A complicated vaginal delivery all depends on many things but most of it starts from little interventions or just lack of knowledge on the mother behalf. Things like an assisted delivery by forceps or ventouse or very preventable. The key is KNOWLEDGE!
Here are just a few…..
# Follow Optimal Fetal Positioning during your third trimester to avoid your baby getting in a bad position which can highly effect how the labour can go and sometimes make it a harder labour ending up with forceps or ventouse
# Do NOT push on your back. Being on your back makes your pelvis much smaller and makes the chances of your baby getting stuck much much higher as they will often get stuck behind your coccyx bone. Being upright opens the pelvis right up and it is also easier for you to push and reduce the chances of tearing. Squatting can open up your pelvis by a major 30%
# Have an active birth. This means you do not get confined to the bed with monitored and that you get upright, change positions, walk around, go in the shower, hop in the tub, lean over a birthing ball
# Choose the right OB or even better to choose an independant midwife or care lead by midwives as the lowest rates of intervention happens at home with private midwives and with midwifery-led care, and the highest rates of intervention happen in private hospitals with private Obstetricians. However this is not to say that you can’t have a natural birth in a hospital – you just need to prepare yourself and your support team very well and be prepared to firmly stand your ground.
# Just get knowledge in general. Do your research. The more knowledge you have the more equiped you will be on how to have the best birth possible and how to avoid nasty interventions which you may constantly hear about.

I highly suggest you read
"Ina Mays Guide To Childbirth"

A MUST watch doco is
"The Business of Being Born"

and a great website (even though Australian based) which is full of wonderful information many women do not hear or learn about through their pregnancy….
http://bellybelly.com.au/articles/birth
References :
Have had two drug-free births in hospital which where wonderful, ecstatic unbelievably awesome and would do in a heartbeat and pregnant with my third and about to have a homebirth

A c-section has the risks of cutting into the bladder as well as the intestines. The mother could be very allergic to some of the medications that they give to you during the surgery, the baby could be allergic to some of the medications. You have a WAY longer recovery time….most people think that a c-section heals within a couple of weeks….in some cases, yes that is true, in other cases though many women end up with infections or other complications and it actually takes MONTHS to heal.

After a vaginal birth you are more then likely able to leave in a day or two, able to eat as soon after you give birth as you want, you have a shorter recovery time, plus the biggest benefit I believe that a vaginal birth can give you that a c-section can not is that fact that you have the bonding time through giving birth then assuming everything is fine with the baby after birth you have that chance of holding your baby right after giving birth. After a c-section you have to wait a while before you can hold your little one, and those first few minutes is more crucial for bonding then any other time in the baby’s and your life!!
References :

I have had two c-sections. My second child I laboured for 24 hrs and would not progress past 8 cm. So I ended up having an emergency c-section.

I would go through that labour over and over if I did not have to have another c-section.

C-sections permanently change your body. It causes problems with pregnancys afterwards.

Our bodies were meant to and built to have vaginal deliverys. C-sections are becoming an unhealthy fad. I would much rather risk having some pee leak out than having to have my stomach and uterus cut open again.

Good Luck with your decision.

P.S. Going through a vaginal delivery will make you feel like such a powerful woman to have gone through all that pain and made it. Also I would rather go through HOURS of pain of labour than deal with the pain of a c-section afterwards while trying to care for a newborn.
References :

Physical problems in mothers: Compared with vaginal birth, cesarean section increases a woman’s risk for a number of physical problems. These range from less common but potentially life-threatening problems, including hemorrhage (severe bleeding), blood clots, and bowel obstruction, to much more common concerns such as longer-lasting and more severe pain and infection. Even after recovery from surgery, scarring and adhesion tissue increase risk for ongoing pelvic pain and for twisted bowel.

Hospitalization of mothers: If a woman has a cesarean, she is more likely to stay in the hospital longer and is at greater risk of being re-hospitalized.

Emotional well-being of mothers: A woman who has a cesarean section may be at greater risk for poorer overall mental health and some emotional problems. She is also more likely to rate her birth experience poorer than a woman who has had a vaginal birth.

Early contact with, feelings toward babies: A woman who has a cesarean usually has less early contact with her baby and is more likely to have initial negative feelings about her baby.

Breastfeeding: Recovery from surgery poses challenges for getting breastfeeding under way, and a baby who was born by cesarean is less likely to be breastfed and get the benefits of breastfeeding.

Health of babies: Babies born by cesarean are more likely to:
be cut during the surgery (usually minor)
have breathing difficulties around the time of birth
experience asthma in childhood and in adulthood.

Future reproductive problems for mothers: A cesarean section in this pregnancy puts a woman at risk for future reproductive problems in comparison with a woman who has a vaginal birth. These problems may involve serious complications and medical emergencies. The likelihood of experiencing some of these conditions goes up sharply as the number of previous cesareans increases. These problems include:
ectopic pregnancy: pregnancies that develop outside her uterus or within the scar
reduced fertility, due to either less ability to become pregnant again or less desire to do so
placenta previa: the placenta attaches near or over the opening to her cervix
placenta accreta: the placenta grows through the lining of the uterus and into or through the muscle of the uterus
placental abruption: the placenta detaches from the uterus before the baby is born
rupture of the uterus: the uterine scar gives way during pregnancy or labor.

Concerns about babies in future pregnancies: A cesarean section in this pregnancy can affect the babies of future pregnancies. Studies have found that they are more likely to:
be born too early (preterm)
weigh less than they should (low birthweight)
have a physical abnormality or injury to their brain or spinal cord
die before or shortly after the birth

ADDITIONAL: Just check out the website below and you will see the cons for vaginal birth vs c-section.
33 cons for c-section 4 cons for vaginal birth…..big difference!

Its totally your choice obviously but I just wanted you to know the risks because doctors these days give out c-sections like they were lollipops. I have had to go through 2 emergency c-sections and it was so traumatic. I didnt get to see my baby till the next day because he had breathing problems and after I had infections and healing was long and painful. Years after I am still having abdominal pain from adhesions. I am trying to go VBAC at the moment but not a lot of doctors will do it. So to have that option is a blessing trust me!
References :
http://www.childbirthconnection.org/article.asp?ck=10166