# Seminar 05: Second and Third Trimester Complications ## Year 3: Obstetrics and Gynecology Clerkship --- ## Learning Objectives By the end of this seminar, students will be able to: 1. Evaluate and manage preterm labor 2. Recognize and treat preterm premature rupture of membranes 3. Identify placental abnormalities 4. Describe intrauterine growth restriction 5. Manage oligohydramnios and polyhydramnios 6. Recognize cholestasis of pregnancy --- ## Seminar Outline ### I. Preterm Labor Preterm birth, defined as delivery before 37 completed weeks of gestation, represents the leading cause of neonatal morbidity and mortality worldwide and requires careful identification and management. The classification of prematurity provides prognostic information, with extremely preterm (less than 28 weeks) carrying the highest risk of death and disability, very preterm (28-32 weeks) having significant but improving outcomes, and late preterm (34-36 weeks) representing the majority of preterm births with better but still elevated risk. Preterm labor is defined as regular uterine contractions associated with cervical change occurring before 37 weeks of gestation. Distinguishing true preterm labor from false labor or Braxton-Hicks contractions is essential to avoid unnecessary intervention. Risk factors for preterm birth should be identified during prenatal care to enable appropriate surveillance and intervention. Prior spontaneous preterm birth is the strongest predictor of recurrence, with risk increasing with each prior preterm delivery. Short cervical length, defined as less than 25 mm on transvaginal ultrasound at 18-24 weeks, identifies patients at elevated risk even without prior history. Multiple gestation creates uterine overdistension predisposing to preterm labor. Infection, including urinary tract infections, bacterial vaginosis, and intrauterine infection, triggers inflammatory pathways leading to preterm labor. Uterine anomalies such as bicornuate or septate uterus increase risk, and smoking remains an important modifiable risk factor. Diagnosis of preterm labor requires documentation of both regular contractions and cervical change. Contractions occurring every 10 minutes or more frequently with associated cervical dilation or effacement meet diagnostic criteria. Fetal fibronectin testing provides valuable risk stratification: a negative result has high negative predictive value, indicating less than 2% likelihood of delivery within two weeks. Conversely, a positive result is less predictive, with only approximately 20% of patients with positive fetal fibronectin delivering within two weeks. Transvaginal cervical length measurement adds complementary information, with length greater than 30 mm indicating low risk and length less than 25 mm indicating increased risk requiring intervention. The combined use of fetal fibronectin and cervical length allows efficient triage of patients presenting with preterm labor symptoms. A negative fetal fibronectin with cervical length greater than 30 mm identifies patients who can be safely discharged without further intervention. Positive fetal fibronectin or short cervical length warrants admission for further evaluation and potential treatment. These tests help avoid unnecessary hospitalization and treatment while ensuring appropriate intervention for patients at genuine risk. The high negative predictive value of these tests is their greatest clinical utility, providing reassurance when negative rather than predicting delivery when positive. Panel A: Classification diagram of preterm birth showing extremely preterm (less than 28 weeks), very preterm (28-32 weeks), moderate preterm (32-34 weeks), and late preterm (34-36 weeks) with associated survival and morbidity rates. Panel B: Risk factor pyramid showing prior preterm birth as strongest predictor, followed by short cervix, multiple gestation, infection, uterine anomaly, and smoking. Panel C: Diagnostic criteria flowchart requiring both regular contractions (every 10 minutes or less) and cervical change (dilation or effacement) for diagnosis. Panel D: Fetal fibronectin and cervical length interpretation matrix showing management based on test combinations. --- ### II. Preterm Labor Management Tocolytic medications aim to delay delivery for 48 hours to allow administration of antenatal corticosteroids and, when necessary, maternal transport to a facility with appropriate neonatal care. Nifedipine, a calcium channel blocker, represents first-line tocolysis with favorable side effect profile including hypotension and headache. Indomethacin, a prostaglandin synthesis inhibitor, is effective but limited to use before 32 weeks due to risk of premature ductus arteriosus