Behavior of Leiomyoma during Pregnancy as Evaluated by Ultrasound

Published in The Scientific Journal
of Al-Azhar Medical Faculty (Girls) vol.17 No.2, July (suppl), 1996 

Abstract

Objective: To evaluate the behavior of uterine leiomyoma and their impact on the course of pregnancy.

Setting: Al-Hussein University Hospital, Cairo.

Subjects and Method

One hundred and six pregnant women diagnosed with Leiomyoma during pregnancy were evaluated clinically and by ultrasound. Leiomyoma size changes were analyzed on the basis of trimesters. The common echotexture pattern and the different echotextures as well as any changes in the echogenicity were noticed during the follow up. The number and location of the myomata were observed with their impact on pregnancy outcome.

Results: Out of 74 patients with fibroids, 50 (67.6%) showed increase in fibroid size during the first and second trimester and 10% showed increase in size in the third trimester. Thirty-seven patients (50%) showed retroplacental fibroids, but only 3(4%) had antepartum hemorrhage. The most common echo pattern was hypoechoic pattern, occurred in 79% in the first trimester, in 53% in the second trimester and in 43.5% in the third trimester. The second common echo pattern was heterogeneous echotexture occurred in 14.3%, 21.6% and 18.8% during the three trimesters respectively. There was no relation between the size of fibroid and its echo pattern changes.The changes in size of fibroid during pregnancy had no significant effect on the course of pregnancy .

Introduction

Uterine leiomyoma occur in 20-40% of women beyond 30-35 years of age(7). In one study, only 40% of fibroids diagnosed during pregnancy were clinically detectable(17). With increasing age of obstetric population and the wide spread use of , uterine fibroids are more frequently detected during pregnancy. Uterine leiomyomata are associated with numerous obstetric complications including; abortion, disseminated intravascular coagulation, hemoperitoneum, premature rupture of membranes, preterm labor, dystocia, uterine inertia, interference with placental separation and postpartum hemorrhage. About 7% of pregnant women with fibroid go into preterm labor(3). The mechanism by which leiomyomas interfere with fertility, gestation and delivery are not fully understood.

We used serial ultrasound (US) to analyze the behavior of leiomyomas during pregnancy.

Subjects and Methods

One hundred and six (106) pregnant patients with a definitive or probable uterine fibroid were seen at Al-Hussein University Hospital during a period of 30 months.

The age range was 23-45 years. Seventy-seven (A) patients were seen in the first trimester and follow up ultrasound examination was done in the late first, second and third trimesters. Twenty-four (B) patients were seen for the first time during the second trimester and follow up was done in third trimester. Five patients (C) were examined in the last trimester for the first time, one of them presented with acute abdomen which was due to fibroid red degeneration, follow up was done in the late third trimester.

The machines used for examination were General Electric 3000 RT. And Esaote Biomedica AU 530, with focus 3.5 MHz sector and linear transducer.

The following parameters for the fibroid were recorded:

Location: Either in the lower uterine segment or the uterine corpus, also the location in relation to the placental site was noted. Retroplacental location was considered when an intramural or submucus mass was present deep to the placenta.

Size: Each fibroid was measured in three dimensions, antero-posterior, transverse and longitudinal.

On follow up examination each fibroid was evaluated for change in average diameter. The change was considered significant when there is increase of at least 1-cm average diameter. If a previously measured fibroid could not be identified on follow up examination, this was considered as late non-detection.

Echotexture: The echotexture of each fibroid was compared to the myometrium.

Six types were defined:1)hypoechoic, 2)heterogeneous, 3)echogenic rim, 4)discrete anechoic or cystic spaces, 5)isoechoic and 6) hyperechoic.

Changes in echotexture during pregnancy were noticed. All patients were followed up by US examination every 4-8 weeks from the first visit to the time of delivery. Patients who were aborted or with preterm delivery were excluded.

 
Results

Table 1. Size changes in 77 fibroids seen from the first trimester

Trimester

No changes

Increase

Decrease

First

24(32.4%)

50(67.6%)

No

Second

28(37.8%)

46(62.2%)

No

Third

69(93.2%)

5(6.8%)

NO

Table 2. Size changes in fibroids seen from the second trimester (n=24) 

Trimester

No changes

Increase

Decrease

Second

4(16.7%)

20(83.3%)

NO

Third

24(100%)

o(0%)

No

Group A comprised 77 patients during the first trimester, 3 cases (4%) aborted and 74 cases was followed. 50(67.6%) patients showed increase in size and 24 (32.4%) showed no significant change in size during the second trimester. Examination during the third trimester showed that out of the 50 cases who had increase in size 46(92%) had increase in size and only 4(8%) had no significant increase during the third trimester. Out of 24 cases that had no increase in size of fibroid no one showed increase in size on the third examination(Fig.1) but 5(10%) showed increase in size on the fourth examination.

