edged, pink spots or patches appears
on the trunk and upper arms. It is not
contagious and mainly affects children
and young adults. Its cause is unknown.
The rash lasts for 4-8 weeks, may cause
itching, and usually clears up without
treatment. Calamine lotion or
tamine drugs
may relieve any itching.
pityriasis versicolor A common skin
condition in which patches of white,
brown, or salmon-coloured flaking skin
appear on the trunk and neck. Also
known as tinea versicolor, it is caused
by a fungus that exists on most people's
skin. Treatment is with
antifungal drugs.
pivampicillin See
penicillin drugs.
pivmecillinam See
penicillin drugs.
pizotifen An
antihistamine drug
used to
prevent migraine in people with fre-
quent, disabling attacks. Adverse effects
can include nausea, dizziness, drowsi-
ness, dry mouth, and muscle pains.
Prolonged use may cause weight gain.
PKU test See
Guthrie test
placebo A chemically inert substance
given instead of a drug. Benefit may be
gained from a placebo because the per-
son taking it believes it will have a
positive effect. As the effectiveness of
any drug may be partly due to this
“placebo effect”, many new drugs are
tested against a placebo preparation.
placenta The organ that develops in the
uterus during pregnancy and that link
the blood supplies of mother and baby.
The placenta develops from the
It is firmly attached to the lining of the
woman's uterus and is connected to the
baby by the
umbilical cord.
It is expelled
shortly after the baby is born.
The placenta transfers oxygen and
nutrients from the mother's circulation
into the fetus's circulation, and removes
waste products from the fetus's blood
into the mother's blood for excretion by
her lungs and kidneys. It also produces
hormones such as
, and
human chorionic gonadotrophin
(HCG). High levels of HCG appear in the
woman's urine during early pregnancy,
and detection of them in the urine forms
the basis of
pregnancy tests
placental abruption Separation of all
or part of the placenta from the wall of
the uterus before the baby is delivered.
The exact cause is not known, but pla-
cental abruption is more common in
women with long-term
in those who have had the condition in
a previous pregnancy or who have had
several pregnancies. Smoking and high
alcohol intake may also contribute to
the risk of placental abruption.
Symptoms usually occur suddenly and
depend on how much of the placenta has
separated from the wall of the uterus.
They include slight to heavy vaginal
bleeding, which can be severe haemor-
rhaging in complete separation; cramps
in the abdomen or backache; severe,
constant abdominal pain; and reduced
fetal movements. If the bleeding does
not stop, or if it
starts again, it may
induce labour (see
induction of labour).
A small placental
abruption is usu-
ally treated with
bed-rest in hospi-
tal. In more severe
cases of placental
abruption, an em-
is often nec-
essary to save the
the life of the fetus.
blood transfusion
is also sometimes
Maternal artery
Flow of oxygen and
nutrients from mother's
blood to fetus's
Umbilical vein
Amniotic fluid
Wall of uterus
Mother's blood
Maternal vein
Lining of
Flow of waste
from fetus's
blood to
Umbilical cord
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