closure and oligohydramnios. Magnesium sulfate has unclear mechanism for tocolysis and is now primarily used for neuroprotection rather than stopping contractions. Terbutaline, a beta-agonist, carries cardiovascular side effects including tachycardia and should not be used for prolonged periods. The goals of tocolysis are limited and should be clearly understood to guide appropriate use. Tocolysis aims to achieve a 48-hour delay to allow corticosteroid effect, not to stop preterm labor indefinitely. Continued tocolytic administration beyond 48 hours is not recommended and does not improve outcomes. Contraindications to tocolysis include chorioamnionitis, in which case delivery is indicated regardless of gestational age; advanced cervical dilation making successful tocolysis unlikely; non-reassuring fetal status requiring delivery; and significant maternal hemorrhage. When tocolysis is contraindicated or fails, delivery should proceed with appropriate neonatal support. Antenatal corticosteroids represent the most important intervention for improving neonatal outcomes in threatened preterm delivery. Betamethasone, given as 12 mg intramuscularly for two doses 24 hours apart, is the most commonly used regimen. Dexamethasone, given as 6 mg intramuscularly for four doses 12 hours apart, provides equivalent benefit. Administration is recommended at 24-34 weeks gestation when delivery within seven days is anticipated. Late preterm administration at 34 weeks to 36 weeks 6 days may be considered but carries potential risk of neonatal hypoglycemia. Corticosteroids reduce respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis, and neonatal death. Magnesium sulfate for fetal neuroprotection reduces the risk of cerebral palsy in surviving preterm infants. Administration is recommended when delivery before 32 weeks is anticipated within 24 hours. The loading dose is 4-6 grams intravenously over 20-30 minutes, followed by maintenance infusion of 1-2 grams per hour. Treatment continues until delivery or until delivery is no longer imminent. The number needed to treat is approximately 63 to prevent one case of cerebral palsy. Magnesium is generally safe but requires monitoring for toxicity, which manifests as loss of deep tendon reflexes, respiratory depression, and cardiac arrest at high serum levels. Panel A: Tocolytic comparison chart showing nifedipine, indomethacin, magnesium sulfate, and terbutaline with mechanisms, dosing, and contraindications for each. Panel B: Tocolysis goal diagram emphasizing 48-hour window for corticosteroids and transport, not prolonged pregnancy delay. Panel C: Antenatal corticosteroid protocol showing betamethasone and dexamethasone regimens with gestational age recommendations and documented benefits. Panel D: Magnesium sulfate neuroprotection protocol showing loading dose, maintenance infusion, indication criteria (less than 32 weeks, delivery within 24 hours), and monitoring parameters. --- ### III. Preterm Prevention Progesterone supplementation reduces preterm birth risk in specific patient populations. Women with prior spontaneous preterm birth benefit from 17-alpha hydroxyprogesterone caproate administered intramuscularly weekly beginning at 16 weeks and continuing through 36 weeks. Women with short cervix (less than 25 mm) without prior preterm birth benefit from vaginal progesterone administered as a gel or suppository. Progesterone is not beneficial for multiple gestations or for women without prior preterm birth who have normal cervical length. The mechanism involves progesterone's role in maintaining uterine quiescence and preventing cervical ripening. Cervical cerclage provides mechanical support to the cervix in women at risk for cervical insufficiency. History-indicated cerclage is placed at 12-14 weeks in women with classic cervical insufficiency history, defined as prior painless cervical dilation and second-trimester loss. Ultrasound-indicated cerclage is placed when short cervix is identified in women with prior preterm birth, typically when cervical length decreases below 25 mm. Rescue cerclage is placed emergently when cervical dilation is discovered without labor, though success rates are lower than prophylactic placement. The McDonald technique, using a purse-string suture at the cervicovaginal junction, is most common, while the Shirodkar technique places suture at the internal os level. Cervical pessary represents a non-surgical alternative for cervical support in some patients. The pessary is a silicone device placed in the vagina to support the cervix mechanically. Evidence for efficacy is mixed, with some studies showing benefit and others finding no improvement over standard care. The pessary may be