The 39-week rule – was established in 2009 that restricts
labor induction in the 37
th and 38
th week of pregnancy
(i.e., in the “early-term period”) unless an accepted/approved “indication” is
present.
The 39-week rule is now a strict clinical guideline that is enforced by
professional organizations, governmental agencies and the medical insurance
industry in US.
In November 2013, ACOG
and Society for Maternal and Fetal medicine(SMFM) made a recommendation of replacing the use of “ term” pregnancy which accommodated gestations
between 37 wks to 42 wks with the following designations:
• Early term: 37 weeks through 38 weeks and 6 days
• Full term: 39 weeks through 40 weeks and 6 days
• Late term: 41 weeks through 41 weeks and 6 days
• Postterm: 42 weeks and beyond
These changes were made by growing research evidence, a part
of which has been led by
Eunice Kennedy Shriver National Institute of Child Health and Human Development, indicating that key developmental process for
the fetus continue well beyond 37 wks till 39 wks. They also advocated that “Babies
born at or after 39 weeks have the best chance at healthy outcomes compared to
those born before 39 weeks.”
But, two recent studies, one by Dr. Nicholson presented at Society
for Maternal-Fetal Medicine (SMFM) 2016 Pregnancy Meeting and the other by Dr Jason
Salemi, assistant professor of family and community medicine at Baylor and lead
author of the study advise caution against the universal application of the
rule.
According to
paper presented at SMFM
2016 Pregnancy Meeting Dr Nicholson said that
“Investigators found that the proportion of
term stillbirths rose from 1.103 per 1000 deliveries before the rule was
adopted to 1.177 per 1000 after. He further added "This study raises the
possibility that the 39-week rule may be causing serious unintended harm."
According to Dr Nicholson "Term stillbirth is clearly one of worst obstetrical
outcomes, and it occurs with relatively high frequency — in one per 1000
deliveries that reach 37 weeks," he explained. "We should place a
high priority on determining the causes, developing preventive interventions,
and studying factors suspected of producing this truly horrible outcome.
He advocated an urgent need of high quality research in this area, and until
we get the evidence the forced imposition of the 39-week rule should be looked
into. The 39 weeks rule was put into action after results of many studies, but
he said that all those studies were flawed; they suffered from incorrect
modeling, were retrospective cohort studies and the confounders were not
corrected for.
He further went to add that "the studies failed to consider ecological
fallacy, which is that we should not determine the treatment of an individual
patient based on studies that examine population-based data," he said.
"Ecological cohort studies should rarely be used to generate policy, yet
that's what I think we did."
Dr. Nicholson and his colleagues requested the state health department to
provide them with data on term still births and term births segregated
according to the weeks of gestation for 3 years before and 3 years after the
rule was in enforced. The data clearly showed an increase in deliveries at 39
weeks. He said that "The greatest increases in term stillbirth occurred at
37, 38, and 39 weeks of gestation," he noted, which is "right where
the 39-week rule is working."
The team observed a clear increase in number of stillbirths when the
rule
was
implemented,
1.103 per 1000
deliveries in 2007-2009 to 1.177 per 1000 in 2011-2013. He further estimated
that it accounts for additional 335 more term stillbirths in 2013 than in 2007.
He acknowledged some shortcoming of his retrospective cohort study, saying it
only identifies association, not causation.
A study published in
JAMA paediatric, documented that
during this period admission to NICU
increased sharply.
The paper was a topic of hot debate and some physicians suggest that benefit
of the rule outweigh the risk.
Dr. Baxi from New York
University Langone
Medical Center
in New York City Opined that timing of delivery is refined decision depending
on many variable and it should be individualized according to the circumstances
and not governed by a rule .
She also emphasized the need to understand more about the pathophysiology of
the stillbirths. "Unless we know the cause, we can't say it's related to
the 39-week rule," Dr Baxi pointed out. "Over time, we have fewer
'unrecognized causes,' but there still are some.
Dr Jason also saw limitations in many studies used to justify the 39-week
rule. They conducted a retrospective cohort study, used state health data
on
675,000 infants and found equivocal
results in elective cesarean sections at 37-38 weeks and those delivered after
39 weeks.
“Each pregnancy is unique,” He said. “I cannot overstate the importance of
open and ongoing communication between pregnant women and their healthcare
providers so that the potential risks and benefits of any pregnancy-related
decision are understood fully.”
Many other studies also have challenged the “39 weeks rule”. A study by Hart
et al published in
ACOG challenged the application of rule in Women who had
prior C-sections. They conclude that their findings suggest the optimal time
for scheduled delivery of women with 2 previous cesarean section deliveries is
between 38 wks 0 and 38wk 6 days and between 37 wks 0 and 37 wks 6 days for
women with ≥ 3 previous cesarean section deliveries
Some physicians said that they do not think that the rule should be dropped
entirely but needs to be revisited.
References:
Hart L, Refuerzo J, Sibai B, Blackwell S. Abstract 40:
Should the “39 week rule” apply to women with multiple prior cesarean
deliveries? American Journal of
Obstetrics & Gynecology 2014; 210(1 Supplement): S27, January 2014
