The different duration of maternity and paternity leave is not discriminatory.

The TCo rejects that the difference in treatment as regards the duration of maternity and paternity leave and benefits infringes the principle of equality before the law, since they pursue a different purpose: the health of the working woman in one case, and the reconciliation of personal, family and working life in the other.
Mr. Álvarez Peralta, together with the association PPiiNA (platform for equal and non-transferable birth and adoption leave) brought an action for amparo before the Constitutional Court to determine whether the INSS's decision, confirmed in the courts, not to grant him the right to receive paternity benefit after the birth of his child for the same duration as that established for maternity leave violated the right to equality before the law and not to suffer discrimination on grounds of sex (Const art.14). The real issue at stake iswhether the legislation applicable at the time of the causal event (which recognised a duration of paternity leave and the corresponding benefit of 13 days, as opposed to the 16 weeks provided for maternity leave), can be considered to be in accordance with the fundamental right to equality and non-discrimination.
The TCo begins by recalling that the principle of equality does not require equal legal treatment in all cases, regardless of any differentiating element of legal relevance. Not all unequal legal treatment is an infringement of Art. 14 of the Constitution, but only those that introduce a difference between situations that can be considered equal, without there being an objective and reasonable justification for this. It also recalls that for the difference in treatment to be constitutionally lawful, the legal consequences deriving from such a distinction must be proportionate to the aim pursued (TCo 22/1981; 117/1998).
The primary aim pursued by the legislator through the suspension of the maternity contract in the event of childbirth (biological maternity) is the protection of the worker's health without detriment to her employment rights, and the substitution of the worker's income during the period of leave by means of the social security benefit. Paternity leave of 13 days (according to the legislation applicable on the date of the causal event) and the corresponding financial benefit have a different purpose, which is to promote the reconciliation of personal, family and working life by encouraging the co-responsibility of mothers and fathers in the care of children.
The protection of working women's health during and after pregnancy is a requirement of Art.39.2 of the Constitution, imposed by the international commitments assumed by Spain, which oblige it to adopt the necessary measures for pregnant workers to enjoy maternity leave, in order to protect women's health (ILO Convention No. 13 Art.10.2; Directive 92/85/EEC Art.8). However, the establishment of paternity leave has not been imposed to date by any rule of international law binding on our country or by European Union law.
Maternity, and therefore pregnancy and childbirth, are a differentiated biological reality of obligatory protection, derived directly from Article 39.2 of the Constitution, and therefore the advantages or exceptions that it determines for women cannot be considered discriminatory for men (TCo 109/1993). The CJEU has ruled along the same lines (CJEU 19-9-13, C-5/12).
The Constitutional Court therefore dismissed the application for amparo.
Note
The judgement contains a dissenting opinion by Judge María Luisa Balaguer, who considers that the appeal should have been upheld and the legal precepts in question declared unconstitutional, as they imply indirect discrimination against women in access to the labour market and promotion in employment.

Suspension of paternity leave