Epidurals and Due Dates

I love my readers' questions.


It's reader-question day. Patricia is six months pregnant with her first baby and has three great ones that a lot of women ask:

Does an epidural slow down labor? Does epidural medication reach the baby? I have a hunch I'm going to delivery early. Why doesn't my doctor agree?

Can an epidural slow down labor? Yes and no. Epidural medications themselves don't slow labor down, but the IV fluids we pre-load you with before you get an epidural can dilute the contraction-causing hormones circulating in your blood stream temporarily. That's why it's not uncommon for your contractions to space out a bit after an epidural. Pre-loading with a liter or two of IV fluid is mandatory, but usually, your body eliminates the extra fluid and picks up the contraction pace again within a couple hours after your epidural is placed. Sometimes, it doesn't though and contractions piddle out. Then, your doctor/midwife might recommend starting Pitocin (the synthetic hormone used for induction and augmentation of labor) to move things along.

The other reason why epidurals inadvertently slow things down is they're frequently given too early in labor when patients should be still up and moving. Even though we know contractions sometimes hurt like the dickens at three centimeters dilation, that's still not technically active labor. When patients get epidurals too early, it knocks out their ability to use gravity and movement to keep labor progressing. If she doesn't mind that she might need Pitocin after her epidural (and increase her chances for a dysfunctional labor), that's cool. Otherwise, wait it out a bit. Use other pain management techniques like a hot bath or change of position; massage, patterned breathing, meditation and even a little IV pain medication if necessary. It's not the magic pain-relief bullet that an epidural provides, but these techniques work for lots of women.

Does epidural medication reach the baby? No, because the pain-relieving medication goes into the space around your spinal cord, not into your bloodstream. IV pain medications, like morphine or Fentanyl, do reach the baby because they travel into your bloodstream and through the placenta into baby's blood stream. Baby doesn't get the full dose you get because your body absorbs most of it before it reaches him. Still, baby gets a dose. That's why we won't give patients IV medication if we think baby might be born within an hour or two.

IV medications work fast and wear off relatively quickly, but if baby is born with too much narcotic on board, he might be too sleepy to bother breathing. We can counter act that with a narcotic antagonist medication (same stuff used for drug overdoses in the ER), but who wants to do that if we don't have to.

Sometimes epidurals drop Mom's blood pressure by dilating her blood vessels. If Mom's BP goes down, baby's will too and his heart rate will slow. That's why we pre-load Mom with lots of IV fluids before an epidural. That usually prevents her BP from bottoming out, but sometimes it happens anyway no matter how much fluid we give her beforehand. We deal with that by pumping in more IV fluid and sometimes give medications that temporarily increase BP. It sounds complicated and it's not ideal, but it's not uncommon and we know how to handle it.

Now about Patricia's hunch she'll deliver before her due date. Part of her "hunch" is based on her ultrasound, which gave her an earlier due date (by a few days) than her doctor gave based on her last menstrual period.

First trimester ultrasounds are fairly accurate for establishing due dates, though a good solid date for the first day of a last menstrual period is better. Ultrasounds done before 20-weeks gestation have a 7-day variation (meaning the due date they give might be off by as much as a week earlier or later). Between 20 and 30 weeks – they can be off by as much as 14 days (two weeks before or after the day they say your baby is due). After 30 weeks – they can be 21 days (or 3 weeks) off. That's why Patricia's doctor didn't think her ultrasound-based due date mattered much. That's also why you should never schedule an induction based on a due dates provided solely by a third-trimester ultrasound. It could mean your baby delivers prematurely.

The "hunch" part of Patricia's feeling that she'll deliver before her due date is unfortunately all too common and not much to bank on. It's hard for most women to believe they'll be pregnant the whole, darn time. They're so big and uncomfortable already, it's inconceivable, unfathomable; simply unbelievable that it could go on for 40 - 42 weeks. Seriously! Who can be pregnant that long? Sorry, sweetie – you can.

I've said it before; I think the whole reason why we're pregnant as long as we are is so labor seems like a good idea. For most of us, being pregnant is all well and good, warm and fuzzy, a soft focus kind of thing, up until the last month. Then, we're willing to do anything, even labor, to be done with it already. Good luck Patricia and keep those questions coming.

Jeanne Faulkner, R.N., lives in Portland, Oregon with her husband and five children. Got a question for Jeanne? E-mail it to jeanne@jeannefaulkner.com.

This Fit Pregnancy blog is intended for educational purposes only. It is not intended to replace medical advice from your physician. Before initiating any exercise program, diet or treatment provided by Fit Pregnancy, you should seek medical advice from your primary caregiver.