Many studies have shown that a history of evacuation in
women is associated with increased risk of preterm birth in subsequent
pregnancy as compared to women with no such history. But, many studies have
failed to prove a direct cause and effect relationship. Other studies have linked
D&C as a cause of subsequent pre term birth (PTB), but no distinction was
made between surgical and medical modality of evacuation.
2 systemic reviews and meta-analysis were recently published
in 2 separate journals. The first was in January, 2016 issue of Human
Reproduction published on behalf of The European
Society of Human Reproduction and Embryology and the second is still in press in the
forthcoming issue of American Journal of Obstetric and Gynecology.
The Primary source of this article is the systemic review
and meta-analysis in the journal of Human Reproduction, although both the
analysis has concluded that Prior surgical uterine evacuation is a risk factor
for subsequent pre term birth (PTB).
This is the first systematic review and meta-analysis
addressing the association between D&C and preterm birth.
Since no Randomized Control Trials (RCT) were available,
only cohort and case–control studies were included. A total of 21 studies
reporting on 1,853,017 women were included out of that 71,231 had a history of
at least one D&C in the first trimester of pregnancy. In 66,003 women,
D&C had been performed for termination of pregnancy.
The control group consisted of 1,781,786 women, out of which
24. 977 women had received a medical treatment for either miscarriage or termination
of pregnancy, while 1189 had had a spontaneous miscarriage and the rest were
without a history of miscarriage or termination of pregnancy.
The primary outcome was a preterm delivery subsequent to an H/O
curettage. The outcome of PTB was divided into 3 categories <37 weeks,
<32 weeks and <28 weeks. The study also investigated a dose –response
relationship by comparing women with a history of multiple D&Cs to women
without a history of D&C. Many other sub-group analysis comparing women with a D&C for miscarriage or termination of
pregnancy to women with medical treatment for miscarriage or termination
of pregnancy on the risk of subsequent preterm birth <37 weeks were also performed.
The important findings of the study were:
- It was seen that that women with a previous D&C, for miscarriage or termination of pregnancy in the first trimester, are at increased risk for preterm and especially very preterm birth, in comparison to women without a previous D&C procedure.
- The increase in risk was statistically significant when it was only run against women who had medical management of pregnancy.
- The risk of preterm birth increases with number of D&C performed, indicating a dose response relationship.
- Reasonably, these findings suggest that it is the surgical management, rather than the actual miscarriage or termination, is the deciding factor about the time of delivery in the following pregnancy.
The studies included had many limitations and bias, but the
strict inclusion and exclusion criteria, sensitivity and robust analysis,
multiple control groups, sub-group analysis and including prospective cohort studies helped to limit it to certain
extent.
The mechanism by which the surgical procedure increases the
risk for preterm birth remains speculative. Multiple hypotheses have been put
forward such as cervical incompetence. Another theory propose a damage to the endometrial lining which might cause
abnormal placentation in a later pregnancy, thus increasing the risk of
placental abruption, pre-eclampsia, placenta praevia and intrauterine growth
restriction.
It is also postulated that cervical damage might impair the
anti-microbial defence mechanism thereby facilitating ascending microbial
colonization, a known cause of preterm births.
The clinical implications of this study are:
Frequent follow up and increase obstetrical care for women
with h/o D&C, including monitoring of early signs and symptoms of
threatened preterm birth.
Avoiding unneeded D&C and going more for non-invasive
management options when possible i.e. expectant management or medical management
in case of miscarriage, and medical management in case of termination of
pregnancy.
No data is yet available on the effect of cervical priming
before the D&C and subsequent risk of preterm labor.
References:
Wieringa-de Waard M, Vos J, Bonsel GJ, Bindels PJ, Ankum WM.
Management of miscarriage: a randomized controlled trial of expectant
management versus surgical evacuation. Hum Reprod 2002;17:2445–2450
M.
Lemmers M,
Verschoor MAC, Hooker
AB, Opmeer
BC, Limpens J., Huirne JAF, Ankum WM, Mol BWM.
Dilatation and curettage increases the risk of
subsequent preterm birth: a systematic review and meta-analysis. Hum.
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34-
History of induced abortion as a risk
factor for preterm birth in European countries: results of the EUROPOP survey Hum.
Reprod. (2004) 19 (3):
734-740 first published
online January 29, 200
You JH, Chung TK. Expectant, medical or surgical treatment
for spontaneous abortion in first trimester of pregnancy: a cost analysis. Hum
Reprod 2005;20:2873–2878
Pregnancy loss managed by cervical
dilatation and curettage increases the risk of spontaneous preterm birth Hum.
Reprod. (2013) 28 (12):
3197-3206 first published
online September 19, 2013 doi:10.1093/humrep/det332
Shah PS, Zao J. Induced termination of pregnancy and low
birthweight and preterm birth: a systematic review and meta-analyses. BJOG
2009;116:1425–1442.
