MACROSOMIA & IUGRPOLYHDRAMINOS AND OLIGOHYDRAMINOS

DR.SHAIMA ABOZEID

MACROSOMIA

Large for gestational age (LGA) is an indication of high prenatal growth rate, often defined as a weight (or length, or head circumference) that lies above the 90th percentile for that gestational age.

Macrosomia, also known as big baby syndrome, is sometimes used synonymously with LGA, or is otherwise defined as a fetus or infant that weighs above 4000 grams (8 lb. 13 oz.) or 4500 grams (9 lb. 15 oz.) regardless of gestational age.incidence is 10% in usa.

diagnosis• LGA is generally not diagnosed until after the

birth, as the size and weight of the child is rarely checked during the latter stages of pregnancy.

• Babies that are large for gestational age throughout the pregnancy can sometimes be seen during a routine ultrasound, although fetal weight estimations late in pregnancy are quite imprecise.

• There are believed to be links with polyhydramnios (excessive amniotic sac fluid).

Predetermining factors• One of the primary risk factors is poorly-controlled diabetes, particularly gestational diabetes (GD),as well as preexisting diabetes mellitus (DM) (preexisting type 2 is associated more with Macrosomia, while preexisting type 1 can be associated with Macrosomia).

• This increases maternal plasma glucose levels as well as insulin, stimulating fetal growth.

• The LGA newborn exposed to maternal DM usually has an increase only in weight. LGA newborns that have complications other than exposure to maternal DM present with universal measurements >90th percentile.

Other determining factors include:Gestational age; pregnancies that go beyond 40 weeks increase incidenceFetal sex; male infants tend to weigh more than female infantsGenetic factors; taller, heavier parents tend to have larger babies, with an obese mother greatly increasing the chancesExcessive maternal weight gainMultiparty (have 2-3x the number of LGA infants vs. primaparas)Congenital anomalies (transposition of great vessels) - Hydrops FetalisErythroblastosis Fetalis - Hydrops FetalisUse of some antibiotics (amoxicillin, pivampicillin) during pregnancy - Hydrops FetalisGenetic disorders of overgrowth (e.g. Beckwith- Wiedemann syndrome, Sotos syndrome)The condition is most common in mothers of African origin, partly due to the higher incidence of diabetes

Risk factors Maternal diabetes Excessive weight gain

Maternal impaired glucose intolerance

Male fetus

Multiparty Parental stature

Previous macrosomic infant Need for labor augmentation

Prolonged gestation Prolonged second stage

Maternal obesity

PREDICTIONCLINICIAN ESTIMATION OF FETAL WEIGHT

The volume of amniotic fluid, the size and configuration of the uterus and maternal body habitus complicate estimation of the size of the fetus by palpation through the abdominal wall. Several studies have documented mean errors of about 300 g

ULTRASONOGRAPHYUltrasonography has been proposed as a more accurate method of estimation of fetal weight. Unfortunately, the typical mean error ranges from 300 to 550 g A study comparing fetal weight estimates of clinicians, multiparous patients and ultrasonography found that ultrasound was the least accurate of the three methods. Limitations in the sensitivity and specificity of ultrasound have been observed in other studies. Despite these limitations, clinicians continue to incorrectly believe that ultrasound is an accurate way of predicting Macrosomia.

Treatment•Depending upon the relative size of the head of the baby and the pelvic diameter of the mother vaginal birth may become complicated. One of the most common complications is shoulder dystocia. •Such pregnancies often end in caesarean sections in order to safely deliver the baby and to avoid birth canal lacerations. Upon birth, early feeding is essential to prevent fetal hypoglycemia. •Early diagnosis of individual problems is required.

FETAL CONSEQUENCES•The delivery of a macrosomic infant has potentially serious consequences for the infant and the mother. The most feared result of macrosomia is shoulder dystocia, and up to one fourth of infants with shoulder dystocia experience brachial plexus or facial nerve injuries, or fractures of the humerus or clavicle. Brachial plexus injuries, such as Erb-Duchenne palsy, are ordinarily attributed to delivery complicated by shoulder dystocia; however, approximately one third of these injuries are not associated with a clinical diagnosis of shoulder dystocia. The most feared complication secondary to shoulder dystocia is asphyxia, which is rare.MATERNAL CONSEQUENCES OF FETAL MACROSOMIA•The mother is at increased risk for cesarean section, which occurs more commonly in pregnancies complicated by macrosomia.• Vaginal delivery of a macrosomic infant increases the risk of third- or fourth-degree lacerations fivefold.

