BJOG. 2021 Nov 14. doi: 10.1111/1471-0528.17013. Online ahead of print.
ABSTRACT
OBJECTIVE: To assess the relationship between preterm first birth and preterm second birth according to gestational age and to determine the role of placental disorder to recurrent preterm birth.
DESIGN: Population-based registry study.
SETTING: Medical Birth Registry of Norway and Statistics Norway.
POPULATION: Women (N=213,335) who gave birth to their first and second singleton child during 1999-2014 (N=426,670 births).
METHODS: Multivariate logistic regression analyses, adjusted for placental disorders, maternal, obstetric, and socioeconomic factors.
MAIN OUTCOME MEASURES: Extremely preterm (<28+0 weeks), very preterm (28+0 -33+6 weeks), and late preterm (34+0 -36+6 weeks) second birth.
RESULTS: Preterm birth (<37 weeks) rates were 5.6% for first births and 3.7% for second births. Extremely preterm second births (0.2%) occurred most frequent among women with an extremely preterm first birth (aOR 12.90; CI, 7.47-22.29). Very preterm second births (0.7%) occurred most frequent after an extremely preterm birth (aOR 12.98; CI 9.59-17.58). Late preterm second births (2.8%) occurred most frequent after a previous very preterm birth (aOR, 6.86; CI, 6.11-7.70). Placental disorders contributed with 30~40% of recurrent extremely and very preterm births and 10~20% of recurrent late preterm birth.
CONCLUSION: A previous preterm first birth was a major risk factor for a preterm second birth. The contribution of placental disorders was more pronounced for recurrent extremely and very preterm birth than for recurrent late preterm birth. Among women with any category of preterm first birth, more than one in six also had a preterm second birth (17.4%).
PMID:34775676 | DOI:10.1111/1471-0528.17013
