MATERNAL-FETAL MEDICINE

Fetal heart rate patterns of pregnancies with vasa previaand velamentous cord insertion

Yael Baumfeld1 • Gil Gutvirtz1 • Iris Shoham1• Eyal Sheiner1,2

Received: 28 September 2014 / Accepted: 13 July 2015

� Springer-Verlag Berlin Heidelberg 2015

Abstract

Objective To investigate the fetal heart rate (FHR) pat-

terns in pregnancies complicated with vasa previa and

velamentous cord insertion (VCI).

Methods A retrospective study comparing FHR patterns

in pregnancies and subsequent pregnancies with/without

VCI and in pregnancies with/without vasa previa was

conducted. For each patient, FHR patterns were compared

to the subsequent pregnancy. Deliveries occurred between

the years 1988 and 2012 in a tertiary medical center. FHR

patterns were evaluated according to the ACOG guidelines.

Results During the study period, there were 184 preg-

nancies with VCI and 37 pregnancies with vasa previa,

undetected during pregnancy. FHR patterns of the VCI

group included more cases of abnormal baseline (7 vs.

2 %, p\ 0.05), out of which 7 % were fetal tachycardia

(vs. 2 %) and 4 % were bradycardia (vs. 1 %). There were

also more cases of abnormal baseline and abnormal vari-

ability (7 vs. 2 % and 32 vs. 22 %, respectively, p\ 0.05)

in the VCI group. FHR categories also differed between the

velamentous cord insertion pregnancies and subsequent

ones. VCI pregnancies had more category 2 patterns, not

statistically significant (64 vs. 55 %, p = 0.11). FHR pat-

terns of the vasa previa group included more cases of

abnormal baseline (27 vs. 7 %, p\ 0.05), out of which

18 % were tachycardia and 9 % were bradycardia. Decel-

erations were recorded in a total of 61 % of the vasa previa

cases (61 vs. 31 %, p = 0.02), most of which were variable

decelerations (48 vs. 17 %). Vasa previa pregnancies had

more category 2 patterns (64 vs. 52 %).

Conclusions Fetal heart rate patterns in pregnancies

complicated with VCI or vasa previa have several non-

specific pathological characteristics; none can be used for

early detection of these conditions.

Keywords Vasa previa � Velamentous insertion �Gestation � Fetal heart rate monitoring

Introduction

Vasa previa is a pathological state defined by the presence

of fetal blood vessels in the membranes covering the

internal cervical os [1]. It is divided into two types: vasa

previa type 1 in which the membranous vessels are asso-

ciated with velamentous umbilical cord, and type 2 in

which the vessels connect the lobes of a bilobed placenta or

the placenta and a succenturiate lobe [1].

The prevalence of vasa previa is 1 in 2500 deliveries

with risk factors including use of assisted reproductive

technologies [2–4, 10], placenta previa, bilobed or suc-

centurinate lobe and multiple gestations [4–9].

Prognosis varies; some of the cases resolve during the

second trimester. More commonly, the vasa previa persists

and is at risk for rupture upon rupture of membranes,

spontaneous or artificial, thus leading to fetal hypotension,

anemia and death due to exsanguination. This can be

reflected by fetal heart rate abnormalities.

There are several ways for the detection of vasa previa,

including transvaginal ultrasound with Doppler, and rare

& Eyal Sheiner

sheiner@bgu.ac.il

1 Department of Obstetrics and Gynecology, Faculty of Health

Sciences, Soroka University Medical Center, Ben-Gurion

University of the Negev, Be’er-Sheva, Israel

2 Department of Obstetrics and Gynecology, Soroka University

Medical Center, POB 151, Beer Sheva 84101, Israel

123

Arch Gynecol Obstet

DOI 10.1007/s00404-015-3819-6

occasions a pulsatile vessel can be palpated in a vaginal

digital examination [11–13].

Diagnosis of vasa previa is of utmost importance con-

sidering the prognosis. In the absence of prenatal diagnosis,

a clinical diagnosis of vasa previa should be suspected in

the setting of vaginal bleeding that occurs upon rupture of

the membranes and is accompanied with fetal heart rate

abnormalities, particularly a sinusoidal pattern or brady-

cardia [14, 15, 28].

