Surveillance And Monitoring Of Twin Pregnancies

Ultrasound surveillance of twin pregnancies starts in the first trimester to assess and screen the growth. It helps in the management of complicated and uncomplicated twin pregnancies. There is always a natural variation in the size of the growth of fetuses in multiple pregnancies.

About the scans and tests to monitor twin or multiple pregnancies

Timely scans help to detect and manage any complications, essential details like chorionicity, which is the type of placenta and membranes your twins have, and check the expected delivery date.

Dating of the pregnancy is suggested before the 14 weeks of gestation period. Delivery of twins is at a high risk of preterm delivery, and calculating the due date is essential for better management of the pregnancy. If the twin pregnancy is through an IVF procedure, the gestational age is calculated as per the date of the transfer of the embryo.

Chorionicity is done to know the exact number of placentae (chorionicity). More than 80% of twin pregnancies are dichorionic, but if it is a monochorionic pregnancy, it can be affected by conditions specific to the sharing of a placental circulation by twins; it calls for more antenatal surveillance.

Amnionicity: This scan is suggested in the second and third trimesters to verify the number of amnions (inner membranes) surrounding the babies.

  • Monoamniotic: All babies share one amniotic sac if it is one amnion.
  • Diamniotic: is described as pregnancies with two amnions.
  • Triamniotic: means there are three amnions.

Twin labelling is done at the first scan and, after that, done on every scan. It is a medical practice to describe each twin with the placement in the womb or any other identification to minimize the chance of confusion at a later stage.

Screening of aneuploidy in twins is done after 10 weeks of gestation. It is a DNA screening to determine the chances of trisomies 13, 18, 21, fetal sex, and sex chromosome aneuploidy.

Anomaly screening in twins is recommended at 18–20+6 weeks gestation. Any fetal anomaly is higher in twin pregnancies than in singleton pregnancies. Cardiac anomalies are more common.

A scan to check the cervical length is suggested at the gestation period of 22-24 weeks and 28 weeks of gestation.

Assessment of fetal growth in twins is recommended to check the normal growth of twins. In the third trimester, the growth pattern differs in multiple pregnancies compared to the singleton.

Conjoined twins are identified in the first trimester so that the parents can opt for the termination of pregnancy due to the high risk of morbidity and mortality.

There are three kinds of twin pregnancies, as shared below:

  • Di-Di twins are at a high risk of premature delivery due to complications like discordant growth and discordant fetal anomalies.
  • Mo-Di twins have unequal placental sharing, discordant growth, TTTS, and congenital anomalies.
  • Mo-Mo twins are high-risk pregnancies and are recommended under the supervision of an MFM (maternal-fetal medicine) specialist from 24-28 weeks onwards.

Risk factors associated with the scans and tests for twin pregnancies

There are no particular risk factors associated with doing the scans and tests. It is done with your doctor’s recommendation and performed in the medical set-up by experts.

Preparing for the scans and tests for twin pregnancies

Normally bladder is to be full at the time of the scan. Wear a two-piece dress so the sonographer can access your abdomen.

What to expect from the scans and tests for twin pregnancies

The complexity, surveillance, and monitoring of twin and multiple pregnancies are purely based on the results of different tests and scans.

Possible results of the scan and test of twin and multiple pregnancies

 It takes two weeks after conception to detect a twin or multiple pregnancies. The results of the further scans are received within a week, and accordingly, the doctor will advise you further.

When to see a doctor

The best time to see the doctor is as soon as you conceive. Discuss the results with your doctor and follow the proper care.


Ultrasounds and tests are important to handle the growth and complications, if any, of twin pregnancies. Depending upon the kind of twin pregnancies, the obstetrician and neonatal expert will advise on the care, monitoring process, and management.

Request an appointment at Apollo Cradle, Amritsar - Abadi Court Road. Call 1860-500-1066 to book an appointment.

1. How are twin pregnancies monitored?

The first ultrasound must be done between 11-14 weeks of gestation and, thereafter, as the doctor recommends.

2. How many scans are required in twin pregnancies?

Scans are typically required every four weeks from the 20th week of the gestation period.

3. What week is full term for twins?

Full-term for a twin pregnancy is the same as full-term for a singleton pregnancy. It is 39 weeks if there is no major complication.

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