Men, if you're wondering whether the lady of your dreams wants a big family, the answer could be staring you in the face.
Women with feminine looks are more likely to long for lots of children, according to research - and the softer their features, the bigger a brood they have in mind.
The study suggests that men desperate to be dads should seek women with button noses, large eyes and full lips, as they are likely to want at least four children.
But those less keen on fatherhood would be better setting their sights on less delicate sorts, who may only be interested in having one child.
The St Andrews University scientists believe their finding can be explained by the female sex hormone oestrogen, with high levels making features softer and nurturing the maternal instinct.
The discovery of a link between broodiness and delicate looks could explain the maternal instincts of Hollywood beauty Angelina Jolie, who has adopted three children and had three of her own.
Jools Oliver, a former model, has a family of four with her chef husband Jamie, while actress Reese Witherspoon had two children by the age of 27.
The researchers asked 25 young women how many children they wanted and when they would like to have them, and measured their oestrogen levels.
Miriam Law Smith of St Andrews University's Perception Lab, which specialises in face research, said: "The more oestrogen they had, the more children they wanted. We were surprised to find such a strong result."
Oestrogen levels were not found to be linked to the age at which a woman wanted to start her family but the researchers believe this could be because, as university students, the women were more focused on careers than average.
In a second experiment, a different group of young women had their photos taken and were asked about their desire for children.
Dr Law Smith then created a composite image of the faces of the women with the strongest maternal instinct, and another based on the women who were least interested in having a family.
The face made up of the features of the most maternal women was judged as more feminine by a group of male and female volunteers.
On average, the most maternal women wanted 4.3 children - almost three more than those judged to be the least feminine, the journal Hormones and Behavior reports.
However, the study found facial features only account for about 20 per cent of a woman's family plans. Social factors, including upbringing and money, make up the rest.
- DAILY MAIL