Association of low pregnancy associated plasma protein-A with placental weight: a retrospective cohort study

Abstract

Objective: The aim of this study is to evaluate if low levels of first trimester PAPP-A can be an independent predictor of low placental weight. Study design: An observational, longitudinal and retrospective study conducted at a tertiary University Hospital. We included pregnant women who did the first trimester combined screening, between May 2013 and December 2022, in Unidade Local de Saúde de São João and gave birth in the same hospital. Low level of PAPP-A was defined as PAPP-A < 0.45 MoM and normal levels of PAPP-A as PAPP-A ≥ 0.45 MoM. We include pregnancies with gestational age at delivery above 24 weeks. Multiple pregnancies were excluded. A total of 12141 pregnancies was considered: 1034 of PAPP-A < 0.45 MoM and 11107 of PAPP-A ≥ 0.45 MoM. For sample characterization, we considered the prevalence of advanced maternal age, obesity, spontaneous conception, gestational diabetes, smoker at enrolment and chronic arterial hypertension. The primary outcome is the difference in placental weight between these two groups. As secondary outcomes were evaluated differences in newborn weight and gestational age at delivery. Results: PAPP-A values were lower in obese women and in pregnant women with gestational diabetes. Placenta weight, gestational age at delivery and newborn weight are lower in the group of PAPP-A < 0,45MoM. ANOVA results showed initial significant differences of placental weight between groups of PAPP-A, with low effect size. ANCOVA was used to compare placental weight by PAPP-A (< 0.45 MoM/ ≥ 0.45 MoM) adjusted for gestational age, newborn weight, gestational diabetes and obesity. After adjusting for these variables significance was maintained. Conclusion: Our study demonstrates the group of low serum maternal PAPP-A during the first trimester had a lower placenta weight, contributing to reinforce that low PAPP-A is an indicator of potential complications during pregnancy.