Do you mean that own birth gave PTSD or that giving birth when previously traumatized reawakes PTSD? See: http://en.wikipedia.org/wiki/Childbirth-related_posttraumatic_stress_disorder
Yóu can also reactivate PTSD due to other traumas not related to delivery but the delivery causes a lot of e.g. nigthmares, flashbacks, difficulties to see deliveries on TV and so forth
If the delivery was traumatic or was perceived as traumatic, yes, there is a relationship. Here is also a link to an article about people who have been in Intensive Care Unity and who developed later PTSD.
I use a technique for resolving PTSD in a single untimed session. A pilot project saw six women traumatised by childbirth resolve their symptoms. At the conclusion of the pilot four of the women had traced their recent childbirth trauma to early traumatic incidents that they had forgotten or repressed. It appears that in some cases childbirth could be the latest, rather than the only, trigger for a traumatic reaction.