Childbirth is one of the main causes of coccyx (tailbone) pain - see the personal experiences below. As the baby is being born, it may force the coccyx back, damaging the joint. Doctors often tell mothers that their tail bone has been 'fractured' or 'broken', but this is misleading - it is not bone that has broken. The coccyx is normally made up of two or three small solid bones, with rudimentary joints (bits of gristle) in between them, and in between the coccyx and the sacrum. The pressure of the baby passing through the birth canal can break open one of these joints. Afterwards the joint may heal, or it may remain loose, causing pain when it is moved by sitting or getting up from sitting.
Sometimes the mother has a coccyx that is already sharply pointing forwards, maybe caused by an earlier injury. This makes it more likely that giving birth will be painful, and that it will re-injure the coccyx. In very rare cases the pressure from the baby can make the coccyx break through into the rectum - see Hemorrhagic rectal ulcer caused by a deformity of the coccyx complicated by normal delivery. One woman wrote to me that her forward pointing taibone had caused her agony during childbirth, and had actually marked her baby.
Giving birth can, in some cases, also cause other trauma, which may result in fecal incontinence. There is discussion of how this can be treated on a National Institutes of Health website. Post Traumatic Stress Disorder can follow a birth. For more details on this, see The Birth Trauma Association, UK.
Emma - Coccyx dislocated through childbirth, elective C-section for second child
Renee - Injured coccyx during childbirth
Kelli - Had tailbone removed--having some trouble with incision
Donna - Operation turned chronic discomfort into pain - now had coccyx removed
Vicki - Update - Coccydinia from childbirth - is there hope?
Nina - Chiropractic seems to be helping
Gwen - Update - My entire day is spent trying to get some pain relief
Rebecca - Childbirth complications
Melissa - Pregnancy and childbirth led to coccyx pain
Erin - Help for women with coccyx pain from having a baby
Denise - Update - Fractured coccyx during childbirth
Anonymous - Coccyx pain after childbirth
Tamela - Had surgery - tailbone was barely attached
Michelle - Update - Decided to jump right to the surgery
Kate - Tailbone removed 17 years ago - worth it, but pain now getting bad again
Christina - Childbirth and broken tailbone
Anonymous - Update - We all heard my tailbone crack during childbirth
Lisa - No treatment 6 months after childbirth
Kerri Johnson - Tailbone pain after childbirth
Deidre - Fractured coccyx during childbirth
Candy - Coccyx removed 7 years ago - no pain now
Penny H. Craig - Coccyx pain during and after childbirth
Jennifer E First - Success - Almost!
Gill - Coccydynia, childbirth and pain relief
Anonymous - Suffering since birth of 2nd child
Many more personal stories are on Babycenter.com - search on 'tailbone' or 'coccyx'.