00:00
Hello.
00:01
I’m Juan Sebastian Sandoval, one
00:03
of the OBGYN residents
00:04
at Duke University.
00:05
And today we’re going to talk
00:07
about prolonged pregnancy.
00:08
Given that this is a review
00:09
of the USMLE,
00:11
we will pay particular attention
00:12
to the key information
00:13
that you need to know and not
00:15
the details
00:16
that, although are
00:16
important for the practice
00:17
of an obstetrician,
00:18
are not
00:19
relevant for these examinations.
00:20
00:24
During this presentation,
00:25
we are going to define
00:26
prolonged pregnancy,
00:27
recognize the etiology and risk
00:28
factors,
00:29
understand the consequences
00:31
of this condition,
00:32
and identify management options.
00:34
00:37
A 25-year-old G2P1001 presents
00:41
to your office to establish
00:42
prenatal care.
00:43
She recently immigrated
00:45
to the United States, hence
00:46
you don’t have any
00:47
of her medical records.
00:48
And she states she is currently
00:50
at 42 weeks and 5 days
00:51
of gestational age.
00:53
According to her, this is based
00:55
on her last menstrual period,
00:56
of which she is certain
00:57
because ever since her menarche
00:59
she annotates in a calendar
01:01
the first day
01:01
of her menstruation.
01:03
On today’s ultrasound, the fetus
01:04
has an estimated gestational age
01:06
of 39 weeks.
01:07
On examination, you find
01:09
her cervix to be 4 centimeters
01:10
dilated, 60% effaced, anterior,
01:13
and soft.
01:14
The fetus is cephalic.
01:17
What is the next step
01:18
in the management
01:19
of this patient?
01:20
01:23
Prolonged pregnancy is defined
01:25
as a gestational equal
01:26
or greater to 294
01:28
days, which is equivalent to 42
01:31
weeks after the first day
01:33
of the last menstrual period.
01:35
Although up until now
01:37
there is no agreement
01:38
on the correct term
01:39
for this condition, ACOG states
01:41
that we should use
01:42
“prolonged pregnancy”
01:43
to describe a pregnancy that has
01:44
lasted more than the upper limit
01:45
of a normal-term gestational.
01:48
The 42-week mark is somewhat
01:49
arbitrary as it was established
01:52
before the widespread use
01:53
of antenatal testing.
01:55
In fact, recent data shows
01:56
that there is a marked increase
01:58
in the prenatal morbidity
01:59
and mortality after 41 weeks
02:01
of gestation.
02:03
Anyway, whether it’s called post
02:04
dates, post terms, post
02:06
maturity, or prolonged
02:08
pregnancy, it is not
02:09
relevant for the purpose
02:10
of the USMLE.
02:11
What you really need to know
02:13
is that this is
02:13
a high-risk condition as it puts
02:15
the fetus at an increased risk
02:17
of poor prenatal outcomes.
02:19
So is it common?
02:21
Yes.
02:22
7% to 12% of pregnancies
02:23
are complicated
02:24
by this condition.
02:25
02:28
When it comes to the etiology,
02:30
it’s key to know that the most
02:31
common cause
02:32
of prolonged pregnancy
02:33
is an error in determining
02:34
the estimated delivery
02:35
date or gestational age.
02:38
This is a consequence
02:39
of variations
02:40
in the menstrual cycle length
02:41
and inaccuracy in remembering
02:43
the date
02:43
of the last menstrual period.
02:45
Conversely, the most common
02:46
cause
02:47
of true prolonged pregnancy
02:48
is idiopathic, apparently
02:50
due to a biological variability
02:52
of the duration of pregnancy.
02:53
02:56
So who’s at risk?
02:58
Although the exact triggers
02:59
for initiation of labor
03:00
have not been completely
03:01
described yet,
03:02
there are
03:03
certain fetal and placental
03:04
abnormalities–
03:05
such as anencephaly,
03:06
placental sulfatase deficiency,
03:08
and fetal adrenal hpyoplasia–
03:10
that have been associated
03:11
with increased risk of prolonged
03:12
pregnancy.
03:14
Since there is up to a 50%
03:15
recurrence risk in mothers who
03:17
previously had a prolonged
03:18
pregnancy,
03:18
the genetic predisposition
03:19
for this condition is evident.
03:21
03:24
Among the most important things
03:25
you have to know about
03:26
the entire presentation is
03:27
that the consequence
03:28
of prolonged pregnancy
03:29
is an increased
03:30
risk in prenatal morbidity
03:31
and mortality.
