Fetal Mortality in the Prolonged Pregnancy
July 1, 1998 2 minutes read
Fetal Mortality in the Prolonged Pregnancy
ABSTRACT & COMMENTARY
Synopsis: Fetal mortality in accurately dated pregnancies increases significantly beyond 41 weeks gestation.
Source: Divon MY, et al. Am J Obstet Gynecol 1998; 178:726-731.
To determine the relationship between gestational age and fetal growth on fetal and neonatal mortality rates in the prolonged or post-term pregnancy, Divon and associates examined pregnancy outcome in 181,524 deliveries in the National Swedish Medical Birth Registry between 1987 and 1992. Inclusion criteria for the study were: a singleton pregnancy, reliable dating including a second trimester ultrasound, gestational age 40 weeks or younger, and maternal age 14-44 years. Fetal growth restriction was defined as a birth weight less than two standard deviations below the mean for gestational age. Fetal and neonatal mortalities at 40 weeks gestation were used for reference.
Fetal death rates increased significantly from 41 weeks gestation on, odds ratio (OR) 1.5 at 41 weeks, 1.8 at 42 weeks, and 2.9 at 43 weeks. Neonatal mortality did not significantly rise. Fetal growth restriction was associated with a marked increase in both fetal and neonatal mortality. With increasing gestation, the OR for fetal death rose from 7.1 to 10.0 and, for neonatal mortality, from 3.5 to 9.4.
Divon et al conclude that fetal mortality in accurately dated pregnancies increases significantly beyond 41 weeks gestation and that fetal growth restriction is independently associated with a higher perinatal mortality in prolonged pregnancies.
COMMENT BY STEVEN G. GABBE, MD
The prolonged or post-term pregnancy has been identified as a risk factor for increased perinatal morbidity and mortality. While congenital malformations, excessive fetal growth and birth trauma, and infection all contribute, the most important etiologic factor may be "uteroplacental insufficiency" resulting in intrauterine fetal death and meconium aspiration. Divon et al have analyzed a large database established in Sweden. The pregnancies were carefully dated. A questionnaire of Labor and Delivery units in Sweden revealed that nearly all began fetal evaluation with non-stress testing and ultrasonographic assessment of amniotic fluid volume by 42 weeks gestation.
The study confirmed several earlier observations, including the increased frequency of a prolonged pregnancy with a male fetus, nulliparity, and advancing maternal age. Most importantly, these data demonstrate a higher fetal death rate at 41 weeks gestation and reveal a marked increase in fetal loss associated with poor fetal growth.
Given these findings, it would appear prudent to consider induction of labor at 41 weeks gestation or the initiation of a program of fetal monitoring at this time. Most would recommend twice weekly non-stress testing with a weekly assessment of amniotic fluid volume. Future studies will be needed to determine if fetal growth restriction can be accurately identified at this gestational age and, if it is, whether intervention will reduce the fetal death rate.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content