Women who have undergone a common gynecological surgical procedure who later become pregnant may be at increased risk of giving birth before the baby reaches full term, new research suggests. 

The procedure, known as dilatation and curettage (commonly called a D&C), is performed on women who have had either a miscarriage or an abortion. The new study shows that the procedure may increase women's risk of preterm birth because it may damage the cervix. This opening at the bottom of the uterus normally stays closed during pregnancy but opens during labor.

The new findings "warrant caution in the use of D&C after miscarriage and induced abortion," said study co-author Dr. Pim Ankum of the Academic Medical Center of the University of Amsterdam, the Netherlands. The findings were presented on Tuesday (June 16) at the Annual Meeting of European Society of Human Reproduction and Embryology in Lisbon, Portugal. [7 Baby Myths Debunked]

Common procedure

D&C is one of the most common surgical procedures performed for abortion and miscarriage. During the 15-minute procedure, doctors dilate, or open, the cervix, then scrape the uterine wall using either a metal implement called a curette or a vacuum suction tube. The procedure is considered very safe, with just a few, extremely rare serious side effects such as heavy bleeding, infection and puncturing of the uterine wall. Rarely, D&Cs can also cause bands of scar tissue, called adhesions, to form in the uterus, making it difficult to conceive later on, according to the American College of Obstetricians and Gynecologists.

To understand more about the risks of D&Cs, Ankum and his colleagues analyzed 21 previously published studies that included a total of more than 2 million women.

The researchers found that compared with women who had never had a D&C, women who had undergone the procedure prior to giving birth were 29 percent more likely to deliver their baby before the 37th week of pregnancy. (Pregnancies are generally considered to reach full term at 37 weeks.) Women who had not undergone a D&C had a 6 percent chance of having a preterm delivery, compared with 7.6 percent for those who had undergone the procedure, the researchers found.

The procedure also increased women's risk of very preterm births, or those occurring before 32 weeks of gestation, by 69 percent. The risks were higher for women who had multiple D&Cs.

There are other options besides undergoing a D&C for women who experience a miscarriage or have an abortion. Women may wait for the contents of the uterus to be expelled naturally, or may take a pill that speeds the clearing.

The researchers found that women who underwent D&C surgeries had an increased risk of preterm birth that was not seen in women who had previously experienced miscarriages but who chose to either take a pill or to wait for the remains of the miscarriage to clear from the body naturally.

But there are benefits to having a D&C rather than taking a pill or waiting for the contents of the uterus to be expelled naturally. The procedure may shorten the time involved to clear the uterus. Women may want to start trying to conceive another pregnancy as soon as possible, or may feel traumatized by the miscarriage and want to avoid the weeks of waiting that it can take for the uterus to clear completely. The pill used to clear a miscarriage from a woman's body, called misoprostol, is only safe and effective earlier in pregnancy, and doesn't always work, meaning women may have to have a D&C anyway.  

Cervical damage

It's not clear why the researchers found the association between D&C and preterm birth, but it's possible that the procedure may damage the cervix. This might later cause it to open before a pregnancy is full term, researchers speculated.

This could mean that other procedures that may damage the cervix, such as biopsy or cauterization, may also lead to preterm births. Another possibility is that damage to the cervix could allow the flourishing of genital tract infections, a known cause of preterm births, the researchers said.

The findings suggest that doctors should be more "restrained" in the use of dilatation, opting to use medicines such as misoprostol to induce miscarriage or to soften the cervix instead of dilatation prior to curettage, Ankum said.

Up to 25 percent of pregnancies end in miscarriage, and in about 50 percent of miscarriages, women undergo a D&C, according to the American Pregnancy Association. 

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