Velamentous insertion is defined by divergent umbilical

vessels in the placental end of the cord [16]. This patho-

logical finding complicates one percent of all pregnancies;

risk factors include placenta previa and in monochorionic

twin gestations, which can be found in 15 % percent of

pregnancies. However, it is one of the most undiagnosed

conditions in obstetrics [17].

Velamentous insertion has been associated with several

obstetrical complications, ranging from fetal exsanguina-

tion due to rupture of vessels with rupture of membranes or

due to kinking and compression of the membranous vessels

leading to a reduction in blood flow, fetal heart rate (FHR)

changes and fetal demise. Other complications include

fetal growth restriction, preterm delivery, congenital

anomalies, fetal distress, low Apgar scores, fetal death, and

retained placenta [18, 26, 27].

Fetal heart rate monitoring is the tool commonly used

for monitoring the wellbeing of the fetus during pregnancy

and labor. The American College of Obstetricians and

Gynecologists (ACOG) published FHR monitoring cate-

gories [19]. The categories were divided according to fre-

quency observed. Category 1 was observed in 99 % of

tracings and in 78 % of labor and is considered normal

because it is associated with the absence of fetal acidemia;

category 2 in 84 % of tracings and in 22 % of labor; cat-

egory 3 in 0.1 % of the tracings and in 0.004 % of labor.

Category 3 is considered abnormal because it is associated

with increased risk of fetal hypoxic acidemia. The inter-

pretation of fetal heart rate monitoring has also been

debated extensively, while fetal heart rate monitoring cat-

egories 1 and 3 are relatively straightforward; the inter-

pretation of a category 2 monitor is complex [23].

The study objective was to explore the characteristics of

FHR monitoring during delivery in vasa previa pregnancies

or velamentous insertion compared to subsequent preg-

nancies of the same patient without cord abnormalities.

Methods

Study population

A retrospective study was conducted including deliv-

eries between 1988 and 2012 at the Soroka University

Medical Center (SUMC). SUMC is a 1007 bed tertiary

teaching hospital and the only provider for inpatient care

for population of 700,000 residing in Southern Israel. A

total of 221 patients were included—37 women with

vasa previa and 184 with velamentous insertion.

The study population consisted of all women who had

the diagnosis of vasa previa and women with the diag-

nosis of velamentous cord insertion (VCI). Data were

collected for both patients with either vasa previa (VP)

or VCI. Data from the subsequent pregnancies of the

study population were collected for the same variables

(controls). The database included information on mater-

nal comorbidities, perinatal assessment, maternal and

fetal complications.

Fetal heart rate monitors

The fetal heart rate tracings at time of the delivery were

examined for those pregnancies as well as the subsequent

ones. The monitors were examined for baseline, tachy-

cardia, bradycardia, variability, decelerations and accel-

erations. They were also divided into the three categories

of fetal heart tracings as defined by the ACOG [18].

FHR monitoring was done continuously throughout the

delivery, interpretation was done by the attending

physician and recorded in the patient file, additional

review and comparison was done by a single observer—

one of the authors. The worst monitor patterns were

recorded.

Definitions

The first fetal monitor category was defined by:

– Baseline rate: 110–160 beats per min

– Moderate baseline fetal heart rate (FHR) variability

(amplitude 6–25 bpm)

– No late or variable decelerations

– Early decelerations may be present or absent

– Accelerations may be present or absent

The third category is defined by:

– Absent baseline fetal heart rate variability and (any of

the following):

– Recurrent late decelerations

– Recurrent variable decelerations

– Bradycardia

Or

– A sinusoidal pattern

The second category includes all the fetal heart rate

patterns that are not classified as class 1 or class 3.

Arch Gynecol Obstet

123

Data analysis

The data on continuous variables with normal distribution

were presented as mean ± SD, and compared between

study groups using Student’s t test. Continuous variables

without normal distribution and ordinal variables were

presented as median with inter-quartile range (IQ range)

and statistical analysis was done using Mann–Whitney.

Categorical data were shown in counts and percentages and

the differences were assessed by Chi Square for general

association; Fisher Exact test was used when appropriate.

P value of less than 0.05 was considered statistically sig-

nificant. The statistical analysis was performed using IBM

SPSS statistics version 20.

Results

The study population consists of 37 cases of vasa previa

and the control group of subsequent pregnancies and a

second study population of 184 cases of velamentous

insertion and the control group of subsequent pregnancies.

