The long anticipated day has arrived….but the baby hasn’t.
What happens when a pregnancy continues after the due date?
Practitioners use pregnancy dating to help track milestones
during a pregnancy. It’s important to have as accurate a “due date” as
possible, however this is sometimes easier said than done. Pregnancy due dates
are calculated in several different ways. A normal, healthy pregnancy is
expected to last 266 days from the day of fertilization. Most women are not
certain of their day of ovulation, but most women can remember the first day of
their last normal menstrual period, so this date is the most commonly used date
to determine a due date1. The Estimated
Date of Delivery, or “due date” is just an estimate. Only 3% of babies are actually
born on this date. A normal, healthy pregnancy is considered full term at 37 –
42 completed weeks.
Another way of determining the due date is through an
ultrasound. Early (first trimester) ultrasounds are very accurate – to within
2-3 days. Later ultrasounds (second and third trimester) are only accurate
within two weeks – not very helpful when determining a due date.
So, you have an estimated due date that has been confirmed by
early ultrasound and now you hit 40 weeks and there are no signs of labor, what
happens? Your midwife will probably ask your permission to perform a pelvic
exam to check to see what progress your cervix has made toward labor
preparation. The changes in the cervix give us information on the readiness of
the cervix. The more ready the cervix, the higher the Bishop’s Score. While not
usually a suggested source for accurate medical information, there is a good
entry on Bishop’s Score at this site http://en.wikipedia.org/wiki/Bishop_score.
At 40 weeks in a first time mother, we are not overly
concerned if there are not many changes in the cervix yet however, I like to
perform a Biophysical Profile2 to ensure that the baby is doing
well, the amniotic fluid volume is adequate and to have a good baseline in case
further evaluation is needed later on.
By 41 weeks, in my practice, I like to see something going
on. The cervix should be a little softer and a little more flexible. I would
really like to see some dilation as well. At this point I like to start a
natural encouragement of labor. I prefer to start off with gentle, natural
methods that can help nudge the body into going into labor on its own. Our
practice does not use any methods that will force a body into labor. We use
gentle methods only.
Somewhere between 41 and 42 weeks I like to see the body
going into labor. A pregnancy that does not have any complications such as
preeclampsia, hypertension, gestations diabetes, etc can be allowed to wait
this long for labor to begin with natural methods. It would be nice to allow a
pregnancy to continue on for as long as it would like to, however we have to be
realistic. Not all women can go into labor without intervention. Once we get
close to the 42 week mark, there are some increased risks to both mother and
baby.
After 42 weeks, a pregnancy is considered post-term.
“Post-term pregnancy is associated with risks
to the fetus, including increased perinatal mortality rate, low umbilical
artery pH levels at delivery, low 5-minute Apgar scores, dysmaturity syndrome,
and increased risk of death within the first year of life3…”
“A number of key morbidities are greater in infants born to post-term pregnancies
as well as pregnancies that progress to and beyond 41 0/7 weeks gestation
including meconium and meconium aspiration, neonatal acidemia, low Apgar
scores, macrosomia, and, in turn, birth injury...Post-term pregnancy is also an
independent risk factor for neonatal encephalopathy and for death in the first
year of life. 4”
The potential complications are not limited to the baby. A
birthing woman is at
”… an increase in labor dystocia,
an increase in severe perineal injury related to macrosomia, and a doubling in
the rate of cesarean delivery. Also, post-term pregnancy can cause anxiety for
the pregnant woman3.”
The risks to the mother can be high, but are very manageable.
The risks to the baby are not. It is important to note that “…evidence shows
that antenatal fetal surveillance for post-term pregnancies does not decrease
perinatal mortality…3”
Statistically, the incident of these risk factors is low, this is your
baby’s life we are “gambling” on. Each practitioner has his/her own set of
practice protocols that must be followed. For some, that means inducing at 40
weeks. Others are more comfortable waiting until the 43rd week
before intervention. When discussing post-term pregnancy with your provider,
remember that your birth plan is important, but the MOST important part of your
birth plan is a safe, healthy baby. Sometimes that means that more intervention
than you planned for is needed.
Trust the practitioner you chose to assist you in bringing
your little bundle into the world. It has been my experience that once that 40
week mark passes women tend to have high levels of anxiety as they begin to
fear losing that birth plan they worked so hard to formulate. The more time
that goes on, the higher the anxiety and the more difficult decisions become
for a woman. Relax (the best you can) and
trust. Your provider is working hard to protect your health AND the health
of your baby. Trust in his/her wisdom and experience and be flexible in your
expectations.
