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Obstetrics 3.5

Postterm Pregnancy and Fetal Growth Disorders

Dr. Salud September 18, 2014

OUTLINE I. Postterm Pregnancy II. Fetal Growth Disorders

a. Intrauterine Growth Restriction b. Macrosomia

REFERENCES 1. Dr. Salud’s lecture and PPT 2. Williams Obstetrics 24th Edition NOTE: Unless otherwise specified, the information from this trans came from the PowerPoint.

POSTTERM PREGNANCY

Delivery of a fetus at 42 completed weeks/294 days or greater from the LMP

Factors affecting diagnostic accuracy: o Wrong or unrecalled LMP o Biological variations in menstrual cycle and ovulation dates

Confirmatory Test: Early Sonography o To date pregnancy done o Preferable in the 1st trimester o Can also be done before the 24th week of pregnancy but error in

estimation is increased

Incidence: approximately 6% of 4 million infants born in the US are born postterm

Predisposing factors o Maternal

Prepregancy BMI >/= 25 Nulliparity Prior Postterm

o Fetoplacental Anencephaly – no fetal head to help dilate the cervix Adrenal hypoplasia Placental sulfatase deficiency

Outcome of postterm pregnancies o Uncompromised placental function which might probably lead to

continued fetal growth — Macrosomia o Placental dysfunction leading to postmaturity syndrome (10%) o Perinatal mortality rates increase after the expected due date has

passed 2

Postmaturity Syndrome o Wrinkled (particularly prominent on palms and soles), patchy,

peeling skin o Long, thin body suggesting wasting o Advanced maturity because the infant is open-eyed, unusually

alert, and appears old and worried o Typically has long nails o Looks like Benjamin Button

Associated pathophysiologic factors o Loss of vernix caseosa o Placental senescence with cell death leading to decreased fetal

oxygenation o Oligohydramnios (10-33%) - scanty amniotic fluid, which can be

assessed by USG (Amniotic fluid index [AFI] ≤5) o Cord compression with non-reassuring fetal heart rate patterns

(e.g. saltatory baseline) o Scanty and viscous meconium which might lead to meconium

aspiration syndrome (most common indication for aggressive management)

o Fetal growth restriction - stillbirths were more common among growth-restricted infants who were delivered after 42 weeks; 33% of postterm stillbirth infants were growth restricted

Major causes of maternal and perinatal mortalities in postterm pregnancy: o Gestational HPN o Prolonged labor with cephalopelvic disproportion o Unexplained anoxia o Fetal malformations

Specific causes of death o Birth asphyxia o Meconium aspiration

Pregnancy Outcomes o Maternal

Increased rate of Cesarean Section Intrapartum complications Medical complications associated with gestational

hypertension and diabetes o Fetal

Increased perinatal morbidity and mortality Fetal distress Shoulder dystocia for big babies Neonatal Seizures Increased admissions to neonatal intensive care Increase in the number of long term developmental

anomalies and abnormalities

MANAGEMENT OF POSTTERM PREGNANCY Management Controversies

Type of intervention and timing of use

The decision centers on whether labor induction is necessary or if expectant management with fetal surveillance is best.

Acceptable indications of earlier intervention or delivery: o Gestational hypertensive disorders o Previous C-section o Diabetes o Oligohydramnios o Fetal compromise – e.g. saltatory patterns on electric heart rate

monitoring Management Strategies

Induction of Labor o Factors affecting success

Favourability of the cervix Bishop score of 7 or more Cervical dilatation Cervical length (estimated by USG: < 3 cm or 25 mm long) Station of the vertex (The Cesarean delivery rate was directly

related to station. It was 6% if the vertex before induction was at −1 station; 20% at −2; 43% at −3; and 77% at –4)2

o Management of unfavourable cervix Ripen with Prostaglandin E2 gel or Mifeprestone Stripping of the membranes

Fetal Surveillance starting at 41 weeks o Fetal movement counting at 2 hour period per day o Nonstress test 3x per week o Amniotic Fluid Volume estimation 2-3x per week

pockets < 3 cm is considered abnormal2

Management Recommendations

The American College of Obstetricians and Gynecologists defines postterm pregnancies as having completed 42 weeks.2

There is insufficient evidence to recommend a management strategy between 40 and 42 completed weeks. Thus, although not considered mandatory, initiation of fetal surveillance at 41 weeks is a reasonable option.2

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OBSTETRICS 3.3

After completing 42 weeks, recommendations are for either antenatal testing or labor induction. Prostaglandins may be used for cervical ripening or induction.2 (see Fig. 1)

Figure 1. Management of Post-term Pregnancy.

a see text on Management Strategies. b Prostaglandins may be used Intrapartum Management

Treated as high risk pregnancy

Women whose pregnancies are known or suspected to be postterm should come to the hospital as soon as they suspect labor. 2

While being evaluated for active labor, we recommend that fetal heart rate and uterine contractions be monitored electronically for variations consistent with fetal compromise.2

The decision to perform amniotomy is problematic. 2 o Further reduction in fluid volume following amniotomy can

certainly enhance the possibility of cord compression.2 o However it will aid in the identification of thickly stained

meconium, which may be dangerous to the fetus if aspirated o Also, after membrane rupture, a scalp electrode and intrauterine

pressure catheter can be placed, which usually provide more precise data concerning fetal heart rate and uterine contractions.2

Identification of thick meconium in the amnionic fluid is particularly worrisome.

