Women with a suspected ectopic pregnancy should be seen by specialists as quickly as possible, NHS officials have urged.
Ectopic pregnancies can lead to serious complications and even death, they warned.
The National Institute of Health and Care Excellence (NICE) said that it is important that these women, and those with suspected miscarriages, should be seen promptly to ensure they receive the best care.
Ectopic pregnancies happen when the embryo implants itself outside the womb - often in the fallopian tube.
NICE said that the condition is difficult to spot but encouraged quick diagnoses which could potentially improve care and even save lives.
If ectopic pregnancy goes undiagnosed it can cause serious problems, such as the bursting of the fallopian tube, and it can also be fatal.
Between 2006 and 2008 more than 35,000 women in the UK were diagnosed with an ectopic pregnancy, figures show.
Six of them died and poor care was linked to four of the deaths.
In its new quality standard, NICE called for women with a suspected ectopic pregnancy or those believed to have suffered a miscarriage to be seen by a pregnancy assessment service within 24 hours of seeing their GP.
But it cautioned that some women should be sent straight to A&E.
Professor Gillian Leng, director of health and social care at NICE, said: “To think that you might be losing your baby, either through miscarriage or ectopic pregnancy, is terrifying. It can have a significant impact on the health and wellbeing of the woman and her family.
“It’s important that these women are seen as soon as possible - a long delay could have a potentially devastating effect. It’s something we originally recommended in 2012 and have identified as a key area still in need of improvement.”