OP18.01: Cardiovascular changes from pre‐pregnancy to early pregnancy in relation to viability of pregnancy

Cardiovascular maladaptation to pregnancy has been postulated as a potential cause or consequence of early pregnancy loss. We investigated pre- and early pregnancy cardiovascular function in women with a viable pregnancy beyond the first trimester, and those with first trimester pregnancy loss. We recruited healthy women trying for pregnancy without assisted reproductive technology and recorded miscarriage as an outcome. Cardiac output (CO) and cardiac index (CIdx) were assessed using a gas rebreathing method in lying and standing postures. Participants who conceived were assessed at 6 weeks gestation with repeat CO/CIdx measurements and a viability scan. We compared change (delta) in CO and CIdx between pre-pregnancy and 6 weeks gestation between participants with sonographic diagnosis of pregnancy of unknown viability and subsequently miscarried (Group 1: 11 women), participants with normal scan at 6 weeks gestation but subsequently miscarried (Group 2: 17 women) and 25 matched controls who had normal 6 week scan and viable pregnancy beyond the first trimester. 176 pregnancies were conceived within 16 months. Fifty-four pregnancies miscarried in the first trimester, 26 before first scheduled post conception visit at 6 weeks. Six week cardiovascular and ultrasound data were available for the 28 women. There was no significant difference between delta lying CO (p = 0.3876, CI −1.733 to 0.733; p = 0.1781, CI −1.326 to 0.267) and CIdx (p = 0.3029, CI −0.767 to 0.627; p = 0.7615, CI −0.78 to 0.587) between the Group 1 and 2 respectively and controls, nor between delta standing CO (p = 0.2251, CI −0.56 to 2.219; p = 0.6137 CI −1.505 to 0.917) or CIdx (p- 0.4658 CI −0.364 to 1.146; p = 0.6349 CI −0.886 to 0.557). There is no difference in maternal cardiovascular adaptation in relation to pregnancy viability at 6 weeks in women who subsequently have a first trimester miscarriage, compared to healthy pregnancies. Changes in maternal cardiac output may be related more to the presence of trophoblast than to a viable embryo.