If you rupture the bag of water and there is thickly stained meconium and very scanty amniotic fluid volume, you may do remedial measures.

Remedial measures for thick meconium and oligohydramnios o Amnioinfusion

introduction of sterile NSS toward the intrauterine cavity through the cervix to dilute the meconium

According to the American College of Obstetricians and Gynecologists, amnioinfusion does not prevent meconium aspiration, however, it remains a reasonable treatment approach for repetitive variable decelerations2

o C-section should be strongly considered for thick meconium when patient is remote from delivery Especially when cephalopelvic disproportion is suspected or

either hypotonic or hypertonic dysfunctional labor is evident.2

Management of Meconium Aspiration o The American College of Obstetricians and Gynecologists does not

recommend routine intrapartum suctioning.2 o Alternatively, if the depressed newborn has meconium-stained

fluid, then intubation is carried out. The American Academy of Pediatrics states that tracheal suctioning is neither supported nor refuted.2

FETAL GROWTH DISORDERS

Human fetal growth is characterized by sequential patterns of tissue and organ growth, differentiation, and maturation

Factors involved in development: o Maternal provision of substrate especially glucose o Placental transfer of nutrients o Fetal growth potential (genes)

Table 1. Three Phases of Cell Growth

PHASE DETERMINANTS

HYPERPLASIA First 16 weeks

Increase in cell number FETAL GENOME

HYPERPLASIA + HYPERTROPHY 17-32 weeks

ENVIRONMENTAL NUTRITIONAL HORMONAL

HYPERTROPHY When most fetal fat and glycogen

are accumulated After 32 weeks

“When IUGR is best diagnosed”

INTRAUTERINE GROWTH RESTRICTION (IUGR)

Low-birthweight infants who are small-for-gestational age (with birthweights falling below the 10th percentile of weight expected for gestational age)2

Birthweight may be affected by normal biological factors like ethnicity, regional differences, parity, weight and height of parents

Figure 2. Smoothed Percentiles of Birthweight (g) for Gestational Age in the

United States. Based on 3,134,879 Singleton Live Births

They are at a higher risk for fetal morbidities and mortalities o Fetal demise, birth asphyxia, meconium aspiration, neonatal

hypoglycemia

Postnatal prognosis of growth restricted fetuses is affected by: o Causes of restriction

Restriction due to chromosomal, viral or maternal size – remains small throughout life (“stunted growth”)

Restriction due to placental insufficiency – increase growth and approach their growth potential (“baby will catch up if nutrition is good”)

o Nutrition in infancy o Social Environment

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OBSTETRICS 3.3

Classification (based on HC/AC ratio)

Symmetrical o Reduced head and body size o Usually occurs in infections o Early insult - for example, global insults such as from chemical

exposure, viral infection, or cellular maldevelopment with aneuploidy may cause a proportionate reduction of both head and body size

o Results in decreased cell number and size

Asymmetrical o Reduced body size o Late pregnancy insult (e.g. placental insufficiency from

hypertension) o Decreased cell size only o Brain sparing – normal head size and growth; “most of the blood

will flow of the head which is more important than the body of the fetus”

Risk Factors

Constitutionally small mother o <100 lbs –2x risk of delivering SGA infant o “When mothers want to maintain their sexiness”

Poor maternal nutrition o low BMI and poor weight gain especially in the 2nd trimester o gestational weight gain during the second and third trimesters

that was less than that recommended by the Institute of Medicine was associated with SGA neonates in women of all weight categories except class II or III obesity2

Social deprivation o lifestyle—smoking, addiction, and poor nutrition

Maternal and fetal infection o CMV – direct cytolysis and loss of functional cells

most of these babies will not survive o Rubella – reduction in cell division and produces vascular

insufficiency most will still be delivered

Congenital malformations o the more severe the malformation the more likely is the fetal IUGR

Chromosomal Aneuploidies o Trisomy 21—mild IUGR o Trisomy 18—severe IUGR o Trisomy 16—fatal

Teratogens o Anticonvulsants, antineoplastic

Vascular Disease o superimposed pre-eclampsia o chronic hypertension

Pre-gestational Diabetes o Maternal vascular disease (fetal substrate deprivation)

Chronic Hypoxia o Uteroplacental hypoxia: preeclampsia, chronic hypertension,

asthma, smoking, high altitude (those that live in high altitude are usually smaller than those living in sea level)