considered when cerclage is contraindicated or declined, or as an adjunct to progesterone in high-risk patients. The non-invasive nature makes it an appealing option, though the evidence base is less robust than for cerclage or progesterone. Lifestyle modifications and treatment of modifiable risk factors complement medical and surgical interventions. Smoking cessation is strongly encouraged, as smoking increases preterm birth risk and cessation reduces risk. Screening and treatment of asymptomatic bacteriuria and symptomatic urinary tract infections prevents ascending infection. The role of bacterial vaginosis treatment in preterm birth prevention remains controversial despite the association between the two conditions. Adequate nutrition and prenatal care, stress reduction when possible, and attention to general health contribute to optimal pregnancy outcomes even when specific preterm birth prevention is not achieved. Panel A: Progesterone indication algorithm showing 17-alpha hydroxyprogesterone caproate for prior preterm birth and vaginal progesterone for short cervix without prior preterm birth, with dosing schedules. Panel B: Cerclage classification diagram showing history-indicated, ultrasound-indicated, and rescue cerclage with timing and cervical findings for each. Panel C: McDonald versus Shirodkar cerclage technique illustration showing suture placement levels and anatomical landmarks. Panel D: Comprehensive prevention strategy integrating progesterone, cerclage, smoking cessation, infection treatment, and prenatal care. --- ### IV. Preterm Premature Rupture of Membranes Preterm premature rupture of membranes (PPROM) is defined as rupture of the amniotic membranes before 37 weeks gestation and before the onset of labor. This condition complicates 2-3% of pregnancies and accounts for approximately one-third of preterm births. The latency period, defined as the time from membrane rupture to delivery, varies considerably and influences management decisions. Accurate diagnosis is essential because management differs significantly from term premature rupture of membranes, where delivery is typically indicated. Diagnosis of PPROM relies on history, physical examination, and adjunctive testing. The classic presentation is a gush of fluid from the vagina, though some patients describe continuous slow leaking. Sterile speculum examination is the preferred initial evaluation to avoid introducing infection, with findings including pooling of amniotic fluid in the posterior vaginal fornix, ferning pattern when dried fluid is examined microscopically, and positive nitrazine testing showing alkaline pH. Digital cervical examination should be avoided as it increases infection risk without improving diagnostic accuracy. When clinical examination is equivocal, AmniSure testing for insulin-like growth factor binding protein-1 (IGFBP-1) provides high sensitivity and specificity for confirming rupture. Complications of PPROM are predominantly related to prematurity and infection and drive management decisions. Prematurity itself carries the risks discussed previously, with outcomes improving significantly with advancing gestational age. Chorioamnionitis, intrauterine infection, complicates 15-35% of PPROM cases and necessitates delivery. Umbilical cord prolapse risk increases, particularly with malpresentation or significant oligohydramnios. Placental abruption risk is elevated in the setting of PPROM. With very early or prolonged rupture, pulmonary hypoplasia from severe oligohydramnios represents a serious potential complication affecting neonatal survival and respiratory outcomes. Recognition of chorioamnionitis is essential as it mandates delivery regardless of gestational age. Maternal fever greater than 100.4 degrees Fahrenheit (38 degrees Celsius) is the cardinal sign, though isolated fever may have other causes. Maternal tachycardia greater than 100 beats per minute and fetal tachycardia greater than 160 beats per minute suggest developing infection. Uterine tenderness, particularly fundal tenderness, indicates myometrial involvement. Purulent or foul-smelling amniotic fluid, when present, is highly suggestive of infection. Laboratory findings including elevated white blood cell count may support the diagnosis but are neither sensitive nor specific. Panel A: PPROM definition diagram distinguishing preterm PROM (before 37 weeks, before labor) from term PROM and showing proportion of preterm births attributable to PPROM. Panel B: Diagnostic approach flowchart showing history, sterile speculum examination (pooling, ferning, nitrazine), avoidance of digital examination, and AmniSure testing for equivocal cases. Panel C: Complication risk diagram showing