Preparing for Birth Australian Edition Partial Preview - Page 6
Anatomy of Pregnancy and Birth
Understanding pregnancy anatomy will help you as you learn more about labour and birth.
umbilical cord Pelvic floor muscles form a multi-layered
hammock that supports the internal
amniotic sac organs and controls urination and bowel
amniotic fluid movements. During labour, they stretch to
allow the baby to pass through the pelvis.
Average Weight Gain Breakdown
Placenta 0.7 kg
Uterus 1 kg
Amniotic fluid 1 kg
Breast tissue 0.5-1.4 kg
• The uterus has grown from about the size
of a pear prior to pregnancy to the size of a
large watermelon by full-term.
• The stomach is compressed and you may feel
full after only a few bites during a meal.
• Breast tissue has expanded and will begin to
produce colostrum, the dense milk that will
nourish baby for the first few days of life.
• Blood volume has increased to about 50%
more than pre-pregnancy levels.
• The average baby has grown to about 51 cm
in length and weighs about 3.4 kg.
• Most babies assume a head-down position by
the time labour begins.
• Amniotic fluid surrounds the baby, providing
cushion and equalising pressure.
• The placenta supplies all of the oxygen and
nutrients necessary for baby and filters waste
products from the baby. The placenta is also
the source for hormones needed to sustain the
• The umbilical cord transfers nutrients, oxygen
and fetal waste between the baby and the
placenta and averages 56 cm long.
Labour and Birth