Interventions for Suspected Macrosomia

•Management strategies for suspected fetal macrosomia include elective cesarean section and early induction of labor

IUGRIntrauterine growth restriction (IUGR) is a common diagnosis in obstetrics and carries an increased risk of perinatal mortality and morbidity. Identification of IUGR is crucial because proper evaluation and management can result in a favorable outcome. Certain pregnancies are at high risk for growth restriction, although a substantial percentage of cases occur in the general obstetric population. Accurate dating early in pregnancy is essential for a diagnosis of IUGR. Ultrasound biometry is the gold standard for assessment of fetal size and the amount of amniotic fluid. Growth restriction is classified as symmetric and asymmetric.

• A lag in fundal height of 4 cm or more suggests IUGR.

• Serial ultra sonograms are important for monitoring growth restriction, and management must be individualized.

• General management measures include treatment of maternal disease, good nutrition and institution of bed rest.

• Preterm delivery is indicated if the fetus shows evidence of abnormal function on biophysical profile testing.

• The fetus should be monitored continuously during labor to minimize fetal hypoxia.

• Fetal growth is dependent on genetic, placental and maternal factors.

• The fetus is thought to have an inherent growth potential that, under normal circumstances, yields a healthy newborn of appropriate size.

• The maternal-placental-fetal units act in harmony to provide the needs of the fetus while supporting the physiologic changes of the mother.

• Limitation of growth potential in the fetus is analogous to failure to thrive in the infant. The causes of both can be intrinsic or environmental

• Fetal growth restriction is the second leading cause of perinatal morbidity and mortality, followed only by prematurity.

• The incidence of intrauterine growth restriction (IUGR) is estimated to be approximately percent in the general obstetric population.

• However, the incidence varies depending on the population under examination (including its geographic location) and the standard growth curves used as reference.

• In assessing perinatal outcome by weight, infants who weigh less than 2,500 g at term have a perinatal mortality rate that is five to 30 times greater than that of infants whose birth weights are at the 50th percentile.

• The mortality rate is 70 to 100 times higher in infants who weigh less than 1,500 g Perinatal asphyxia involving multiple organ systems is one of the most significant problems in growth-restricted infants.

• Timely diagnosis and management of IUGR is one of the major achievements in contemporary obstetrics. If the growth-restricted fetus is identified and appropriate management instituted, perinatal mortality can be reduced, underscoring the need for assessment of fetal growth at each prenatal visit.

Classification and Etiology• IUGR is the pathologic counterpart of small-for-

gestational-age. The latter includes fetuses that are small but have reached their appropriate growth potential.

• Many babies are simply genetically small and are otherwise normal. Some women have a tendency to have constitutionally small babies.

• Although both parents' genes affect childhood growth and final adult size, maternal genes mainly influence birth weight.

• Parity, age and socioeconomic status are intercorrelated and may also influence the pregnancy and the infant's birth weight.

• Table 1 summarizes clinical situations in which IUGR may occur.

Placental insufficiencyUnexplained elevated maternal alpha-fetoprotein level

IdiopathicPreeclampsia

Chronic maternal diseaseCardiovascular diseaseDiabetesHypertension

Abnormal placentationAbruptio placentaePlacenta previaInfarctionCircumvallate placentaPlacenta accretiaHemangioma

Genetic disordersFamily historyTrisomy 13, 18 and 21TriploidyTurner's syndrome (some cases)

MalformationsImmunologic

Antiphospholipid syndromeInfections

CytomegalovirusRubellaHerpesToxoplasmosis

MetabolicPhenylketonuriaPoor maternal nutrition

Substance abuse (smoking, alcohol, drugs)Multiple gestationLow socioeconomic status

Definition of IUGR

•The most widely used definition of IUGR is a fetus whose estimated weight is below the 10th percentile for its gestational age and whose abdominal circumference is below the 2.5th percentile. At term, the cutoff birth weight for IUGR is 2,500 g Growth percentiles for fetal weight versus gestational age are shown in Figure 1. •Approximately 70 percent of fetuses with a birth weight below the 10th percentile for gestational age are constitutionally small ; in the remaining 30 percent, the cause of IUGR is pathologic.

