If you go past your expected due date (EDD) at 40 weeks, and you and your baby are stable, the standard of care is to wait to see if you will go into spontaneous labor (expectant management), according to the Mayo Clinic. This sets the stage to put a protocol into action and plan ahead for fetal surveillance or labor induction if you do not go into labor on your own by 41 completed weeks of pregnancy.
Putting a Protocol Into Action
In general, the protocol to manage your pregnancy and the decision between labor induction or surveillance usually occurs as follows:
- As soon as you pass 40 weeks, if you have no signs of spontaneous labor, your obstetrics doctor or midwife will plan ahead and schedule your labor induction and fetal surveillance tests to make it easier to manage the scheduling and your time.
- During each prenatal visit, your OB specialist checks your cervix to see if it's dilating or getting effaced (becoming softer, thinner, and shorter) and favorable for labor.
- At 41 weeks, if you still have no signs of spontaneous labor, your doctor or midwife will now have to decide whether to induce labor or monitor your baby while you wait longer for spontaneous labor.
Defining the Decision-Making Point
The choice of 41 weeks (and not 40 weeks) as the point to make the decision between continuing the pregnancy under fetal surveillance or to proceed to induction of labor is based on expert consensus. In a 2013 joint opinion of the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM):
- The societies refined the definitions of term and overdue pregnancies based on years of data on fetal and maternal outcomes according to the of weeks of pregnancy at birth.
- The experts made the clarifications to reduce the incidence of poor outcomes due to the number of premature inductions of labor done before 39 weeks in years past - often done for convenience of patients or OB providers.
- The consensus highlighted that data shows:
- Babies born at 39 weeks to 40 weeks and six days (full term) have the best birth outcomes.
- At 41 weeks and after (late-term or early overdue), a pregnancy is considered prolonged, and there is an increased risk of stillbirths and other poor outcomes to baby and mother. Therefore, OBs have to make the critical choice between inducing labor or continuing expectant management at this point.
- At 42 completed weeks and after (post-term or late overdue) the risk of poor outcomes is even greater.
This obstetrical definition of being overdue at 41 weeks, for the purpose of deciding between fetal surveillance and labor induction, is in contrast to the public's generally held conception of an overdue pregnancy being any time past 40 weeks. Ensure that any discussion of the management of your pregnancy after your due date takes the ACOG 2013 refined terminology into account.
Guidelines for Making the Decision
The modern era of fetal monitoring techniques allows doctors and mothers with low risk pregnancies to wait confidently for as long as three weeks past the due date to see if spontaneous labor occurs. OB specialists have the 2014 ACOG guidelines for the management of late-term and post-term pregnancies to help them decide between fetal surveillance or induction of labor.
Unless the mother or fetus is at risk, ACOG recommends:
- Between 41 and 42 weeks of pregnancy, if there are no signs of labor:
- Induction of labor "can be considered" if the cervix is favorable.
- Fetal surveillance can proceed if the cervix is unfavorable for induction of labor.
- Between 42 weeks and one day and 42 weeks and 6 days, induction of labor "is recommended."
- A woman should not go past 43 completed weeks of pregnancy because of the greater risk of poor outcomes for mother and baby.
The ACOG guidelines take into account that pregnancy dating is not precise, especially dating by the last menstrual period alone. Some babies will be delivered prematurely if labor is induced too soon after the calculated due date.
Usual Obstetrics Practice
The ACOG guidelines are not cemented in stone because not every pregnancy and circumstance fit neatly into a category. In general, the usual practice for most OBs is:
- If the cervix is favorable at 41 weeks, induce labor.
- If the cervix is unfavorable at 41 weeks, doctors might chose:
- Either to proceed with fetal surveillance and plan for delivery by 42 weeks; some women will go into spontaneous labor while waiting longer and avoid induction of labor
- Or to induce labor instead, despite an unfavorable cervix
Deciding to Induce Labor Despite an Unfavorable Cervix
A 2014 review of the management of late-term and post-term pregnancies by American Family Physician advises if the cervix is unfavorable, and the pregnancy is low risk, the best practice is to avoid induction of labor at 41 weeks (or before). However, an OB provider might choose to ripen an unfavorable cervix and induce labor at 41 weeks or before 42 weeks, rather than start or continue fetal surveillance, because of:
- Scheduling challenges
- A woman's preference
- Other factors that develop that increase the risks to the baby or mother that outweigh the benefits of waiting. These factors include:
- The baby becomes less active.
- There is decreased amniotic fluid.
- A fetal surveillance test is abnormal, or there is other evidence of fetal distress.
- A past history of delivery complications or current fetal anomalies is seen.
- Complications develop, such as increased blood pressure or preeclampsia, or worsening heart or kidney disease, or other maternal medical conditions.
