Bma Illustrated Medical Dictionary

may involve counsellingor psychother-

apy. (See also conversion disorder.)

pregnancy, multipleThe presence of

more than 1 fetus in the uterus. Multi-

ple pregnancy can occur if 2 or more

ova (eggs) are fertilized at the same

time, or if a single fertilized egg divides

early in development.

Twins occur in about 1 in 80 pregnan-

cies, triplets in about 1 in 8,000, and

quadruplets in about 1 in 73,000. Multi-

ple pregnancies are more common in

women who are treated with fertility

drugsor if a number of fertilized ova are

implanted duringin vitro fertilization.

pregnancy testsTests on urine or blood

performed to determine whether or not

a woman is pregnant. Pregnancy testing

kits that are available from pharmacies

allow testing to be carried out at home.

All of the kits test for the presence of

human chorionic gonadotrophin(HCG) in

a sample of urine.This hormone is nor-

mally produced only by a developing

placenta, and therefore the tests are

extremely accurate (about 97 per cent

accurate for a positive result and about

80 per cent accurate for a negative

result), even in early pregnancy. Details

for using a test vary with different

brands; but all kits involve dipping a

test stick that has been treated with a

chemical that reacts with HCG into a

sample of urine. Blood tests for detect-

ing pregnancy produce a result from

9–12 days after conception.

PREGNANCY, MULTIPLE PREMENSTRUAL SYNDROME

P

PREGNANCY TEST

NEGATIVE RESULT

POSITIVE RESULT

HOME PREGNANCY TEST

Result

window

Urine

sample

Result

window

Indicator

showing

that test

has

worked

Band

indicator

showing

presence

of HCG

Chemically

treated test

stick

premature ejaculationSee ejacula-

tion, disorders of.

prematurityBirth of a baby before 37

weeks’ gestation. The premature infant

may not be sufficiently developed to

cope with independent life and needs

special care. About 5–10 per cent of

babies are born prematurely.

Some 40 per cent of premature deliv-

eries occur for no known reason. The

remainder are due to conditions such

as pre-eclampsia, hypertension, diabetes

mellitus, long-standing kidney disease,

and heart disease. Other causes are

antepartum haemorrhage, intrauterine

infection, or premature rupture of mem-

branes. A common cause is multiple

pregnancy (see pregnancy, multiple).

A premature infant is smaller than a

full-term baby, lacks subcutaneous fat,

is covered with downy hair (lanugo),

and has very thin skin. The baby’s inter-

nal organs are also immature. The

major complication is respiratory dis-

tress syndrome. There is increased risk

of brain haemorrhage, jaundice, and

hypoglycaemia. The baby has a limited

ability to suck and maintain body tem-

perature, and is prone to infection. The

earlier a baby is born, the more likely it

is to have such problems.

Premature infants are usually nursed

in a special baby unit that provides

intensive care. The baby is placed in an

incubator, and may have artificial venti-

lation to assist breathing, artificial

feeding through a stomach tube or into

a vein, and treatment with antibiotic

drugsand ironand vitamin supplements.

With modern techniques, some infants

survive even if they are born as early as

24 weeks’ gestation.

premedicationThe term applied to

drugs given, often by injection, 1–2

hours before an operation to prepare a

person for surgery. Premedication usu-

ally contains a opioid analgesic drug

and often an anticholinergic drug.

premenstrual syndromeThe com-

bination of physical and emotional

symptoms that occurs in many women

in the week or so before menstruation.

Premenstrual syndrome (PMS) may be

so severe that work and social relation-

ships are seriously disrupted.