Importance of Accurate Dating•Accurate dating in early pregnancy is essential for making the diagnosis of IUGR. The usual qualifier for reliable dating and establishment of an accurate gestational age is a certain date for the last menstrual period in a woman with regular cycles or assessment of gestational age by an ultrasound examination performed no later than the 20th gestational week, when the margin of error is seven to 10 days. •Early ultrasound examination, ideally at eight to 13 weeks of gestation, is more accurate for estimating gestational age than ultrasound assessment later in pregnancy. •An error that is commonly made is to change a patient's due date on the basis of a third-trimester ultra sonogram.•Doing so can result in failure to recognize IUGR.

Symmetric and Asymmetric IUGR

IUGR is usually classified as symmetric and asymmetric. . •Symmetric growth restriction implies a fetus whose entire body is proportionally small. •Asymmetric growth restriction implies a fetus who is undernourished and is directing most of its energy to maintaining growth of vital organs, such as the brain and heart, at the expense of the liver, muscle and fat. This type of growth restriction is usually the result of placental insufficiency.

A fetus with asymmetric IUGR has a normal head dimension but a small abdominal circumference (due to decreased liver size), scrawny limbs (because of decreased muscle mass) and thinned skin (because of decreased fat). If the insult causing asymmetric growth restriction is sustained long enough or is severe enough, the fetus may lose the ability to compensate and will become symmetrically growth-restricted. Arrested head growth is of great concern to the developmental potential of the fetus

Ultrasound Biometry•Ultrasound biometry of the fetus is now the gold standard for assessing fetal growth (Figure 2). The measurements most commonly used are the biparietal diameter, head circumference, abdominal circumference and femur length. Percentiles have been established for each of these parameters, and fetal weight can be calculated. The most sensitive indicator of symmetric and asymmetric IUGR is the abdominal circumference, which has a sensitivity of over 95 percent if the measurement is below the 2.5th percentile.• Accurate dating of the pregnancy is essential in the use of any parameter.

• Also useful is the ratio of the head circumference to the abdominal circumference (HC/AC). Between 20 and 36 weeks of gestation, the HC/AC ratio normally drops almost linearly from 1.2 to 1.0. The ratio is normal in the fetus with symmetric growth restriction and elevated in the infant with asymmetric growth restriction.

• Another important use of ultrasound is estimating the amount of amniotic fluid.

• A decreased volume of amniotic fluid is closely associated with IUGR. Significant morbidity has been found to exist in pregnancies with an amniotic fluid index value of less than 5 cm. The amniotic fluid index is obtained by summing the largest cord-free vertical pocket in each of the four quadrants of an equally divided uterus.

• The combination of oligohydramnios and IUGR portends a less favorable outcome, and early delivery should be considered

• The management of IUGR must be individualized for each patient. In addition to managing any maternal illness, a detailed sonogram should be performed to search for fetal anomalies, and karyotyping should be considered to rule out aneuploidy.

• Symmetric restriction may be due to a fetal chromosomal disorder or infection. This possibility should be discussed with the patient, who may decide to undergo a diagnostic procedure such as amniocentesis.

• It should be remembered, however, that many infants with evidence of growth restriction are constitutionally small.

• Serial ultrasound examinations are important to determine the severity and progression of IUGR.

• A controversy involves the timing of delivery to prevent intrauterine demise because of chronic oxygen deprivation.

• Preterm delivery is indicated if the growth-restricted fetus demonstrates abnormal fetal function tests, and it is often advisable in the absence of demonstrable fetal growth. The risks of prematurity must be weighed against the complications unique to IUGR.

• General management measures include treatment of maternal disease, cessation of substance abuse, good nutrition and institution of bed rest.

• Although not of proven benefit, bed rest may maximize uterine blood flow. In any case, antenatal testing should be instituted.

• Options include the nonstress test, the biophysical profile and an oxytocin (Pitocin) challenge test.

• The biophysical profile involves assessment of fetal well-being with a combination of the nonstress test and four ultrasonographic parameters (amniotic fluid volume, respiratory movements, body movements and muscle tone).

• The use of Doppler flow velocimetry, usually of the umbilical artery, identifies the growth-restricted fetus at greatest risk for neonatal morbidity and mortality. In controlled trials, Doppler analysis has been associated with improved outcome.

• Combination testing is thought to more accurately predict the status of the fetus .

• For this reason, close antenatal surveillance is encouraged, with a well-timed delivery.

