The second baby window: As a new study analyses the mental and physical effect of the 'interpregnancy interval' on mothers, what is the right amount of time to wait before conceiving again?

  • A study found women with short birth intervals have increased health risks
  • Women who waited longer than 60 months can suffer physical harm too
  • Pre-eclampsia, anaemia and emotional anguish are risk to mums
  • The 'ideal' time for women to space births is at least 24 months apart

Pregnancy might not always be planned, but a new study suggests timing is everything.

The study found that the gap between the birth of one child and the conception of another, also known as the 'interpregnancy interval' (IPI) can significantly affect the mental and physical condition of the mother-to-be.

Analysing the data of 1,723,084 women who had births from 2011, the Centers for Disease Control and Prevention (CDCP) found the IPI can have adverse health outcomes for women both with short birth intervals and long birth intervals.

How long should you wait? a study has found that the gap between the birth of one child and the conception of another can significantly affect the mental and physical condition of the mother-to-be

A short interval is defined as women who fall pregnant in less than 18 months and long intervals extent to a gap of 60 months. 

From those surveyed, it was found that 30 per cent didn't wait long enough, falling pregnant again in less than 18 months after giving birth.

The study found short intervals may affect the risk of pregnancy complications to the baby such as pre-term birth, low birth weight, and small gestational age.

There is also a impact on the mothers too.

Leading Sydney obstetrician and senior lecturer at the University of Sydney, Dr Sean Seeho said for women conceiving in a short interval, it's often a case of whether they are emotionally and physically ready for the next pregnancy. 

Age gap: The study found an interval of less than 18 months may affect the risk of pregnancy complications to the baby such as pre-term birth, low birth weight, and small gestational age

Age gap: The study found an interval of less than 18 months may affect the risk of pregnancy complications to the baby such as pre-term birth, low birth weight, and small gestational age

'There is a burden on mothers to produce red blood cells so that babies can get folate and because mums become anaemic following the birth of a baby it means they don’t get much time to recover from birth before pregnant again.'

Dr Seeho notes that the stress of a first time mum can also play a large role.

'One in five women get the baby blues, so if they go into a pregnancy and haven’t dealt with their post natal depression then they will definitely have issues again during that pregnancy as they haven't left time to treat it adequately,' he said.

Peace Mitchell, a Melbourne-based mother and entrepreneur who has had three children in under four years said her third pregnancy took its toll.

'The third pregnancy was quite hard physically, towards the end I had difficulty walking and I couldn't carry the other children because the pregnancy was taking such a toll on my body.'

Physical stress: Peace Mitchell, a Melbourne-based mother and entrepreneur who has had three children in under four years said her third pregnancy took its toll

Physical stress: Peace Mitchell, a Melbourne-based mother and entrepreneur who has had three children in under four years said her third pregnancy took its toll

'It was also hard because they were still little they need a lot of extra attention, so I struggled. My middle child also wasn't impressed at all when I had my third son 20 months later,' she adds.

'He didn't want to look at the baby, he would try to hurt it and be aggressive and that was difficult, he was a baby himself and I couldn't give him the attention he needed.'

A previous study as reported in the Iowa Medicaid Birth Certificate Report also found short birth intervals can have a higher risk of maternal mortality and hypertensive disorders during pregnancy including bleeding and anaemia.

Those in developing countries are likely to be the most affected though, according to Dr Seeho as they have a higher risk of blood loss and nutritional deprivation.

Yet, on the other side, women who wait up to five years to have another child can also face increased health risks.

Leading Sydney obstetrician Dr Sean Seeho said for women conceiving in a short interval, it's often a case of whether they are emotionally and physically ready for the next pregnancy

Leading Sydney obstetrician Dr Sean Seeho said for women conceiving in a short interval, it's often a case of whether they are emotionally and physically ready for the next pregnancy

'We know that high blood pressure increases in older mums, as does the risk of kidney disorders and diabetes so if there is a pre-existing condition, there's a need to optimise blood pressure and make sure physical and emotional health is good first,' says Dr Seeho. 

'Also, if in five years the woman has changed partners there are high risks associated with pre-pre-eclampsia.'

Overall Dr Seeho's believes there isn't one window that best works for the woman as long as she is physically and emotionally ready.

Mitchell also can attest to this, when eight years on she had a fourth child and had no issues at all.

'I turned 40 and was worried my body wouldn't hold up but it was the best pregnancy I had. I also had the boys at school and had time and energy to give to her.'

However the CDCP study did find factors such as age and race can also affect the impact on birth and that women under aged 20 tend to have closer interpregnancy intervals of 11-14 months whereas women aged 40 or older would wait between 39-76 months.

While the verdict is still out on whether there is one optimal interpregnancy interval, the World Health Organisation currently suggests a interval period of at least 24 months is the best outcome for mums.

 

 

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