Only 30% are TRUE postdates pregnancies (pregnancy lasting beyond 42 completed weeks) The most common cause: inaccurate estimation of gestational age. Yes, wrong date of last menstrual period. Usually because pregnant women forget or have an irregular menstrual period. The more accurate the assignment of gestational age, the lower the likelihood that a pregnancy will extend beyond 42 weeks.
Post-term pregnancy or Prolonged pregnancy
AKA Postdatism pregnancy or Postmaturity
Is a pregnancy lasting beyond 42 completed weeks (> 41 weeks and 6 days) or > 294 days LMP (this gives best diagnose) or 280 days after ovulation/fertilization.
Causes
Still unknown. In accurately dated pregnancies may be related to nulliparity or first-time baby and male gender, previous post-term pregnancy, mother obesity, even there is some evidence that shows some genetic factor, if the mother was born post-term, her baby has a higher probability of being born post-term.
Postdate pregnancy marker
Is the amniotic fluid volume, this fluid in the last few weeks of pregnancy drops significantly so, fetal renal blood flow is reduced due to limited fetal swallowing, associated with oligohydramnios (low amniotic fluid) usually because theplacenta is not functioning adequately (placenta ages at the end of pregnancy).
Maternal risks
Maternal trauma (cuts, lacerations or other injuries caused by a newborn during labor or delivery) usually occurring due to baby large size in relation to the mother’s pelvis.
Labor induction, may be considered at 41 weeks, and is recommended at 42 weeks. This is to reduce the risks of perinatal morbidity and mortality associated with post-term pregnancies.
Cesarean delivery, because of the size of the baby some woman prefers c-section childbirth.
Fetal risks
- Oligohydramnios, the urine production by the baby decreases, in order to protect babies’ brain (blood flow that was going to the kidneys goes to the brain) resulting in low amniotic fluid.
- Meconium stained fluid, fetuses are more likely to have a bowel movement, directly related to the increased gestational age. What we don’t want is that this baby doesn’t swallow this contaminated fluid (it’s poop) because the risk of Meconium aspiration syndrome (MAS) which can lead to some serious complications.
- Macrosomia, babies who continue to grow after the due date (greater than 4000g or 8 pounds 13 ounces)
- Stillbirth or neonatal death, there is an increased risk of fetal death in pregnancies beyond 42 weeks due to the related complications.
- Post maturity syndrome, this is diagnosed after baby born.
Management
Accurate assessment of gestational age.
Confirm estimated delivery date (EDD) by ultrasound.
Membrane sweeping/stripping at 38 weeks.
Antepartum fetal surveillance at 41 weeks and twice weekly thereafter.
Induction of labor or cesarean delivery.