prematurity, chorioamnionitis, cord prolapse, abruption, and pulmonary hypoplasia with gestational age correlations. Panel D: Chorioamnionitis diagnostic criteria illustration showing maternal fever, tachycardias (maternal and fetal), uterine tenderness, and purulent fluid. --- ### V. PPROM Management Initial assessment of the patient with PPROM establishes diagnosis, gestational age, fetal status, and presence or absence of infection. Diagnosis is confirmed with sterile speculum examination demonstrating pooling, ferning, or positive nitrazine, or with AmniSure testing when findings are equivocal. Accurate gestational age dating is crucial as it determines management approach. Fetal status is assessed with non-stress testing and biophysical profile to evaluate wellbeing and detect signs of compromise or infection. Ultrasound documents amniotic fluid volume and fetal presentation, and laboratory studies include complete blood count, blood type with antibody screen, and group B streptococcus culture. Management approach varies by gestational age, balancing risks of prematurity against risks of infection and other complications. Before 24 weeks (periviable), counseling addresses the extremely high risks of both immediate delivery and expectant management, with patient wishes guiding care. From 24-34 weeks, expectant management in the hospital is typically recommended to allow fetal maturation while monitoring for infection, with administration of corticosteroids, antibiotics, and magnesium for neuroprotection if less than 32 weeks. From 34-37 weeks, delivery is generally recommended as the risks of prematurity are low and continuing expectant management provides minimal benefit with ongoing infection risk. At 37 weeks or beyond, delivery is indicated as for term PROM. Latency antibiotics are administered to prolong the interval from membrane rupture to delivery and reduce infection risk. The traditional regimen consists of ampicillin 2 grams intravenously every 6 hours plus erythromycin 250 mg intravenously every 6 hours for 48 hours, followed by amoxicillin 250 mg orally every 8 hours plus erythromycin 333 mg orally every 8 hours for 5 days. Azithromycin has replaced erythromycin in many protocols due to better tolerability and equivalent efficacy. Antibiotics prolong latency, reduce chorioamnionitis, and improve neonatal outcomes. Group B streptococcus prophylaxis is also indicated during labor regardless of culture status due to membrane rupture. Delivery is indicated regardless of gestational age in specific circumstances. Chorioamnionitis requires prompt delivery as the infection will not resolve with the fetus in utero and may worsen with expectant management. Non-reassuring fetal heart rate patterns that do not improve with resuscitative measures indicate fetal compromise requiring delivery. Advanced labor with cervical dilation and regular contractions makes expectant management futile. Cord prolapse is an emergency requiring immediate delivery. Reaching 34 weeks gestational age during expectant management is an indication for delivery in many protocols, though some continue to 37 weeks. Panel A: Initial assessment checklist showing diagnostic confirmation, gestational age dating, fetal status evaluation (NST, BPP), ultrasound findings, and laboratory studies. Panel B: Gestational age-based management algorithm showing counseling and patient choice before 24 weeks, expectant management with steroids and antibiotics from 24-34 weeks, and delivery recommendation from 34-37 weeks and beyond. Panel C: Latency antibiotic protocol detailing intravenous regimen for 48 hours followed by oral completion, with azithromycin alternative noted. Panel D: Delivery indication summary showing chorioamnionitis, non-reassuring fetal status, advanced labor, cord prolapse, and gestational age threshold as indications. --- ### VI. Placenta Previa Placenta previa is defined by placental implantation over or near the internal cervical os and represents a significant cause of third-trimester bleeding. Complete previa describes placenta completely covering the internal os. Partial previa indicates partial coverage of the os. Marginal previa exists when the placental edge is within 2 cm of the os but not covering it. Low-lying placenta describes implantation in the lower uterine segment with the edge more than 2 cm from the os. The classification determines clinical management and delivery planning. Risk factors for placenta previa relate primarily to uterine scarring and require large placental surface area. Prior cesarean delivery is the most significant risk factor, with risk increasing with each additional cesarean. Prior placenta previa increases recurrence risk