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Why you should avoid 'eating for two' during pregnancy

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Doubling down on food during pregnancy is out, unless it’s diet quality we’re talking about.

If you think pregnancy is an excuse to start chowing down on doughnuts and chips – or simply to start eating larger quantities of healthy food – think again.

Although you may be “eating for two”, that doesn’t mean you can eat twice as much; instead, you should be eating twice as well. It’s a case of out with the chips and in with the kale.

Ministry of Health guidelines say that a woman who begins pregnancy at a healthy weight (with a body-mass index [BMI] between 18.4 and 24.9) doesn’t need to eat any extra food during the first 12 weeks. After that, she only needs to increase her daily intake by about 837kJ – the equivalent of a wholegrain peanut butter sandwich and an apple.

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Weight gain is inevitable during pregnancy. As well as the baby, the placenta, amniotic fluid, extra blood and an increase in the size of the uterus and breasts all add kilos. The body also stores fat to help it cope with pregnancy and breastfeeding.

It’s this extra fat that can cause problems. Gaining too much of it is associated with a range of complications. These include high blood pressure, gestational diabetes, pre-eclampsia, longer labours and higher caesarean rates.

There can be consequences for the baby, too. “If you gain more than the recommended amount, your child is more likely to end up with a high BMI,” says Dr Helen Paterson, a senior lecturer in women’s health at the University of Otago.

Gaining too little weight can also cause problems for mothers and babies. These include higher stillbirth rates and – paradoxically – a higher likelihood that your child will become overweight or obese later in life.

But women are much more likely to gain too much weight than too little during pregnancy. A recent review of more than a million pregnancies found that 47% of women put on too many kilos and 23% added too few.

The increasing number of women who enter pregnancy already overweight or obese makes the weight-gain tendency even more of a problem. That’s because carrying extra weight on its own can cause pregnancy complications. Gaining too much weight increases the risks.

Dr Helen Paterson: working with midwives.

Paterson says there’s no point in berating pregnant women for being overweight – particularly as they can’t do anything about it while they are pregnant. It’s more important to find ways to help them to keep their weight gain within the recommended guidelines.

“The message we need to be selling is that women who gain the appropriate amount of weight have better outcomes and their children have better outcomes.”

It used to be that all women – whatever their initial weight – were told to gain no more than 12kg during pregnancy. That has now been recalibrated to reflect a woman’s BMI when she first becomes pregnant. The recommended weight gain for a newly pregnant woman with a BMI of 30 or more – which puts her in the obese category – is now 5-9kg. That compares with a recommended weight gain of 12.5-18kg for an underweight woman with a BMI of less than 18.5. The recommended weight gain for a healthy-weight woman is 11.5-16kg.

Paterson and her Otago colleague Dr Kirsten Coppell are applying for funding to test a midwife-led weight-management intervention to help pregnant women achieve optimal weight gain. This will include using a specially developed booklet on healthy food and lifestyle choices during pregnancy.

“We’re looking at a really pragmatic approach and we’re working with midwives because they deliver most babies,” says Coppell. “It’s about providing a service to enable a healthy pregnancy.”

Jacqui Anderson of Christchurch, an adviser with the College of Midwives, says midwives are already aware of the importance of talking to women about good nutrition and healthy weight gain.

She says they routinely weigh and measure women on their first visit to establish their BMI, and are likely to take special care with a woman who is obese or morbidly obese. This may include regular weighing and possibly a referral to a dietician.

“We probably wouldn’t regularly weigh a normal-weight woman, but we would be having conversations about nutrition and healthy eating and the importance of not ‘eating for two’.”

This article was first published in the November 3, 2018 issue of the New Zealand Listener.