Both of these pathologies were undetected during preg-

nancy and diagnosed during labor.

Vasa previa compared to subsequent pregnancies

Table 1 presents the comparison the vasa previa pregnan-

cies to subsequent pregnancies in the same women (i.e.

non-VP group). The major difference between the VP

group and the non-VP group is the rate of cesarean sec-

tions; the rate in the VP group was significantly higher

as compared with subsequent pregnancies (79 vs. 40 %,

p = 0.01).

The VP group had lower Apgar scores compared to the

control group, without a significant difference in the pH

levels. A total of four cases of fetal demise occurred, all of

which were in the VP group; however, this did not reach

statistical significance. Three of which were stillbirths

(antepartum fetal death) and one case of intrapartum fetal

death.

Fetal heart rate monitoring characteristics

Table 2 presents the fetal heart rate monitor characteristics.

A. Fetal monitor categories—category 2 was more preva-

lent in the VP group, however, they were not found

statistically significant.

Table 1 Baseline

characteristics of vasa previa

pregnancies vs. subsequent

pregnancy

Variables Vasa previa n = 37 No vasa previa n = 37 P value

Singleton (%) 36 (97.3) 29 (96.7) [0.99

Multiple (%) 1 (2.7) 1 (3.3)

Delivery (%)

Vaginal 6 (20.7) 13 (52.0)

Assisted 0 (0.0) 2 (8.0)

CS 19 (65.5) 7 (28.0)

Elective CS 4 (13.8) 3 (12.0)

CS total 23 (79.3) 10 (40.0) 0.01

Vaginal 6 (20.7) 15 (60.0)

Neonatal outcomes

pH (mean ± SD) 7.29 ± 0.06 7.30 ± 0.06 0.21

Apgar1

Median, IQ range 9 (1.75–9) 9 (9) 0.32*

\7 13 (36.1) 2 (6.7) 0.01

C8 23 (63.9) 28 (93.3)

Apgar 5

Median, IQ range 10 (8–10) 10 (10) 0.32*

\7 8 (22.2) 0 (0.0) 0.01

C8 28 (77.8) 30 (100)

Fetal demise (%)

Total 4 (10.8) 0 (0.0) 0.12

Stillbirth 3 (8.1) 0 (0.0) 0.24

Intrapartum death 1 (2.7) 0 (0.0) [0.99

Post-partum death 0 (0.0) 0 (0.0)

* Using Mann–Whitney test for non-parametric variables

Arch Gynecol Obstet

123

B. Pulse baseline—in the VP group there were signifi-

cantly more cases of fetal tachycardia (18 vs. 3 %) and

fetal bradycardia (9 vs. 3 %). This was statistically

significant (p\ 0.05).

C. Variability—abnormal variability (absent and minimal

variability) was found in 39 % of the VP group and

35 % of the non-VP group. These differences were not

statistically significant.

D. More accelerations were found in the non-VP group

(76 vs. 52 %; p = 0.05).

E. Decelerations were more common in the VP group (61

vs. 31 %, p = 0.02), mostly variable decelerations.

Velamentous cord insertion compared to subsequent

pregnancies

Table 3 presents the comparison of the VCI pregnancies to

subsequent pregnancies of the same women (i.e. non-VCI

group). The major difference between the VCI group and

the non-VCI group is the rate of cesarean sections; the rate

in the VP group was significantly higher (38 vs. 26 %,

p = 0.02).

The Apgar scores both at the 1st and 5th min were lower

in the VCI group (p = 0.01), no statistically significant

difference was found in neonatal pH. A total of 14 cases of

fetal demise occurred, 11 in the VCI group and 3 in the

non-VCI group (p = 0.001). Four of which were stillbirths

(antepartum fetal death) and one case of intrapartum fetal

death. A total of nine cases of neonatal deaths, six in the

VCI group and three in the non-VCI group.

Fetal heart rate monitoring characteristics

Table 4 presents the FHR monitor characteristics.

A. Fetal monitor categories—category 2 was more preva-

lent in the VCI group, not statistically significant.

B. Baseline fetal heart rate—more cases of fetal tachy-

cardia (5 vs. 1 %) and fetal bradycardia (3 vs. 1 %)

occurred in the VCI group (p = 0.02).

