Maternity leave should be a time of joy, a chance to bond with a new child. It should not be a time when women have to pour over their employee handbooks and legal textbooks, trying to work out what they should or shouldn't be getting.

However, the rules covering non-cash benefits will change this year for pregnant employees with a expected week of 5 October 2008 or later. And what happens to their pension isn't clear at all.

At present the obligation to provide non-cash benefits continues only for the duration of ordinary maternity leave (OML), which is the first 26 weeks. Under the changes, employers' obligations to provide non-cash benefits will extend to cover the entire additional maternity leave (AML) period, the second 26 weeks. This is regardless of any contractual arrangement between employer and employee.

It's clear this covers the ongoing provision of such things as company cars, company mobile phones, living accommodation, a wide range of insurance policies including medical, critical illness and car insurance and will extend to accrued contractual holiday entitlement. What's not so clear is what happens to pension contributions.

The good news is HM Revenue & Customs (HMRC) has published guidelines. The bad news is they might be wrong.

HMRC state "employers need not continue during unpaid AML to make employers' occupational pension contributions or to count unpaid AML as a reckonable service for the purposes of occupational pension contributions". It say employers continue to be required to provide occupational pension contributions during any period of paid maternity absence, and are required to continue pension contributions during OML regardless of whether the employee is in receipt of maternity pay. Advice on the Department for Business, Enterprise and Regulatory Reform (BERR) website appears to be in line with the HMRC guidance.

It states: "The employer need not continue the pension contributions during the unpaid leave unless the contract of employment provides otherwise."

That doesn't seem to reflect the new law, and actually, law and practice may have diverged for a while.

What seems to have happened was this: OML lasts for 26 weeks and AML a further 26 weeks, but statutory maternity pay (SMP) is payable (subject to eligibility) for a 39 week period, which goes part way into AML. Plus, there is nothing to stop employers from being more generous, and many are.

Social security legislation now requires that paid maternity leave has to be pensionable – and that means paid with SMP or through more generous contractual terms. Meanwhile, employment legislation (different subject, different statute) used to require (until the changes flagged at the start of this piece) that there must be no discrimination in respect of benefits, other than pay during OML. These provisions dovetailed neatly when the only period of paid leave was OML, but not since April 2006 when the SMP went up to 39 weeks and thus included 13 weeks of AML.

That means even before these upcoming changes, members should have continued in pensionable service or have been receiving employer contributions during OML and the 13 weeks of paid AML. The new changes will now take away the current difference in treatment of benefits between paid and unpaid maternity leave. The effect is that the entire maternity leave period (52 weeks, OML plus AML) becomes pensionable.

This means the guidance issued might not comply with the law. Non-cash benefits including, on the face of it, pension contributions - appear to extend to the entire AML period. If that's right, the social security legislation on this point is redundant. The fact that a pregnant employee does not qualify for SMP is irrelevant. Pension contributions continue in any event.

Now, HMRC is not daft and it appears to take a different view. Maybe it thinks that a pension contribution is not a 'non-cash benefit'. Whatever, this is crying out for clarification. In the meantime employers might want to hold back making the entire maternity period pensionable. They can always point to guidance from not one but two government departments which suggest that is the right thing to do.

By 2010 it is expected that the entire period of maternity leave will be paid so there is an inevitability about pension contributions being payable in the longer term anyway!

A version of this article first appeared in Pay Magazine, visit http://www.paymagazine.com/ for more details.