How Often Do You Need Scans in a Twin Pregnancy?

Twin pregnancy brings joy and extra responsibility. Because twins are more likely to be born early or to grow unevenly, doctors schedule more scans than in a single pregnancy. The exact schedule depends mainly on the type of twins you carry.

Why are more scans needed?

Twins have higher risks of:

• Preterm birth
• Growth differences between the babies
• Problems related to the placenta
• Twin-to-twin transfusion syndrome (TTTS) in shared placentas
• Pre-eclampsia and gestational diabetes in the mother
• Short cervix

Regular scans detect these early, when treatment works best.

What is the usual schedule?

Guidelines such as those from NICE (UK) and international fetal medicine societies suggest the following. Local practice and your risk factors may vary.

Dichorionic diamniotic twins (separate placentas and sacs)

| When | Purpose |

|---|---|

| 6 to 9 weeks | Confirm twins and heartbeat |

| 11 to 13 weeks | Dating, NT, chorionicity |

| 18 to 22 weeks | Anomaly scan (TIFFA) |

| Every 4 weeks from 20 to 24 weeks | Growth, fluid, Doppler if needed |

| About 32 and 36 weeks | Growth and presentation |

| 36 to 37 weeks | Delivery planning |

Monochorionic diamniotic twins (shared placenta, separate sacs)

| When | Purpose |

|---|---|

| 11 to 13 weeks | Dating, NT, chorionicity |

| Every 2 weeks from 16 weeks | Look for TTTS, growth difference, fluid |

| 18 to 22 weeks | Detailed anomaly scan and fetal echo in some cases |

| Every 2 weeks until delivery | Growth, fluid, Doppler |

| Delivery planning | Often at 36 weeks |

Monochorionic monoamniotic twins (shared placenta and sac)

These are rare and high risk. They need very close monitoring, often with admission to hospital in the late second or third trimester, and early planned delivery by caesarean section.

What does each scan check?

• Growth: Estimated weights, and the difference between the two babies. A difference over 20 to 25 percent may signal selective growth restriction.
• Amniotic fluid: Each baby's fluid pocket. Big differences may suggest TTTS.
• Doppler: Blood flow in the cord and baby's vessels.
• Cervical length: Often measured at 18 to 24 weeks to assess the risk of early birth.
• Position: For delivery planning.
• Bladder and heart: In monochorionic twins, to catch early TTTS signs.

What else is needed besides scans?

• Regular antenatal visits every 2 to 4 weeks
• Blood pressure checks and urine tests
• Early gestational diabetes screening
• Iron, folic acid and calcium supplements
• Advice on diet, rest and warning signs
• Aspirin in selected women at risk of pre-eclampsia

What symptoms need urgent review?

• Sudden rapid increase in belly size
• Severe abdominal pain or tightening
• Leaking fluid or bleeding
• Reduced movements in either baby
• Severe headache, visual changes or swelling
• Persistent vomiting

When is delivery planned?

Dichorionic twins are often delivered at 37 weeks, monochorionic diamniotic at 36 weeks, and monoamniotic at about 32 to 34 weeks. The plan depends on each pregnancy.

If you remember one thing

A good schedule gives you safety and peace of mind. Your care plan will be tailored to your twins. For specialist twin pregnancy care, consult Dr Malathi G. Prasad, a fetal medicine specialist at Trichy Fetal Medicine and Fertility Centre in Trichy.

When you are ready, the twin specialised clinic service page covers timings and preparation; questions about your own situation are best put to our specialists.

Related guides

• When Can Twins Be Detected on an Ultrasound?
• Monochorionic vs Dichorionic Twins: What Is the Difference?