Influence of threatened miscarriage on pregnancy and early postpartum period: a case-control report.

Objective: To evaluate the influence of threatened miscarriage on obstetric complications during pregnancy and early postpartum period.
Methods: In this case-control study, hospital records of 12,050 first-trimester patients between January 2011 and December 2012 at the Research and Educational Hospital in Ankara, Turkey, were used. Of the 12,050 patients, 481 threatened miscarriage patients were evaluated. The control group was formed by age- and body mass index-matched cases without first trimester bleeding. Abortion, intrauterine foetal demise, preterm birth, preeclampsia, antenatal haematoma, uterine atony placental abruption and low birth-weights were compared between the study and the control group.
Results: When compared with the control group, the risk of having a preterm birth (p = 0.014; OR: 1.95; 95% CI: 1.15-3.24), low-birth-weight infant (p = 0.001; OR: 2.33; 95% CI: 1.45-3.83) and abortion (p = 0.00; OR: 2.55; 95% CI: 1.62-3.91) increased in cases of threatened miscarriage. However, the risk of uterine atony was decreased (p = 0.006; OR: 0.09; 95% CI: 0.12-0.7) in the threatened miscarriage group when compared with the control group. Threatened miscarriage did not increase the risk of placenta praevia, placental abruption or intrauterine foetal demise.
Conclusion: Increased complications after threatened miscarriage is probably due to the persistence of a triggering mechanism. As preterm birth and abortion rate increased, whilst uterine atony rate decreased, one of the mechanisms causing threatened miscarriage might be increased uterine contractility.