Declining folic acid supplement use before pregnancy is undermining progress in preventing serious birth defects say leading health experts.
Recent national data for England shows fewer than one in five women are now taking folic acid before pregnancy.
The researchers from the University of Southampton warn that the trend could slow progress in reducing preventable birth defects and increase health inequalities unless action is taken.
The experts are all part of the National Institute for Health and Care Research (NIHR) Inequalities Challenge: Maternity Disparities Consortium.
Their paper has been published today [10 August] in BJOG: An International Journal of Obstetrics and Gynaecology .
Folic acid, a form of vitamin B9, plays a vital role in helping a baby's brain and spinal cord develop during the earliest weeks of pregnancy.
Taking a daily folic acid supplement before pregnancy and during the first 12 weeks of pregnancy can significantly reduce the risk of neural tube defects, including conditions such as spina bifida.
The challenge is that these defects develop before many women realise they are pregnant. Researchers note that although more women are starting folic acid after their pregnancy is confirmed, this is often too late to provide maximum protection because closure of the neural tube is usually complete by the end of the fourth week after conception.
The new BJOG paper highlights new NHS data showing that the proportion of women taking folic acid before pregnancy has fallen from 26% in 2020/21 to below 20% in 2024/25.
The findings come as the UK prepares to introduce mandatory folic acid fortification of non-wholemeal wheat flour from December 2026. While the researchers welcome the move, UK government advice stresses that fortification alone will not provide enough folic acid for everyone and should not replace supplements for women who are planning a pregnancy.
Dr Danielle Schoenaker , an NIHR Advanced Fellow at the University of Southampton and NIHR Biomedical Research Centre: Southampton, was lead author of the commentary.
She said: "Taking folic acid before pregnancy is one of the simplest and most effective steps women can take to support a healthy start for their baby. It is therefore worrying to see the number of women taking supplements before pregnancy continuing to fall.
"Many people do not realise that the baby's brain and spinal cord begin developing very early in pregnancy, often before a pregnancy has been confirmed. This means that waiting until after a positive pregnancy test can be too late to gain the full protective benefits of folic acid.
"The planned fortification of flour is an important and positive development, but it should be seen as part of the solution rather than the complete answer. Women who are planning a pregnancy will still need clear advice and support to take folic acid supplements."
The authors also highlight major differences in folic acid use between different communities and regions of England. Uptake remains lower among women living in more deprived areas and among some ethnic minority groups. While London has seen increasing rates of folic acid use, several other regions have experienced notable declines.
Professor Keith Godfrey , a co-author of the paper from the University of Southampton and NIHR Biomedical Research Centre: Southampton, added: "We need a joined-up approach - this should combine effective fortification at higher levels than mandated in the UK with better education, accessible preconception care and targeted support for communities where supplement use remains low.
"By helping more women to take folic acid before pregnancy, we have an opportunity to reduce preventable health problems and give more children the best possible start in life."
The authors are calling for renewed public health campaigns clearly communicating the benefits, strong rebuttal of misinformation, better preconception care and continued monitoring of folic acid use and birth outcomes. They argue that preventing neural tube defects requires both effective food fortification and continued support for women to take folic acid supplements before pregnancy.
