the production of sperm. Low sperm
production may be treated with gon-
adotrophins (FSH or HCG). (See also
The union of a
and an
cell). In natural fertilization (see the
illustrated box), the sperm and ovum
unite in the woman’s
fallopian tube
sexual intercourse.
Fertilization may also occur as a
result of semen being artificially intro-
duced into the cervix (see
insem ination)
or it may take place in a
laboratory (see
in vitro fertilization).
festinating gait
An involuntary style of
in which
a person moves, often on tiptoe, with
progressively shortening and accelerat-
ing steps. A festinating gait is a feature
of an individual suffering from the
movement disorder
fetal alcohol syndrome
A rare combination of birth defects
that occur as a result of continued,
consumption by the
baby’s mother during
The affected baby has diminished
growth, a small head and brain, and
small eyes. He or she may also have a
cleft palate, a small jaw, heart defects,
and joint abnormalities. As a newborn,
the baby sucks poorly, sleeps badly, and
is irritable due to alcohol
Some affected babies die during the
first few weeks of life. Those who sur-
vive may experience delayed mental
development and are, to some degree,
mentally and physically handicapped.
fetal circulation
Blood circulation in the fetus is differ-
ent from the normal circulation after
birth (see
circulatory system).
The fetus
neither breathes nor eats, so oxygen
and nutrients are obtained, via the
umbilical cord,
from the
mother’s blood. The other fundamental
difference in circulation is that blood
bypasses the lungs in the fetus.
Oxygen and nutrients enter the fetal
blood through the placenta, an organ
embedded in the inner lining and wall
of the uterus and connected to the
fetus by the umbilical cord. The mater-
nal and fetal circulations are separated
by a thin membrane in the placenta,
which allows the exchange of nutri-
ents and waste products.
Before birth
After birth
Fetal heart circulation
In the fetus, blood passes directly from the right
atrium of the heart to the left atrium through the
foramen ovale. Another channel, the ductus
arteriosus, allows blood to pass from the
pulmonary artery to the aorta. After birth, both
channels close redirecting blood through the lungs.
Oxygenated and nutrient-rich
flows from the mother to the fetus
along a vein in the umbilical cord
before entering the right atrium (upper
chamber) of the heart. Then, instead of
flowing to the lungs, it bypasses them
by flowing into the left atrium via an
opening known as the foramen ovale.
From there, the blood passes to the left
ventricle (lower chamber), where it is
pumped to the upper parts of the body
to provide the tissues with oxygen.
Blood returning to the heart flows
into the right atrium and from there
into the right ventricle. In the fetus, the
blood is only partly deoxygenated at
this stage and has more tissues to sup-
ply with oxygen. Bypassing the lungs
again, it flows from the pulmonary
artery into the aorta, through a channel
called the ductus arteriosus. The aorta
carries the blood to the lower parts of
the body. From there, completely de-
oxygenated blood is carried via the
umbilical cord to the placenta, where
carbon dioxide and other waste diffus-
es into the mother’s blood.
After birth, the foramen and the
ductus arteriosus normally close. Blood
pumped from the right ventricle passes
via the pulmonary artery to the lungs
for reoxygenation and elimination of
carbon dioxide and other wastes. In
rare cases, the foramen ovale or ductus
arteriosus fails to close after birth,
causing a congenital heart disorder
heart disease, congenital).
fetal death
fetal distress
The physical stress experienced by a
fetus during
as a result of not
receiving enough oxygen. During each
contraction, the uterus tightens and
thus reduces the oxygen supply from
the placenta to the fetus. If there are
also problems, such as pressure on
umbilical cord
or the mother losing
blood, there may be an inadequate
amount of oxygen reaching the fetus.
Various monitoring techniques may be
used during childbirth to detect signs
of fetal distress. A cardiotocograph (see
whether the baby’s heart rate is slow or
if it is failing to show normal variabili-
(high acidity in the body),
which indicates that the oxygen supply
to the fetus is inadequate, can be de-
tected in a sample of blood taken from
the baby’s scalp. Signs of
(fetal faeces) in the amniotic fluid can
also be an indication of fetal distress.
Fetal distress sometimes occurs as a
temporary episode, but, if acidosis is
severe, the distressed fetus may need to
be delivered promptly by
caesarean sec-
tion, forceps delivery,
vacuum extraction.
(See also
fetal heart monitoring
The use of an instrument to record
and/or listen to an unborn baby’s
heartbeat during
The fetal heart is checked routinely dur-
ing pregnancy with a fetal stethoscope or
Doppler ultrasound
scanning. Additional
monitoring is carried out if tests indi-
cate that the placenta is not functioning
normally or if the baby’s growth is slow.
Uterine contractions or other stimuli,
such as reflex kicking, increase the heart
rate in a healthy fetus; the midwife or
obstetrician can detect this using a fetal
heart monitor. During labour, monitor-
ing can detect
fetal distress,
in which
oxygen deprivation causes abnormali-
ties in the fetal heart rate.
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