ACOG advises against inducing labor for the convenience of parents or OB providers. However, sometimes practical factors come into the decision, such as a woman's distance from the hospital or planning for an induction on a weekday because more personnel are present.
When the Pregnancy Is Preterm
When there are complications in a preterm pregnancy (less than 37 weeks) or early term pregnancy (between 37 weeks and 38 weeks, 6 days) the choice between fetal surveillance and induction of labor is often more difficult than at 41 weeks. The OB specialists have to make one of two decisions:
- The baby is "better in than out." In this case, they will monitor the baby so she can grow, and her brain and lungs can develop further before inducing labor.
- The baby is "better out than in." If they decide the risk of a poor outcome for you or your baby outweighs the benefits of keeping her in, the doctors will proceed with labor induction.
The decision rests on several factors, including the gestational age of the baby, and the complication that is triggering the decision before full term. These complications include:
- Maternal high risk factors, such as diabetes or preeclampsia
- Decreased fetal movement
- Fetal abnormalities
- Decreased or increased amniotic fluid
- Previous preterm or early term intrauterine fetal death
According to the American Family Physician reference above, fetal surveillance studies are usually not as useful before 32 weeks of pregnancy. However, they can be started around 26 to 28 weeks, if indicated, to assess concerning high risk problems.
The Induction of Labor
Induction of labor initiates contractions that progress to active labor. There are various methods that can cause this to happen, including:
- Stripping the membranes, which peels away the part of the amniotic membranes attached to the cervix
- Amniotony, or rupturing the membranes (breaking your water)
- Pitocin (oxytocin), a synthetic hormone infused by vein
- Prostaglandins inserted in the vagina or cervix
These agents induce contractions by different mechanisms of action. Membrane stripping and prostaglandins also ripen the cervix in preparation for labor.
Benefits and Risks
According to a 2012 Cochrane Database System Review, inducing labor at 41 weeks compared to expectant management decreases risks to the baby and mother. The benefits include less risks for:
- Fetal distress
- Still birth
- Newborn death
- Meconium aspiration
- Cord accidents
- Large baby
- Maternal hemorrhage
- Emergency delivery
The risks of labor induction, especially with an unfavorable cervix, include:
- Prolonged labor and delivery
- Increased risk of fetal distress during labor
- Uterine rupture from high doses of pitocin
- Increased chance of having a forceps, vacuum, or cesarean section delivery.
- Delivery of a premature infant with under-developed lungs because the due date was inaccurate
Fetal surveillance, or electronic fetal monitoring, is frequently done to monitor the fetus at various stages if there is a high risk pregnancy. In the management of overdue pregnancies, the 2014 ACOG guidelines cited above writes there are no well-designed studies to prove standard fetal monitoring reduces risks when used at and after 41 weeks but "may be indicated."
Nevertheless, if your doctor or midwife chooses this option, the usual practice is to begin fetal surveillance at 41 weeks, at least twice a week. Your doctor will decide which study to order based on certain factors in you and your baby. The surveillance studies include:
- The nonstress test (NST): Looks at how your baby's heartbeat responds when he moves spontaneously
- The contraction stress test (CST): Observes how your baby's heartbeat responds to a stress, such as your contractions
- The biophysical profile (BPP): This is a more informative test that examines your baby's NST plus, by ultrasound, his breathing pattern, movement, muscle tone, and the amount of amniotic fluid
- The modified biophysical profile: Combines the NST results with the measurement of the biggest pockets of amniotic fluid on ultrasound
- Umbilical artery blood flow: Assesses the speed of blood flow in the artery. This test is mostly done when the fetus lags behind in growth (intrauterine growth restriction or IUGR)
In addition, your OB provider will ask you to focus on your baby's activity (kick counts), which monitors your baby's kicks, rolls, and other movements. In general, a healthy baby is expected to move at least 10 times within two hours. Based on the results of the fetal surveillance, your OB might advise inducing labor early rather than continuing with fetal monitoring.
There is always a chance your due date is inaccurate because of an incorrect last menstrual period date, irregular menstrual cycles, or inadequate ultrasound dating. As noted previously, expectant management and fetal surveillance decreases the chance of your baby being born at a premature stage because of an inaccurate due date.
The increased risks of expectant management with fetal surveillance of a prolonged pregnancy at 41 weeks and after include:
- Stillbirth while waiting
- Aging of the placenta
- Decreasing amniotic fluid (which reflects placental function)
- Umbilical cord accidents
- Meconium aspiration
- Newborn seizures
These risks increase the longer you are overdue, especially after 42 weeks.
The Critical Decision
Deciding between fetal surveillance and induction of labor is one of those critical decisions doctors have to make every day. If you go past your due date, your OB specialist will make a decision based on expert guidelines, as well as the risks and benefits of each option to your situation. Ask your doctor or midwife to help you understand how the decision is being made for you and your baby.