Twin Pregnancy Obstetric Care Guidelines

Many aspects of the obstetric management of a twin pregnancy are different than for a singleton pregnancy. Therefore, the maternal-fetal medicine specialists at Brigham and Women’s Hospital (BWH) compiled the following guidelines for the obstetric care of women with twin pregnancies. These guidelines are based on current research, professional society guidelines and the combined knowledge and experience of BWH’s maternal-fetal medicine specialists.

Printable Diagram of the Classification of Identical Twins

What is the recommended timing for office visits for twin pregnancies?

Uncomplicated Twin Pregnancy Recommended Timing of Office Visits




Dichorionic-Diamniotic (Di-Di)

  • First prenatal visit
  • 28 weeks
  • 36 weeks
  • Every four weeks
  • Every two weeks
  • Every week until delivery

Monochorionic-Diamniotic (Mo-Di)

  • First prenatal visit
  • 16 weeks
  • 36 weeks
  • Every four weeks
  • Every two weeks
  • Every week until delivery

Monochorionic-Monoamniotic (Mo-Mo)

  • First prenatal visit
  • 16 weeks
  • Recommend inpatient admission with daily fetal surveillance at 24-28 weeks (after individualized discussion with patient)
  • Every four weeks
  • Every two weeks

Click here for an illustrated and printable diagram of the classification of identical twins that you can share with your patient.

What are imaging protocol recommendations for twin pregnancies?

Below are imaging protocol recommendations adapted from the executive summary on fetal imaging published in the American Journal of Obstetrics & Gynecology in May 2014.*




Pregnancy dating

First trimester

  • Optimal during 7-10 weeks
  • Measure crown-rump length

Determination of chorionicity

First trimester

  • High accuracy, if performed during the first trimester

Assessment of nuchal translucency

10-13 weeks

  • Increased with aneuploidy malformations and twin-twin transfusion syndrome

Anatomic survey and placental evaluation

Second trimester

  • Optimal during 18-20 weeks

Follow up for Di-Di twins

Starting at 24 weeks

  • Assess every 4 weeks for uncomplicated Di-Di twins

Follow up for Mo-Di twins

Starting at 16 weeks

  • Assess bladder and amniotic fluid every 2 weeks
  • Assess growth every 4 weeks. Assess more frequently if abnormal.
  • Assess more frequently for
    Mo-Mo twins

Amniotic fluid evaluation

As indicated

  • A maximum vertical pocket of 2-8 centimeters is normal

Doppler scan

As indicated

  • Not recommended without an indication (e.g., abnormal growth)

* Reddy, UM, Abuhamad AZ, Levine D, Saade GR for the Fetal Imaging Workshop Invited Participants. Fetal imaging: Executive Summary of a Joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging Workshop. Am J Obstet Gynecol 2014; 210 (5): 387-397.

What are the nutritional needs for women carrying twins?

A woman carrying twins has unique nutritional needs, especially for additional calories. Because the patient most often experiences early satiety and loss of appetite, we recommend a consult with a nutritionist to address this and other issues.

  • She must increase her daily dietary intake by about 600 calories per day, 300 calories more than a woman carrying a singleton gestation.
  • High-protein shakes are recommended given the high nutritional value.
  • Because women carrying twins are at an increased risk of developing anemia, the Society of Maternal-Fetal Medicine recommends 30 milligrams of iron during the first trimester and 60 milligrams of iron until delivery. The Society of Maternal-Fetal Medicine also recommends that they take 1 mg of folic acid to prevent neural tube defects (most prenatal vitamins have 0.4 to 0.8 mg of folic acid so extra supplementation is recommended).

Below are the Institute of Medicine’s recommendations for weight gain while carrying twins.



<18.5 (underweight)

No recommendation due to insufficient data.

18.5-24.9 (normal weight)

37-54 pounds or 16.8-24.5 kilograms

25.0-29.9 (overweight)

31-50 pounds or 14.1-22.7 kilograms

≥30.0 (obese)

25-42 pounds or 11.4-19.1 kilograms

What are aneuploidy screening recommendations for twin pregnancies?

All women carrying twins — regardless of age — are candidates for routine aneuploidy screening. For dizygotic twins, there is a higher probability that one or more of the fetuses will have a trisomy, resulting in a higher overall risk to the pregnancy.

  • We recommend that all women carrying twins have integrated serum screening with a first trimester nuchal translucency measurement.
  • Invasive diagnostic testing with chorionic villus sampling (CVS) or amniocentesis are available options.
  • Cell-free fetal DNA from the mother’s plasma is available as a screening test for singleton pregnancies at higher risk of aneuploidy. The use of cell-free fetal DNA in twin pregnancies is currently not supported by ACOG. However, understanding the higher risk of false positives and false negatives associated with the use of cell-free fetal DNA in twin pregnancies, this test can be offered to patients who are over the age of 33 or 35 (depending on the kind of twins).

The incidence of congenital anomalies is 3-5 fold higher in monozygotic twins than in singletons or dizygotic twins; thus, we stress the importance of an early anatomy ultrasound. The concordance rate of major congenital malformations is approximately 20% in monozygotic twins.

What are the preterm labor monitoring recommendations for twin pregnancies?

