230 likes | 1.6k Views
Post-term Pregnancy. Khalid A. Yarouf. . www.4MedStudents.com. Gestational age at pregnancy termination. Abortion: < 24 weeks from LMP. Preterm delivery: 24-37 weeks. Term: 38-42 weeks. Post-term: > 42 weeks. 10% of pregnancies.
E N D
Post-term Pregnancy Khalid A. Yarouf . www.4MedStudents.com
Gestational age at pregnancy termination • Abortion: < 24 weeks from LMP. • Preterm delivery: 24-37 weeks. • Term: 38-42 weeks. • Post-term: > 42 weeks. • 10% of pregnancies. • Occur more frequently in primigravida, who are younger or older than average childbearing age, and in grandmultiparas (women who have had ≥ 6 successful pregnancies).
What is the best estimate for gestational age? • Hx: • LMP tends to be reliable if LMP was definite, cycle was normal, and pregnancy was planned. • Quickening (maternal perception of fetal movement) occurs at about 16-20 weeks. • P/E: • Size of uterus at early examination in 1st trimester should e consistent with dates.
Con’t • Apply Naegele’s rule: • Add 7 days to the date of the first day of the LMP count back 3 months. • e.g. LMP was March 7, 2001 EDD would be January 14, 2002. • Note that the length of gestation increases approx. 1 day for each day the menstrual cycle is > 28 days.
Con’t • Obtain US (confirmatory): • Fetal heart can be heard starting at 11 weeks. • Crown-rump length (CRL): • Most accurate in 1st trimester to within ± 5 days. • At ≥ 12 weeks, fetus begins to curve & this measurement becomes < accurate. • Biparietal diameter (BPD) from 12-18 weeks is most accurate to ± 7 days.
What are the causes of post-term pregnancy? • Potential causative factors: • Deficiency of ACTH in fetus & placental sulfatase deficiency. • Exact mechanism of spontaneous onset of labor in unclear, but fetus, placenta & mother are all involved. The longest pregnancy on record is 1 year & 24 days, ending in a liveborn anencephalic infant. CNS abnormalities, e.g. anencephaly, are a/w prolonged pregnancy.
What are the complications of prolonged pregnancy? • Incidence of fetal mortality for all groups is as follows: • 40-41 weeks’ gestation: 1.1% • 43 weeks’ gestation: 2.2% • 44 weeks’ gestation: 6.6% • Macrosomia: • Commonest outcome (75%). • Occurs if placental function is maintained. • Cx of large uterus: • Arrest of labor + Cesarean delivery + Traumatic vaginal delivery.
Con’t • Dysmaturity syndrome: • Normally, there’s little growth of fetus post-term. • This syndrome is observed in 30% of post-term infants & in 3% of term infants. • CFx: • Loss of subcutaneous fat. • Dry, wrinkles, cracked skin. • Long nails. • Unusual degree of alertness. • Cx: Fetal hypoxia & Meconium aspiration syndrome.
Con’t • Placental aging / senescence Critically ↓ nutritional & O2 supply Fetal compromise 2 to placental insufficiency (major concern in post-term pregnancy). • Oligohydramnios: • Morbidity increased with HTN/ preeclampsia, DM, abruption, IUGR, multiple gestation.
How can you assess the post-term fetus antenatally? • FHR testing: • NST (non-stress test): • Non-invasive test of fetal activity that correlates with fetal well-being. • Fetal heart rate accelerations are observed during fetal movement. • External monitor is used to record FHR & mother precipitates by indicating fetal movement. • NST can be reactive or non-reactive. • Contraction Stress test: not used anymore.
Con’t • Biophysical profile (BPP): • Composite of tests designed to identify a compromised fetus during antepartum period.
How can you manage suspected post-dates pregnancy? • Determine gestational age dating. • Establish how favorable cervix is (dilated, effaced, soft). • Assess fetal well-being [e.g. with NSTs & amniotic fluid indices (AFIs)]. If fetal jeopardy is evident, immediate delivery is appropriate.
Con’t • Use the following triage method: • Dates are certain & cervix is favorable. Neither the mother nor the fetus benefits from waiting induce labor promptly with IV oxytocin & rupture of membranes. • Dates are certain but cervix is unfavorable. Risk of failed induction is high. If fetal macrosomia is suspected, induce labor with PGE2. Alternatively, if the estimated fetal weight (EFW) is normal, manage expectantly with twice-weekly NSTs & AFIs. • Dates are unsure. Because it’s not known if the patient is post-dates, delivery is not indicated. Manage expectantly with twice-weekly NSTs & AFIs awaiting spontaneous labor.
Con’t • Intrapartum Mx of Cx: • Meconium staining: • Prior to delivery Amnio-infusions: • = infusion of NS thru intrauterine catheter. • to dilute meconium. • After delivery of fetal head suctioning meconium from nose & pharynx to prevent aspiration. • After delivery of entire fetus, but before the first neonatal breath aspirate neonatal tracheal meconium using laryngoscope.
Con’t • When macrosomia is suspected, US should be performed to estimate fetal weight. Clinician should always be prepared to deal with a potential shoulder dystocia. • Intrapartum asphyxia: Careful monitoring should be instituted when this is suspected.