Table 2 Fetal heart rates

monitor characteristics in vasa

previa pregnancies vs.

subsequent pregnancies

Variables Vasa previa n = 37 No vasa previa n = 37 P value

Monitor (%)

1st category 12 (36.4) 14 (48.3) 0.34

2nd category 21 (63.6) 15 (51.7)

3rd category 0 (0.0) 0 (0.0)

2nd and 3rd 21 (63.6) 15 (51.7) 0.34

Baseline fetal heart rate (%)

Normal 24 (72.7) 27 (93.1)

Tachycardia 6 (18.2) 1 (3.4)

Bradycardia 3 (9.1) 1 (3.4)

Abnormal baseline 9 (27.3) 2 (6.9) 0.04

Variability (%)

Absent 0 (0.0) 0 (0.0)

Minimal 13 (39.4) 10 (34.5)

Moderate 20 (60.6) 19 (65.5)

Abnormal (absent and minimal) 13 (39.4) 10 (34.5) 0.69

Normal (moderate and marked) 20 (60.6) 19 (65.5)

Accelerations (%)

Absent 16 (48.5) 7 (24.1) 0.05

Present 17 (51.5) 22 (75.9)

Decelerations (%)

Absent 13 (39.4) 20 (69.0)

Early 4 (12.1) 3 (10.3)

Late 0 (0.0) 1 (3.4)

Variable 16 (48.5) 5 (17.2)

Present 20 (60.6) 9 (31.0) 0.02

Sinusoidal pattern (%) 0 (0.0) 0 (0.0)

* Using Mann–Whitney test for non-parametric variables

Arch Gynecol Obstet

123

C. Variability—abnormal variability was found in 32 %

of the VCI group and 22 % of the non-VCI group

(p = 0.05).

D. More accelerations were found in the non-VCI group

(70 vs. 64 %), not statistically significant.

E. Decelerations were found more often in the VCI group

(57 vs. 54 %, p = 0.65). Most were variable deceler-

ations (47 vs. 39 %, p = 0.02).

Discussion

Vasa previa and VCI are obstetrical pathologies that are

both difficult to diagnose and might have serious implica-

tions and complications during labor, including fetal

demise and life threading vaginal bleeding. FHR monitor is

one of the most available and commonly used tools. The

aim of this study was to define the monitor characteristics

of these obstetrical pathologies.

Vasa previa

The main results of our study include several significant dif-

ferences between the FHR monitors of the VP pregnancies.

The VP group had significantly different FHR monitoring

compared to subsequent pregnancy. These differences inclu-

ded baseline abnormalities and periodic changes (less accel-

erations and more decelerations). The majority of the fetal

heart ratemonitors found in the VP group were categorized as

type 2, whereas the fetal heart rate monitors found in the VP

group were mainly categorized as type 1.

However, no category 3 monitors were observed in

either group. This might be due to a relatively small sample

size or due to quick clinical decision-making, thus not

allowing for the deterioration of the fetal monitor from

category 2 to category 3.

There were significant differences in the neonatal

outcomes both in the Apgar score and fetal demise. The

Apgar scores were also significantly different between

the VP and non-VP groups showing a greater ratio of

Apgar scores under 7 in both the 1st and 5th min

(p = 0.01). There was also a higher prevalence of fetal

demise in the VP group with all four cases of fetal

demise in the VP group. The cases of fetal demise were

mostly stillbirths with only one case of intrapartum

death; this was not statistically significant, possibly due

to the small number of cases.

Table 3 Baseline

characteristics of velamentous

insertion pregnancies vs.

subsequent pregnancy

Variables Velamentous insertion n = 184 No velamentous insertion n = 184 P value

Singleton (%) 153 (80.1) 183 (99.5) \0.001

Multiple (%) 38 (19.9) 1 (0.5)

Delivery (%)

Vaginal 114 (60.3) 110 (69.6) 0.01

Assisted 3 (1.6) 7 (4.4)

CS 60 (31.7) 27 (17.1)

Elective CS 12 (6.3) 14 (8.9)

CS total 72 (38.1) 41 (25.9) 0.02

Vaginal 117 (61.9) 117 (74.1)

Neonatal outcomes

pH (mean ± SD) 7.28 ± 0.10 7.30 ± 0.07 0.09

Apgar1

Median, IQ range 9 (9) 9 (9) 0.01

\7 29 (14.9) 11 (6.3) 0.01

C8 165 (85.1) 164 (93.7)