  • The use of FFN as a screening method for risk of preterm labor in asymptomatic women is not recommended.
  • Data from meta-analyses have shown that cervical shortening on transvaginal ultrasound examination identifies twin pregnancies that are at high risk for preterm birth. However, the positive predictive value for preterm birth is low.
  • We recommend the assessment of cervical length at the anatomy ultrasound, at 22-24 weeks, and at 28 weeks.
  • If cervical length is a concern, the length should be more closely evaluated.
  • If the cervical length measures less than 1 centimeter or there is a rapid change in the cervical shortening, the administration of steroids for fetal lung maturity should be considered after 24 weeks since the risk of preterm labor is high.
  • The optimal management of women with a current twin gestation and a prior singleton preterm birth is unclear. Data shows that a prior singleton preterm birth is an independent risk factor for preterm birth in twins. Currently, since there is no data clearly showing harm or lack of efficacy, the use intramuscular 17-OH progesterone caproate in women with a current twin gestation and a history of a prior preterm birth remains controversial.
  • The use of vaginal progesterone for shortened cervix in twin pregnancies is controversial and it is currently not supported by ACOG and SMFM.
  • Data from a meta-analysis published by Dr. Romero and his colleagues has demonstrated that the use of vaginal progesterone for prevention of preterm birth in twin gestations with a shorter cervix is associated with a non-significant reduction in preterm birth, but a significant reduction in composite neonatal morbidity and mortality. Based on this data, the use of vaginal progesterone seems to be a reasonable option for cervical shortening in twin pregnancies.**

Arabin Pessary diagram

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  • The placement of an Arabin pessary may be considered to manage progressive cervical shortening to prevent preterm birth and reduce neonatal morbidity.
  • While randomized studies are being conducted, we recommend using an Arabin pessary to manage progressive cervical shortening because it is non-invasive, inexpensive, and not known to cause harm to the patient or fetuses.
  • The Arabin pessary is inserted by the provider and remains in place until 36-37 weeks. It does not need to be removed or cleaned. Patients should be informed that they will very likely experience daily watery white vaginal discharge and sometimes could be confused with rupture of membranes.
  • If vaginal bleeding, preterm labor, or rupture of membranes becomes a concern, the Arabin pessary should be removed for adequate assessment. If there are no changes and patient is stable, it may be re-inserted.
  • Prophylactic cerclage, prophylactic tocolytics, routine hospitalization, and bed rest have not been proven to decrease neonatal morbidity and mortality and therefore, they are not recommended.
  • Magnesium sulfate administration is recommended to decrease the risk of cerebral palsy if your patient is at risk of preterm delivery before 32 weeks
  • A course of antenatal corticosteroids is recommended if your patient is between 24 and 34 weeks of gestation and is at risk of preterm delivery within 7 days.
  • A single repeat course of antenatal corticosteroids (“rescue course”) should be considered in women who remain at risk of preterm birth before 34 weeks of gestation.

** Romero R, Nicolaides K, Conde-Agudelo A, Tabor A, O'Brien JM, Cetingoz E, Da Fonseca E, Creasy GW, Klein K, Rode L, Soma-Pillay P, Fusey S, Cam C, Alfirevic Z, Hassan SS Vaginal progesterone in women with an asymptomatic sonographic short cervix in the midtrimester decreases preterm delivery and neonatal morbidity: a systematic review and metaanalysis of individual patient data.

Am J Obstet Gynecol. 2012;206(2):124.e1.

What are the recommendations for observing discordant fetal growth in twin pregnancies?

Discordant fetal growth is defined as a 20% difference in the estimated fetal weight between the larger and the smaller twin. Those pregnancies with discordant growth and at least one growth-restricted fetus have been associated with a 7.7 fold increased risk of major neonatal morbidity. Thus, pregnancies affected by twin growth discordance should have closer surveillance.

In twin pregnancies, what are the recommendations following the death of one fetus?

It is common for a twin pregnancy to undergo spontaneous reduction in the first trimester. In the second trimester, up to 5% of twins undergo death of one or more fetuses.

Following the demise of one twin after 14 weeks, the risk of demise of the co-twin is 12-15% in a monochorionic pregnancy and 3-4% in a dichorionic pregnancy. The risk of neurologic abnormality is greater in monochorionic twins (18-26%) than dichorionic twins (1-2 %).***

Immediate delivery after the demise of a twin in the late second or early third trimester has not been shown to be of benefit for the other twin.

The surveillance and delivery recommendations should be individualized, but generally, in the absence of any other complications, delivery before 34 weeks is not recommended.

*** Ong SS, Zamora J, Khan KS, Kilby MD. Prognosis for the co-twin following single-twin death: a systematic review. BJOG. 2006 Sep;113(9):992-8. Epub 2006 Aug 10.

Hillman SC, Morris RK, Kilby MD. Co-twin prognosis after single fetal death: a systematic review and meta-analysis.

Obstet Gynecol. 2011 Oct;118(4):928-40. doi: 10.1097/AOG.0b013e31822f129d.

When is additional care from a maternal-fetal medicine specialist recommended?

In addition to a woman’s routine care from her obstetrician, consultation with and additional care from a maternal-fetal medicine specialist is recommended in different cases

  • Di-Di twins: with complications such as discordant growth, high risk of preterm delivery, discordant fetal anomalies.
  • Mo-Di twins: with concern for congenital anomalies, unequal placental sharing, discordant growth, TTTS.
  • Mo-Mo twins: we recommend to transfer these patients to MFM specialist for inpatient admission between 24-28 weeks

The maternal-fetal medicine specialists at BWH are always happy to answer questions or provide a consult. You can send a question via email or call us directly.

Carolina Bibbo:
Phone: (617) 732-5452

When is antepartum fetal surveillance recommended in twin pregnancies?

There is no role in antepartum fetal surveillance for uncomplicated Di-Di or Mo-Di twin gestations. Antepartum fetal surveillance is reserved for twin pregnancies complicated by maternal or fetal disorders that require antepartum testing, such as fetal growth restriction.

Have a Question?

We are happy to respond to general questions about twin pregnancies. Please use our online form to send us your twin pregnancy question, and one of our maternal-fetal medicine specialists will respond. Please note that your question will be emailed and responded through a private and secure system.

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