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The NICHD Fetal Growth Study: Twin Gestations

This study has been completed.
Information provided by (Responsible Party):
National Institutes of Health Clinical Center (CC) ( Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) ) Identifier:
First received: June 8, 2011
Last updated: August 2, 2017
Last verified: August 1, 2017
June 8, 2011
August 2, 2017
May 29, 2011
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Complete list of historical versions of study NCT01369940 on Archive Site
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The NICHD Fetal Growth Study: Twin Gestations
NICHD Fetal Growth Study: Twin Gestations


-Normal growth and development of twins are important for a healthy pregnancy and the long-term health of the children. This study will look at how twins grow and develop inside the womb. This knowledge may reduce and/or prevent pregnancy and newborn health problems in the future.


-To describe how twins grow.

To describe how identical (from the same egg) and fraternal (from different eggs) twins grow.

  • To compare growth patterns between twin and single pregnancies.
  • To find out how many babies have growth problems and why they have them.


-Women from nine U.S. clinical centers who are in the first three months of a twin pregnancy.


  • Participants will answer questions about personal characteristics (age, education, race). They will also answer questions about pregnancy history, health behavior, and their environment. This will take about 30 minutes. They will also fill out a questionnaire about physical activity, and mood and depression. An ultrasound will be done to check on the babies measurements.
  • Participants will return for six visits during their pregnancy. Each follow-up will include an ultrasound and a test to measure the length of the cervix. We will ask questions about health and any events or symptoms since the visit before. We will also take body measurements.
  • A nutrition questionnaire will be completed at the first visit and at follow-up visits 2 and 5.
  • Blood will be drawn at the beginning of the study, at three follow-up visits, and just before delivery.
  • When the babies are born, they will have placenta and cord blood samples, measurements, and swabs from the inside of the mouth.

Fetal growth is an important determinant of health and disease in the perinatal period, childhood and adult life. NICHD is conducting an ultrasound study in singleton pregnancies to establish a national standard for normal fetal growth by gestation and interval velocities. Twins represent 3.2% of all births in the U.S, and these pregnancies are at increased risk for fetal growth disorders, preterm and, most importantly, very preterm delivery. The rate of small-for-gestational-age (SGA) defined as below the 10th percentile using a singleton birth weight-for-gestational-age reference is 35%. Neonatal morbidity is higher in twin gestations than in singletons (25.6 versus 4 per 1,000), and the infant mortality rate is also higher (31 versus 6.4 per 1,000). Discrepancy in the sizes of twins at birth is a frequent phenomenon, and is associated with an increased risk of perinatal morbidity and mortality.

The trajectory of fetal growth in twins throughout gestation has been observed and described in a few studies, both using ultrasonography and ultrasonography combined with birth weight. The findings suggest a slowing of growth for almost all twins after 28-30 weeks gestation, and even twins who had been growing at rates similar to singletons before 28 weeks may show slowed rates of growth in the third trimester. It has been hypothesized that this pattern of growth for even well-growing twins is a normal down-regulation in response to a constricted uterine environment and may underscore the need for a birth weight-for-gestational-age or ultrasound reference that is specific for twins. As for singleton births, however, such slow-downs later in pregnancy appear to be associated with earlier delivery and a greater risk for morbidity associated with preterm birth. This would argue against a separate reference for twins or, at least, for the development of a growth velocity standard for singletons and twins to allow for the accurate assessment of interval growth to better manage these cases.

We propose to conduct the NICHD Fetal Growth Study Twin Gestations, which is a prospective cohort study with longitudinal measurement of fetal growth conducted in nine clinical centers. Overall, there are four main research objectives: 1) to describe fetal growth trajectories in twins using two- and selected three-dimensional ultrasound measures; 2) to compare and contrast fetal growth trajectories for twins with the newly established fetal growth standard developed for singletons to determine its applicability for monitoring the growth of twin fetuses and discordant growth of the pair; 3) to estimate the incidence of growth restriction (with SGA as a proxy) in singleton and twin gestations (by zygosity), however, growth restriction may be defined by the new growth standard; and 4) to compare singleton and twin gestations with respect to maternal biomarkers of fetal growth, well-being and maternal nutritional status using banked biospecimens to determine if the biomarkers ranges established for singletons are applicable to twin gestations.

This study will recruit 350 pregnant women with a twin gestation from nine clinical centers. The study is designed to enroll approximately 350 dichorionic twin pairs based upon incidence figures for twinning at the population level. Women will be recruited during the first trimester and followed until delivery. Serial ultrasound assessments of fetal growth are the standard of care for twin pregnancies, and we will coordinate the timing of research ultrasounds to the fullest extent possible with clinical scans to minimize exposure as further described in this protocol. Each woman will have seven scheduled ultrasound examinations, including fetal biometry at all visits, fetal Doppler studies, and four blood draws at baseline and at targeted gestational ages for the eventual identification of biomarkers indicative of fetal growth. After delivery, neonatal anthropometric measures will be assessed for each twin, and select information about the obstetrical course and newborn status will be abstracted from medical charts.

Time Perspective: Prospective
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  • Fetal Growth Restriction
  • Growth Discordancy
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*   Includes publications given by the data provider as well as publications identified by Identifier (NCT Number) in Medline.
August 1, 2017
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  • Twin, viable pregnancy
  • 8+0 13+6 weeks of gestation
  • Maternal age 18 45 years
  • Spontaneous pregnancy or pregnancy from ovulation induction or in-vitro fertilization with known date of transfer
  • Pregnancy from egg donor or embryo donor (record if anonymous or known source)
  • LMP-date and crown-rump length measurement match within certain number of days according to a standard scheme (for larger


- Expect to deliver at one of the participating hospitals


  • Fetal reduction (medically induced only)
  • Congenital anomalies (structural or chromosomal)
  • Either twin with an increased nuchal translucency (>99th percentile for crown-rump length; i.e. 3.5 mm or more)
  • Monochorionic twins
  • Crown-rump length discordancy >10% in dichorionic twin pregnancies74
Sexes Eligible for Study: Female
18 Years to 45 Years   (Adult)
Contact information is only displayed when the study is recruiting subjects
United States
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National Institutes of Health Clinical Center (CC) ( Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) )
Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
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Principal Investigator: Germaine M Louis, M.D. Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
National Institutes of Health Clinical Center (CC)
August 1, 2017

ICMJE     Data element required by the International Committee of Medical Journal Editors and the World Health Organization ICTRP