Placental & Cord Abnormalities o Chorioangioma, marginal or velamentous cord insertion,

circumvallate placenta o This will lessen the flow of substrate oxygen to your fetus

Antiphospholipid Antibody Syndrome o Adverse obstetrical outcomes including fetal-growth restriction

have been associated with three species of antiphospholipid antibodies: anticardiolipin antibodies, lupus anticoagulant, and antibodies against beta-2-glycoprotein-I

o Antibodies—maternal platelet aggregation & plasma thrombosis

Genetics o Inheritance of certain substance that interfere with folate

metabolism

Multiple Fetuses o The higher the number of fetuses in the mother’s womb the

higher the chance it will affect the growth of the fetuses

Identification of IUGR

Fundic height measurement o At 18-30 weeks, fundic height in centimeters should coincide with

2 weeks of gestational age o Thus, if the measurement is more than 2 to 3 cm from the

expected height, inappropriate fetal growth is suspected

Sonographic Measurements o 16-20 weeks for identification of anomalies o 32-34 weeks for growth monitoring o Establish the diagnosis of IUGR by:

Femur length Biparietal Diameter Abdominal Circumference (most commonly abnormal in IUGR

because soft tissue is involved)

Amniotic Fluid Measurement o For determination of associated oligohydramnios

Doppler Velocity on fetal vessels with the following results: o Umbilical Artery/ Middle Cerebral Artery abnormality

mild dysfunction detects early changes in placenta-based growth restriction

o Ductus Venosus or Aorta Abnormalities detects late changes progressive dysfunction

Figure 3. Doppler velocimetry. (A) Normal velocimetry pattern with a systolic to diastolic (S/D) ratio of <3. (B) The diastolic velocity approaching zero reflects increased placental vascular resistance. (C) During diastole, arterial flow is reversed (negative S/D ratio), which is an ominous sign that may precede fetal demise.

Prevention

Preconceptional counseling on risk factors

Correction of nutritional deficiencies

Prophylaxis in early gestation with low dose aspirin (effective only in 10% of cases)

Management

Guidelines o Confirm diagnosis o Assess fetal condition by surveillance o Evaluate for anomalies

≥ 34 weeks: Prompt delivery o Vaginal delivery for reassuring Fetal Heart Rate (FHR) pattern o Caesarean Section (CS) for non-reassuring FHR during labor

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OBSTETRICS 3.3

< 34 weeks o Observation & monitoring until fetal maturity is attained o Qualifications:

Normal fetus Normal AFI (amniotic Fluid Index) Normal fetal surveillance Fetal growth continues

Management decisions must be based on relative risks of fetal death with expectant management or risks from preterm delivery

Conduct of Labor & Delivery

High risk intrapartum monitoring

Watch out for fetal decompensation

Immediate care of the newborn for: o Hypoxia o Meconium aspiration o Hypothermia o Hypoglycemia

MACROSOMIA

Infants above the 90th percentile for a given age of gestation or newborns weighing >4000g o ACOG: Fetuses who weigh 4500g or more at birth

Risk Factors: o Obesity o Gestational diabetes and DM type 2 o Postterm gestation o Multiparity o Large size of parents o Advancing maternal age o Previous macrosomic infant o Racial & ethnic factors

Diagnosis o Sonographic fetal weight estimation - head, femur & abdominal

circumference However, sonography can also make a mistake. If you are

going to assess the fetal weight at a later gestation, it should be +/- 500g.

Routine use to identify macrosomia is not recommended Findings of several studies indicate that clinical fetal-weight

estimates are as reliable as, or even superior to, those made from sonographic measurements

o Clinical estimate by PE Inaccuracy is often attributable to maternal obesity

Management o Trial of Labor

Concern: possible shoulder dystocia resulting into brachial plexus injury (brachial plexus palsy)

o Planned Cesarian Section A reasonable strategy for diabetic women with estimated

fetal weight ≥4250g planned cesarean delivery on the basis of suspected

macrosomia to prevent brachial plexopathy is an unreasonable strategy in the general population2

o In summary, when fetal overgrowth is suspected, the obstetrician naturally seeks to balance the risks to the fetus with maternal risks. 2

o Although interventions to prevent shoulder dystocia may someday prove beneficial, eliminating shoulder dystocia will likely remain an impossible goal. 2

o For the American College of Obstetricians and Gynecologists, elective delivery for the fetus that is suspected to be overgrown is inadvisable, particularly before 39 weeks’ gestation. 2

o Elective cesarean delivery is not indicated when estimated fetal weight is <5000 g among women without diabetes and < 4500 g among women with diabetes.2

Edited by: Venus Rojas

Group#28| Zabetty, Lea, and Mark Villanueva Page 5 of 5

Obstetrics 3.5

Postterm Pregnancy and Fetal Growth Disorders

Dr. Salud September 18, 2014

Algorithm for management of IUGR at Parkland Hospital