History of uterine evacuation is an independent risk factor for preterm birth: a systematic review and meta-analysis.

Preterm birth(PTB) is the birth of an infant before 37 weeks of pregnancy, according to WHO statistics an estimated 15 million babies born preterm out of whom 1 million succumb. PTB is also responsible for long term neurological complications in children like cerebral palsy, learning disabilities and visual and hearing problems.

The current global preterm birth rate is 5% to 18% and statistic shows a steady increase recently.More than 60% of preterm births occur in Africa and South Asia, India topping the list with 3 519 100 PTBs

Three forth of these births could be prevented, saving lives and money across the globe.

CDC data quotes that in the year 2014, every 1 in 10 infants was born preterm in US. For physician across the globe, PTB remains a challenge as the factors leading to preterm births are numerous, complex and not well understood. Among various contributing factors prior uterine surgery, especially those performed on cervix (induced termination of pregnancy (I-TOP) or spontaneous abortion (SAB)) has been implicated in its causation. Studies till now have shown mixed results.

The current research published in May 2016 issue of American Journal of Obstetrics and Gynecology evaluated the risk of PTB in women with a history of uterine evacuation for I-TOP or SAB.

For the data source electronic databases (MEDLINE, Scopus, ClinicalTrials.gov, EMBASE, and Sciencedirect) were searched from their inception until January 2015. Women with prior history of uterine evacuation for either I-TOP or SAB, compared with a control group without a history of uterine evacuation were included in the study.

Total 36 case control studies involving 1,047,683 women (31 studies for I-TOP, 5 studies for SAB) met the inclusion criteria and were included in the analysis.

The primary outcome was relationship between prior evacuation and subsequent preterm births while the secondary outcome studied were low birthweight (LBW) and small for gestational age (SGA). 

Relationship between PTB and prior H/O surgical vs spontaneous evacuation was studied separately and combined both.

The study found that:

• When all procedures combined there were increased odds of having a preterm birth, LBW and SGA babies being born after a history of surgical evacuation.
• Vacuum evacuation and sharp curettage were associated with PTB when analyzed in combination. When analyzing separately sharp curettage was associated with higher risk.
• Medical termination was found quite safe and did not result in PTB in subsequent surgery.
• Women with a prior history of spontaneous abortion(SAB) have a higher risk of PTB, as compared to those with no history of SAB.
• A very important observation as a result of meta-analysis is evacuation before 14 weeks of pregnancy (Spontaneous or induced) was not associated with increased risk for PTB.
• Expectant management of missed abortion is an option with ending in spontaneous loss, but sometimes may end up in heavy bleeding requiring immediate evacuation.

References:

http://www.ncbi.nlm.nih.gov/pubmed/24625129

http://www.ncbi.nlm.nih.gov/pubmed/22682464

http://www.who.int/mediacentre/factsheets/fs363/en/

http://www.cdc.gov/reproductivehealth/maternalinfanthealth/pretermbirth.htm

Prior First Trimester Uterine evacuation augments the risk for preterm birth in subsequent pregnancies!

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. Reprod. (2016) 31 (1): 34-

http://www.ajog.org/article/S0002-9378%2815%2902596-X/abstract

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.