Do women with a previous miscarriage or termination of pregnancy have an increased risk of spontaneous preterm birth and is this related to previous cervical dilatation and curettage?
A single previous pregnancy loss (termination or miscarriage) managed by cervical dilatation and curettage is associated with a greater risk of SpPTB.
Miscarriage affects 20 of pregnancies and as many as a further 20 of pregnancies undergo termination.
We utilized data from 5575 healthy nulliparous women with singleton pregnancies recruited to the Screening for Pregnancy Endpoints (SCOPE) study, a prospective cohort study performed between November 2004 and January 2011.
The primary outcome was spontaneous preterm birth (defined as spontaneous preterm labour or preterm premature rupture of membranes (PPROM) resulting in preterm birth 37 weeks gestation). Secondary outcomes included PPROM, small for gestational age, birthweight, pre-eclampsia and placental abruption.
Women with previous pregnancy loss (miscarriage or termination) were compared with those with no previous pregnancy loss. There were 4331 (78) women who had no previous pregnancy loss, 974 (17.5) who had one early previous pregnancy loss, 249 (4.5) who had two and 21 (0.5) who had three or four losses. Women with two to four previous losses, but not those with a single loss, had an increased risk of spontaneous preterm birth (adjusted OR 2.12; 95 CI 1.55, 2.90) and/or placental abruption (adjusted OR 2.30; 95 CI 1.36, 3.89) compared with those with no previous pregnancy. A single previous miscarriage or termination of pregnancy where the management involved cervical dilatation and curettage was associated with an increased risk of spontaneous preterm birth (adjusted OR 1.64; 95 CI 1.08, 2.50; 6 absolute risk and adjusted OR 1.83; 95 CI 1.35, 2.48; 7 absolute risk, respectively) compared with those with no previous pregnancy losses. This is in contrast with women with a single previous miscarriage or termination managed non-surgically who showed no increase risk (adjusted OR 0.86; 95 CI 0.38, 1.94; 3.4 absolute risk and adjusted OR 0.87; 95 CI 0.69, 1.12; 3.8 absolute risk, respectively).
Although every effort was made to record accurate previous pregnancy data, it was not feasible to confirm the history and management of previous pregnancy loss by hospital records. This may have introduced recall bias.
This large prospective cohort study of healthy nulliparous women has demonstrated that women with either a previous miscarriage or termination of pregnancy were at increased risk of spontaneous preterm birth if they were managed by procedures involving cervical dilatation and curettage. However, overall, women with a single pregnancy loss did not have an increased risk of having any other of the adverse pregnancy outcomes examined. In contrast, two to four previous pregnancy losses were associated with an increased risk of having a pregnancy complicated by spontaneous preterm birth and/or placental abruption. Research is required to determine whether non-surgical management of miscarriage or termination of pregnancy should be advocated over surgical treatment.