Physiological changes due to
as a woman gets pregnant, there is a dramatic physiological adaptation to
pregnancy in various systems of the body especially in the reproductive system
so that her body can cope with added work and nurture the fetus and prepare for
labour and lactation.
changes is sometimes under estimated but the effects vary from one woman to
another. Midwife’s understanding of the physiological changes will enable her
to identify deviation from normal and will be able to provide adequate care to
the woman or take appropriate stop to solve her problems.
conception the uterus provides a nutritive and protected environment for the
fetus to grow and develop.
Size: The size increases progressively
so that at term it is from7.5 x 5 x 2.5cm to 30 x 23 x 20cm.
The Weight: From about 60gm to 90gm.
The position: changes from pelvic organ to
abdominalorgan. By the 12th weeks of pregnancy it is no longer
anteverted and anterflexed but become more vertical and
towards the right as pregnancy progresses.
Shape – As it fills up with the growing
fetus the uterus becomesmore globular. It changes from the ovoid shape when it
was in the pelvic cavity to become globula.
The Decidua: becomes more thicker and
increased vascularity ofthe lining. This is more marked in the fundus and the
upper body of the uterus. The deciduas and trophoblast produce relaxin which
relaxes the myometriam relaxation and play a role in ripening of the cervix at
term and rupture of the membranes.
Each muscle fibre increases to about ten times its length and at least three
times its width due to hyperplasia and hypertrophy of the myometrial cells
under the influence of oestogen.
Blood supply – increases to almost ten times due
to increasedcardiac output from about 50mls/min to 450 -700ml/min at term.
Eighty percent of the blood flows through the placenta there is enlargement of
the blood vessels and give rise to a sound known as uterine “soufflé”.
Support – the greatest strain is on the
round ligament the changesin the size vary with each woman and the gestational
uterus grows at such a regular rate that it is possible to estimate period of
gestation by size. There is of course room for error as uterus may contain more
than one fetus, large baby or excessive amount of amniotic fluid. Before 12th
weeks the uterus remains a pelvic organ and maintains the ovoid –sha pe.
12th Week –The
uterus fills the pelvic cavity and fundus just reaches the summit of the
symphysis pubis. It is globular in shape about the size of a grape fruit. It is
more upright usually incline to the right.
16th Week – the
uterus has risen to less than halfway between thesymphysis pubis and the
umbilicus or about 7.5cm above the symphysis pubis. The shape is more ovoid
than global because it is in contact with the abdominal wall quickening is
felt. Uterine soufflé can be heard. The isthmus andthe cervix develop into the
lower uterine segment.
20th Week – the
fundus is about the level of the umbilicus. Fromthis stage the uterus become
more ovoid in shape. Positive signs of pregnancy can be elicited without
ultrasound (fetal heart, fetal parts and fetal movement.
24th Week – Fundus is
at the upper margin of the umbilicus 20cm.the uterus tends to lean and rotates
on its axis towards the right.
30th Week –The
fundus can be palpated midway between the umbilicus and xiphisternum. The
assessment may be subjective as the level of umbilicus may vary in size.
36th Week – The
fundus rises to the highest level, in contact withthe xiphisternum. No finger
breadth between the xiphisternum and the fundus.
38th Week –The lower
uterine segment is formed. The fetal presenting part descends and the fundal
height drops, this is known as lightening, leaving pressure on upper abdomen
engagement may occur in some women.
40th Week - The
uterus is ready to go into labour. The loweruterine segment is relaxed and
stretched the cervix is effaced and soft. The fetus further sinks down into the
lower segment and the fundal height drop to about 34 week when the head is
The Cervix – During pregnancy the cervix
remain closed.Blood supply is increased that it becomes softer and more bluish
in colour. The cervical glands secrete more mucus. A plug of this viscous
mucoid material fills the cervical canal. It is known as operculum. It
minimizes the risk of ascending infection into the uterus. Collagenase and
protoglandin are involved in cervical ripening. Theoretically effacement takes
place about 2 week before term in primigravidae and when labour begins in
The vagina: there is some degree of
hypertrophy of themuscle layer of the vagina causing the epithelium to become
thicker. Increase blood supply (hyperaemia) result in the blue discoloration
and increase pulsation at the fornix. The Doderlein bacilli act upon the
vaginal collegen resulting in lactic acid which increases pH of Vaginal
secretion to 4.5 – 5.0. Thi s increases vaginal secretion – ( Leuchorrhoea)
during pregnanc y.
supply to these organs increases. They become more vertical in position as the
growing uterus fills the abdominal cavity. The corpus luteum enlarges,
producing high level of oestrogen and progesterone in the first 10-12 weeks.
