Changes in fetal death during 40 years-different trends for different gestational ages: a population-based study in Norway.

OBJECTIVE: To study changes in gestational-age-specific fetal death risks during a 40-year period. DESIGN: Register-based observational study. SETTING: The Medical Birth Registry of Norway. POPULATION: All pregnancies after 16 weeks of gestation in Norway from 1967 to 2006 (n = 2, 182, 756). METHOD: Changes in fetal death risk since 1967-1971 (reference) were estimated as absolute risks (rates) and relative risks (RR) in ongoing pregnancies at the following gestational weeks; 16-22, 23-29, 30-36 and 37-43. MAIN OUTCOME MEASURES: Fetal death. RESULTS: In all pregnancies lasting longer than 22 weeks, the fetal death rate decreased during 1967-2006. The greatest decline was in term pregnancies (37-43 weeks) from 10.8 to 3.3 fetal deaths per 1000 at risk (crude RR 0.35; 95% CI 0.31-0.38) comparing 1967-1971 with 2002-2006. In pregnancies at 30-36 weeks the fetal death rate declined from 4.5 to 1.1 per 1000 (crude RR 0.23; 95% CI 0.21-0.26). At 23-29 weeks, the rate declined from 2.8 to 1.3 per 1000 (crude RR 0.46; 95% CI 0.40-0.52). An opposite trend was observed at early gestation (16-22 weeks) with an increase from 1.7 to 3.4 fetal deaths per 1000 ongoing pregnancies (crude RR 2.05; 95% CI 1.84-2.27). Adjustments for maternal age, parity, multiple pregnancies, paternal age and pre-eclampsia did not significantly alter the estimated associations. CONCLUSION: Since 1967 the risk of fetal death has been reduced by almost 70% in pregnancies lasting longer than 22 weeks; however, at 16-22 weeks of gestation there was an increase in risk. The causes of this increase should be further explored because it may be attributed to an increase in early delivery caused by the increased proportion of women being treated with cervical cone excision before pregnancy.

Maternal human parvovirus B19 infection and the risk of fetal death and low birthweight: a case-control study within 35 940 pregnant women.

OBJECTIVES: To assess the association between maternal parvovirus B19 infection and fetal death, birthweight and length of gestation. DESIGN: Case-control study. SETTING: Population based. POPULATION: Cases were all 281 women with fetal death within a cohort of 35 940 pregnant woxmen in Norway. The control group consisted of a random sample of 957 women with a live born child. METHOD: Information on pregnancy outcome was obtained from the Medical Birth Registry of Norway. First trimester serum samples were tested for antibodies against parvovirus B19 (IgM and IgG). In seronegative women, further serum was analysed to detect seroconversion during pregnancy. MAIN OUTCOME MEASURES: Fetal death, length of gestation and birthweight. RESULTS: Two of 281 (0.7%) of the women who experienced fetal death and nine of 957 (0.9%) of the controls had presence of IgM antibodies, crude odds ratio 0.8; 95% CI (0.2-3.5). In initially, seronegative women, 3.1% (2/65) with fetal death and 2.6% (8/307) with a live birth seroconverted, crude odds ratio 1.2; 95% CI (0.2-5.7). Presence of maternal parvovirus-specific IgG or IgM antibodies in the first trimester, or seroconversion during pregnancy were not associated with lower birthweight or reduced length of gestation in live born children, but was associated with low birthweight in stillborn offspring. CONCLUSION: Maternal parvovirus B19 infection was not associated with fetal death in our study. Very few cases of fetal death may be attributed to maternal parvovirus B19 infection.