Computerised evaluation of fetal heart rate in post-term fetuses: long term variation

Area of Science:

• Maternal-Fetal Medicine
• Fetal Physiology
• Obstetric Ultrasound

Background:

• Postdate pregnancies require careful monitoring to assess fetal well-being.
• Fetal heart rate (FHR) variation is a key indicator of fetal oxygenation.
• Established reference values for FHR variation in late gestation are crucial for clinical management.

Purpose of the Study:

• To investigate the trend of fetal heart rate variation in postdate pregnancies.
• To establish reference values for long-term pulse interval variation at 41, 42, and 43+ weeks of gestation.
• To provide data supporting the conservative management of postdate pregnancies.

Main Methods:

• Cross-sectional study utilizing computerized fetal heart rate (FHR) records from 1987-1993.
• Analysis of 1502 FHR records from 567 singleton pregnancies at 41, 42, and 43+ weeks gestation.
• Gestational age verified by early pregnancy ultrasound; FHR variation measured by the mean minute range of long-term pulse interval variation.

Main Results:

• A progressive decrease in mean minute range of long-term pulse interval variation was observed with advancing gestational age.
• Average values decreased from 48.5 ms at 41 weeks to 46.4 ms at 42 weeks, and 42.4 ms at 43+ weeks.
• This decrease in FHR variation is correlated with fetal oxygenation status.

Conclusions:

• Fetal heart rate variation, specifically long-term pulse interval variation, declines in postdate pregnancies.
• The study provides essential reference values for pulse interval variation at later gestational ages.
• These reference values are vital for accurately assessing fetal condition during conservative management of postdate pregnancies.