Reproductive system

1. The Anatomy And Physiology Of
Pregnancy
Chikwala victor
BScM

2. Learning objectives
• At the end of this session students should be
able to
• Define of terms related to pregnancy
• Describe the anatomical and physiological
adaptations to pregnancy

4. Definition of terms
• Pregnancy or gestation: the time during which one or
more offsprings develop inside a women.
• Gravida: a woman who is pregnant
• Gravidity: pregnancy
• Multigravida: a woman who has had two or more
pregnancies
• Multipara: a woman who has completed two or more
pregnancies to 20 or more weeks of gestation
• Nulligravida: a woman who has never been pregnant

5. Definition of terms
• Nullipara: a woman who has not completed a
pregnancy with a fetus or fetuses who have reached 20
weeks of gestation
• Parity: the number of pregnancies in which the fetus or
fetuses have reached 20 weeks of gestation when they
are born, not the number of fetuses (e.g., twins) born.
• Fetus born alive or stillborn does not affect parity
• postdate or postterm: a pregnancy that goes beyond
42 weeks of gestation
• Preterm: a pregnancy that has reached 20 weeks of
gestation but ends before completion of 37 weeks of
gestation

6. Definition of terms
• Primigravida : a woman who is pregnant for the
first time
• Primipara: a woman who has completed one
pregnancy with a fetus or fetuses who have
reached 20 weeks of gestation
• Term: a pregnancy from the completion of 37
weeks of gestation to the end of week 42 of
gestation
• Viability: capacity to live outside the uterus;
there are no clear limits of gestational age or
weight.

7. Adaptations to pregnancy
• During pregnancy anatomical, physiological
and biochemical change occur
• Changes occur to the genital organs and all
systems of the body
Changes are due to:
• The hormones of pregnancy
• Mechanical pressure due to increasing size of
uterus and fetus

8. Adaptations to Pregnancy
Adaptations occur in order to;
• Protect the woman’s normal physiologic
functioning,
• Meet the metabolic demands pregnancy
imposes on her body,
• Provide a nurturing environment for fetal
development and growth.

9. The Reproductive System
• Vulva and vagina
• Vulva becomes vascular and hypertrophied,
pigmented and superficial varicosities may
appear.
• Vagina becomes vascular and hypertrophied,
looks bluish, fells soft.
• Increased blood supply of the venous plexus
surrounding the walls gives the bluish colouration
of the mucosa(Jacquemier’s sign)
• Vaginal secretion, increases in amount and is
acidic (3.5-6) due to the production of lactic acid

10. The cervix
• Remains 2.5 cm long throughout pregnancy,
• There is hypertrophy and hyperplasia of the
elastic and connective tissues
• Oestrogen increases cervical vascularity and if
viewed through a speculum the cervix looks
purple
• Marked hypertrophy and hyperplasia of the
glands
• All these lead to marked softening of the cervix
(Goodell’s sign) evident as early as 6 weeks

11. The cervix
• Cervical mucosa undergo hypertrophy and
hyperplasia and occupies inner half of cervix.
• A mucus plug called “operculum” is formed
between the internal and external os .
• The cervix is directed posteriorly but after the
engagement of the head, directed in line of vagina
• Unfolding of the isthmus; beginning 12 weeks
onwards and takes part in the formation of the
lower uterine segment
• In pregnancy the changes in the cervix facilitate
its dilatation during labor

12. Cervical Changes in Pregnancy

13. The Uterus
• Early uterine enlargement results from;
Increased vascularity and dilation of blood
vessels
Hyperplasia
Hypertrophy
Development of the decidua
• By 12 weeks of gestation uterine enlargement
is due to mechanical pressure of the growing
fetus

14. The uterus
• Non-pregnant state measures about 7.5 cm in
length, 5 cm in breadth and 2.5 cm in thickness.
• Gravid uterus gradually enlarges from 60 gm
muscular organ to 900 gm at term pregnancy.
• Length becomes 35 cm; breadth 22.5 cm and
thickness 20 cm.
• Uterine wall forms a sac containing amniotic
fluid and foetus

15. Arrangement of the muscle fibres
• 1)Outer longitudinal – follows a hood like
arrangement over the fundus.
• 2) Inner circular – It is scanty and have sphincter
like arrangement around the tubal orifices and
internal os
• 3) Intermediate – It is the thickest and strongest
layer arranged in criss-cross fashion through
which the blood vessels run.
• Apposition of two double curve muscle fibres
give the figure of ‘8’ form, it called as living
ligature

