What is the recommended comprehensive management for a twin pregnancy, including prenatal care, supplementation, screening, prophylaxis, monitoring, and delivery timing?

Comprehensive Management of Twin Pregnancy

Initial Assessment and Chorionicity Determination

Establish chorionicity and amnionicity by first-trimester ultrasound at 10-13 weeks' gestation—this single determination dictates all subsequent management and is the most important prognostic factor in twin pregnancy. 1, 2

• Perform dating when crown-rump length is 45-84 mm in the first trimester 2
• Dichorionic (DC) twins have approximately 2-fold lower perinatal mortality compared to monochorionic (MC) twins 2, 3
• MC twins account for 20% of twin pregnancies but 30% of all complications, with an overall mortality rate of approximately 10% 1
• MC monoamniotic (MA) twins represent only 1% of monozygotic pregnancies but require the most intensive management 1

Aneuploidy Screening

• Offer first-trimester combined screening with nuchal translucency measurements at 11-14 weeks, which provides detection rates over 85% in DC twins 2
• Use a threshold of ≥3 mm to define increased nuchal translucency 2
• Generate individual fetus-specific risks for each twin rather than a single combined risk 2
• Sample both twins during diagnostic testing even if only one appears at risk, to avoid missed diagnoses 2
• Perform detailed anatomic survey and fetal echocardiography in the second trimester for twins with increased nuchal translucency or diagnosed aneuploidy 2

Nutritional Supplementation

• Prescribe 40-45 kcal/kg daily for normal-BMI women with twins 4
• Supplement with iron, folate, calcium, magnesium, and zinc beyond standard prenatal vitamins 4
• Consider daily docosahexaenoic acid (DHA) and vitamin D supplementation 4
• Provide antepartum lactation consultation to improve postpartum breastfeeding rates 4

Ultrasound Surveillance Protocol

Dichorionic Diamniotic Twins

• Perform fetal anatomic survey at 18-22 weeks to screen for anomalies (occur in approximately 1 in 25 DC pregnancies) 2
• Measure cervical length via transvaginal ultrasound at the time of anatomic survey to assess preterm birth risk 2
• Screen for vasa previa and velamentous cord insertion, which are more common in multiple gestations 2
• Perform ultrasound surveillance every 3-4 weeks starting from the anatomy scan for uncomplicated DC pregnancies 2

Monochorionic Diamniotic Twins

Begin ultrasound surveillance every 2 weeks starting at 16 weeks of gestation and continue until delivery 1, 3

Each surveillance visit must include:

• Maximum vertical pocket (MVP) measurement in each amniotic sac 1, 3
• Visualization of urine-filled bladder in each fetus 1, 3
• Umbilical artery Doppler studies 1, 3
• Middle cerebral artery peak systolic velocity (MCA-PSV) Doppler to screen for twin anemia-polycythemia sequence (TAPS) 1, 3

Monochorionic Monoamniotic Twins

• Perform biweekly ultrasound surveillance starting at 16 weeks for TTTS and TAPS 5
• Initiate frequent nonstress testing or biophysical profile after viability (typically 24-28 weeks), with some protocols using daily or twice-daily NST as delivery approaches 5

Diagnosis and Management of Monochorionic Complications

Twin-Twin Transfusion Syndrome (TTTS)

Diagnose TTTS when MVP <2 cm in one sac (donor with oligohydramnios) AND MVP >8 cm in the other sac (recipient with polyhydramnios) 1, 3

Management algorithm:

• Stage I TTTS: Manage expectantly with at least weekly fetal surveillance (natural history shows 86% perinatal survival and >75% remain stable or regress) 1
• Consider fetoscopic laser surgery for stage I with maternal polyhydramnios-associated symptoms 1
• Stages II-IV TTTS presenting between 16-26 weeks: Refer immediately to fetal intervention center for fetoscopic laser photocoagulation of placental anastomoses 1, 3
• After laser therapy, perform weekly surveillance for 6 weeks, then resume every-other-week surveillance unless concern exists for post-laser complications 1

Twin Anemia-Polycythemia Sequence (TAPS)

Diagnose TAPS when MCA-PSV >1.5 multiples of the median (MoM) in donor twin AND <1.0 MoM in recipient twin, OR intertwin difference >0.5 MoM 1, 3

Management algorithm:

• Stage I TAPS: Close monitoring with serial ultrasounds 5, 3
• Stage II or higher TAPS before 32 weeks: Mandatory referral to specialized fetal care center for laser therapy evaluation 1, 5
• Stage I TAPS at or after 32-34 weeks: Consider delivery rather than laser therapy 5

Corticosteroid Administration

• Administer one course of corticosteroids for fetal lung maturation at 24 to 33 6/7 weeks if preterm delivery is anticipated 1, 2
• Particularly important in pregnancies complicated by stage III TTTS and those undergoing invasive interventions 1

Delivery Timing

Dichorionic Diamniotic Twins

Plan delivery at 37-38 weeks of gestation for uncomplicated DC diamniotic twins 2

Monochorionic Diamniotic Twins

Deliver at 34-36 weeks of gestation for uncomplicated MC diamniotic pregnancies 2, 3

After successful laser therapy for TTTS:

• Both twins surviving: Deliver at 34-36 weeks 1, 3
• Single fetal demise post-treatment: Deliver surviving co-twin at 39 weeks (full-term) to avoid complications of prematurity unless other indications exist 1, 3

Monochorionic Monoamniotic Twins

Studies show survival rates >90% with early diagnosis, serial sonograms, and antenatal surveillance, with planned preterm cesarean delivery to avoid cord compromise 1

Mode of Delivery

• Base mode of delivery on standard obstetric indications and fetal presentation, not chorionicity alone 2
• Fetoscopic laser surgery should not influence mode of delivery 1

Critical Pitfalls to Avoid

• Never assume chorionicity based on gender or number of placental masses—only first-trimester ultrasound is reliable 1, 2
• Do not use the same surveillance intervals for MC and DC twins—MC twins require twice the frequency 1, 2, 3
• Never delay referral to a fetal intervention center for stage II-IV TTTS or stage II TAPS before 32 weeks—outcomes are time-sensitive 1, 5
• Do not rely on umbilical artery Doppler alone in DC twins without growth restriction—its role remains uncertain 2
• Avoid sampling only the "at-risk" twin during diagnostic testing—both twins must be sampled to prevent missed diagnoses 2
• Increase surveillance frequency immediately if complications develop, including cervical shortening, fetal anomalies, growth disturbances, or amniotic fluid abnormalities 2, 3