Corpus inturm degenerates after the 12th week and placenta take over
The Breast: Owing to increase blood supply
and the effectof oestrogen and progesterone new duct and actini cells are
formed. The breast increases in size. There is tingling sensation in early
pregnancy, the breast is more firm and tender. The nipple becomes more dark and
prominent. The primary areola becomes darker at the 12th week.
Dilated veins may be open on the chest and breasts. Clear fluid may be
expressed. At 16th week colestrum may be expressed, and secondary
areola is formed around the primary areola .
8th week montgomany’s tubercles are formed in the areola. They
secret sebum to keep the nipples soft and pliable.
Cardiovacular system: Profund changes take place
incordiovasular system during pregnancy. The heart slightly enlarges to about
12% to meet the challenges of increase blood volume – the blood volume
increases by 50% plasma volume in the mid trimester (hydraemia) being mainly
water volume. This leads to what is known as physiological anaemia. Blood
vessels are dilated due to action of progesterone and this predisposes to
varicose veins and haemorrhoids. Cardiac output increases.
pressure - Even with raised cardiac output arterial blood pressure is reduced
by 10%. Early pregnancy is associated with decreased diastolic blood pressure
but little change in systolic by mid trimester the blood pressure slightly
increases 5 -10mm/g in systolic and 10-15mm/mg in diastolic but soon return to
normal before term.
can affect blood pressure – supine position can decrease cardiac out put by as
much as 25%.There is increase production of red blood cell to meet the needs of
the mother and baby .Despite this there is decrease haemoglobin concentration
because of increase plasma volume.
Metabolic Rate (BMR) is increased during pregnancy. Increased cardiac output
leads to increase in tidal volume that enters and leaves the lungs during
normal respiration. The rising uterine fundus compresses the base of the lungs
making respiration to become costal. Up to 70% of pregnant women experience
dyspnoea beginning from first or second trimester. Cardiac and pulmonary
disease must be ruled out.
becomes oedematous, soft and spongy. It is easily brushed. Sometimes gingivitis
(epulis) may develop.
and morning sickness occurs during the first three months of pregnancy in about
50% pregnant women.
hormone – Progesterone affect all smooth muscles of the gut resulting in
indigestion, heart burn and constipation.
third month until term, some degree of skin darkening is observed in about 90%
of pregnant women. The abdominal skin stretches to accommodate the enlarging
uterus and extra fat deposit resulting in small tears in the deeper layers of
the skin. These are the stretch mark on the abdomen known as triae gravidarum.
It may also occur in the breasts, thigh and back of the legs. More marked in
multiple pregnancies and polyhydranios.
of the skin occurs on the face – norma lly referred to as chloasma or pregnancy
mask. The mid lime seen to be extending from xiphistermum to the symphysis
pubis area become darker and more pronounced. It disappears few days after
delivery. It is known as linea nigra.
alteration in the gait of the woman in an attempt to maintain balance due to
the weight of the growing uterus. There is increase movement in the joints due
to relaxing effect of the pregnancy hormones on the ligament.
instability is common in pregnancy and the woman cries easily. There is
increase tendency to anxiety, fear and even depression.
A steady and adequate weight gain is necessary for the health and well being of the woman and the fetus. An average maximum weight gain of 11.5kg is expected during pregnancy. During the 1st trimester
a weight gain is slow most weight gain occurs in the second and third
trimesters. It results from increase muscle tissue and fat, especially the
breast, buttocks and loins and thighs. Growth of the uterus and the product of
conception, fluid retention increase blood volume. Increase of 20% of the non
gravid uterus is considered normal. The first 20 weeks the average weight gain
is 2kg, weight gain is rapid during the second 20 week, a gain of 0.5kg per
week making a total of 11 -12kg. Any weight above this should be investigated.