16. Arrangement of the muscle fibres

17. Arrangement of the muscle fibres
• The outer longitudinal layer of muscle fibres
contract and retract during labour causing upper
segment to thicken.
• The thickened upper segment acts as a piston to
force the foetus into the receptive, passive lower
segment

18. Uterine position
• Normal anteverted positions exaggerated up to
8 weeks
• The enlarged uterus may lie on the bladder
• Afterwards, it becomes erect, the long axis of
the uterus conforms more to the axis of the
inlet.
• Primigravidae with good tone of the abdominal
muscles, it is held firmly against the maternal
spine

19. Uterine Contractions
• Braxton-Hicks : Irregular, infrequent,
spasmodic and painless without any effect on
dilatation of the cervix.
• These contractions facilitate uterine blood flow
through the intervillous spaces of the placenta
• Endometrium : structural and secretory
activity of the endometrium

20. Isthmus
• During the first trimester:
• Isthmus hypertrophies and elongates to about 3
times its original length.
• It becomes soft
• Beyond 12 weeks, it unfolds from above, until it
is incorporated into the uterine cavity.
• The circularly arranged muscle fibers in the
region function as a sphincter in early pregnancy
and thus help to retain the fetus within the uterus.

21. Elongation and formation of the lower
uterine segment

22. Ovaries
• Ovulation ceases throughout pregnancy.
• Corpus luteum of usual menstrual cycle persists and
enlarges to 2.5 cm till 8th week due to the changes in the
fertilized ovum (trophoblast) and
• Helps in producing hormones.
• Oestrogen and progesterone secreted by the corpus luteum
maintain the environment for the growing ovum
• Control the formation and maintenance of decidua of
pregnancy
• Inhibit ripening of the follicles
• At 6-7 wks the placenta begins manufacturing progesterone, &
involution of the corpus luteum begins.

23. Breasts
• Under the stimulation of estrogen and
progesterone the breasts increase in size,
nodularity and sensitivity throughout pregnancy
with increased vascularity.
• Total weight becomes 0.4 kg volume.
• Enlargement is due to alveolar proliferation and
deposition of fat.
• Sebaceous glands (5-15) become hypertrophied
and are called Montgomery’s tubercles

24. Breasts
• Areola becomes dark pigmented, which is
primary areola,
• A second zone of pigmentation appears around
the primary areola in second trimester, which
is secondary areola.
• Secretion (colostrum) can be squeezed out of
the breast at about 12th week

26. CUTANEOUS CHANGES
•
• Face (chloasma gravidarum or pregnancy
mask) an extreme form of pigmentation
around the cheek, forehead and around the
eyes

27. ABDOMEN
• Linea nigra : a brownish black pigmented area in
the midline stretching from the xiphisternum to the
symphysis pubis
• Straie graviderum :slightly depressed linear
marks with varying length and breadth found in
pregnancy

29. CHANGES IN OTHER SYSTEMS
OF THE BODY
Cardiovascular System
• Heart works more during pregnancy.
• Increase in the cardiac volume by 10%
• No change in E.C.G.
• Cardiac output increases by 15-30% due to
increased heart rate and increase stroke volume.
• Pulse rate near term increases by 10 per minute.
• Platelet count shows slight decrease due to
increased concentration

30. Blood Pressure and Blood volume
• Blood pressure remains within normal limits
• Due to pressure of gravid uterus on pelvic
veins Venous pressure– Femoral venous
pressure rises.
• Blood volume increases from 3rd month and
reaches a peak of 25% rise at 32 weeks.
• The red cell volume increases by 200 ml,
• Plasma volume increases to 1000 ml

31. Respiratory System
• Increased inspiration so the increased oxygen
intake results in improved oxygen supply to the
foetus.
• Increased expiration, more carbondioxide is
expelled,
• There is low maternal carbondioxide leading to
easy transfer of CO2 from foetus to mother’s
blood.
• Breathing difficulty which is relieved after
lightening.

32. Digestive system
• Regurgitation of stomach juice and heart burn
• Slow emptying of stomach
• Constipation.
• Gums become spongy and vascular and may
bleed during brushing in many women.

