Relationship between type and weight of placenta and neonate birth weight in twin pregnancy

The relationship between the type and size of placenta and the development of twin fetuses is still discussed in perinatology. The objective of this paper is to answer the question whether the final weight and size of placenta is a limiting factor for fetal growth in twin pregnancy. The study material consisted of 1,261 pairs of fetuses from monochorionic (MC) and dichorionic (DC) twin pregnancies, born by cesarean section between pregnancy weeks 22 and 41 at the Perinatology and Gynecology Department of the Poznan University of Medical Sciences between 2003 and 2009. Histological examination of secundines, placental weights, and birth weight of twins were evaluated, and the newborn condition was assessed by the Apgar score. Statistical evaluation by analysis of variance assessed placental growth related to gestational age and also the effect of placental-fetal weight ratio on neonate clinical condition. We observed an increase in placenta growth until 38 weeks of pregnancy in twins sharing one placenta and until 36 weeks of pregnancy in twins with separate placentas. Between 22 and 35 weeks of pregnancy, the placental-fetal weight ratio in twins sharing one placenta was higher and they were also smaller than twins with separate placentas The placental-fetal weight ratio was comparable in all twins at delivery and was associated with the clinical condition of newborns. Newborns who received an Apgar score of 8 or more 10 minutes post delivery had a lower ratio than neonates with Apgar score equal to or lower than 7 (p≤0.01). Although these latter twins had both smaller placentas and smaller birth weights, their placental-fetal weight ratios were significantly higher than those of twins born in good condition. Placental growth decreases before pregnancy term but does not limit fetal birth weight in twin pregnancy.