In vitro fertilization, known as IVF, is a medical procedure in which a woman has an already fertilized egg inserted into her womb to become pregnant.
It is used when couples are unable to conceive naturally, and a sperm and egg are removed from their bodies and combined in a laboratory before the embryo is inserted into the woman.
Once the embryo is in the uterus, the pregnancy should continue as normal.
The procedure can be performed using eggs and sperm from a couple or from donors.
Guidelines from the National Institute for Health and Care Excellence (NICE) recommend that IVF be offered on the NHS to women under the age of 43 who have been trying to conceive through regular unprotected intercourse for two years.
People can also pay for IVF privately, which costs an average of £3,348 for a single cycle, according to figures published in January 2018, and there is no guarantee of success.
The NHS says that success rates for women under 35 are around 29 per cent, with the chance of a successful cycle reducing as they age.
Around eight million babies are believed to have been born due to IVF since the first case, British woman Louise Brown, was born in 1978.
Opportunities for success
The success rate of IVF depends on the age of the woman undergoing treatment, as well as the cause of the infertility (if known).
Younger women are more likely to have a successful pregnancy.
IVF is generally not recommended for women over the age of 42 because the chances of a successful pregnancy are believed to be too low.
Between 2014 and 2016 the percentage of IVF treatments that resulted in a live birth was:
29 percent for women under 35
23 percent for women ages 35 to 37
15 percent for women ages 38 to 39
9 percent for women ages 40 to 42
3 percent for women ages 43 to 44
2 percent for women over 44 years of age
