Cardiac autonomic modulation in normal, high-risk, and in vitro fertilization pregnancies during the first trimester

The purpose of this study was to test the adaptation of autonomic modulation of heart rate in high-risk or in vitro fertilization (IVF) pregnancies during the first trimester.

Thirty-three pregnant women were studied between 6.0 and 12.5 weeks of gestation and were divided into three groups: normal (n=17), high-risk (n=7), and IVF pregnancies (n=9), together with 9 nonpregnant women of comparable age. All subjects underwent a short-term continuous electrocardiographic recording to measure short-term heart rate variability (HRV).

Average values of mean R-R interval, total power, and low-frequency (LF) component were similar in nonpregnant and normally pregnant women. The high-frequency (HF) component was only slightly increased in normal pregnant women but no difference was observed in LF/HF ratio. High-risk and IVF pregnancies were characterized by a significant increase in LF component in comparison to normal pregnancies. In pregnancies that had obstetric complications, signs of abnormal autonomic modulation of the sinus node were particularly evident.

Short-term analysis of HRV in high-risk and IVF pregnancies was significantly different from that observed in normal pregnancies. These differences were more significant in those pregnancies later complicated by an adverse outcome, suggesting an early origin of these pathologic conditions.