substantially. Multiple gestation requires more placental implantation area, increasing lower segment implantation likelihood. Advanced maternal age is associated with increased previa risk. Smoking damages the uterine vasculature and may predispose to abnormal implantation. Multiparity also increases risk, possibly related to cumulative uterine trauma. The classic clinical presentation of placenta previa is painless vaginal bleeding in the third trimester. Bleeding episodes may be recurrent with unpredictable timing and severity. The absence of abdominal pain distinguishes previa from placental abruption, which typically presents with painful bleeding. Diagnosis is established by ultrasound, which should be performed transabdominally initially and followed by transvaginal ultrasound for accurate assessment of the relationship between placental edge and internal os. Digital vaginal examination is absolutely contraindicated in suspected previa as it may precipitate life-threatening hemorrhage. Management of placenta previa depends on bleeding severity, gestational age, and maternal stability. Asymptomatic previa identified on ultrasound requires serial imaging as many cases resolve with lower segment formation. First bleeding episode often occurs around 28-30 weeks and typically warrants hospitalization. Blood should be available and large-bore intravenous access maintained for patients with previa experiencing bleeding. Delivery by cesarean section is indicated for complete or partial previa and is typically scheduled at 36-37 weeks if the patient remains stable. Emergency cesarean is performed for life-threatening hemorrhage at any gestational age. Panel A: Classification diagram showing complete previa (placenta completely covering os), partial previa (partial coverage), marginal previa (edge within 2 cm), and low-lying placenta (lower segment, edge greater than 2 cm from os). Panel B: Risk factor hierarchy showing prior cesarean as highest risk, followed by prior previa, multiple gestation, advanced maternal age, smoking, and multiparity. Panel C: Clinical presentation comparison between placenta previa (painless bleeding) and abruption (painful bleeding) with diagnostic approach including ultrasound and contraindication of digital examination. Panel D: Management algorithm based on bleeding severity and gestational age, showing observation for asymptomatic cases, hospitalization for bleeding episodes, and cesarean delivery timing. --- ### VII. Placental Abruption Placental abruption describes premature separation of the placenta from the uterine wall before delivery and carries significant maternal and fetal risk. The separation may be partial or complete and may result in revealed hemorrhage (visible vaginal bleeding) or concealed hemorrhage (blood trapped behind the placenta). Abruption complicates approximately 1% of pregnancies and accounts for significant proportions of perinatal mortality and maternal morbidity. The severity ranges from mild marginal separation with minimal clinical consequence to complete separation with fetal death and maternal disseminated intravascular coagulation. Risk factors for placental abruption include conditions affecting placental implantation and conditions causing acute placental injury. Chronic hypertension and preeclampsia represent the most significant medical risk factors, likely through effects on placental vasculature. Prior abruption confers approximately 10% recurrence risk in subsequent pregnancies. Cocaine use causes acute vasoconstriction and is strongly associated with abruption. Abdominal trauma, including motor vehicle accidents, domestic violence, and falls, can cause direct placental injury. Preterm premature rupture of membranes increases abruption risk, possibly through uterine decompression. Smoking increases risk through chronic vascular effects. Clinical presentation of abruption classically includes vaginal bleeding with abdominal pain, though approximately 20% of cases have concealed hemorrhage without visible bleeding. The uterus is typically tender and may demonstrate increased tone or tetanic contractions. Fetal heart rate abnormalities occur with significant abruption and may progress to fetal death. Maternal instability with tachycardia and hypotension indicates severe hemorrhage. Disseminated intravascular coagulation may develop with large abruptions due to release of thromboplastin from the placental site. Laboratory evaluation shows falling hemoglobin, thrombocytopenia, elevated fibrin degradation products, and prolonged clotting times with DIC. Diagnosis of placental abruption is primarily clinical, as imaging findings are often absent or nonspecific. Ultrasound may show retroplacental