SOMETIMES in life, timing is everything. Although not a farmer, I understand the meaning of “closing the barn gate after the horse has bolted”. Among midwives and obstetricians, the equivalent is “starting to take folic acid after the foetus has developed neural tubes”.

The neural tubes are essential to our lives and wellbeing because they are what eventually become, if all goes well, our central nervous system (our brain and spinal cord). If they do not grow normally, the result is spina bifida or other neural tube defects among babies born alive. Neural tube defects (NTDs) can also contribute to miscarriages and stillbirths.

As we know, Zika virus can cause severe microcephaly (babies born with pitiably small heads and brains). Besides spina bifida, neural tube defects include four types of “cephaly”. These are rare, but include the worst one: anencephaly (no or almost no brain).

Read more: Holyrood urged to lead way over birth defect risk by adding folic acid to flour

Here is why timing matters so much. Neural tube development is basically complete before the fifth week of pregnancy; that is, before most women even know they are pregnant. Despite this fixed biological reality, the social reality across Scotland is that many women arrive at first booking (eight to 12 weeks pregnant) enquiring about whether they should start taking folic acid supplements. Barn gates, horses ...

This is not just random medical information. It is an emerging political issue in which knowledge about the timing of neural tube development is crucial. The issue is whether to fortify our grain supply with folic acid. This is a good news, bad news story. The good news is that most neural tube defects are preventable. An adequate level of folates/Vitamin B9/folic acid in a woman’s system before conception has been shown internationally to reduce the incidence of NTDs by up to 72 per cent.

This does not happen overnight. Our bodies do not store Vitamin B9 well, so it can take up to three months of daily folic acid supplements and healthy eating to reach the level at which prevention works. Eating lots more spinach and other folate-rich foods during pregnancy is sound nutritional advice, but it is too little too late to prevent NTDs.

Read more: Holyrood urged to lead way over birth defect risk by adding folic acid to flour

The bad news is that UK-wide strategies for increasing folic acid supplementation are not working equitably. They are based on educating women about the advantages of daily doses of folic acid and then counting on each individual to change her preconception behaviours by buying and taking folic acid supplements every day for months before pregnancy and continuing during the first trimester.

This has resulted in a health inequality gap. Relatively well-educated, well-informed, well-off and well-motivated women follow the advice while their less advantaged sisters often do not. The gap grows between women with well-planned and well-timed pregnancies and the large percentage of women who become pregnant unintentionally or with minimal preparation.

For more than a decade, the UK Food Standards Agency, and its associated scientific panels (and the new Food Standards Scotland) have endorsed the value of fortifying the grain supply with folic acid. This step already has been taken in Canada, Australia and more than 70 other nations. Last year, all four of the UK’s Chief Medical Officers (CMOs) agreed to advocate folate fortification.

Taking this step is a devolved power. Scotland’s CMO, Dr Catherine Calderwood, is an obstetrician who knows this is the right public health action. The benefits of preventing NTDs will be distributed universally across women. Our Minister of Public Health announced her intention for Scotland to act independently without waiting for the other UK nations. Planning is now under way. Our female health leaders should be strongly supported to make prevention real in this tangible way.

Read more: Holyrood urged to lead way over birth defect risk by adding folic acid to flour

There is no serious, evidence-based, scientific case against folate fortification. It is a great opportunity to be the first nation in the UK to leave the starting gate and bolt toward a future of better pregnancy outcomes, delivering social justice among parents and babies less likely to be burdened with birth defects that could have been prevented.

Dr de Caestecker is Public Health Director of NHS Greater Glasgow and Clyde. She was on secondment last year as Deputy Director of the International Federation of Gynecology and Obstetrics.