Report of the Office of Population Affairs’ expert work group meeting on short birth spacing and adverse pregnancy outcomes: Methodological quality of existing studies and future directions for research

Abstract

Background The World Health Organization ( WHO ) recommends that women wait at least 24 months after a livebirth before attempting a subsequent pregnancy to reduce the risk of adverse maternal, perinatal, and infant health outcomes. However, the applicability of the WHO recommendations for women in the United States is unclear, as breast feeding, nutrition, maternal age at first birth, and total fertility rate differs substantially between the United States and the low‐ and middle‐resource countries upon which most of the evidence is based. Methods To inform guideline development for birth spacing specific to women in the United States, the Office of Population Affairs ( OPA ) convened an expert work group meeting in Washington, DC , on 14‐15 September 2017 among reproductive, perinatal, paediatric, social, and public health epidemiologists; obstetrician‐gynaecologists; biostatisticians; and experts in evidence synthesis related to women's health. Results Presentations and discussion topics included the methodological quality of existing studies, evaluation of the evidence for causal effects of short interpregnancy intervals on adverse perinatal and maternal health outcomes, good practices for future research, and identification of research gaps and priorities for future work. Conclusions This report provides an overview of the presentations, discussions, and conclusions from the expert work group meeting.

Good practices for the design, analysis, and interpretation of observational studies on birth spacing and perinatal health outcomes

“…This manuscript is part of a theme issue on the Office of Population Affairs’ expert workgroup meeting on birth spacing and adverse pregnancy outcomes, which includes a separate summary of the overall meeting proceedings …”

Short interpregnancy interval and poor fetal growth: Evaluating the role of pregnancy intention

“…However, a recent expert working group on birth spacing convened by the US office of population affairs concluded that many of the studies included in this review had serious methodological concerns. 28 Several studies F I G U R E 2 Estimated mean birthweight z-score by interpregnancy interval category, before and after adjusting for maternal age at last delivery, parity, smoking at time of conception, last pregnancy stillbirth or neonatal death, occupation, can raise 5000 NOK in 1 wk, rating of own/family wealth, pregnancy intention have since attempted to address possible confounding using withinwoman and within-family analyses, which compare multiple interpregnancy intervals in the same woman (ie between siblings), or in the same family (ie between first cousins). This approach aims to reduce confounding by factors that tend to remain consistent within one woman or family (eg socio-economic status).…”

“…found interpregnancy intervals of less than 18 months and greater than 60 months to be significantly associated with small for gestational age birth, despite adjustment for at least maternal age and one marker of socio‐economic status. However, a recent expert working group on birth spacing convened by the US office of population affairs concluded that many of the studies included in this review had serious methodological concerns . Several studies have since attempted to address possible confounding using within‐woman and within‐family analyses, which compare multiple interpregnancy intervals in the same woman (ie between siblings), or in the same family (ie between first cousins).…”

Birth spacing in the United States—Towards evidence‐based recommendations

“…12 The supplement also includes two updated systematic reviews on short interpregnancy interval and perinatal 13 and maternal 14 health outcomes in high-income settings; preliminary results from these systematic reviews were presented at the meeting and are briefly summarised in the meeting proceedings. 11 These reviews include an assessment of study quality that reflects the good practices discussed at the expert work group meet- 16 provides an analysis of interpregnancy interval and small for gestational age birth using data from Scandinavia, controlling for pregnancy intention and enhanced information on socio-economic factors, both of which were highlighted by the expert work group as being important potential confounders.…”