What causes stretch marks and can they be avoided?
Stretch marks are a direct result of the distension of the abdomen, which causes
rupturing of the connective tissue beneath the skin. This is why stretch marks are
invariably a late feature in pregnancy.
Some people are more prone than others. Obesity increases the risk of this happening.
Among Caucasians, blonde women are more prone.
The stretch marks may actually become pigmented, sometimes becoming dark brown, even
black. The pigmentation fades after delivery, leaving silvery-white irregular lines
(known as striae).
While many types of lotions, so-called natural oils and creams have been claimed
to be effective, there is no evidence that any of them can actually prevent stretch
marks from appearing.
It is said contractions of the uterus start early in pregnancy. Is this true and,
if so, why?
Experience of pre-labour contractions differs quite widely among pregnant women.
They will also differ from one pregnancy to another for the same woman.
Painless contractions, to which the pregnant woman remains oblivious, commence as
early as fourteen weeks of gestation. They will continue off and on for the reminder
of the pregnancy.
At about thirty weeks, the woman may start being aware of them but they are almost
always painless at this stage. They are then known as Braxton-Hicks.
The placenta and the fetus produce a variety of hormones which act to promote these
contractions. There are however other hormones - including progesterone - which oppose
this effect, maintaining a balance which may help prevent inadvertent pre-term labour.
Weight and pregnancy
How much weight should a pregnant woman expect to put on during pregnancy?
Again, this differs widely among individuals. The rough average is an overall gain
of about 12 kg (26 lb). About 5 kg of this will be accounted for by the uterine contents
(i.e. the baby, the placenta and amniotic fluid). That weight will therefore be lost
immediately on delivery. The remainder of the weight gain is due to the increase
in the size of the uterus itself, increase in the blood volume, fluid retention and
some fat put on. Most of this weight is lost within the first few days after delivery.
The fat may be a little more difficult to shift. Weight is discussed in more detail
in Section 26, "Weight and Pregnancy".