1.5 Multiple Gestation: Chorionicity, Surveillance & Complications

Multiple Gestation: Chorionicity, Surveillance & Complications

Multiple gestation increases physiologic demand and introduces risks that depend strongly on placentation. The first nursing question is not simply “twins or triplets?” but “How many chorions and amnions?” Chorionicity describes placentas; amnionicity describes amniotic sacs. These findings determine surveillance intensity, counseling, and emergency readiness.

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Classification & Ultrasound Clues

Assign chorionicity from the earliest reliable ultrasound; later crowding can obscure membranes. Discordant fetal sex establishes dichorionicity, but same-sex fetuses do not establish monochorionicity. If the report is uncertain, escalate for maternal-fetal medicine review.

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Maternal & General Fetal Risks

Compared with singleton pregnancy, multifetal gestation increases nausea, anemia, hypertensive disorders, gestational diabetes, venous thromboembolism risk, preterm labor, preterm prelabor rupture of membranes, malpresentation, cesarean or operative birth, and postpartum hemorrhage from overdistention. Assess blood pressure and preeclampsia symptoms, nutrition and iron needs, contractions or membrane rupture, fetal movement, psychosocial strain, and ability to attend surveillance.

Each fetus must be labeled consistently—such as Twin A nearest the cervix—and matched across ultrasound, monitoring, medication, specimen, and newborn records. A change in apparent order after birth can create identification errors; use the institutional identification process.

Growth surveillance compares each estimated fetal weight with its gestational-age reference and evaluates discordance. Discordance alone does not diagnose pathology; interpret it with growth percentiles, fluid, Dopplers, chorionicity, and trend. Selective fetal growth restriction in monochorionic pregnancy can reflect unequal placental sharing and requires specialist surveillance.

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Monochorionic Complications

Twin-Twin Transfusion Syndrome

Unbalanced flow through placental vascular connections produces a donor twin with decreased volume and oligohydramnios and a recipient twin with volume overload, polyhydramnios, and cardiac strain. The classic ultrasound pattern is oligohydramnios in one sac and polyhydramnios in the other, with bladder and Doppler findings used for staging.

MCDA twins undergo frequent ultrasound surveillance beginning in the second trimester under the maternal-fetal medicine plan. Report rapid abdominal enlargement, dyspnea, contractions, or a sudden movement change. Fetoscopic laser ablation of communicating vessels may be offered at a specialty center; serial amnioreduction treats fluid burden but not the vascular cause.

TAPS, Monoamnionicity & Other Emergencies

Very small placental connections can cause twin anemia-polycythemia sequence without marked fluid discordance. Middle cerebral artery Doppler patterns suggest anemia in one fetus and polycythemia in the other. Doppler is a screening and surveillance tool, not a stand-alone diagnosis.

MCMA twins can become entangled because they share a sac. Surveillance and planned birth require appropriate maternal and neonatal capability. Twin reversed arterial perfusion involves an acardiac mass perfused by the structurally developed “pump” twin and can cause high-output cardiac failure.

The demise of one fetus in a monochorionic pregnancy can acutely affect the cotwin through shared vessels. Notify the specialist team immediately; do not assume the surviving fetus is unaffected.

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Intrapartum & Postpartum Nursing Care

Before labor or induction, confirm chorionicity, presentations, placental locations, estimated weights, and the birth plan. Ensure two distinguishable fetal heart-rate signals; verify each against maternal pulse and use ultrasound when identity is uncertain. Prepare separate neonatal teams and equipment.

Mode of birth is individualized. Confirm chorionicity, presentation of each fetus, estimated weights and discordance, placental location, and available obstetric and neonatal expertise. When the first twin is cephalic and no other contraindication exists, vaginal birth may be reasonable with a clinician skilled in twin delivery. The second twin may change lie after the first birth, so maintain monitoring and prepare for ultrasound, internal maneuvers, operative delivery, or cesarean. A non-cephalic first twin, monoamniotic pregnancy, major complication, or lack of expertise may change the plan.

After birth, maintain hemorrhage readiness because uterine overdistention predisposes to atony. Quantify loss, assess uterine tone and bladder, administer uterotonics as ordered, and support lactation and adaptation. Discharge teaching addresses preterm needs, safe sleep for each infant, feeding, mood symptoms, transportation, and support.

Discharge and Escalation Teaching

Teach urgent reporting of bleeding, fluid leakage, regular contractions, dyspnea, severe headache, rapid abdominal change, or reduced movement. Follow the chorionicity-specific surveillance and birth plan rather than applying singleton intervals. Anticipate preterm birth, neonatal-team involvement, feeding support, transportation, leave, equipment, and mental-health needs for more than one infant.