A Brisbane judge has made what is believed to be a world-first ruling on conception that will have a significant impact on Queensland parents who have children through surrogacy.

The decision, made by Brisbane Children’s Court judge Leanne Clare on Wednesday, ruled conception only occurred when a fertilised egg was implanted in a woman’s womb - that is, the moment of pregnancy - rather than at the moment the egg was fertilised.

The point of conceiving a child is the commencement of the pregnancy, which involves an active process within a woman’s body. 

While the ruling has no impact on birth through natural conception, it has a major impact on surrogate parents and those with children born after in-vitro fertilisation programs.

The ruling will stop disputes in parenting orders when couples seek to have a child through a surrogacy arrangement.

Under Queensland and New South Wales surrogacy legislation, surrogacy arrangements - where the birth mother assigns parenthood to the surrogate parents - must be signed before a child is ''conceived’’.

However, as Judge Clare wrote in her judgement, Queensland surrogacy legislation, under the Surrogacy Act 2010 (Qld), offered no definition of what ''conceived'' meant.

The judge wrote it seemed it was the first time a court had been asked to interpret the word.

''Nonetheless, the answer seems obvious,'' she wrote.

''Whatever approach to statutory interpretation is applied, whether it be to view “conceive” as a technical term, or its everyday meaning, or the meaning that best advances the purposes of the Act, the result is the same.

''The point of conceiving a child is the commencement of the pregnancy, which involves an active process within a woman’s body.''

Before the Brisbane court decision, there has never before been a court ruling - including on IVF procedures - on whether conception was when an egg was fertilised and frozen for later transplant, or when a fertilised egg was placed in a woman’s womb.

If Judge Clare had ruled conception started when an egg was fertilised, it would mean no successful parenting arrangements for surrogacy could be made in Queensland or New South Wales because the arrangements would have been made after conception.

Queensland Family and Surrogacy lawyer Stephen Page - who represented the birth mother in the case - has welcomed the ruling which he describes as an ‘‘important world-first’’.

‘‘There has been a worry from day one, that conception was not defined; therefore there was the potential that they would not get the parentage orders,’’ Mr Page said.

‘‘So this is a world-first ruling; there has been no ruling anywhere in the world on what is conception.''

Mr Page has published Judge Clare’s ruling in this week’s Children’s Court matter on his blog about surrogacy and adoption law.

‘‘I am satisfied that in the ordinary everyday language of the community, the term 'conceive a child' means more than what can be achieved in a test tube and refers to the commencement of a pregnancy in a woman’s body,’’ Judge Clare ruled.

‘‘This is consistent with the current editions of both the Oxford English dictionary and the Macquarie Dictionary.  They define 'conceive' as, inter alia. 'to become pregnant'.''

The Oxford English also defined “conceived”, the adjective, as “brought into embryonic existence in the womb”.

Judge Clare said she had sought medical evidence from obstetricians and a gynaecologist before making her ruling.

In the specific case before the Brisbane Children’s Court that resulted in the ruling, an embryo was created in 2008 but a surrogacy arrangement was not signed until April 2011. Implantation in the womb was in July 2011.

Judge Clare also referred to a doctor’s evidence during the hearing.

‘‘Many eggs fertilise but many fewer pregnancies are conceived,'' the doctor said.

‘‘The act of conception, or the act of conceiving the pregnancy was the actual embryo transfer and the subsequent implantation of that embryo into the uterus of [the birth mother] over the next couple of days with the eventual positive pregnancy test approximately two weeks after July 2011.’’

Mr Page said there were no ‘‘retrospective’' difficulties as a result of the ruling and no changes were needed to Queensland legislation.

‘‘Hopefully it will also have an impact in New South Wales,’’ he said.

Under New South Wales surrogacy legislation, the requirement is for ‘‘a pre-conception’’ surrogacy arrangement.

‘‘But again conception isn’t defined. No doubt judges in New South Wales will be referring to this judgment.’’

In 2010, the then-Queensland attorney general said there had been five court applications to transfer parentage after a surrogacy.