Belinda Slaughter, now 47, gave birth to her first child in September, her doctor, Mark Trolice of Winter Park, said in an interview on Tuesday.
Key to the record is that the eggs were fresh, just a few days old, rather than frozen or donated.
Slaughter, who named the boy Jackson, also beat the odds of delivering a child with chromosomal abnormalities, such as Down Syndrome, which increase with maternal age.
"She had a guardian angel watching over this pregnancy from the get-go," Trolice said.
The case should be considered an anomaly, said Stan Williams, chairman of the department of obstetrics and gynaecology at the University of Florida's medical school, in Gainesville.
Williams said the university's in-vitro programme does not accept women over 43, because the low probability of success, and medical and financial risks exceed potential benefits. Slaughter had been turned away by another clinic, Trolice said.
"I'm hoping that women in their mid-40s aren't going to look at this and say 'Oh, I can do that too.' Being a world's record, people need to understand this is a very rare event," Williams said.
Trolice said Slaughter's success at least rivals and might exceed that of a woman in Italy who gave birth several years ago, also at around age 46. Her doctor reported the feat but not the woman's precise age at conception and birth - details needed to determine which woman was oldest.
Trolice said the birth reflects the continued improvement of in-vitro pregnancy rates since the first such successful birth in 1978 but agreed it should not provide false hope to women over 45.
In rare cases, women in their 60s have been known to give birth via in-vitro fertilisation using donated eggs.
The news was first reported in the May issue of the Fertility and Sterility, a journal of the American Society for Reproductive Medicine.
© Thomson Reuters 2014