At the onset of labour, painful and regular uterine
contractions begin and the cervix (the neck ofthe womb)
starts to dilate (widen). The mother is usually examined
vaginally every two to four hours to assess the extent of
dilation. The duration ofthe first stage of labour depends
on several factors, but primarily on whether the baby is the
mother’s first or a subsequent child.
F e t a l h e a r t m o n i t o r i n g
is often carried out, and the frequency, strength, and duration
ofthe mother’s contractions are recorded. During the second
stage of labour, the contractions become stronger and the
woman feels the urge to push; however, she is advised to
push onlyduring a contraction. Once the baby is delivered, he
or she is usually laid on the mother’s abdomen, but may first
be warmed, dried, and checked by a midwife or doctor.
With the first contractions,
the normallythick, tough
cervixbecomesthinned and
softened and is gradually
pulled up until it becomes
effaced (merged with the walls
ofthe uterus). The cervixthen
begins to dilate (stretch open)
with each contraction. It is
fully dilated when the opening
is about 10 cm in diameter.
This stage of labour can take
12 hours or more for first
babies, but only a few hours
for subsequent babies.
C e r v ix
C e r v ix
c l o s e d
d i l a t e d
U te r u s
As the baby’ s head descends, it reaches the pelvic floor muscles, which
cause the head to rotate until eventually the baby’ s chin is pointing down
towards the mother’ s rectum. As the baby is pushed further down the birth
canal, the mother’ s anus and perineum (the area between the vulva and
anus) begin to bulge out, and soon the baby’ s head can be seen atthe
opening of the vagina. As the head emerges, the perineal tissues are
stretched very thin; sometimes it is necessary to perform an
e p isio to m y
(cutting ofthe tissues under local anaesthetic) to prevent them from tearing.
As soon asthe baby’s head emerges, it turns, usually aided bythe midwife,
so it is once more in line with the body. With the next few contractions, one
shoulder is delivered at a time; then the rest ofthe baby slides out. After
delivery, the cord is clamped and cut.
The head
At this point, an
episiotomy is
performed to
from tearing.
W i d e n e d v a g in a
U m b i lic a l c o r d
Delivery of
the baby
Once both of the
shoulders are
out, the rest of
the baby’s body
emerges easily.
B a b y ’s h e a d
— i s s u p p o r t e d
S h o u l d e r s
s l i d e o u t
This may be performed ifthe fetus is at risk, or as a
routine check. The fetal heart rate and the mother’s
uterine contractions are recorded.
Fetal monitoring devices
In the procedure shown above, the
baby’s heartbeat is detected by a
metal plate strapped to the lower belt.
A plate beneath the upper belt detects
the contractions. An alternative
method is to attach an electrode to the
baby’s head; the electrode is linked to
the monitor by a wire passed through
the mother’svagina.
F e t a l h e a r t r a t e
Three to 10 minutes after the birth, the placenta (afterbirth) separates from
the uterine wall and is removed bygentle traction on the cord. Drugs such
as ergometrine or oxytocin may be used to aid its expulsion and to reduce
bleeding. Rarely, the placenta may have to be manually removed, under
general or epidural anaesthetic, by an obstetrician. Anytears or incisions
are cleaned and stitched. This maybe done while the mother holds her baby.
Placenta being delivered
The placenta is usually expelled within
a few minutes ofthe baby’s birth.
P la c e n t a
U m b i lic a l
c o r d
previous page 162 BMA A Z Family Medical Encyclopedia   2004 read online next page 164 BMA A Z Family Medical Encyclopedia   2004 read online Home Toggle text on/off