Prevalence and risk factors of inadequate cervical dilation following laminaria insertion in second-trimester abortion — case control study

Abstract

Objective

The objective was to explore the prevalence of and risk factors for inadequate cervical dilation following insertion of a single set of laminaria in women scheduled for dilation & evacuation (D&E) at 14–24 weeks' gestation.

Study design

We retrospectively reviewed all cases of women who underwent pregnancy termination by D&E at 14–24 weeks’ gestation between January 2003 and December 2013. All cases in which the surgical procedure was cancelled due to failure to achieve adequate cervical dilation after a single set of laminaria inadequate cervical dilation were included. The control group was women who underwent D&E following adequate cervical dilation after a single set of laminaria, and were matched according to gestational week in a ratio of 1:3.

Results

The overall dilation failure rate was 3.2%, with 4.0% among the induced-abortion patients and 1.5% among the patients with fetal demise (p=.002). Patients who had inadequate cervical dilation had lower rates of gravidity (p=.002) and previous spontaneous vaginal delivery (p<.001), along with higher rates of primigravidity, nulliparity (p<.001), previous cesarean section/s (p=.041), previous abdominal surgeries (p=.001) and previous cervical procedures (p=.003), compared to controls. A multivariable logistic regression analysis revealed two risk factors for inadequate cervical dilation following laminaria insertion, namely, previous cesarean section (p=.002) and previous cervical procedure (p<.001), whereas increased gravidity was found to protect against inadequate cervical dilation (p=.002).

Conclusions

Previous cesarean section/s, cervical procedures and primigravidity were found to be risk factors for failure to achieve adequate cervical dilation after a single set of laminaria. Women who are scheduled for D&E, and in whom one of these risk factors exists, might benefit from additional interventions to achieve better cervical preparation.

Introduction

Abortion during the second trimester of pregnancy accounts for 10%–15% of abortions performed worldwide [1], [2]. Pregnancies most commonly are terminated in the second trimester by induction of labor or dilation and evacuation (D&E). D&E generally is the preferred method when skilled providers and facilities are available because it is safe, cost effective and efficient [3].

Late second-trimester abortion by D&E is associated with low complication rate. A Cochrane review that compared surgical and medical methods used for inducing abortion in second-trimester pregnancy with regard to efficacy, side effects, adverse effects and acceptability found that D&E is superior to instillation of prostaglandin F2α, mifepristone and misoprostol [3]. D&E was found to be safe in the presence of placenta previa [4], multiple pregnancies [5] and scarred uterus [6], [7].

Preoperative preparation of the cervix is recommended before surgical evacuation of second-trimester pregnancies [8]. The cervix may be prepared with osmotic dilators, pharmacologic agents or both. The most common method for second-trimester D&E is by overnight laminaria placement [9]. Retrospective studies have shown that use of osmotic dilators such as laminaria tents decreases the risk of cervical laceration and uterine perforation [10]. The minimal dilation required depends on the type of instrument and gestational age [11]. Cervical preparation for D&E is deemed essential at 14weeks’ gestation and beyond [12], [13] and can be achieved through the use of pharmacologic agents, osmotic dilators and Foley balloon catheters [14], [15], [16], [17], [18], [19], [20].

Osmotic dilators exist in three main forms: laminaria tents, Lamicel TM, and Dilapan-STM. Laminaria tents are dried, compressed seaweed stems that absorb fluid and gradually expand, providing both mechanical dilation and dilation from endogenous prostaglandin release [21], thus making adjunctive manual dilation easier. Laminaria absorb fluid within the cervix and swell to about three to four times their original diameter. Most of this dilation occurs within the first 6h, with the maximum effect occurring in 12 to 24h. Reports regarding laminaria use date back to 1862, giving laminaria a long record of successful dilation with an excellent safety profile [22], [23].

Occasionally, the internal os of the uterine cervix fails to dilate following a single set of laminaria insertion. These cases usually are diagnosed during the D&E procedure. Many surgeons would not cancel the D&E but instead would mechanically dilate the cervix or place a set of Dilapan and do the case later in the day. Some providers schedule the patients who may not have received an adequate number of dilators for gestational duration to come in early on the operative day to remove the dilators to assess the cervix. If the cervix is too closed and/or too noncompliant, they then place an additional set of dilators and/or use adjuvant misoprostol before taking the patient to the operation room either for later that day or for a subsequent day. Although used for many decades, studies of cervical preparation offer few data about success of cervical preparation with different patient characteristics. Therefore, the current study aims to explore the prevalence and potential risk factors for inadequate dilation.