The Causes of Placenta Previa

Yesterday, after my Level 2 ultrasound, conducted at 21 weeks of pregnancy, my doctor gave me the following directives because I am suffering from placenta previa, a condition in which the placenta covers the cervix, the baby’s exit from the uterus:

  • Lots of extra rest
  • No lifting
  • No intercourse

I know that my uterine abnormality, initially a T-shaped uterus now stretched by my previous full-term pregnancy into a slightly larger arcuate uterus, is the reason I battled infertility. 

I know that my uterine abnormality and a prior surgery to remove precancerous cells from my cervix are the causes of my cervical incompetence during pregnancy. 

I know diethylstilbestrol (DES), the useless synthetic estrogen given to my mother when she was pregnant with me, is the reason my uterus never fully formed—and is therefore deformed. 

I know the sexually transmitted Human Papilloma Virus (HPV) is the reason I had precancerous cervical tissue, hence the reason part of my cervix is missing in action.

But, I had no idea why I am currently experiencing placenta previa, yet another complication in my already high-risk pregnancy.  Being an information junkie, I’ve looked it up.

You and Your Baby: Pregnancy by Dr. Laura Riley, OB/GYN (Meredith Books, 2006), the book given to me by my high-risk pregnancy practice, states that placenta previa “happens in about 1 in 200 pregnancies.  You’re more at risk if you’re older, if you’ve had several babies, if you’ve had a prior birth by cesarean, or if you smoke cigarettes.” 

What to Expect When You’re Expecting by Heidi Murkoff, Arlene Eisenberg and Sandee Hathaway, B.S.N (Workman Publishing, 2002) gives the following explanation for placenta previa in its “When There’s a Problem” chapter:

“The risk of having placenta previa is higher in women who have scarring of the uterine wall from cesareans, uterine surgery, or D & Cs following miscarriage.  The need for greater placental surface area due to an increased need for oxygen or nutrients on behalf of the fetus (because of smoking, living at a high altitude, or carrying more than one fetus) may also increase the risk of placenta previa.

In Your Pregnancy Week by Week by Dr. Glade B. Curtis, OB/GYN, and Judith Schuler, M.S. (Da Capo Press, 2004), the authors state the following:

“Placenta previa also occurs more frequently among smokers.  The rate of occurrence increases by 25% in moderate smokers and 90% in heavy smokers.”

and

“This problem is not common; it happens about once in every 170 pregnancies. …  The cause of placenta previa is not completely understood.  Risk factors for an increased chance of placenta previa include previous Cesarean delivery, many previous pregnancies and increased maternal age.”

Older?  Increased maternal age?  Yes.  Advanced maternal age starts at 35, and I’m 41.

Several babies?  No.  I’ve had only one.

Many previous pregnancies?  Yes, but except for my pregnancy with my 4-year-old son and my currrent pregnancy, I’ve only had a prior pregnancy last until the 6th week.

Birth by cesarean?  None.

Scarring of the uterine wall from cesareans, uterine surgery, or D & Cs following miscarriage?  I’ve had none of these three procedures.

Smoker?  I’ve never smoked cigarettes.

Living at a high altitude?  Nope.  I live in a Chicago suburb.

Carrying more than one fetus?  I was carrying twin boys, one of whom passed away during the 8th week of pregnancy, then was absorbed by my body, making him a “vanishing twin.”  His gestational sac was at the top of my uterus, with my surviving baby’s at the bottom.

So, based on these three pregnancy books, I can conclude that I am one of .005% of pregnant women to have placenta previa because of my age and/or because I was originally carrying twins. 

Of course, I wonder if my DES-induced uterine abnormality is also a cause.  My uterus is one-third normal size, so it contains less surface area for implantation as it is.  Then, during my second attempt at in vitro fertilization (IVF), I became miraculously pregnant with not one, but two, embryos, both of whom had to fight to implant, with one going high and one going low.

Normal Uterus vs My T-shaped Uterus

The fact that I am one of .001% of women to have a congenital uterine abnormality has to be a factor…  How could it not be? 

I am so sick of the havoc and horrors DES continues to wreak on my life—and the life of yet-another of my unborn children.

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