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The amniotic fluid index in late pregnancy
R H Stigter1, E J H Mulder, H W Bruinse
1Department of Perinatology and Gynecology, University Medical Center Utrecht, The Netherlands.
Summary
The amniotic fluid index (AFI) remains stable until the final 11 days before labor onset. This reduction in amniotic fluid is linked to the labor process, not just gestational age.
Area of Science:
- Obstetrics and Gynecology
- Perinatal Medicine
- Fetal Monitoring
Background:
- Amniotic fluid index (AFI) is a key indicator in pregnancy monitoring.
- Understanding AFI changes near term is crucial for assessing fetal well-being.
- Previous studies have yielded varied results regarding AFI trends in late gestation.
Purpose of the Study:
- To investigate amniotic fluid index (AFI) changes in term pregnancies.
- To correlate AFI variations with both gestational age and the onset of spontaneous labor.
- To clarify the relationship between AFI, gestational age, and labor initiation.
Main Methods:
- Prospective observational study involving 137 women with uneventful term pregnancies.
- Performed 220 amniotic fluid index (AFI) measurements.
- Collected serial AFI data from 51 participants for longitudinal analysis.
Main Results:
- Amniotic fluid index (AFI) showed no significant change between 37 and 42 weeks' gestation.
- A significant AFI reduction was observed in the 11 days preceding spontaneous labor onset (R = -0.37, p < 0.001).
- Amniotic fluid index (AFI) corrected for gestational age remained stable within individuals for up to two weeks; meconium staining and fetal distress were not correlated with AFI.
Conclusions:
- The observed decrease in amniotic fluid index (AFI) in pregnancies extending beyond term is associated with the labor process.
- Gestational age alone does not fully explain the reduction in amniotic fluid near labor.
- Amniotic fluid index (AFI) reduction appears to be a marker related to impending labor rather than solely post-term status.