This study was conducted to investigate the relationship between diastolic notching on uterine artery Doppler and serum apelin-13 and 36 concentrations between 11 and 14 weeks of gestation.

Apelin-13 and apelin-36, which provide vasodilatation through a nitric oxide-dependent mechanism, also play a role in trophoblasts' survival, proliferation, and migration.

Based on this, we aimed to investigate serum apelin-13 and apelin-36 concentrations in pregnant women with and without diastolic notch on uterine artery Doppler between the 11th and 14th weeks of pregnancy.

We hypothesized that apelin-13 and apelin-36 might be associated with the formation of diastolic notch in uterine artery Doppler and serum apelin-13 and apelin-36 concentrations would be lower in the group with a notch in the uterine artery Doppler than in the group without a notch.

Inclusion Criteria:

1. Nonsmokers,
2. Singleton pregnancies between 11 and 14 weeks of gestation
3. Pregnant women who did not conceive with assisted reproductive methods

Exclusion Criteria:

1. Smokers
2. Pregnant women who conceived with assisted reproductive techniques
3. Pregnant women with multiple pregnancies
4. Pregnant women who started with multiples and continued with singletons
5. Pregnant women with any pregestational disease, thrombophilia
6. Pregnant women with any congenital uterine anomaly
7. Pregnant women with a history of recurrent pregnancy loss
8. Pregnant women using aspirin or heparin

44 singleton pregnant women with unilateral or bilateral diastolic notching detected in uterine artery Doppler between the 11th and 14th weeks of pregnancy formed the study group (uterine artery notch positive group). 44 singleton pregnant women who did not have diastolic notching in uterine artery Doppler between the 11th and 14th weeks of pregnancy constituted the control group (uterine artery notch negative group).