Trends in preterm birth in twin pregnancies in Victoria, Australia, 2007–2017

Abstract

Background Preterm birth is a major cause of perinatal morbidity and mortality worldwide. In many countries, the preterm birth rate in women with a multiple pregnancy is increasing, mostly due to an increase in iatrogenic preterm birth. Aims To investigate trends in preterm birth in twin pregnancies in Victoria, Australia, in relation to maternal and perinatal complications. Materials and methods We conducted a retrospective population‐based cohort study in all women with a twin pregnancy who delivered at or after 20 weeks of gestation in the state of Victoria, Australia between 2007 and 2017. Annual spontaneous and iatrogenic preterm birth rates were calculated and trends analysed. Incidence of adverse pregnancy outcomes, maternal complications and risk factors for preterm birth were analysed. Results We studied 12 757 women with a twin pregnancy. Between 2007 and 2017 the preterm birth rate increased from 641/1231 (52%) to 803/1158 (69%), mainly due to an increase in iatrogenic preterm birth from 342/1231 (28%) to 567/1158 (49%). This was irrespective of the presence of pregnancy complications. Our study showed neither a decrease in perinatal mortality from 28 weeks of gestation nor in preterm average weekly prospective stillbirth risk. Conclusion Preterm birth rates in twins in Victoria are increasing, mainly driven by an increase in iatrogenic preterm birth. This occurred both in complicated and non‐complicated twin pregnancies, and has not been accompanied by reduction in perinatal mortality from 28 weeks.

Trends in singleton preterm birth in Victoria, 2007 to 2017: A consecutive cross‐sectional study

“…26,27 Alternatively, it can be reasoned that it is a direct result of more iatrogenic preterm birth. 13 Changes in the baseline characteristics in our study were small and clinical relevance is doubtable.…”

“…The substantial increase in iatrogenic preterm birth found in our study cannot be explained by these recommendations. However, as was argued previously for twin pregnancies, 13 increased awareness and monitoring could have contributed to more interventions in the late preterm phase, and in pregnancies with minor or less well studied conditions 22 . Increased societal risk adversity and improvements in neonatal care, and subsequent survival of the neonate and the perception of low morbidity could also have lowered the threshold at which timing of birth is considered 13,23‐25 …”

“…This may be a reflection of advances in obstetric management in the prevention of spontaneous preterm birth, or of other influences with a less clear impact, including vaccination and lifestyle improvements 26,27 . Alternatively, it can be reasoned that it is a direct result of more iatrogenic preterm birth 13 …”

“…Annual average weekly prospective risks of stillbirth were calculated for 20 +0 ‐27 +6 , 28 +0 ‐33 +6 , 34 +0 ‐36 +6 and 37 +0 ‐41 +6 weeks using a “fetus‐at‐risk” approach, dividing the number of stillbirths in that gestational age period by the number of women at risk in the same period and expressed as the average weekly risk by further dividing it by the number of weeks in the period. 13 , 17 …”

“…The aim of this study is to analyze trends in singleton preterm birth in Victoria in relation to trends in perinatal outcome, as we did earlier for twin pregnancies. 13 Simultaneous evaluation of these trends is essential, because although iatrogenic birth aims to prevent adverse maternal and perinatal outcome, overtreatment poses a risk. We sought to identify possible driver(s) for change and opportunities to improve clinical care.…”