The NICHD Fetal Growth Study: Twin Gestations
Condition: Fetal Growth Restriction; Growth Discordancy
MeSH terms: Fetal Growth Retardation
Study type: Observational

Summary: 
      Normal growth and development of twins are important for the long-term health of the
      children. The purpose of this study was to empirically define the trajectory of fetal growth
      in dichorionic twins using longitudinal two-dimensional ultrasonography and to compare the
      fetal growth trajectories for dichorionic twins with those based on a growth standard
      developed by our group for singletons. This knowledge may lead to interventions that could
      minimize or prevent pregnancy and newborn health problems in the future.
    

Detailed description: 
      A prospective cohort of 171 women with twin gestations was recruited from eight U.S. sites
      from 2012 to 2013. After an initial sonogram at 11w0d-13w6d where dichorionicity was
      confirmed, women were randomized to one of two serial ultrasonology schedules. Ultrasound
      measurements at each follow-up visit included standard fetal biometrics ((BPD, HC, AC, FL);
      estimated fetal weight was calculated using a Hadlock formula. Growth curves and percentiles
      were estimated using linear mixed models with cubic splines. Percentiles were compared
      statistically at each gestational week between the twins and 1,731 singletons in the Fetal
      Growth Studies-Singletons cohort.

      In addition to 2-D ultrasound measures for analyzing fetal growth, this study recorded
      maternal anthropometrics and a brief interview to capture changes in health status, stress
      and depression, and physical activity at each follow-up visit. Four blood draws at baseline
      and at targeted gestational ages for the eventual identification of biomarkers indicative of
      fetal growth were collected. After delivery, neonatal anthropometric measures were assessed
      for each twin, placental biospecimens were collected, and select information about the
      obstetrical course and newborn status were abstracted from medical charts. These exposures
      and outcomes provide opportunities to further 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.

      Biospecimen Description:

        -  Maternal blood sample (serum, plasma, white blood cells, red blood cells and PAXgene
           RNA) at enrollment, 1st, 3rd, 5th follow-up visits, and delivery

        -  Cord blood and placentas for consenting women collected at delivery

        -  Placenta sample or buccal swab (determining zygosity by DNA probe for same sex pairs),
           collected at delivery
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Women with dichorionic twin gestations, irrespective of the mode of conception, maternal
        medical history or obesity status, were enrolled from eight U.S. clinical centers. Women
        were enrolled between 8w0d and 13w6d, and accurate dating was required for enrollment. A
        total of 171 women were recruited, with 152 gestations resulting in live birth.
      
Keywords: Growth Discordancy; Fetal Growth; Twin Growth