clot when present, but absence of visible clot does not exclude abruption. The combination of vaginal bleeding, uterine tenderness, and fetal heart rate abnormalities strongly suggests the diagnosis. Management depends on severity and gestational age. Mild abruption with reassuring fetal status may be managed expectantly with close monitoring. Moderate abruption with stable mother and fetus warrants delivery if the fetus is mature or close monitoring if premature. Severe abruption with fetal compromise or maternal instability requires emergency delivery by the fastest route, with aggressive resuscitation and blood product replacement. Panel A: Abruption anatomy diagram showing partial versus complete separation and revealed (external bleeding) versus concealed (trapped blood) hemorrhage patterns. Panel B: Risk factor illustration showing hypertension/preeclampsia, prior abruption, cocaine use, trauma, PPROM, and smoking with relative risk estimates. Panel C: Clinical presentation triad of vaginal bleeding, abdominal pain/uterine tenderness, and fetal heart rate abnormalities with DIC laboratory parameters. Panel D: Management algorithm stratifying by severity and maternal-fetal stability from expectant management through emergency cesarean delivery. --- ### VIII. Placenta Accreta Spectrum Placenta accreta spectrum disorders represent abnormal placental attachment to and invasion of the uterine wall with potentially catastrophic hemorrhagic consequences. Placenta accreta describes attachment of the placenta directly to the myometrium without the normal intervening decidual layer. Placenta increta indicates invasion into the myometrium. Placenta percreta describes penetration through the myometrium to the uterine serosa or beyond, potentially involving bladder or other adjacent structures. The incidence has increased dramatically in recent decades, paralleling the increase in cesarean delivery rates. Prior cesarean delivery is the dominant risk factor for accreta spectrum disorders, with risk increasing with each additional cesarean. The combination of placenta previa and prior cesarean creates particularly high risk: with placenta previa and one prior cesarean, accreta risk is approximately 3%; with previa and two prior cesareans, risk increases to 11%; with previa and three or more prior cesareans, risk exceeds 40%. Prior uterine surgery including myomectomy and dilation and curettage also increases risk. Advanced maternal age is an independent risk factor. Recognizing patients at risk allows appropriate preparation and delivery planning. Antenatal diagnosis significantly improves outcomes through appropriate preparation and multidisciplinary planning. Ultrasound findings suggestive of accreta include loss of the normal hypoechoic retroplacental zone, placental lacunae (irregular vascular spaces within the placenta), bladder wall interruption, and increased vascularity at the uterine-bladder interface on Doppler. MRI provides additional information about depth of invasion and involvement of adjacent structures. When accreta is suspected, delivery should be planned at a center with appropriate expertise, blood bank resources, and multidisciplinary team availability. Management of confirmed or suspected accreta spectrum requires careful planning and multidisciplinary coordination. Delivery is typically planned at 34-36 weeks to balance risks of emergent presentation against neonatal prematurity. Cesarean hysterectomy is the standard treatment, as attempts to remove the placenta will cause massive hemorrhage. The placenta is left in situ, the hysterotomy is closed, and hysterectomy is completed. A multidisciplinary team including maternal-fetal medicine, gynecologic oncology, urology, anesthesia, and blood bank services optimizes outcomes. Massive transfusion protocol should be activated early with blood products readily available. Attempting manual removal of an accreta placenta is contraindicated and may result in uncontrollable hemorrhage. Panel A: Classification diagram showing accreta (attachment to myometrium), increta (invasion into myometrium), and percreta (penetration through myometrium and potentially into bladder) with anatomical illustrations. Panel B: Risk stratification table showing accreta risk by number of prior cesareans, particularly with concurrent placenta previa, from 3% with one prior cesarean to greater than 40% with three or more. Panel C: Ultrasound and MRI diagnostic features including loss of retroplacental zone, placental lacunae, bladder wall irregularity, and increased Doppler vascularity. Panel D: Planned cesarean hysterectomy approach showing multidisciplinary team composition, delivery timing, surgical technique