Risks of adverse pregnancy and birth outcomes according to maternal age and inter-pregnancy interval

Project number: 
15-109
Approval date: 
Thursday, March 3, 2016
Principal Investigator: 
Schummers,Laura
Institution: 
Harvard Medical School
Funding Agency: 
NIH (US)
Datasets requested: 
Medical Services Plan (BC Ministry of Health)
Deaths (BC Vital Statistics Agency)
PharmaNet
Hospital Separations (BC Ministry of Health)
Income band (Statistics Canada)
Consolidation - demographic (Ministry of Health)
Perinatal Services BC
consolidation - census geocodes
Research objective: 

Specific Aim 1: Estimate the absolute risk of 14 adverse pregnancy and birth outcomes according to 1-year increments of maternal age at pregnancy. We will estimate the absolute risks of preeclampsia, gestational diabetes, spontaneous preterm delivery, indicated preterm delivery, cesarean delivery, spontaneous vaginal delivery, severe postpartum hemorrhage, severe maternal morbidity, in-hospital maternal mortality, stillbirth, small for gestational age birth (SGA), neonatal intensive care unit (NICU) stay >=48 hours, neonatal mortality, and a composite maternal-perinatal adverse outcome index according to maternal age at first pregnancy in 1-year increments. Findings will inform prepregnancy counseling and public health messaging.

Aim 1b. Determine how sensitive previous findings are to exposure and referent group definitions. We will conduct analyses using each dichotomous cutoff (e.g., >=35 or >=40) and each referent group (e.g., 20-24,

Specific Aim 2: Use a causal framework to estimate the proportion of the effect of age at pregnancy on adverse birth outcomes that would be eliminated if multiple pregnancies and adverse complications of pregnancy were completely prevented. We propose to conduct a mediation analysis to identify the extent to which the effect of age at first pregnancy on the risk of adverse outcomes (cesarean delivery, spontaneous and indicated preterm delivery, severe postpartum hemorrhage, severe maternal morbidity, maternal mortality, stillbirth, SGA, NICU stay >=48 hours, and newborn death) is mediated by preeclampsia, gestational diabetes, and multiple gestations.

Specific Aim 3: Identify the optimal inter-pregnancy interval for women aged 30 or older. We will compare the outcomes of pregnancies to women aged 30 or older according to different inter-pregnancy intervals. We will examine whether the recommended inter-pregnancy interval for the general population (18-23 months between delivery and subsequent pregnancy) is applicable to this specific population or whether specific guidelines targeting an older population are necessary. We will examine separately nulliparous and parous women in this age group, as parity may modify these effects. To date, this population has little evidence to guide timing of subsequent pregnancies. These results will fill this knowledge gap, with immediate application to clinical practice, practice guidelines, and public health communication.

Publications: 

Journal Publication

  • Schummers L, Hutcheon JA, Hernandez-Diaz S, Williams PL, Hacker MR, VanderWeele TJ, Norman WV. Association of short interpregnancy interval with pregnancy outcomes according to maternal age. JAMA Internal Medicine. 2018; Oct 29 doi:10.1001/jamainternmed.2018.4696. e1-e11.

Academic thesis or dissertation

  • Schummers L. (2018). Large population-based healthcare databases for maternal and infant outcomes: The role of maternal age, Race and interpregnancy interval. Harvard University; Doctoral dissertation.

Interview (radio/newspaper/television/internet etc.)

Presentation of research material (poster/seminar/lecture etc.)

  • Schummers L. Is the effect of short interpregnancy interval on adverse pregnancy outcomes modified by maternal age? Presented at the BC Children’s Health Research Institute Research Day. Vancouver, BC: Feb 6, 2019.
  • Schummers L, Hacker M, Hutcheon J, VanderWeele T, Williams P, McElrath T, Hernandez-Diaz S. Effect of exposure and referent group definitions on observed associations between maternal age and risk of adverse pregnancy outcomes. Poster presented at 30th Annual Meeting of the Society for Perinatal Epidemiologic Research; June 19-20, 2017: Seattle, WA.
  • Schummers L, Hutcheon JA, Hernandez-Diaz S, Williams PL, Hacker MR, VanderWeele TJ, Norman, WV. Short interpregnancy interval and pregnancy outcomes: the role of maternal age. Poster presented at 31st Annual Meeting of the Society for Perinatal Epidemiologic Research; June 18-19, 2018: Baltimore, MD & presented at 51st Annual Meeting of the Society for Epidemiologic Research; June 19-22, 2018: Baltimore, MD
  • Schummers L, Hutcheon J, Hacker M, VanderWeele T, Williams P, McElrath T, Hernandez-Diaz S. Absolute risks of adverse pregnancy and birth outcomes according to maternal age at first birth: results from a population-based cohort study. Poster presented at the 2017 Annual Meeting of the Society for Perinatal Epidemiologic Research, June 19-20 & Annual Meeting of the Society for Epidemiologic Research, June 20-23 Seattle, WA.
  • Schummers L (invited). Interpregnancy interval and pregnancy outcomes: what is the role of maternal age? BC Women’s Hospital Research Rounds. Vancouver, BC: April 26, 2019.
  • Schummers L, Hutcheon JA, Hernandez-Diaz S, Williams PL, Hacker MR, VanderWeele TJ, Norman WV. Hernandez-Diaz. Is the effect of short interpregnancy interval on adverse pregnancy outcomes modified by maternal age? Presented at the Women’s Health Research Institute World Sexual Health Day. Vancouver, BC: Sept 5, 2018.
  • Schummers L. Association of short interpregnancy interval with pregnancy outcomes according to maternal age. Presented at the BC Children’s Health Research Institute Research Day. Vancouver, BC: Feb 6, 2019.

Conference abstract/presentation

  • Schummers L, Hutcheon JA, Hernandez-Diaz S, Williams PL, Hacker RM, VanderWeele TJ, Norman WV. The effect of short interpregnancy interval on adverse pregnancy outcomes for older mothers: a population-based cohort. Contraception. 2018; 98(4): 361.

Page last revised: September 2, 2019