Polyhydramnios

Excess amniotic fluid volume for gestational age. Roughly 50 to 60% are idiopathic. Identifiable causes include maternal diabetes (a leading identifiable cause, via fetal osmotic diuresis from hyperglycemia), fetal structural anomaly impairing swallowing or fluid absorption (esophageal or duodenal atresia, anencephaly, and other central nervous system or gastrointestinal anomalies), fetal anemia (from red cell alloimmunization or parvovirus B19 infection, driving high-output cardiac failure), multiple pregnancy (particularly twin-to-twin transfusion syndrome in monochorionic twins), and fetal hydrops.

Amniotic fluid index above 24 to 25 cm, or single deepest vertical pocket above 8 cm, defines polyhydramnios on ultrasound
Screening for the underlying cause: OGTT for undiagnosed maternal diabetes, detailed fetal anatomy survey for structural anomaly, maternal red cell antibody screen and middle cerebral artery Doppler peak systolic velocity for fetal anemia, and assessment for multiple pregnancy and its specific complications

Treat the identifiable underlying cause where present, optimize glycemic control if diabetes is diagnosed or worsened
Mild, idiopathic polyhydramnios generally requires only increased surveillance
Amnioreduction (therapeutic amniocentesis to drain excess fluid) is considered for severe, symptomatic polyhydramnios causing significant maternal discomfort or respiratory compromise, though fluid tends to reaccumulate and repeated procedures may be needed
Indomethacin has historically been used to reduce fetal urine output and amniotic fluid volume in selected cases, but carries a risk of premature ductus arteriosus closure and is generally avoided beyond 32 weeks and used only under specialist guidance
Increased vigilance for preterm labor, and, at membrane rupture (spontaneous or for induction), controlled amniotomy (slow drainage rather than rapid rupture) to reduce the risk of cord prolapse and placental abruption from sudden uterine decompression
Active management of the third stage with vigilance for postpartum hemorrhage, given elevated risk from uterine overdistension and atony

Referral: fetal medicine specialist for moderate to severe polyhydramnios or where a structural or hematological fetal cause is identified or suspected.

Multiple Pregnancy

Pregnancy with two or more fetuses, classified by zygosity and chorionicity, the latter being the single most important determinant of risk and management pathway.

Dichorionic diamniotic (DCDA) twins (either dizygotic, or monozygotic splitting within 3 days of fertilization) have separate placentas and carry the lowest risk.

Monochorionic diamniotic (MCDA) twins (monozygotic splitting 4 to 8 days post-fertilization) share a single placenta with a shared circulation, carrying specific risks including twin-to-twin transfusion syndrome.

Monochorionic monoamniotic (MCMA) twins (splitting after day 8) share both placenta and amniotic sac, carrying the highest risk given the potential for cord entanglement.

Uterine size greater than expected for dates, exaggerated pregnancy symptoms (nausea, breathlessness), and, later in pregnancy, palpation of multiple fetal poles.

Multiple pregnancy carries substantially elevated risk of nearly every obstetric complication: hyperemesis, pre-eclampsia, gestational diabetes, anemia, preterm labor (the leading cause of perinatal morbidity in twins), malpresentation, and postpartum hemorrhage.

Chorionicity must be determined by ultrasound in the first trimester (ideally 11 to 14 weeks), since it becomes progressively harder to assess later and dictates the entire subsequent management pathway; the lambda sign (a triangular projection of placental tissue between the membranes at the base) indicates dichorionicity, while the T-sign (membranes meeting the placenta at a right angle) indicates monochorionicity
Serial growth scans are more frequent than in singleton pregnancy: every 4 weeks from 20 weeks in DCDA twins, every 2 weeks from 16 weeks in MCDA twins, given the need for early detection of twin-to-twin transfusion syndrome
Screening for twin-to-twin transfusion syndrome in monochorionic twins uses ultrasound assessment of amniotic fluid discordance (oligohydramnios in one sac, polyhydramnios in the other) and bladder visualization, staged using the Quintero staging system

Aspirin 75 to 150 mg PO od from 12 weeks, given multiple pregnancy is itself a risk factor for pre-eclampsia
Increased iron and folate supplementation given elevated anemia risk
Twin-to-twin transfusion syndrome (MCDA twins): significant or progressive disease (Quintero stage II or above) is treated with fetoscopic laser ablation of the shared placental vascular anastomoses at a specialist fetal medicine center, offering the best outcomes compared with amnioreduction alone
Timing of delivery: uncomplicated DCDA twins, offer delivery from 37 to 37+6 weeks; uncomplicated MCDA twins, offer delivery from 36 to 37 weeks (after a course of corticosteroids given the earlier timing); MCMA twins are typically delivered by planned cesarean around 32 to 34 weeks, given the ongoing cord entanglement risk, often with prior admission for continuous monitoring from around 26 to 28 weeks
Mode of delivery: vaginal delivery is generally appropriate if the first (presenting) twin is cephalic, with cesarean considered for a non-cephalic first twin, MCMA twins, or other specific complications; delivery of twins should occur in a unit with immediate access to cesarean facilities given the risk of complications with the second twin
Active management of the third stage is essential given substantially elevated postpartum hemorrhage risk from uterine overdistension, with oxytocin infusion often continued for a longer duration postpartum

Referral: obstetric-led care for all multiple pregnancies; specialist fetal medicine center for monochorionic twins and any suspected twin-to-twin transfusion syndrome.

Polyhydramnios

Overview

Clinical Features

Diagnosis

Management

Overview

Clinical Features

Diagnosis

Management