OP23.06: Effects of method of conception and gestational age on first trimester biochemical markers

Abstract

Objectives: First-trimester levels of PAPP-A and free β-hCG are decreased in pregnancies conceived as a result of assisted reproduction, especially in-vitro fertilization (IVF). The aim of this study was to evaluate if sub-fertility, measured as increased timeto-pregnancy (TTP) in spontaneously conceived pregnancies, affects the levels of PAPP-A and free β-hCG. Methods: We included 13,935 singleton pregnant women, who attended the prenatal screening program between January 2005 and December 2010 and gave birth at Aarhus University Hospital, Denmark. TTP was evaluated through a questionnaire completed by the pregnant women in the first trimester. PAPP-A and free β-hCG were measured between gestational week 8+0 and 13+6. IVF pregnancies (n = 962) were used for comparison, and we excluded unintended pregnancies (n = 2.797) and pregnancies with no information about TTP (n = 460), which left 9,507 spontaneous pregnancies with information about TTP. Results: The median PAPP-A MoM was significantly lower in pregnant women with a TTP ≥24 months compared with the reference group with a TTP < 6 months (0.96 MoM vs. 1.06 MoM, P = 0.003). The levels were not as low as in IVF pregnancies (0.89 MoM). The median level of free β-hCG was also significantly lower in pregnancies with a TTP ≥24 months compared with pregnancies with a TTP < 6 months (1.04 MoM vs. 1.12 MoM, P = 0.03). TTP at 6–11 months and TTP at 12–23 months did not significantly affect levels of PAPP-A or free β-hCG. Conclusions: Increased time-to-pregnancy in spontaneously conceived pregnancies is associated with decreased levels of PAPP-A and free β-hCG measured in the first trimester, suggesting that some of the well-known decrease in IVF-pregnancies could be related to sub-fertility instead of the infertility treatment per se. OP23.06 Effects of method of conception and gestational age on first trimester biochemical markers