C3. Cardiovascular changes from pre-pregnancy to early pregnancy in relation to viability of pregnancy.

INTRODUCTION: Inadequate cardiovascular adaptation to pregnancy has been postulated as a potential cause or consequence of early pregnancy loss. We sought to investigate pre- and early pregnancy cardiovascular function in women with a viable pregnancy beyond the first trimester, and those suffering a first trimester pregnancy loss.

METHODS: We recruited healthy women trying for pregnancy without assisted reproductive technology into an observational pre-conception study, and recorded pregnancy loss as a clinical endpoint. The participants underwent comprehensive cardiovascular testing, including assessments of cardiac output (CO) using a noninvasive gas rebreathing method in lying and standing position. CO values were adjusted for body surface area and reported as cardiac index (CIdx). Participants that conceived a pregnancy were assessed at 6 weeks gestation with repeat CO and CIdx measurements, and a fetal viability scan. We compared change (delta) in CO and CIdx between pre-pregnancy and 6 weeks gestation between participants who had sonographic diagnosis of pregnancy of unknown viability (PUV) and subsequently miscarried (Group 1 - 11 women), participants who had a 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.

RESULTS: From 292 participants recruited pre-pregnancy, 176 pregnancies were conceived within 16 months. Fifty-four pregnancies miscarried in the first trimester, 26 before their first scheduled post conception visit at 6 weeks. In the 28 women in whom cardiovascular and ultrasound data were obtainable at 6 weeks, there was no significant difference between delta lying CO (p =0.3876, 95%CI-1.73 to 0.73; p = 0.1781, 95%CI-1.326 to 0.267) and CIdx (p = 0.3029, CI-0.833 to 0.628; p = 0.7615, 95%CI-0.787 to 0.587) between the Group 1 and 2 respective and controls. Similarly there was no significant difference between the groups and controls in delta standing CO (p = 0.2251, 95%CI-0.565 to 2.129; p = 0.6137, 95%CI-1.505 to 0.917) and CIdx (p = 0.4658, 95%CI-0.364 to 1.146; p = 0.6349, 95%CI-0.886 to 0.557).

CONCLUSIONS: There is no evidence of differences in maternal cardiovascular adaptation in relation to pregnancy viability at 6 weeks in women with pregnancies of unknown viability or those destined to miscarry compared to healthy pregnancies. Changes in maternal cardiac output may be related more to the presence of trophoblast than to a viable embryo.