Fetal death ratios in a prospective study compared to state fetal death certificate reporting.

A cohort of 6,254 pregnancies surviving at least 20 weeks of gestation was identified through pregnancy testing and follow-up at three Kaiser Permanente medical offices in northern California in 1981-82. Fetal death ratios per 1,000 live births were 12.1 for all fetal deaths versus 5.0 for the subset of fetal deaths reported to the California state registrar. Only fetal deaths resulting in overnight hospitalization of the mother were reported. Seventy-nine percent of fetal deaths over 28 completed weeks since the last menstrual period (LMP) were reported versus only 10 percent between 20 and 28 completed weeks since the LMP. Ninety-three percent of fetuses over 400 grams were reported. The unreported fetal deaths were mainly those perceived by attending physicians as spontaneous abortion, especially missed or incomplete spontaneous abortion. Physicians apparently preferred the label of spontaneous abortion over stillbirth or fetal death whenever fetal maturity could not be substantiated, regardless of prior estimates of the date of the LMP. Fetuses as large and developed as potentially viable infants were the most likely to be reported.