Fig 1.1 : 40 x 40mm Fibroid seen at 8 weeks.

Fig 1.2 : Same fibroid seen at 24 weeks, no change in size, fibroid became hypoechoic.

Fig 1.3 : Same fibroid seen at 32 weeks, no significant change in size.

Group B comprised 24 patients seen for the first time during the second trimester. Subsequent US examination (4-8weeks), 20(83%) cases showed increase in size while 4(17%) cases showed no change in size. The third US examination done 4-8 weeks later showed no change in size.

Group C comprised 5 patients seen for the first time during the third trimester . Subsequent US examination showed no increase in size.

During the course of pregnancy 50(67.6%) of fibroids increase in size during the first trimester and 66(67%) showed increase in size during the second trimester and only 5(4.8%) of fibroids showed increase in size during the third trimester.(Fig.2)

Fig 2.1 : 53 x 61mm hyperechoic fibroid seen at 5 weeks.

Fig 2.2 : Same fibroid seen at 14 weeks, hypoechoic but enlarged 78 x 77mm.

Out of 37 patients with retroplacental fibroid, 3(8%) cases had antepartum hemorrhage, which responded to conservative treatment.

Echotexture of Fibroid during Pregnancy

Table 3. Echotexture changes during the second trimester (N=77, aborted =3)

Initial appearance
(No. of fibroid)

Hypoechoic

Heterogeneous

Echogenic
rim

Anechoic/
Cystic

Isoechoic

changes

Hypoechoic
(61)

35

8

8

4

3

39.7%

Heteroechoic
(11)

1

8

2

0

0

27.3%

Echogenic rim
(0)

0

0

0

0

0

0%

Anechoic/Cystic spaces (3)

0

0

1

2

0

33.3%

Isoechoic

0

0

0

2

0

0%

Total
(77)

36

16

11

6

5

N/A

Table 4. Echotexture changes during the third trimester (Group A=74,Group B=24)

Initial appearance
(No. of fibroid)

Hypoechoic

Heterogeneous

Echogenic
rim

Anechoic/
Cystic

Isoechoic

changes

Hypoechoic
(36+15)

41

2

6

1

1

18.5%

Heteroechoic
(16+5)

2

15

3

1

0

28.6%

Echogenic rim
(11+2)

0

0

13

0

0

0%

Anechoic/Cystic spaces (6+1)

0

0

0

7

0

0%

Isoechoic
(5+1)

0

2

1

0

3

50%

Total
(98)

43

19

23

9

4

N/A

In group, A which comprised 77 patients, 61 had hypoechoic texture, 11 had heteroechoic texture, 3 anechoic, 2 isoechoic and no case had echogenic rim(table 3).

In-group B which comprised 24 patients, 15 were hypoechoic, 5 heteroechoic, 2 echogenic rim, 1 anechoic and 1 isoechoic.

In-group C the 5 patients seen showed hypoechoic pattern in 3 cases and echogenic rim in 2 cases.

The most common pattern of fibroids in pregnancy was hypoechoic compared with myometrium. This pattern was present in 69% of cases seen during the first trimester, 53% of cases seen during the second trimester and 43.5% of cases seen during the third trimester The second most common pattern was the heterogeneous echotexture comprising 14.3%, 21.6% and 18.8% during the three trimesters respectively.

The third most common appearance is an echogenic rim. This echogenic rim (Fig.3) constitutes the periphery of fibroids with diverse internal echotexture most commonly hypoechoic(3). This pattern was present in 14.8% of cases in the second trimester and in 22.8% of cases in the third trimester and no single case noticed in the first trimester. This echogenic rim sometimes is complete but usually it is incomplete.

Fig 3 : Fibroid with echogenic rim.

Fig. 4 : Fibroid with Cystic Changes

Another patterns were observed; fibroids with anechoic or cystic spaces (Fig.4), isoechoic fibroid and only two cases of hyperechoic texture. Changes in echotexture were frequently observed during the three trimesters. Some fibroids showed cystic spaces, other became heterogeneous and other became isoechoic. Some fibroids developed complete or incomplete echogenic rim. The development of this rim appears to be a final change with no cases progressing to any other pattern. Calcification was also observed in some fibroids. The echotexture changes were not accompanied by significant changes in size.

