The court may have quashed a gay Singaporean doctor's bid to adopt his American-born biological son fathered through surrogacy, but the bond between father and child has not been materially affected, said the judge who presided over the case.

Agreeing, family lawyer Yap Teong Lian said that as the boy's biological father, the doctor will still enjoy the traditional rights of parents, such as the right to decide on health, religion and education matters for the child.

Institute of Policy Studies senior research fellow Mathew Mathews added that the failed adoption should not bring about any change to the parent-child bond.

"The child is being raised by his biological father and one can safely assume that he will ensure that the child will be nurtured to the best of his ability," he said.

In judgment grounds released on Tuesday, District Judge Shobha Nair laid out the reasons for denying the adoption application.

The case involved a doctor who travelled to the United States and paid US$200,000 to father a boy through surrogacy arrangements. He returned with the boy, who is now four years old.

The doctor, who has been in a gay relationship for 13 years, then applied to adopt the child.

The judge pointed out that as a doctor, the man was fully aware that Singapore does not condone surrogacy. Also, the use of in-vitro fertilisation (IVF) is confined to married couples, under Singapore law.

Related Story Ruling puts spotlight on gay couples who want to start families

Related Story Gay man fails to adopt child he had via surrogacy

Lawyers pointed out that not being recognised as the legitimate child of the man may lead to some issues down the road, though.

For one thing, the child is not automatically recognised as an heir. This, however, can be resolved with a will. But when it comes to whether the child, who is an American citizen, can remain in Singapore with his Singaporean father, it can get a bit more complicated.

The Immigration and Checkpoints Authority (ICA) said male Singaporeans are generally eligible to sponsor their children for long-term stay in Singapore, including citizenship and permanent residency, "if their children are either born to them within the context of legal marriage, or have been legally adopted by them".

But for couples who do not meet such a requirement, there is great uncertainty over whether the ICA would approve various visas like a dependant's pass or a long-term visit pass for their children, said family lawyer Rajan Chettiar.

Ms Olivia Chiong, an Indonesian permanent resident who married a Singaporean woman in the US, recounted her own experience of visiting the ICA every year to renew one of her biological daughters' Long Term Visit Pass. Her daughter is Indonesian.

Then, there are issues about citizenship and its attendant benefits - such as access to education subsidies, grants and childcare leave.

While adoption does not guarantee citizenship, it makes it easier to secure a child's residential status.

Eversheds Harry Elias lawyer Ivan Cheong, who is one of the lawyers acting for the doctor, said: "Ultimately, it is a pressing and understandable concern of an adoptive single parent that his or her child's residential and legal status in the parent's home country be secure. It is against this that the aim to obtain citizenship for their biological children should be understood."