33. Nervous System
• Slumpliness is common and mood changes occur
in many.
• Pregnancy is one of the periods in a woman’s life
when there seems to be lowering of the ability to
cope with emotional experiences in life.
• Even the cases where the coming of the baby is
welcome a mild degree of depression or
irritability may be evident during the early
months.

34. Urinary System
• Frequency of micturition
• Stress incontinence
• Due to dilatation of uterus and renal pelvis during
early pregnancy which continues till mid-
pregnancy there is a tendency for urinary stasis
and these favours infection.
• Glomerular filtration rate (GFR ) increases by
50% early in pregnancy, increasing creatinine
clearance.
• Serum creatinine and urea will fall by about 25%.

35. Urinary System
• Increased GFR also increases filtered sodium.
• Aldosterone levels rise by 2-3 times to
reabsorb the filtered sodium.
• Increased GFR and impaired tubular
reabsorption of glucose produce glucosuria in
approximately 15% of normal pregnancies.
• Proteinuria is abnormal in pregnancy

36. Musculoskeletal System
• The body's posture changes as the pregnancy
progresses.
• The pelvis tilts and the back arches to help
keep balance.
• Poor posture occurs naturally from the
stretching of the woman's abdominal muscles
as the fetus grows.
• These muscles are less able to contract and
keep the lower back in proper alignment.

37. Musculoskeletal System
• The pregnant woman has a different pattern of
gait.
• The step lengthens as the pregnancy progresses,
due to weight gain and changes in posture.
• The influences of increased hormones such as
estrogen and relaxin initiate the remodeling of
soft tissues, cartilage and ligaments.
• Increased ligamental laxity caused by increased
levels of relaxin contribute to back pain and pubic
symphysis dysfunction.
• Shift in posture with exaggerated lumbar lordosis
leading to the typical gait of late pregnancy.

38. Hematology
• During pregnancy the plasma volume
increases by 50% and the red blood cell
volume increases only by 20-30%.
• Consequently, the hematocrit decreases on lab
value; this is not a true decrease in hematocrit,
however, but rather due to the dilution.

39. Hematology
• A pregnant woman will also become
hypercoagulable , leading to increased risk for
developing blood clots and embolisms, due to
increased liver production of coagulation factors,
mainly fibrinogen and factor VIII
• Hypercoagulable state along with the decreased
ambulation causes an increased risk of both DVT
and PE

40. .
• Edema , or swelling, of the feet is common
during pregnancy, partly because the enlarging
uterus compresses veins and lymphatic drainage
from the legs.

41. Maternal Weight Gain
• In normal pregnancy the average gain is 0.3
Kg/week up to 18 weeks, 0.45 Kg/week from
18-28 weeks and a slight reduction with a rate
of 0.36-0.41 Kg/week until term.
• Failure to gain weight and sometimes slight
weight loss may occur in the last 2 weeks.
• The average weight gain for primigravidae for
is 12.5 Kg. and is probably about 0.9 Kg. less
for multigravidae.

42. Weight gain is produced by:
• Fetus 3.63-3.88 Kg
• Placenta 0.48-0.72 Kg
• Amniotic fluid 0.72-0.97 Kg
• Uterus and breasts 2.42-2.66 Kg
• Blood and fluid 1.94-3.99 Kg
• Muscle and fat 0.48-2.91 kg
Total= 9.70-14.55Kg

43. Endocrine System
• Thyroid activity is increased – In normal
pregnancy thyroid gland increases in size by
about 13 % due to hyperplasia and increased
vascularity.
• There is normaly an increased uptake of iodine
during pregnancy , which may be due to
compensate for renal clearance of iodine
leading to a reduced level of plasma iodine

44. Role of Estrogen in Pregnancy:
• Increasing blood flow to the uterus by
promoting vasodilation.
• Changing the sensitivity of the respiratory
system to carbon dioxide.
• Softening of the cervix, initiating uterine
activity, and maintaining labor.
• Developing the breasts in preparation for
lactation and secretion of prolactin by the
pituitary gland.

45. Role of Progesterone in Pregnancy:
• Ready the uterus for implantation.
• Relaxes smooth muscle to prevent spontaneous abortion.
• Works to prevent a maternal immunologic response to
the fetus.
• Relaxes smooth muscle
– to decrease motility & improve absorption of
nutrients.
– Enlarges the ureters & bladder to increase capacity.
• Plays a role in development of the alveoli & ductal
system to prepare for lactation.