PREGNANCY
m a y b e n e c e s s a r y . T h e c o n d i t i o n c a n b e
p r e v e n t e d
b y
f r e q u e n t
b l o o d
p r e s s u r e
c h e c k s a n d
u rin a ly s is
( t o l o o k f o r p r o t e i n
i n t h e u r i n e ) a s p a r t o f
a n te n a ta l ca re.
p re g n a n c y
T h e p e r i o d f r o m
c o n c e p tio n
t o b i r t h . P r e g -
n a n c y b e g i n s w i t h
fe rtiliz a tio n
o f a n o v u m
( e g g )
a n d
i t s
i m p l a n t a t i o n .
T h e
e g g
d e v e l o p s i n t o t h e
e m b ry o ,
w h i c h b e c o m e s
t h e
fe tu s,
a n d t h e
p la c e n ta ,
t h e o r g a n t h a t
n o u r i s h e s t h e e m b r y o a n d t h e n t h e f e t u s .
M o s t
e g g s
i m p l a n t
i n t o
t h e
u t e r u s .
V e r y o c c a s i o n a l l y , a n e g g i m p l a n t s i n t o
a n
a b n o r m a l
s i t e ,
s u c h
a s
a f a l l o p i a n
t u b e , r e s u l t i n g i n a n
e c t o p ic p r e g n a n c y .
STAGES AND FEATURES OF PREGNANCY
P r e g n a n c y
i s
t r a d i t i o n a l l y
d a t e d
f r o m
t h e f i r s t d a y o f a w o m
a n ’s l a s t m e n s t r u a l
p e r i o d
( L M P ) ,
a l t h o u g h
c o n c e p t i o n
w o u l d n o t h a v e t a k e n p l a c e u n t i l t w o
w e e k s a f t e r t h i s . A n o r m a l p r e g n a n c y i s
c o n s i d e r e d t o l a s t b e t w e e n 3 7
a n d 4 2
w e e k s ;
i t
i s
d i v i d e d
i n t o
t h r e e
s t a g e s
( t r i m e s t e r s )
o f t h r e e m o n t h s e a c h . F o r
t h e f i r s t e i g h t w e e k s o f p r e g n a n c y , t h e
d e v e l o p i n g
b a b y i s
c a l l e d a n
e m b r y o ;
t h e r e a f t e r i t i s c a l l e d a f e t u s .
I n t h e f i r s t t r i m e s t e r t h e b r e a s t s s t a r t
t o s w e l l a n d m a y b e c o m e t e n d e r .
M o r n -
in g s ic k n e s s
i s c o m m o n . T h e b a b y ’s m a j o r
o r g a n s h a v e d e v e l o p e d b y t h e e n d o f t h i s
s t a g e .
D u r i n g
t h e
s e c o n d t r i m e s t e r ,
t h e
m o t h e r ’s n i p p l e s e n l a r g e a n d d a r k e n a n d
w e i g h t r i s e s r a p i d l y . T h e b a b y i s u s u a l l y
f e l t m o v i n g b y 1 6 - 2 2 w e e k s . D u r i n g t h e
t h i r d
t r i m e s t e r ,
s t r e t c h m a r k s
a n d
c o lo -
s tru m
( n i p p l e s e c r e t i o n s ) m a y a p p e a r , a n d
B raxton H ic k s ’ co n tra ctio n s
m a y b e f e l t . T h e
b a b y ’s h e a d e n g a g e s a t a b o u t 3 6 w e e k s .
F o r
d e t a i l s
o n
t h e
p h y s i c a l
f e a t u r e s
a n d c h a n g e s o f p r e g n a n c y , s e e t h e i l l u s -
t r a t e d
b o x
b e l o w .
F o r
i n f o r m a t i o n
o n
t h e
h o r m o n e s
i n v o l v e d
i n
s u s t a i n i n g
p r e g n a n c y , s e e t h e b o x o v e r l e a f .
PROBLEMS IN PREGNANCY
I n a d d i t i o n t o t h e e x p e c t e d f e a t u r e s o f
p r e g n a n c y , s u c h a s e x p e r i e n c i n g n a u s e a
STAGES AND FEATURES OF PREGNANCY
Pregnancytypically lasts 40 weeks, counted from the first
day ofthe pregnant woman’s last menstrual period, and is
conventionally divided into three trimesters, each lasting
three months. For the first eight weeks following conception,
the developing baby is referred to as an embryo; thereafter,
it is known as a fetus. It is during the early part of pregnancy
(first trimester), while the growing baby is still an embryo, that
it is at its mostvulnerable to damage.
First trimester (0 to 12 weeks)
The first sign of pregnancy is usuallythe
absence ofa menstrual period, although
some women have breakthrough bleeding. The
breasts start to swell and may become tender
as the mammary glands develop to prepare
for
b r e a s t - f e e d i n g .
The nipplesstartto enlarge
and the veins over the surface ofthe breasts
become more prominent. A supportive bra
should be worn.
Nausea and vomiting are common, and
are often worse in the morning; these problems
usually persist for sixto eight weeks (see
V o m i t i n g in p r e g n a n c y
). There is a need to
pass urine more frequently and there is often a
creamywhite discharge from the vagina. Many
women feel unusuallytired during the early
weeks of pregnancy. Some notice a metallic
taste in the mouth or a craving for certain foods
or non-edible products. Weight begins to
increase towards the end ofthis stage.
Second trimester (13 to 28 weeks)
From 16 weeks, the enlarging uterus is easily felt
from the outside and the woman begins to look
noticeablypregnant. The nipples enlarge and
darken, and skin pigmentation may deepen. Some
women may feel warm and flushed. Appetite tends
to increase and weight rises rapidly. The woman’s
facial features tend to become heavier. By 22
weeks (and usually between the 16th and 20th
weeks), most pregnant women have feltthe baby
moving around (a sensation that is sometimes
known as “quickening”).
During the second trimester, nausea, vomiting,
and frequency of urination diminish, and the
woman may feel generally better and more
energetic than she did during the earlyweeks. The
heart-rate increases, as does the volume of blood
pumped bythe heart; these changes allow the
fetus to develop properly. However, they put
an extra strain on the heart ofwomen who have
pre-existing heart disease.
Third trimester (29 to 40 weeks)
In some women, stretch marks develop on the
abdomen, breasts, and thighs. Also, a dark line
may appear that runs from the umbilicus to the
pubic hair.
C o l o s t r u m
(secretions from the
nipples) can be expressed from the nipples.
Minor problems are common. Manywomen
become hot and sweat easily because body
temperature rises slightly. More rest may be
needed atthis stage, although for many
women it is difficult to find a comfortable
position.
B r a x t o n H i c k s ’ c o n t r a c t i o n s
may
startto get stronger.
The baby’s head engages (drops down low
into the pelvis) around the 36th week in a first
pregnancy, but not until a few weeks later in
subsequent pregnancies. This so-called
“lightening” may relieve pressure on the upper
abdomen and on breathing, but it increases
pressure on the bladder and may result in a
more copious vaginal discharge.
P
623
previous page 622 BMA A Z Family Medical Encyclopedia   2004 read online next page 624 BMA A Z Family Medical Encyclopedia   2004 read online Home Toggle text on/off