Discussion

Ultrasound is useful in the detection of uterine leiomyomas and is especially useful in screening, however, it has its limitations in the assessment of the obese patients(1).

In our study we found that difficulty to visualize the fibroid was limited to the obese patients only during the first trimester, but with advancing of the pregnancy no difficulties encountered, as the gravid uterus stretches the abdominal wall and displaces the bowel.

The predominant view in obstetric literature is that fibroids enlarge during pregnancy and inviolate during the puerperium(13). However, several clinical histologic studies refute this concept of true fibroid growth during pregnancy(6). One group reported no significant size change in 38 of 41 fibroids during the second half of pregnancy (11). Another group reported that 31 of 54 fibroids developed red degeneration during pregnancy without any size change while the remaining fibroids tended to increase in size rapidly during pregnancy(9).

In the present study we monitored size changes during the three trimesters of pregnancy. The results showed that about 67% of fibroids diagnosed in the first trimester increase in size and about 62% increase in size during the second trimester and only 6.8% increase in size during the third trimester. It was noticed that fibroids which increase in size during the first trimester usually increase during the second trimester.

Anna et al (1) found that about half of all fibroids do not change significantly in size and growth changes demonstrated by the remainder of fibroids depend on their previous size, they found that small fibroids tend to increase in size during the first and second trimesters and decrease in size during the third trimester. They also found that large fibroids tend to increase in size only in the first trimester and decrease in size during the second and third trimesters.

In our study we found no decrease in size during the three trimesters.

True increase in fibroid size during pregnancy may not be explained by myoma cell proliferation because no proliferation takes place during pregnancy (14). Myoma cell hypertrophy, does occur during pregnancy and possibly explain the measured fibroid growth trends. The cells in small fibroids hypertrophy during pregnancy and shrink in late pregnancy (10)

The decrease in size observed in late pregnancy, by other studies, could be explained in part by the decrease in cell size.

Myoma cells have a greater number of estrogen receptors than surrounding normal myometrial cells(16). Therefore, these cells should be more responsive to the increased concentrations of estrogens present during pregnancy and exceed the growth of the surrounding myometrium.

Progesterone on the other hand may inhibit the growth of fibroids(8) and even induce degenerative changes and involution(6). The increasing progesterone level in late pregnancy could explain the decrease in fibroid size during that period. Another theory implicates the arterial supply of fibroid as a cause of degenerative and size changes (15). Fibroids are supplied by one or more nutrient arteries entering from the periphery and encircling the tumor. As the tumor rotates as a result of passive stretching of the uterine wall and active muscle contraction these arteries may be twisted. Also upward migration of fibroids out of the pelvis may also result in vessel torsion comprising the blood supply to fibroid(4).

In the present study, The echo characteristics in more than two thirds of fibroids showed no changes during pregnancy. However, anechoic cystic spaces and coarse heterogenicity patterns represent a special clinical group. The available data suggest that red degeneration appears on sonogram as an area of high through transmission with moderate to marked echoes. In the present study, this echotexture pattern was infrequent, only two cases were reported and diagnosed as red degeneration. The frequency of this echotexture pattern. In a study done by Anna et al (1) 10 out of 113 cases diagnosed as having red degeneration.

Faulkner et al (5) found that red degeneration occurs in medium-size fibroids in pregnant state as opposed to large fibroids in the nonpregnant state. Location of the fibroid in the lower uterine segment predispose towards a higher frequency of Cesarean section by obstruction of the birth canal(15). Also, it predisposes to retained placenta, which may be related to some degree of mechanical obstruction.

In the present study only 3 cases out of 37 with retroplacental fibroid reported antepartum hemorrhage (Fig.5). Anna et al (1) showed that cases with retroplacental fibroids had no significant increase in cases with antepartum hemorrhage. However, Winer-Muram et al (17) reported antepartum hemorrhage in 25 of 35 patients with defined retro-placental fibroids.

Fig. 5 : Retroplacental Fibroid

To summarize, the most common type of echogenic pattern of fibroid during pregnancy was the hypoechoic texture. The echogenic changes were more common towards the echogenic rim and the heterogeneous types. It was noticed that the size and echogenic changes were predominant in the second trimester. Also, it was found that there was no relationship between the size and echo pattern changes.

In conclusion, fibroids may adversely affect the course of pregnancy depending on their location. The changes in size during pregnancy has no significant effect on the course of pregnancy.

References:

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