phonocardiography.
Murmurs Systolic functional murmurs develop in most of women, usuallyearly systolic, but mid systolic murmurs may occur and heard over the left sternal edge, they are thought to be due to functional tricuspid regurgitation
ECG CHANGES • The main features of ECG may be attributed to the changes in the position of the heart. • The axis undergoes left shift by 15 - 28°. • The QRS complexes become of low voltage, and T waves become flattened.