Differences in late fetal death rates in association with determinants of small for gestational age fetuses: population based cohort study |
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| Authors: | Sven Cnattingius Bengt Haglund Michael S Kramer |
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| Affiliation: | aDepartment of Medical Epidemiology, Karolinska Institute, S-171 77 Stockholm, Sweden, bCentre for Epidemiology, National Board of Health and Welfare, Stockholm, Sweden, cDepartment of Pediatrics, McGill University Faculty of Medicine, Montreal, Quebec, Canada |
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| Abstract: | Objective: To examine differences in late fetal death rates in association with determinants of small for gestational age fetuses. Design: Population based cohort study. Subjects: 1 026 249 pregnancies without congenital malformations. Setting: Sweden 1983-92. Main outcome measure: Late fetal death rate. Results: Depending on underlying determinants late fetal death rates were greatly increased in extremely small for gestational age fetuses (range 16 to 45 per 1000) compared with non-small for gestational age fetuses (1.4 to 4.6). In extremely small for gestational age fetuses late fetal death rates were increased from 31 per 1000 in mothers aged less than 35 years to 45 per 1000 in older mothers, and from 22 per 1000 in women <155 cm in height to 33 per 1000 in women ⩾175 cm tall. Late fetal death rates were also higher in extremely small for gestational age fetuses in singleton compared with twin pregnancies and in non-hypertensive pregnancies compared with pregnancies complicated by severe pre-eclampsia or other hypertensive disorders. Slightly higher late fetal death rates were observed in nulliparous compared with parous women and in non-smokers compared with smokers.Conclusions: Although the risk of late fetal death is greatly increased in fetuses that are extremely small for gestational age the risk is strongly modified by underlying determinants—for example, there is a lower risk of late fetal death in a small for gestational age fetus if the mother is of short stature, has a twin pregnancy, or has hypertension. Key messages - Small for gestational age fetuses are at increased risk of late fetal death regardless of the underlying determinants
- The effect of birthweight ratio on risk of late fetal death is modified by underlying determinants, except maternal age
- Regardless of birthweight ratio the rates of late fetal death are higher among women aged 35 years or older compared with younger women
- In pregnancies of extremely small for gestational age fetuses lower rates of late fetal death are associated with a maternal age of less than 35 years, short maternal stature, multiple births, and hypertensive disorders
- In pregnancies with non-malformed fetuses late fetal death rates are increased in smokers, in multiple births, and in women with severe pre-eclampsia.
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