• A proposed management approach for IUGR is shown in the following figure:

• This approach is based on outstanding advances in neonatal care and improved outcome for the low-birth-weight infant

Labor and Delivery•Because of the increased risk of intrapartum asphyxia, the fetus should be monitored carefully and continuously during labor. Delivery should be in a hospital capable of dealing with the various neonatal morbidities associated with growth restriction, including asphyxia, meconium aspiration, sepsis, hypoglycemia and malformations. •Preterm induction of labor is often required. •Amnioinfusion may be of benefit in the presence of a nonreassuring fetal response during labor and a low amniotic fluid index or oligohydramnios. •In the face of deteriorating fetal status, a cesarean section should be performed

Outcome•Most infants who had growth restriction in utero have normal rates of growth in infancy and childhood, although studies have demonstrated that at least one third of them never achieve normal height.• Many of these infants also are born prematurely, with its similar, independent, morbidities. •The lower the birth weight and the earlier the gestational age, the less the child's chance of catching up. Neurologic development is also related to the degree of growth restriction and prematurity. Decreased intrauterine growth may possibly have a negative effect on brain growth and mental developmental potential. At baseline, children with a history of IUGR have been found to demonstrate attention and performance deficits.• Minimizing hypoxic episodes during labor and delivery, as well as optimizing neonatal care for these infants, will likely produce the healthiest outcome

Polyhydramnios& oligohydramnios

Definition•Polyhydramnios is a high level and oligohydramnios is low level of amniotic fluid, and ahydraminos is no amniotic fluid.•Polyhydramnios in the second trimester is found in about 1 per 200 pregnancies.

• Amniotic fluid is the liquid that surrounds the developing fetus during pregnancy. It is contained within the amniotic membrane that forms the amniotic sac (bag of waters).

• During the first three months after conception (first trimester), amniotic fluid is mainly derived from the blood plasma that diffuses through the thin tissues of the fetus into the surrounding space.

• After the fetal kidneys form and become functional at about 10-11 weeks, fetal urine becomes the main source of amniotic fluid and remains so for the rest of the pregnancy. In addition, the lungs also produce liquid that becomes part of the amniotic fluid.

• Other contributions come from fetal oral and nasal secretions and from the fetal surface of the placenta.

• Amniotic fluid removal is largely due to fetal swallowing and absorption into the fetal blood. Uptake also occurs across the placental surface. The volume of amniotic fluid normally increases throughout pregnancy, reaching a peak at about 32-33 weeks and remaining fairly constant or decreasing slightly thereafter.

• There is a wide range of normal fluid volumes with an average of 700-800 ml at 32-33 weeks. Through the processes of swallowing and urination, a fetus can recycle the entire volume in less than 24 hours.

• Because the normal values for amniotic fluid volume increase during pregnancy, the actual volume that constitutes polyhydramnios is dependent on the gestational age of the fetus.

• During the last two months of pregnancy, polyhydramnios usually refers to amniotic fluid volumes greater than 1,700-1,900 ml.

• Severe cases are associated with much greater fluid volume excesses.

• The range of fluid values diagnostic of oligohydramnios is not as wide as that for polyhydramnios.

• Less than 300 ml, or lower than the 5% percentile for gestational age, is usually considered the upper threshold.

• Diagnosis:• The diagnosis of polyhydramnios is usually

made subjectively. Quantitatively, polyhydramnios is defined an amniotic fluid index (the sum of the vertical measurements of the largest pockets of amniotic fluid in the four quadrants of the uterus) of 20 cm or more.

• Alternatively, the vertical measurement of the largest single pocket of amniotic fluid free of fetal parts is used to classify polyhydramnios into mild (8-11 cm), moderate (12-15 cm) and severe (16 cm or more).

Causes and symptoms•Polyhydramnios, also referred to as hydramnios, can have any one of a number of causes related either to an underlying maternal or fetal condition. Maternal diabetes, which is associated with a macrosomic (enlarged) fetus, is a common cause. The medication lithium, used to treat depression, can also increase amniotic fluid levels. Twin gestations are prone to polyhydramnios. Infections passed from mother to fetus such as rubella, cytomegalovirus, and toxoplasmosis, can also result in damage to the fetus and elevated amniotic fluid levels. •Fetal abnormalities, including many that are life-threatening or lead to a significant impairment in the quality of life, are found in up to a quarter of all patients. For this reason, the initial finding of excess amniotic fluid should be followed by thorough diagnostic studies to determine the cause and the prognosis.

• Because fetal swallowing is a major factor in amniotic fluid removal, fetal abnormalities that prevent fluid uptake should be investigated. These include gastrointestinal obstructions such as esophageal atresia and duodenal atresia, as well as neurological conditions that affect swallowing including anencephaly. Certain cardiac abnormalities, kidney disorders, and genetic conditions such as myotonic dystrophy and alpha-thalassemia can also cause polyhydramnios.

