Retrieving about 15 eggs from a woman’s ovaries in a single cycle gives the best chance of having a baby through in-vitro fertilisation, according to researchers.

Investigators led by Arri Coomarasamy of the University of Birmingham in central England looked at data from more than 400,000 IVF cycles in Britain between 1991 and 2008.

Harvesting around 15 eggs in one go gave the best statistical chance of a live birth, they found. This finding is in line with middle-range doses of powerful hormones to stimulate egg production, they found.

The chances of a baby level off between 15 and 20 eggs and then steadily decline beyond 20 eggs.

The success rate for 15 eggs in 2006-2007 was 40 percent among women aged 18-34, 36 per cent for those aged 35-37, 27 per cent for those aged 38-39 and 16 percent for women aged 40 or more.

The findings should be a useful tool for fertility doctors who want to make IVF as efficient as possible, avoid wasting precious eggs and limit the risk of dangerously overstimulating the ovaries, say the authors.

Previous research has looked at the link between egg numbers and pregnancy rates, but this is the first to explore the outcome in terms of live births.