In total, 1577 answers were obtained, of which 1393 were considered valid after applying the criteria of inclusion.

Table 1 shows the participants’ sociodemographic data and Table 2 the current level and field of study of the participants.

Most of the participants were aged between 18 and 25 years (61.1%), 68.5%, 45.3% were in no relationship, and only 11.6% had children. More than half were undergraduate students (52.0%), and the most frequent fields of study were Health Sciences (34.2%), Engineering (12.9%), Psychology, Sociology or Philosophy (8.1%), and Basic Sciences (5.1%). Only 0.8% of the participants had donated gametes before, 27.3% of them in a fully anonymous regime.

Regarding their motivations for a potential donation, 82.9% would donate to help heterosexual couples overcome infertility, 55.7% to help same-sex couples to have children, 50.4% to help avoid the transmission of genetic disorders, 46.5% for monetary compensation, and 45.5% to help single people to have children (Table 2).

Students were poorly informed regarding current legislation on gamete donation, 71.1% of the students said they were not informed at all. Regarding the nonidentification of donation in Portugal, 65.8% of the participants do not know whether the procedure was identified or not and only 5.9% thought it was identified. Regarding the gamete donation procedure itself, 71.1% of the students stated that they were not informed at all (Table 3).

Figure 1 shows the opinion of the participants concerning the different regimes of donation.

Participants’ opinion regarding the disclosure of the identity of the three parties (donor, recipients, and offspring) between each other

When asked if recipients should have the right to know the identity of the donor, 49.2% of participants disagreed or strongly disagreed, 25.4% expressed a neutral opinion, and the remaining 25.4% expressed a favorable opinion (Fig. 1). There was a higher percentage of disagreement among students with a partner (53.5%; p < 0.001) and postgraduate education (57%; p < 0.001), but no differences were observed between genders or participants with or without children.

Likewise, if recipients should have the right to choose the donor, 43.7% of the participants had a favorable opinion, 22.6% were neutral, and 33.7% were against it. Only the participants with a partner showed more disagreement concerning this aspect (37%, p = 0.002), with no differences according to the level of studies, sex, or previous children (Fig. 1).

About the offspring, 40.1% were against the offspring having the right to know the identity of the donor and 33.7% were in favor (Fig. 1). On this topic, participants with a partner (44%; p = 0.001), postgraduation (46.8%; < 0.001), and children (51.9%; p = 0.005) showed more disagreement, with no differences regarding gender.

In addition, 42.6% of the participants expressed an opinion against the right of the offspring to know their genetic siblings and 28.4% were of a favorable opinion (Fig. 1). On this matter, opposition was significantly higher in participants with a partner (46.6%, p < 0.001), of postgraduate education (48.9%; p < 0.001), and with children (53.1%; p = 0.017).

Concerning the donors’ right to know the identity of the offspring, 53.7% of the participants were against while 23.4% agreed or strongly agreed (Fig. 1). Again, only participants with a partner (57.9%; p < 0.001) and postgraduate (60.4%; p < 0.001) showed greater disagreement.

In a total nonidentifed regime, most participants (53.2%) considered themselves as likely or very likely to donate gametes, while 25.4% said it is unlikely or very unlikely to donate gametes (Fig. 2). The undergraduate students were slightly more willing to donate under this regime (55.1% would probably or very probably donate, p = 0.048), but no differences were found regarding gender, previous children, or current relationship status.

Likelihood of donation under different anonymity regimes

In case recipients had the right to know the identity of the donor, 54.6% of the participants said it would be unlikely or very unlikely to donate gametes, while 26.1% would likely or very likely donate (Fig. 2). In this case, a higher percentage of unpartnered (30.3%, p = 0.005) and undergraduate education (29.1%, p < 0.001) participants answered it was likely or very likely to donate. No differences were found concerning sex or relationship status.

Likewise, in the event recipients could choose the donors, 42.6% stated that they would unlikely or very unlikely donate, while 35.3% stated that donation was likely or very likely (Fig. 2). There were no differences regarding gender, level of studies, current relationship status, or previous children.

If the offspring could know the identity of the donor, 53.4% of the participants were unlikely or very unlikely to donate gametes while 25.9% were likely or very likely (Fig. 2). Only undergraduate students responded that they would likely donate (29.8%, p < 0.001).

Of those who would probably/very probably donate if gamete donation was completely nonidentified, 48.2% would not donate if the offspring had the right to know the identity of the donor. On the other hand, of those who would probably/very probably donate if the offspring had the right to know the identity of the donor, 15.8% would not donate if the gamete donation was completely nonidentified. Interestingly, however, of those who agree that the offspring should have the right to know the identity of the donor, only 5.7% would donate under those conditions, but 59.7% of them would donate if the donation was completely nonidentified.

Concerning a possible future contact with the offspring, 47.6% of the participants stated that they would be happy or very happy with that, while 13.3% would be unhappy or very unhappy (Fig. 3). A higher percentage of undergraduates assume that they would be happy or very happy in this situation (51.9%, p = 0.003), but there were no differences according to gender, relationship status, or previous children.

Answer to the question “how happy would you be if the offspring contacted you?”