High placental index and poor pregnancy outcomes: a retrospective study of 18 386 pregnancies

Introduction: Our aim was to state the correlation between placental index and pregnancy outcomes or in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) pregnancies. Materials and methods: We included in this retrospective study all singleton births in a third level clinic during the period 2001-2011 (n = 18 386). We divided placental index into quartiles and analyzed the differences between the groups in term of pregnancy outcomes. Then, we estimated crude and adjusted odds ratios (ORs) for placental index over the third centile of the distribution to correlate with pregnancy outcomes. We also analyzed the correlation between IVF/ICSI conceived pregnancies and placental index. Results: Poor pregnancy outcomes were overrepresented in the highest quartile of placental index distribution. Thus, placental index was higher in pregnancies characterized by pregnancy-related hypertensive disorders (PRHDs), small for gestational age infants, newborn needing cardiopulmonary resuscitation or hospitalization in neonatal intensive care unit. These findings were independent of maternal age, length of gestation at delivery, IVF/ICSI conception and ethnicity. For IVF/ICSI pregnancies, the OR for being over the third quartile of placental index distribution was 2.01 (CI. 95 1.40-2.90) after adjustment for maternal age, length of gestation, ethnicity, birth weight, parity, fetal sex, alteration of glucose metabolism in pregnancy and PRHDs. Conclusions: We found a high placental index among pregnancies characterized by poor outcomes and conceived by IVF/ICSI.