Bma Illustrated Medical Dictionary

childbirthThe process by which an
infant leaves the uterusand enters the
outside world. Childbirth (labour) normal-
ly takes place between 38 and 42 weeks
of pregnancy and occurs in 3 stages.
The onset of the 1st stage of labour is
marked by regular contractions which
become progressively more painful, and
occur at shorter intervals. The cervixbe-
comes thinned and softened and then
begins to dilate with each contraction.
During this time, there may be a “show’’,
the mucous plug that blocks the cervi-
cal canal during pregnancy is expelled
as a bloody discharge. “Breaking of the
waters’’, the rupture of the amniotic sac,
may occur as a slow trickle of fluid or a
sudden gush. The cervix is fullydilated
when the opening has widened to about
10 cm in diameter. This may take 12
hours or more for a first baby, but only a
few hours for subsequent babies.
In the 2nd stage of labour, the woman
feels the urge to push with each strong
contraction. As the baby’s head descends
into the vagina, it rotates to face the
mother’s back. The perineumis stretched
thin at this stage, and an episiotomy
may be performed to prevent it from
tearing. Once the baby’s head is deliv-
ered, the rest of the body follows with
the next contractions. After delivery, the
umbilical cordis clamped and cut.
In the 3rd stage of labour, the delivery
of the placenta takes place.
The various forms of pain relief avail-
able during normal labour and delivery

include opioid analgesic drugs, epidural

anaesthesia, and pudendal block.

childbirth, complications ofDifficul-

ties and problems occurring after the

onset of labour. Some complications are

potentially life-threatening, especially if

they impair the baby’s oxygen supply

(see fetal distress). Premature labour

may occur, with the delivery of a small,

immature baby (see prematurity). Pre-

mature rupture of the amniotic saccan

lead to infection in the uterus, requiring

prompt delivery of the baby and treat-

ment with antibiotic drugs.

Slow progress in the 1st stage of a

normal labour due to inadequate con-

tractions of the uterus is usually treated

with intravenous infusions of synthetic

oxytocin. If the mother cannot push

strongly enough, or contractions are in-

effective in the 2nd stage of labour, the

baby may be delivered by forceps deliv-

ery, vacuum extraction, or caesarean

section. Rarely, a woman has eclampsia

during labour, requiring treatment with

anticonvulsant drugsand oxygen, and

induction of labouror caesarean section.

Bleeding before labour (antepartum

haemorrhage) or during labour may be

due to premature separation of the pla-

centafrom the wall of the uterus or, less

commonly, to a condition called placenta

praevia,in which the placenta lies over

the opening of the cervix. Blood loss

after the delivery (postpartum haemor-

rhage) is usually due to failure of the

uterus to contract after delivery, or to

C

Vagina (birth

canal)

Dilated

cervix

Baby’s

head

CERVIX DILATED EMERGENCE OF HEAD

Placenta Bladder Widened vagina

Baby’s
head
Mother’s spine Rectum

CHILDBIRTH

CHILDBIRTH CHILDBIRTH, COMPLICATIONS OF

Contracting uterus