Physiology of pregnancy


1- Hormonology:


* FOLLICULAR PHASE: high FSH (low estrogen) => follicular maturation -> Graafian follicle -> secretion of estrogen (granulosa cells); theca interna secretes androgens which will be converted into estrogen in the granulosa cells.

– The increase in estrogen levels is accompanied by a low and slow LH surge

* PHASE ovular: estradiol increases max => sudden increase in LH => = progesterone discharge> ovulation

* Luteal phase: increasing estradiol inhibits the secretion of FSH and LH in pituitary secretes greater quantity => luteum which secretes progesterone (granulosa).

+ The simultaneous secretion of progesterone (dominant) and estrogen progesterone causes transformation of the endometrium (hyperplasia)

+ It is the elimination of the endometrial estrogenic impregnation with prostaglandin production which triggers menstruation.


+ HCG appears 8 days after fertilization (5 days before the expected date of menstruation); it is max 2 ½ months and then decreased -> 4 months -> Tea -> delivery -> disappears after 4 days.

+ The growth hormone chorionic (placental lactogenic hormone) promotes fetal development by potentiating GH.

+ Steroids come in the first 2 months of the corpus luteum; placental secretion becomes exclusive in the last 2 quarters

+ The 3 types of estrogen secreted by the placenta (estradiol, estrone, estriol). Estriol is synthesized from the precursor of fetal origin. Estriol is the estrogen dominant; it reflects the growth and vitality of the fetus in the third quarter.

+ Progesterone: Fetal corticosteroids are dependent on the formation of progesterone placen-silent. The rate increases during pregnancy and collapses during childbirth. It is related to the placental growth.

Note: the FSH receptors are found in granulosa and those of LH in the theca interna


1- Progesterone:

Inhibits the contractile potential of the uterus

2- Estrogen:

Increased excitability of uterine fibers and are important in the development of myometrium. They augmentent concentration of uterine oxytocin receptor. They are also involved in prostaglandin synthesis

3- Reflex Fergusson:

Distention of the uterus (during labor) triggers a reflex and utero-hypothalamic increase secretion of oxytocin

4- Oxytocin:

They do not intervene in the work of the trigger mechanism; it is useful in the pursuit thereof and acts only after the cervical transformation due to prostaglandins

5- prostaglandins:

Ripening effect on the cervix and increases uterine contractility

6- fetal Role:

Fetal ACTH secretion plays a role in the induction of labor; adrenal hypertrophy is responsible for prematurity …



– The lactation occurs 48 hours after delivery as a result of pituitary prolactin. During pregnancy prolactin is inhibited by estrogen and progesterone through the FIP.Oxytocin stimulates contraction of the myoepithelial cells

– Lactation sounds on balance the hormonal balance of the puerperium; the menstrual cycle and menstruation are often suspended (PRL inhibits the production of FSH). Menstruation may be the only suspended => ovulation (40th day).

2- Changes in the mother’s body:


– Gastric and intestinal function is slowed: the secretory activity is decreased; tone and intestinal motility is low => constipation

– Intrahepatic bile retention => cholestasis of pregnancy


– Tidal volume gradually increases; the residual volume was reduced by 20%

– The ventilatory rate increases by 40% without changing the respiratory rate

– Oxygen consumption increases by 15%; PCO2 decrease (30 mmHg)


– ECG: electrical axis deviated to the left ….

– Cardiac output increases during the first 10 weeks of 1.5 L / min and it is maintained until the end (6L / min)

– Heart rate increases by 15 / min

– The PA decreases by 5 10 mmHg in the first half of pregnancy (by considerable decrease in peripheral resistance)

– PVC is not changed

– Stress response -> vasodilation (instead of the usual vasoconstriction)


– Dilatation of the renal pelvis and ureters

– Renal blood flow increases and decreases in supine position => inversion of the diurnal rhythm of salt and water excretion

– The glomerular filtration rate increases by 50% (decrease in creatinine and blood urea)

– Increased excretion of uric acid

– The balance is positive soda (by stimulation of the renin-angiotensin system) -> increase blood volume

– Decreased oncotic pressure (hypoalbuminemia by hemodilution)


– The average plasma volume increases by 50% at 32 SA; Blood volume increases; The cell volume increases although the GR decreases

– Hemoglobin decreases; hematocrit decreases; serum iron decreases; capacity of transfer of oxygen increases

– Coagulation factors increases; fibrinolytic activity decreases and AT III => hypercoagulable

3- Diagnosis during pregnancy:

– The neck is not changed or in its dimensions or its form, barely in his position (posterior). It would be in its consistency: Softening

– The softening of the body is constant (at the isthmus -> Hegar’s sign); anteflexion exaggerated

– Fundus position: 3 months, it is equal distance between the pubis and the umbilicus; it reaches the navel to 4 ½ months (22 weeks).

– Uterine height: 20 cm 5th month (24 weeks); 24 cm at 6 months (28 weeks).

– Ultrasound: the best precision to date the beginning of the pregnancy is obtained 9-10 SA. Beyond the 15th SA it can no longer express the gestational age with such precision. The placenta appears on ultrasound to 9-10 SA.Morphological abnormalities (malformations) can be detected from the 19th SA by ultrasound

– At the beginning, a large number of placenta are inserted down (sometimes overlapping). After 20 weeks, the placenta seems to move away from the cervix.

– The ERCF is not systematic; a first time between 28 and 32 weeks and then every 15 days.

4- Work:

* EARLY WORK: it is defined by the combination of two phenomena

– Uterine contractions: involuntary; total; rhythmic; regular; progressively increasing and painful

– Cervical changes: softening, shortening, cervical dilation beginning; the lower segment is amplié

Other phenomena may herald the coming into work: loss of mucus plug (slimy leucorrhoea, thick, blood-tinged), which has little value; rupture of the amniotic sac (known rupture of membrane -> outside of work).


– The collar will delete then dilated (in multiparas dilatation is often accompanied by erasure). Full dilatation -> 10 cm

– The average length of expansion (1 -> 10cm) is 5 to 10 hours in primiparas; March-June pm in multiparas

– The normal RCF during this phase is between 120 and 160 / min, with oscillation> 5 beats / min (without deceleration) during or after contraction.

– The most effective witness a contraction pattern is a regular cervical dilatation

– Often it makes an artificial rupture of membranes, between 3 and 5 cm (when the presentation is sufficiently enforced -> commitment of the presentation