• Fetal chromosome abnormalities are frequently associated with elevated amniotic fluid levels. The more severe the polyhydramnios the more likely it is that fetal abnormalities will be present. In addition, there are other, infrequent causes, and in

• a number of cases, no cause can be found. Polyhydramnios can lead to maternal abdominal discomfort and respiratory difficulties as well as preterm labor.

• When polyhydramnios is associated with fetal abnormalities, perinatal mortality is significantly increased.

• Oligohydramnios is most commonly associated with abnormalities of the fetal kidneys. Since fetal urine is the main source of amniotic fluid in the latter two-thirds of pregnancy, any condition that interferes with fetal urine production can lead to oligohydramnios.

• Oligohydramnios in the second trimester is found in about 1 per 500 pregnancies

• Renal agenesis, cystic kidneys, and bladder outlet obstructions are common. Meckel -Gruber syndrome, a lethal autosomal recessive genetic disorder featuring brain and kidney abnormalities and extra digits is one specific cause.

• Placental insufficiency and fetal growh retardation can also result in oligohydramnios

The diagnosis of oligohydramnios is usually made subjectively.

Quantitative criteria include:

(a) the largest single pocket of amniotic fluid being 1 cm or less, or

(b) amniotic fluid index (the sum of the vertical measurements of the largest pockets of amniotic fluid in the four quadrants of the uterus) of 5 cm.

• Premature rupture of membranes, especially between 16 and 24 weeks is another cause and, because amniotic fluid is important in lung growth, it can lead to underdevelopment of the lungs (pulmonary hypoplasia).

• In general, regardless of the cause, oligohydramnios that arises early in a pregnancy, can cause hypoplastic lungs.

• It can also result in space limitations within the amniotic sac that cause fetal compression and orthopedic abnormalities such as clubbed feet in the newborn. In general, oligohydramnios that begins near the time of delivery is associated with a better outcome than cases than have an onset earlier in pregnancy

Diagnosis

•In current obstetrical practice, polyhydramnios and oligohydramnios are usually detected during a routine prenatal ultrasound.• If the ultrasonographer suspects that excess or reduced fluid is present, it is customary to take measurements of pockets of fluid visualized around the fetus, calculate the amniotic fluid index (AFI), and compare it to AFI values found in standard tables. •Subsequent ultrasound measurements can then be used to track the increase or decrease in fluid

• It is extremely important that the cause of an abnormal AFI be sought. Because of the high risk of fetal abnormalities, detailed ultrasound exams (targeted exams) should then be performed.

• The mother should be counseled about the possible complications and offered additional testing as necessary. For example, an amniocentesis for prenatal chromosome analysis may be important because of the high risk of fetal chromosome abnormalities.

• This test is usually indicated if fetal abnormalities are suspected on the basis of the ultrasound exam. An amniocentesis can also be used to check for fetal infections and some rare single gene defects

Treatment•Effective treatments for polyhydramnios and oligohydramnios are limited. To relieve maternal discomfort, an excess fluid level can be reduced by inserting a needle into the amniotic sac and using a syringe to withdraw excess fluid. This can be done repeatedly, if necessary.• In oligohydramnios, the opposite approach of adding fluid either by increasing oral intake in the mother or by directly infusing saline into the amniotic sac has been tried in select cases. If the cause of oligohydramnios is a fetal bladder obstruction, it may be possible to place a small tube in the bladder to shunt the fluid into the amniotic sac.

• Alternative treatment

• In select cases where polyhydramnios is thought to be due to an increased output of fetal urine, the drug indomethicin has been used with some success, but there is concern about side effects, particularly on the fetus.

• Another similar drug, sulindac, is currently

being investigated.• If oligohydramnios is due to premature

rupture of the membranes, a protocol to manage complications should be instituted.

Prognosis•The prognosis for both polyhydramnios and oligohydramnios depends on the cause. If excess or reduced amniotic fluid is the result of an underlying fetal abnormality, the nature of that abnormality will determine the prognosis. This is one reason why it is important to perform the necessary follow-up studies. A woman who has been diagnosed with polyhydramnios or oligohydramnios needs to be made fully aware of the types of testing available and carefully counseled about the diagnosis and its impact on the chance for a successful pregnancy out-come and a healthy infant. Prevention•In order to prevent polyhydramnios or oligohydramnios, it would be necessary to prevent the underlying cause. Good control of maternal diabetes and the prevention of infections transmittable from mother to fetus are two approaches for a subset of cases, but, in general, prevention is not possible.