F99The influence of maternal hematocrit on placental size and growth from the first to mid‐second trimesters of pregnancy

Objectives To study the association of maternal hematocrit (Ht) levels with placental size and growth in the first and mid-second trimesters of pregnancy. Subjects/methods One hundred and forty pregnant women with a singleton pregnancy were recruited at 11–14 weeks’ gestation. For each case we performed three scans of the placenta the first at recruitment and the following two in three weeks intervals. The volume of the placenta was measured at each visit using a three dimensional ultrasound scanner. The Hb and Ht were measured within two weeks from the first scan. Results The placental growth from early second (14–17 weeks) to mid-second (17–20 weeks) trimesters was inversely related to the Ht levels (r = −0.263, P < 0.01). Similar results were observed for the overall placental growth (r = −0.27, P < 0.01). The placental volume at mid second trimester* (17–20 weeks) was also inversely related to Ht (r = −0.18, P < 0.05). However, the placental volume at the first trimester*, early second trimester* and the placental growth from 11 to 17 weeks were not found to be associated with ht levels. Discussion This study demonstrates the effects of maternal environment on placental growth. Our data suggests that the levels of Ht appear to affect the placental size mainly at the second trimester. Further studies about the factors that regulate placental growth are needed to elucidate the pathophysiology of these interactions and their effect to the pregnancy outcome. *(Corrected for gestational age)