leaving placenta in situ, and blood product preparation. --- ### IX. Fetal Growth Abnormalities Intrauterine growth restriction (IUGR) is defined as estimated fetal weight below the 10th percentile for gestational age and requires distinction between constitutionally small fetuses and those with pathologic growth restriction. Small for gestational age (SGA) is a descriptive term applying to any fetus below the 10th percentile, while IUGR implies pathologic restriction with associated risk. Symmetric IUGR, where all fetal measurements are proportionally small, suggests early insult such as chromosomal abnormality or infection. Asymmetric IUGR, with relatively preserved head size compared to abdominal circumference, suggests placental insufficiency with brain-sparing and is more common. Etiologies of IUGR are classified as placental, maternal, or fetal causes. Placental causes, the most common, include preeclampsia, chronic hypertension, placental infarction, and abruption, all of which compromise uteroplacental blood flow. Maternal causes include severe chronic disease, malnutrition, smoking, substance use, and certain medications. Fetal causes include chromosomal abnormalities (particularly triploidy and trisomy 18), structural anomalies, and congenital infections including cytomegalovirus and toxoplasmosis. Approximately 30-40% of cases remain unexplained despite thorough evaluation. Evaluation of IUGR aims to identify the underlying cause and assess fetal wellbeing. Detailed ultrasound examines for fetal anomalies that might explain the growth restriction. Doppler velocimetry of the umbilical artery provides important prognostic information, with elevated systolic-to-diastolic ratio indicating increased placental resistance and absent or reversed end-diastolic flow indicating severe compromise with high perinatal mortality. Aneuploidy testing should be considered when IUGR is identified early or is symmetric. Infection screening for CMV and toxoplasmosis may be warranted in early symmetric cases. Serial growth ultrasounds monitor the growth trajectory. Management of IUGR depends on Doppler findings, gestational age, and overall fetal condition. With normal umbilical artery Doppler, serial growth assessment every 2-4 weeks and antenatal testing are appropriate. Abnormal Doppler with elevated resistance warrants increased surveillance frequency with consideration of early delivery based on gestational age. Absent end-diastolic flow indicates severe compromise requiring hospitalization and very close monitoring with delivery consideration. Reversed end-diastolic flow carries high mortality risk and typically warrants delivery at viable gestational age. Delivery timing balances risks of continued intrauterine environment against prematurity, with corticosteroids and magnesium for neuroprotection when delivery is anticipated at early gestational ages. Panel A: Growth restriction classification showing IUGR definition (less than 10th percentile with pathologic restriction), symmetric versus asymmetric patterns, and clinical implications of each. Panel B: Etiology categories showing placental causes (most common, including preeclampsia and abruption), maternal causes (disease, smoking, drugs), and fetal causes (aneuploidy, anomalies, infection). Panel C: Umbilical artery Doppler waveforms showing normal, elevated S/D ratio, absent end-diastolic flow, and reversed end-diastolic flow with associated prognosis for each. Panel D: Management algorithm stratifying by Doppler findings from normal (serial monitoring) through abnormal (increased surveillance) to absent/reversed flow (hospitalization, delivery consideration). --- ### X. Amniotic Fluid Abnormalities Oligohydramnios is defined as decreased amniotic fluid with amniotic fluid index (AFI) less than 5 cm or maximum vertical pocket (MVP) less than 2 cm. Causes include preterm premature rupture of membranes, uteroplacental insufficiency causing decreased fetal urine output, fetal renal anomalies or obstruction preventing urine production, and post-term pregnancy with placental senescence. Complications of oligohydramnios include cord compression from decreased fluid buffering, pulmonary hypoplasia from prolonged severe oligohydramnios, and limb deformities from compression. Management involves determining the underlying cause, increased fetal surveillance, and delivery timing based on cause and gestational age. Polyhydramnios is defined as increased amniotic fluid with AFI greater than 24-25 cm or MVP greater than 8 cm. Etiologies include fetal gastrointestinal obstruction preventing swallowing of amniotic fluid, fetal neurologic abnormalities affecting swallowing, fetal aneuploidy, twin-twin transfusion