Expert: Catherine Beier MS CBE - 2/20/2008

Question
Hi,
I'm due March 20th and i will be 36 weeks tomorrow my doctor told
me last week i was 1cm dilated and the week before that my baby is at
least 6lbs (i also have gestational diabetes) in the last 4-6 days I've
been feeling alot of pressure way more then i have ever it almost hurts to walk sometime and they also told me i was having contractions last week & today @ the doctors but i didn't feel them last week but now this week i can so my question is
could labor be around the corner is there any way i can tell? and since my baby is bigger then
normal and i have gestational diabetes is it safe to go beyond the 40 weeks?

cant wait to hear your response
thanks
-Paige :)"


Answer
Paige,

The contractions, cervical changes, and increased pressure are all signs that things are moving in the right direction.  However, there is simply no way to tell when "the" day will be.  It could be tomorrow or another 5 weeks from now.  

You didn't specify whether you had an ultrasound to estimate fetal weight or whether the doctor gave you an estimate after examining your fundal height and feeling the baby.  In either case, take the estimate of 6lbs, even with gestational diabetes, with a fistful of salt.

Late term ultrasound is notoriously inaccurate at predicting fetal weight.  It has an error of measure of +/- 2 pounds.  This means that the baby could weigh as much as 8lbs or as little as 4lbs.  

A baby's weight alone has little to do with it's ability to fit through a woman's pelvis.  Head circumference, shoulder width, the mother's position during labor, and the baby's positioning are the biggest factors in whether or not it will fit.  A baby with a very long, thin frame and small head might weigh 10lbs and be born effortlessly, where a 6lb baby might be very stocky with a large head and wide shoulders and be hard to birth.

Weight alone is not a reason to induce labor early.  Fetal macrosomia (a "big baby") by itself is not considered a valid reason for induction by the American College of Obstetricians and Gynecologists (ACOG).  

In terms of gestational diabetes, when your sugars are well-controlled, there is not an immediate indication to induce labor early.  The average length of a first pregnancy worldwide is 41.1 weeks.  Research does not show that risks increase until the pregnancy goes over 42 weeks.  After 42 weeks, the placenta can start to calcify, which means that its function begins to decline and the baby starts to receive less nutrients.

However, placental calcification is a more common risk factor of gestational diabetes.  Fortunately, there are relatively easy and noninvasive ways to assess the condition of the placenta should you not go into labor by 40 weeks.  Most doctors will perform a weekly Biophysical Profile or BPP, which consists of a non-stress test and an ultrasound that will check such factors as the baby's heart rate, respirations, movement, placental function and level of amniotic fluid to ensure that the baby is still developing well.

For mothers with gestational diabetes, many doctors will start these each week after 38 weeks since the risk of placental deterioration can be greater if sugars are not well-controlled.  As long as the baby passes the BPP, you should be able to safely wait for labor to start on its own.

So, you may be in labor in just a few days or still have a few weeks to go.  In either case, remember that although the final days of pregnancy may be uncomfortable, it will all be forgotten when you look into that little face.

Best,
Catherine