http://www.nhs.uk/chq/Pages/1645.aspx?CategoryID=60
So Does having an abortion really significantly decreases fertility rates?
The claim does appear to be correct though "significantly" would only be in the statistical sense, ie it does and it's real but the effect is small.
Does having an abortion first time you are pregnant decreases fertility rates?
I can find no data on this specific claim.
In the UK, most women who have an abortion don’t have any
complications and their fertility isn’t affected.
However, a small number of women (see below) have complications, such
as:
- a severe infection, such as pelvic inflammatory disease (PID)
- damage to the womb (uterus)
Complications such as these can affect fertility. Also, repeated
abortions can cause damage to your cervix and increase the risk of
late miscarriages. Infection after an abortion
Taking antibiotics before an abortion may reduce your risk of
infection. The healthcare professionals treating you will provide
advice about taking antibiotics.
Most infections are easy to treat. However, an infection, such as PID,
that’s not treated could lead to a more severe infection of your
reproductive organs. This can cause infertility or an ectopic
pregnancy (when a fertilised egg implants itself outside the womb).
Damage to the womb during an abortion
The risk of damage to the womb during an abortion is low in the UK:
- damage to the cervix (the neck of the womb) occurs in less than 10 in
every 1,000 abortions
- damage to the womb occurs in less than one in 1,000 medical abortions
carried out at 12-24 weeks, and up to four in every 1,000
surgical abortions
A medical abortion involves taking medication that causes you to have
a miscarriage. A surgical abortion is a procedure to remove the foetus
from the womb. Read information about how abortions are performed.
Damage to the cervix can make it weaker. If the cervix can’t stay
tightly closed in a future pregnancy (cervical incompetence), this can
increase the risk of miscarriage. However, cervical incompetence can
be treated with an operation to put a small stitch of strong thread
around your cervix to keep it closed.