The episode damages the reputation of in-vitro fertilisation (IVF), which has enabled millions to know the joy of parenthood, they said.
"It's the kind of tale which makes headlines around the world and skews the image of our field," said Francoise Shenfield, a specialist in reproductive medicine and bioethics at University College London.
The controversy swirls around Annegret Raunigk, a Berlin teacher near retirement age who is the oldest woman to have given birth to quadruplets.
The babies weighed between 655 and 960 grams (1.4 to 2.1 pounds) at birth, have since gained between 30 and 50 per cent in weight "and are developing well", Berlin's Charite Hospital said today.
One is on respiratory assistance and the others "require milder aids for breathing", it added, but medical confidentiality barred it from saying more.
One baby required surgery for an intestinal problem, doctors said last month.
Specialists interviewed at the annual conference of the European Society of Human Reproduction and Embryology (ESHRE), closing in Lisbon Wednesday, highlighted ethical concerns about the mother's age and risks for the babies.
A general age limit for IVF is about 50, close to the typical onset of menopause, the experts said.
Women in Germany today live to around 85, "so you could argue that a 65-year-old's got 20 years and could see that child through to adult life," said Adam Balen, a professor of reproductive medicine and chairman of the British Fertility Society.
A much bigger concern, he said, was that the clinic had implanted numerous embryos to boost chances of a live birth.
"Multiple pregnancies are dangerous. They're dangerous for the mother, but they're more dangerous for the babies," said Balen.
The evidence shows that babies born from such multiple transplants generally enter the world with lower birthweight and higher risk of ill health and cognitive difficulties.