Apgar 5

Median, IQ range 10 (10) 10 (10) 0.26*

\7 10 (5.2) 5 (2.9) 0.01

C8 184 (94.8) 170 (97.1)

Fetal demise (%)

Total 11 (5.6) 0 (0.0) 0.001

Stillbirth 4 (2.1) 0 (0.0) 0.12

Intrapartum death 1 (0.5) 0 (0.0) [0.99

Post-partum death 6 (3.1) 3 (1.5) 0.50

* Using Mann–Whitney test for non-parametric variables

Arch Gynecol Obstet

123

Velamentous cord insertion

More main results of our study include the significant

differences between VCI fetal heart monitors and of sub-

sequent pregnancies included abnormal baseline and vari-

ability. Previous studies found that the FHR monitors of the

VCI group had more variable decelerations and less

accelerations [19]. Similarly, we also found more variable

decelerations but the difference was not found statistically

significant.

FHR monitors pathologies have been found in correla-

tion with fetal academia [25], although the clear interpre-

tation of such is complicated [24], particularly category 2

monitors [23]. This is the reason we also analyzed the

neonatal outcomes. Interestingly, the Apgar scores were

significantly lower in the VCI group, both in the first min

and the fifth min scores. The low Apgar scores did not

reflect perinatal mortality or low pH values. The finding of

an increased risk of low Apgar scores and a higher fetal

mortality rate is similar to findings in previous findings

[20–22].

It should be noted that the rate of cesarean section was

higher both in the VP group and the VCI group compared

to the control, there are several possible explanations. First

of all, as the hypothesis of the study the rate of non-

reassuring fetal heart rate is greater in the VP group,

second having that the known complications of VP include

hemorrhage- yet another possible indication is suspected

placental abruption. There were no available data regard-

ing these indications or the rate of previous cesarean

delivery, which could also explain higher rates of cesarean

sections.

The strengths of the study are being a single center for a

large population, having very little lost for follow-up.

However, the weaknesses of the study are that it is a ret-

rospective cohort with a relatively small sample size

probably due to the low incidence of VP and VCI in the

general population.

Table 4 Fetal heart rates monitor characteristics in velamentous cord insertion pregnancies vs. subsequent pregnancies

Variables Velamentous insertion n = 184 No velamentous insertion n = 184 P value

Monitor (%)

1st category 54 (35.3) 70 (44.3)

2nd category 98 (64.1) 87 (55.1)

3rd category 1 (0.7) 1 (0.6)

2nd and 3rd 99 (64.7) 88 (55.7) 0.11

Baseline fetal heart rate (%)

Normal 141 (92.8) 154 (98.1)

Tachycardia 7 (4.6) 2 (1.3)

Bradycardia 4 (2.6) 1 (0.6)

Abnormal baseline 11 (7.2) 3 (1.9) 0.02

Variability (%)

Absent 1 (0.7) 0 (0.0)

Minimal 48 (31.6) 35 (22.3)

Moderate 102 (67.1) 121 (77.1)

Marked 1 (0.7) 1 (0.6)

Abnormal (absent and minimal) 49 (32.2) 35 (22.3) 0.05

Normal (moderate and marked) 103 (67.8) 122 (77.7)

Accelerations (%)

Absent 55 (36.2) 47 (29.9) 0.24

Present 97 (63.8) 110 (70.1)

Decelerations (%)

Absent 65 (42.8) 72 (45.9) 0.02

Early 7 (4.6) 21 (13.4)

Late 8 (5.3) 3 (1.9)

Variable 71 (46.7) 61 (38.9)

Present 85 (57.0) 85 (54.1) 0.65

Sinusoidal pattern (%) 1 (0.7) 1 (0.6) 1.00

* Using Mann–Whitney test for non-parametric variables

Arch Gynecol Obstet

123

In conclusion, it seems that FHR patterns cannot predict

either VP or VCI. FHR monitoring can only raise suspicion

for obstetrical pathologies such as vasa previa and vela-

mentous insertion prior to the development of clear-cut

fetal distress. Further large-scale probably multi-centric

studies should investigate EFM patterns of such

pathologies.

Compliance with ethical standards

Conflict of interest All authors have no conflict of interest to

declare including financial or otherwise.

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