The Equality Act 2010 protects women from discrimination “because of the pregnancy”, or because of illness suffered by her as a result of the pregnancy. In employment cases, the relevant section is Section 18. The core protection is against being treated “unfavourably”. It needs to be read in conjunction with Section 39.
Discrimination because of pregnancy is, by all reports, widespread. A recent Equality and Human Rights Commission stated that around one in nine mothers felt that they were either dismissed, made compulsorily redundant (where others in their workplace were not), or treated so poorly that they had to leave their job. Scaled up, that would amount to around 54,000 mothers per year. The link to the reports (both the full report and the summary of key findings) is here.
The Equality Act 2010 refers to “employees”, but “employment” in the Equality Act 2010 has a much wider meaning than “employment” for the purposes of unfair dismissal claims. The key section of the Equality Act 2010 is Section 83. We know from case law (Pimlico Plumbers and anor v Smith  UKSC 29 and Clyde & Co LLP and anor v Bates van Winkelhof  UKSC 32) that “employee” in the Equality Act covers “workers” within the meaning of s 230(3) Employment Rights Act 1996.
That has important consequences for “zero-hours” workers. A “zero-hours” contract is one where the worker does not have an obligation to accept work, and the employer does not have an obligation to provide work. As a result, the worker will generally not be an employee (in the unfair dismissal sense), but is still protected by discrimination law (although Tribunals have sometimes found that the worker is an employee when they are actually at work, although not a worker in between periods of work).
So a worker on a zero-hours contract still has rights, and those rights include the right not to be discriminated against because of pregnancy. That is an important point, because zero-hours contracts may be particularly attractive to expectant mothers who want flexible working arrangements. Employers may be concerned that expectant mothers will require restricted duties, and this will place a financial burden on the business. Can the employer then rely on the fact that the contract is a “zero-hours” contract, and simply choose not to offer work?
The short answer is “no”. Under s 18 of the 2010 Act, the woman is protected against unfavourable treatment. Unfavourable treatment is essentially the same as “detriment”, and the threshold is “relatively low” (Trustees of Swansea University Pension and Assurance Scheme and anor v Williams  UKSC 65, para 27). The test is whether the treatment is “of such a kind that a reasonable worker would or might take the view that in all the circumstances it was to his [or her] detriment” (Shamoon v Chief Constable of the Royal Ulster Constabulary  UKHL 11). If there is a legitimate expectation of work, then it is very likely that a failure to offer work would constitute unfavourable treatment. That is the first ingredient of a claim under Section 18 of the 2010 Act.
Furthermore, the test for whether the treatment is “because of” pregnancy is relatively easy to meet. It is sufficient that the protected characteristic (here, pregnancy) has a “significant influence” on the reason why: Nagarajan v London Regional Transport  IRLR 572. Moreover, the treatment will still be “because of pregnancy” if the reason is the economic consequences for the employer of employing a pregnant woman (Dekker v VJV Centrum C-177/88) or the health and safety implications of pregnancy, including a prohibition on performing certain work (Bush v Klinikum Neustadt Gmbh and Co Betriebs-KG C-320/01).
Furthermore, unfavourable treatment of a woman because of pregnancy is direct discrimination (in European terms), and so cannot be justified: see Webb v EMO Air Cargo (UK) Ltd C-32/93.
It follows that economic loss or disruption to work caused by pregnancy or absence because of pregnancy-related illness or maternity leave cannot negate pregnancy or maternity discrimination (see, for example, Tele Danmark A/S v Handels- og Kontorfunktionaerernes Forbund i Danmark (C109/00)  E.C.R. I-6993 at para 23; “…the employer has to assume the risk of the economic and organisational consequences of the pregnancy of employees”).
So, if a worker on a zero-hours contract becomes pregnant, and as a result would need to go onto restricted duties (suppose, for instance, that the work has a substantial manual handling component), the employer cannot simply decide not to offer work. To do so would (very likely) constitute unlawful discrimination, and the worker could (in principle) claim for injury to feelings as well as for lost earnings.
If the employer’s concerns are health and safety concerns, then there is a potential statutory defence in Schedule 22 to the 2010 Act. It is not a particularly transparent piece of legislation. But the Explanatory Notes to Schedule 22 make it clear that Schedule 22 permits differential treatment based on sex or pregnancy and maternity at work which is required to comply with laws protecting women who are pregnant, who have recently given birth, or against risks specific to women.
One potentially relevant piece of legislation is the Management of Health and Safety at Work Regulations 1999, which require employers to carry out risk assessments (Regulation 3) and to carry out specific assessments where the workers include women of child-bearing age, if the work might be risky to the health and safety of a new or expectant mother (Regulation 16). If the risk assessment highlights a risk, then the employer is (as always) required to take steps to avoid that risk.
If those steps won’t avoid the risk, then the employer shall (if it is reasonable to do so, and would avoid the risk) alter the woman’s working conditions or hours of work. And it isn’t reasonable to do that, or if altering working conditions or hours won’t remove the risk, then the employer shall suspend the employee from work – subject to Section 67 Employment Rights Act 1996, which gives the employee the right to be offered to be provided with suitable alternative work (if it is available). Refusing suitable alternative work may mean that the employer can refuse to provide paid suspension.
Where employees (in the Employment Rights Act 1996 sense) are involved, it is clear that the suspension must be on full pay if the suspension is on maternity grounds (Section 68 of the 1996 Act). The 1996 Act is also clear that the employee is to be regarded as suspended from work on maternity grounds only if and so long as she continues to be employed, but is not provided with work or does not perform the work she normally performed before the suspension (Section 66 of the 1996 Act). The Explanatory Notes (see above), I think, make the answer clear – giving the example of a care home which cannot lawfully dismiss, but can lawfully suspend, a night-shift worker because she is pregnant. Regulation 16 MHSWR 1999 implements the Pregnant Workers Directive (Directive 92/85), which addresses “workers”. A failure to carry out a risk assessment will (if the employer is notified of the pregnancy) amount to a detriment: Hardman v Mallon t/a Orchard Lodge Nursing Home  CMLR 59. So the protection offered by Regulation 16 must cover “workers” (in the extended sense) as well as “employees” (in the narrow sense). If suspension is the only option, it is hard to see how a failure to offer paid suspension, following a Regulation 16 risk assessment, could amount to anything other than unfavourable treatment within the meaning of Section 18 Equality Act 2010.
There is also an “occupational requirement” exception in Schedule 9 to the 2010 Act (which is specifically provided for by Article 14(2) of the Recast Equal Treatment Directive). The Explanatory Notes to Schedule 9 give the example of a modelling job which requires someone of a particular race, age or sex. But that “occupational requirement” must be crucial to the post, and not merely an important factor; and the application of that requirement must be proportionate so as to achieve a legitimate aim.
To recap: a pregnant worker on a zero-hours contract is still entitled to ask for work. If there is a legitimate expectation of work – and this does not require a contractual entitlement to work – then it will very likely be unfavourable treatment not to offer the employee work. If a reasonable worker might take the view that it is a detriment, then the threshold for “unfavourable treatment” is met.
If the consequence is that the employer is put to additional cost, then so be it. The law is clear that the employer, not the pregnant worker, is to bear the economic consequences of pregnancy.