03:32
Data shows that this effect is
03:34
even greater in fetuses
03:35
small for gestational age
03:36
when compared to the ones
03:37
adequate for gestational age.
03:40
The main determinant of the type
03:41
of morbidity and mortality
03:43
associated with prolonged
03:44
pregnancy
03:44
is the placental function.
03:46
The fetus relies 100%
03:48
on the placenta
03:48
for its nutrition.
03:50
If it continues to work
03:51
appropriately, he will continue
03:52
to grow, being
03:53
adequate for gestational age
03:55
but having a high risk
03:56
of macrosomy.
03:57
Conversely,
03:58
if the placental function is
04:00
inadequate, the fetus will be
04:02
literally starving, which
04:04
increases its risk for being
04:05
small for gestational age
04:06
and having dysmaturity syndrome.
04:08
04:11
80% of babies born
04:12
after a prolonged pregnancy
04:13
will continue to have
04:14
adequate placental function,
04:16
making them macrosomic.
04:17
The main risk in this group
04:19
of patients
04:19
is labor dysfunction, which
04:21
increases occurrence of shoulder
04:22
dystocia and its complications;
04:24
cesarean section; postpartum
04:25
hemorrhage;
04:26
operative vaginal deliveries–
04:27
like forceps-assisted vaginal
04:28
delivery
04:29
and vacuum-assisted vaginal
04:30
delivery;
04:31
and birth trauma in general.
04:32
04:36
20% of babies born
04:37
after a prolonged pregnancy
04:39
will have inadequate placental
04:40
function, leading them to suffer
04:41
from dysmaturity syndrome.
04:43
These neonates are at a higher
04:45
risk of being
04:46
small for gestational age,
04:47
having fetal growth restriction,
04:49
oligohydramnios, fetal distress,
04:51
meconium-stained fluid,
04:53
acidosis, and needing a cesarean
04:55
section.
04:55
04:58
So, what will you do
05:00
if your patient suffers
05:01
from this condition?
05:03
The first step is to determine
05:04
if there is good dating.
05:06
So let’s assume there’s poor
05:07
dating.
05:08
The management should be
05:09
expectant.
05:10
Remember that the further
05:11
the gestational age, the less
05:13
reliable an ultrasound is
05:14
for estimating it.
05:16
In this case,
05:16
you have to perform
05:17
twice-weekly fetal well-being
05:18
testing
05:19
with a biophysical profile
05:20
and non-stress tests.
05:23
If there’s good dating– meaning
05:24
there’s a reliable LMP and/or
05:27
early first trimester
05:28
ultrasound– the next step is
05:30
to evaluate the cervix.
05:32
If the cervix is favorable,
05:33
there’s no benefit of keeping
05:34
the fetus in utero.
05:36
You have to manage the patient
05:37
actively to promote labor.
05:39
A first step could be sweeping
05:42
the amniotic membranes, which
05:43
can trigger labor by the release
05:45
of factors
05:45
such as prostaglandins.
05:48
Another option is to induce
05:49
labor with any
05:50
of the multiple mechanical or
05:52
pharmaceutical methods
05:53
of labor induction–
05:55
in example, misoprostol,
05:56
pitocin, laminaria, or cervical
05:59
ripening balloons.
06:01
Now, if the cervix isn’t
06:03
favorable, the management
06:04
is controversial.
06:05
There are multiple factors that
06:07
have to be put
06:07
into consideration in order
06:09
to counsel the patient
06:09
about management options.
06:11
Luckily for you, it’s not
06:12
typical for USMLE
06:13
to include questions
06:14
about controversial subjects
06:16
where there is no consensus
06:18
of only one clear best answer.
06:19
06:23
Having said all of this,
06:24
the key elements
06:25
that you need to know back
06:26
and forth about prolonged
06:28
pregnancy are, first, it’s
06:31
defined as a pregnancy that has
06:32
reached or exceeded 42 weeks
06:35
of gestational age.
06:37
Second, the most common cause
06:40
of prolonged pregnancy
06:41
is poor dating.
06:43
Third, morbidity and mortality
06:45
depend on placental function,
06:47
which, if it’s decreased,
06:50
the consequence is
06:50
dysmaturity syndrome
06:52
and, if it’s maintained,
06:53
macrosomnia syndrome.
06:56
Fourth and finally,
06:57
the management depends
06:59
on the dating and the cervix.
07:01
If poor dating, it should be
07:02
expectant.
07:03
If good dating, the next step
07:05
is to check the cervix.
07:06
If it’s favorable,
07:07
you should proceed
07:08
with induction of labor.
07:09
If unfavorable, the management
07:11
is controversial.