Could prior Pregnancy Termination increase Preterm Delivery Risk?

Pregnancy Loss Managed by Cervical Dilatation and Curettage Increases the Risk of Spontaneous Preterm Birth
Preterm delivery (PTD) is defined as a delivery before the 37th week of gestation. PTD is associated with significant morbidity and mortality of the newborn.[1,2] The severity depends on the gestational age at delivery and includes respiratory difficulty, intraventricular hemorrhage, retinopathy, increased risk for infections, and delayed motor-neurodevelopment in the neonatal period. PTD is also a source of increased maternal morbidity and mortality. Furthermore, it is associated with significant healthcare expenses. Prior uterine surgery, especially procedures performed on the cervix, has been identified as a risk factor for PTD.[1,3] This meta-analysis evaluated the impact of prior pregnancy termination on subsequent risk for PTD.
The Study
Thirty-six case-control and cohort studies involving over 1 million women who underwent induced termination of pregnancy or spontaneous abortion were identified. The association between prior surgical or medical pregnancy termination and PTD, low birth weight (LBW), and small for gestational age (SGA) were evaluated. Terminations done electively or as part of a completion of a miscarriage were analyzed combined and separately as well. The researchers reported:
When all procedures were combined, an increased risk for PTD (5.7% vs 5%; odds ratio [OR], 1.44; 95% confidence interval [CI], 1.09-1.90), LBW (7.3% vs 5.9%; OR, 1.41; 95% CI, 1.22-1.62) and SGA (10.2% vs 9%; OR, 1.19; 95% CI, 1.01-1.42) was found.
When induced pregnancy terminations were analyzed separately, the risk for PTD, LBW, and SGA were higher as compared with in women with no previous induced termination.
Both vacuum and sharp curettage were associated with an increased risk, though when the two procedures were compared, the risk for PTD was higher among those with prior sharp curettage (5.5% vs 3.6%; OR, 1.54; 95% CI, 1.38-1.73).
When gestational age at termination was evaluated, those with an induced termination prior to week 14 were not at increased risk for PTD when compared with controls.
No increased risk was found for PTD among those with one prior medical termination of pregnancy when compared with controls.
Those with surgical completion of a spontaneous abortion were at a higher risk for PTD in a subsequent pregnancy when compared with those who had no previous spontaneous abortions.
Viewpoint
Prior to uterine evacuation, the cervix needs to be dilated to gain access to the uterine cavity. This could happen spontaneously or medically using prostaglandins, with osmotic dilators that are placed in the cervix, or mechanically using metal dilators with increasing diameter. The latter is the most likely to induce damage in the structure of the cervix. This study found that those who had prior evacuation of the uterus (electively or as part of managing a loss) were at higher risk for subsequent PTD, LBW, and SGA.
There are important observations of this meta-analysis. An earlier procedure is less likely to be associated with subsequent adverse outcome as those who had the intervention in the first trimester were not at an increased risk for PTD.
If a surgical procedure is chosen, vacuum aspiration is less likely to result in adverse outcome when compared with sharp curettage. It is likely that the softer instruments used during vacuum aspiration are less likely to damage the cervix or uterine cavity.
Medical abortion was not associated with an adverse outcome. It is true that medical abortion is more likely to be offered at an earlier gestational age, but it is also associated with prostaglandin ripening and gradual cervical dilatation.
Expectant management of missed abortions is an option with the benefit of eventual spontaneous loss. The drawback is that the timing is not known, and it may be associated with heavy bleeding, a prolonged period of painful cramping, and an ultimate need for surgical intervention. Still, with expectant management and ultimate spontaneous loss, the cervix is dilated spontaneously and gradually, inducing less trauma in the cervix.
It is always best to involve the patient in the decision-making process. She should be aware of the steps of the various methods and the associated short- and long-term side effects. A surgical dilatation and curettage is a quick, controlled procedure done under sedation and, therefore, is the least uncomfortable for the patient. In addition, it is associated with the least amount of blood loss and painful cramps. It may, however, be associated with adverse outcome in a later pregnancy. Therefore, this could be a good choice for those who do not plan future pregnancies. The vacuum aspiration is a good alternative for those who still desire fertility. Medical options should also be offered to those who plan further pregnancies. Ultimately, the experience of the operating surgeon also needs to be considered. It is also important to point out that while the relative risk is increased for PTD, LBW, and SGA with most methods, the absolute differences are small.
(The article was published at the medscape.com.)