syndrome in monochorionic pregnancies, and maternal diabetes causing fetal polyuria. Complications include preterm labor from uterine overdistension, malpresentation, umbilical cord prolapse with membrane rupture, and placental abruption. Management depends on severity and cause, with mild idiopathic polyhydramnios often requiring only observation while severe symptomatic cases may benefit from amnioreduction. Intrahepatic cholestasis of pregnancy presents characteristically with pruritus, particularly of the palms and soles, typically appearing in the third trimester without primary skin lesions. Laboratory evaluation reveals elevated total bile acids (greater than 10 micromoles per liter) as the defining finding, with liver transaminases often mildly elevated. The maternal symptoms, while distressing, are not dangerous; however, the fetal risks include stillbirth, with risk increasing with higher bile acid levels. Treatment with ursodeoxycholic acid reduces bile acids and improves pruritus, though evidence for reducing stillbirth risk is limited. Delivery is recommended at 36-37 weeks to prevent stillbirth, with earlier delivery considered for very high bile acid levels. Other third-trimester complications require awareness for prompt recognition and management. HELLP syndrome, discussed with hypertensive disorders, represents severe preeclampsia variant with hemolysis, elevated liver enzymes, and low platelets. Acute fatty liver of pregnancy is a rare but life-threatening condition presenting with liver failure, coagulopathy, and encephalopathy requiring delivery and supportive care. Uterine rupture, a catastrophic complication primarily affecting women with prior cesarean, presents with sudden abdominal pain, fetal heart rate abnormalities, and loss of station requiring emergency delivery. Panel A: Oligohydramnios definition, causes (PPROM, uteroplacental insufficiency, fetal renal anomalies, post-term), complications (cord compression, pulmonary hypoplasia), and management approach. Panel B: Polyhydramnios definition, causes (GI obstruction, neurologic abnormality, aneuploidy, TTTS, diabetes), complications (preterm labor, malpresentation, cord prolapse), and management based on severity. Panel C: Cholestasis of pregnancy presentation (pruritus without rash, palms and soles), laboratory findings (elevated bile acids, elevated transaminases), fetal risks (stillbirth), and treatment (ursodeoxycholic acid, delivery at 36-37 weeks). Panel D: Third-trimester complication summary including HELLP syndrome, acute fatty liver, and uterine rupture with key distinguishing features. --- ## Summary - Preterm labor definition: regular contractions plus cervical change before 37 weeks gestation - Fetal fibronectin: negative result has high negative predictive value (less than 2% deliver within 2 weeks) - Antenatal corticosteroids: betamethasone 12 mg intramuscularly for 2 doses at 24-34 weeks reduces RDS, IVH, NEC, and death - Magnesium neuroprotection: indicated for delivery anticipated before 32 weeks to reduce cerebral palsy risk - PPROM diagnosis: sterile speculum examination showing pooling, ferning, nitrazine positive; avoid digital examination - PPROM management 24-34 weeks: expectant management with corticosteroids, latency antibiotics, delivery for chorioamnionitis - Placenta previa: painless third-trimester bleeding; digital examination absolutely contraindicated; cesarean delivery - Placental abruption: painful bleeding with tender, hypertonic uterus; may cause DIC; emergent delivery if unstable - Placenta accreta: prior cesarean plus previa is major risk factor; planned cesarean hysterectomy with multidisciplinary team - IUGR: umbilical artery Doppler guides management; absent or reversed end-diastolic flow indicates severe compromise --- ## Key Terms | Term | Definition | |------|------------| | Preterm | Delivery before 37 completed weeks of gestation | | Tocolysis | Medications administered to suppress uterine contractions and delay preterm delivery | | PPROM | Preterm premature rupture of membranes; membrane rupture before 37 weeks and before labor onset | | Placenta previa | Placental implantation over or near the internal cervical os | | Placental abruption | Premature separation of the placenta from the uterine wall before delivery | | Placenta accreta | Abnormal placental attachment directly to myometrium without intervening decidua | | IUGR | Intrauterine growth restriction; pathologic fetal growth below 10th percentile | | Oligohydramnios | Decreased amniotic fluid with AFI less than 5 cm or MVP less than 2 cm | --- *This content is subject to the [MIT License](https://opensource.org/licenses/MIT). © 2024–2026 Hibbert School of Medicine.*