How Your Babies Grow: Twins and Triplets

Back To Part 2 Back to Part 2
Research has shown that the overall pattern of growth before birth for well-grown multiples does not differ from that of singletons until late in pregnancy, when the rates of growth for multiples slow down. Twins and triplets growing at the 90th%ile had birthweights equal to the singleton 50th%ile by 38 weeks (twins) and 34 weeks (triplets)—as shown in the solid lines in the graphs (singleton growth curves are shown in the dotted lines).
  • The rate and pattern of maternal weight gain has a strong influence on the rate of fetal growth and ultimate birthweight.
  • The rate of fetal growth is significantly associated with length of gestation.
  • Babies who are well-grown and mature are healthier at birth and throughout childhood.




Birthweight Reference for Twins and Triplets


Weeks of Gestation
    24 26 28 30 32 34 36 38 40
                     
Mean Weight Singletons 677 885 1133 1455 1852 2314 2805 3244 3562
(grams) Twins 687 909 1152 1424 1721 2037 2375 2659 2854
  Triplets 652 853 1080 1330 1619 1876 --- --- ---
                     
                     
10th Percentile Twins 500 691 898 1130 1382 1650 1930 2154 2333
  Triplets 472 657 848 1060 1287 1529 --- --- ---
                     
                     
50th Percentile Twins 678 897 1144 1412 1711 2030 2363 2657 2847
  Triplets 656 857 1084 1335 1626 1893 --- --- ---
                     
                     
90th Percentile Twins 888 1133 1419 1732 2078 2444 2831 3160 3420
  Triplets 825 1053 1317 1619 1959 2262 --- --- ---





Singletons birthweights adapted from Kramer, Platt, Wu, et al, Pediatrics, 2001.
Twin birthweights adapted from Min, Luke, Gillespie, et al, Am J Obstet Gynecol, 2000.
Triplet birthweights adapted from Min, Luke, Min, et al, Am J Obstet Gynecol, 2004.