Artificial insemination is a common fertility treatment
Women undergoing fertility treatment with artificial insemination may boost their chances of pregnancy if they lie still afterwards, a study shows.
Researchers found 27% of women who lay down for 15 minutes after the procedure went on to have a baby compared with 17% who got up and moved around.
Writing in the British Medical Journal, the researchers said lying down may prevent "leakage" of sperm.
One UK doctor said fertility clinics should test the findings further.
A total of 390 couples undergoing intrauterine insemination - which involves placing sperm in the womb after stimulation of ovulation or during natural ovulation - were included in the study.
The technique is the main fertility treatment offered to couples before they go on to try IVF, particularly when the cause of infertility is unclear.
In the UK, figures suggest 12% of women under 35 who get the procedure become pregnant at the first cycle, a success rate that increases with repeat attempts.
All the couples in the study were given three cycles of treatment but half of the women were able to move around immediately after the procedure and half were asked to lie still for 15 minutes.
After the first cycle the success rate was 10% in the group asked to stay still followed by a further 10% and 7% in the second and third cycles.
This compared with 7%, 5% and 5% after each cycle in the group who could move around.
Study leader Dr Inge Custers from the Academic Medical Center in Amsterdam said the results had prompted clinics in the Netherlands to rearrange their clinics to allow women to remain laid down for quarter of an hour after their treatment.
"Although immobilisation takes more time and occupies more space in busy rooms, the intervention will be economic in the long run, as pregnant patients will not return in subsequent cycles," she said.
The researchers said they had not expected the results because other studies had shown the sperm reaches the egg within a couple of minutes.
In an accompanying article, Professor William Ledger from the University of Sheffield, said the findings were promising and support the "intuitive idea" that lying with your feet up after insemination allows gravity to give sperm a helping hand.
But he said overall pregnancy rates seen in the study were lower than those seen in many centres who do not use the "immobilisation" technique.
He said a 15 minute delay would affect how many treatments busy clinics can carry out but clinics should test the theory "in the real world".
"If successful, more couples could be spared the rigorous and costly process of IVF," he said.