Regarding Simon Stevens' opinion piece, it is good to see a debate on maternity services in HSJ, writes Karlene Davis

And it is always entertaining to read Mr Stevens' thoughts - or should I say Comrade Stevens, given his previous incarnation as cheese commissar in Guyana!

However, now that he is no longer an adviser at Downing Street and is instead heading up a division of UnitedHealth in the US, I fear he is losing his grip on reality. His portrayal of NHS maternity services planning as being analogous with that of cheese production in Guyana contains more holes than a piece of gruyere.

I can assure Simon that graduate unemployment among student midwives is a reality in many parts of England. This is not the result of Soviet-style central planning leading to a surplus of midwives. Rather, it is because some NHS trusts, particularly those required to squeeze out deficits, have sought to cut costs by employing maternity support workers instead of newly qualified midwives and by cutting existing establishments.

I am not sure where Simon is getting his figures from but, for the record, the number of births in England last year was 635,748 - far higher than the figure he quotes. According to figures published on 23 October by the Office for National Statistics, this will rise to 652,000 in 2006-07 and then to 673,000 by 2009-10. If this official prediction is right, by 2009-10, the number of births in England will have increased by more than 100,000 in less than a decade.

Unfortunately, the recruitment and retention of midwives has not kept pace with the rising birthrate. In 1997, there were the equivalent of 18,053 full-time midwives in the NHS in England. By 2006 this had risen to just 18,862: a rise of just 809 (or 4 per cent) in nine years. In fact, the number of midwives working in England actually fell at the last count - down the equivalent of 87 full-time midwives on the year before.

Perhaps one reason why maternity services are not better staffed is because for too many years planners at the Department of Health have adopted Simon's back-of-the-envelope methodology for calculating staffing numbers.

Simply dividing the number of births by the number of midwives employed is grossly simplistic, ignores the varying degrees of complexity and medical and social need between different births and overlooks the fact that, for most midwives, the majority of their time is spent providing antenatal and postnatal care.

All women in labour require careful monitoring of their physical condition and the process of their labour, accurate assessment of the condition of the fetus and sensitive emotional support. Such aspects of care are regarded as basic for all women. Birthrate Plus is designed to identify and weight these fundamental requirements together with other key indicators of increased needs. Birthrate Plus has been used to assess the midwifery workforce requirements of more than 100 maternity units since 2005, and its recommendations are based on staffing requirements to deliver NICE guidance and a minimum of one-to-one care in labour for all women, plus increased midwife time for women and babies with greater needs because of their medical or social circumstances.

Using Birthrate Plus, the Royal College of Midwives calculates that to provide one-to-one care for every woman during labour and childbirth, England's NHS needs the equivalent of around 24,000 full-time midwives to cope with the current birth rate, rising to more than 25,000 by 2009-10, if the birth rate rises in line with ONS estimates. This equates to a ratio of approximately one full-time midwife for every 28 hospital births and one full-time midwife for every 35 homebirths, including stillbirths and multiple births.

When speaking at a recent NHS Employers conference, Alan Johnson said there was little to disagree about with our assessment. I know the old outriders for Blairism are critical of the health secretary, but I would have thought that even in his base in Minneapolis Simon would have known that having a named midwife for every new mother is current government policy and was in the Labour Party manifesto for the last general election.

While there is much to criticise in Simon's article, I actually agree with most of his conclusions. His call for choice to be extended to include pain relief, delivery method and antenatal care is one that the RCM has no difficulty in supporting. We believe the block contract system has held back innovation and limited choice and that it is right that the money should follow the woman. We have also pressed the government to introduce incentives that would enable midwives to explore new models of service delivery, including midwifery-led care and self-managed group practices.

Dame Karlene Davis DBE is general secretary of the Royal College of Midwives.