• Birthweight;
  • percentiles;
  • placental weight;
  • population;
  • singleton

Objective  To produce population-based, gender- and gestational-age-specific centile curves for placental weight.

Design  Population study.

Setting  Medical Birth Registry of Norway

Population  All singleton live births in Norway from 1 January 1999 to 31 December 2002.

Methods  In a cohort of children born in Norway, placental weights and the ratio of the birthweight to the placental weight were analysed to produce percentile curves.

Main outcome measures  Placental weight, birthweight-to-placental weight ratio.

Results  Tables and figures are presented for placental percentiles curves according to gestational age and gender. Also, tables and figures are presented for the ratio of birthweight to placental weight.

Conclusions  To our knowledge, this is the first time that population percentile curves have been produced for placental weights and hence for the ratio of birthweight to placental weight. These percentile curves may act as a reference for other populations as well until population-specific curves can be produced.