The miracle of pregnancy

pregnant woman touching her belly


We all know the saying ‘the miracle of birth’.  Have you ever stopped to think about the miraculous changes that a woman’s body undergoes during pregnancy?  A pregnant woman changes in nine months from an everyday female body to one that nurtures, grows and delivers another human being. That’s amazing!  Here’s the science behind the incredible changes that happen to a woman’s body during pregnancy.

As soon as the fertilised egg implants in the wall of the uterus, the hormones in the body start to change. An ovarian hormone called relaxin is released. The job of this hormone is to gradually loosen the ligaments around the pelvis in preparation for childbirth.  All ligaments in the body are affected.  Ligaments aren’t the only tissues affected by relaxin.  It also softens vein walls which can contribute to varicose veins.

Heart rate (pulse) changes.  A pregnant woman’s resting pulse increases by about 7 beats per minute in the first four weeks of pregnancy and by 15-20 beats per minute by mid-pregnancy.  This would be an ‘exercise’ heart rate for the non-pregnant body.  However, pregnant women can still exercise safely by exercising at a lower level of intensity.  In fact, exercise during pregnancy should be encouraged as the appropriate intensity of exercise has been shown to have a positive effect on placental function, baby growth and the general well-being of the mother.

In the pregnant body, Blood Volume increases by up to 40-50%.  Combined with the softened vein walls, this can cause fluid retention leading to swelling of the ankles.

New blood vessels form within the uterus to supply the growing baby which causes the mother’s blood pressure to drop during the second trimester.  This can be a cause of the dizziness that many pregnant woman experience with rapid changes in position.

Metabolic rate is the amount of energy expended by the body for the functioning of its vital organs.  In pregnancy, metabolic rate is increased by 20%.  Combined with the calorific requirements of ‘eating for two’, this means that the expectant mother requires more nutrition than normal.  A further effect of an increase in metabolic rate is a rise in core temperature by 0.5 degrees.

The body undergoes significant muscle changes during pregnancy.  As the baby grows, the abdominal muscles lengthen and a separation of the ‘six pack’ occurs to make room.  The pelvic floor muscles, which are the sling of muscles under the pelvis that support the internal organs, have an extra workload during pregnancy as they are supporting a growing baby as well.

One of the most obvious changes is the pregnant woman’s body shape.  When standing, our centre of gravity falls between our feet. Because the baby is carried in front, as it grows, it moves the woman’s centre of gravity forwards.  As a reaction to this, the arch in the lower back increases.  As well as the growing baby pushing forwards, it also pushes up and down.  Pressure upwards is on the diaphragm which can, at times, make the mother feel short of breath.  Pressure downwards is on the bladder which is why pregnant woman have to go to the bathroom more often.

The average increase in body weight is 10-15 kg. 50% of this increase is the baby, the uterus and amniotic fluid and 50% is body fat stores and fluid retention.

Wow!  All that in nine months!  This process is not designed by a complicated computer programme or driven by anything external.  It’s the human body’s most dramatic, natural change.  And when it’s done all that, it goes full circle and returns to its original state.