Objective
The objective of the study was to determine whether 1 previous miscarriage is associated with an increased rate of adverse pregnancy outcomes in the following pregnancy.
Study Design
Second pregnancies of women with and without a miscarriage in their initial pregnancy were compared. Multivariable logistic regression models were constructed to control for confounders.
Results
Of 35,125 singleton deliveries in the second pregnancy, 5777 (16.4%) were of patients with an initial miscarriage. Multivariable analysis showed a significant association between a previous miscarriage and the following adverse pregnancy outcomes including premature rupture of membranes (odds ratio [OR], 2.22; 95% confidence interval [CI], 2.01–2.44), preterm delivery (OR, 1.34; 95% CI, 1.21–1.48), intrauterine growth restriction (OR, 1.24; 95% CI, 1.04–1.47), hypertensive disorders (OR 1.41; 95% CI 1.07–1.85), preeclampsia (OR, 1.63; 95% CI, 1.22–2.18), and cesarean delivery (OR, 1.59; 95% CI, 1.46–1.73). Perinatal mortality was significantly higher among women with an initial miscarriage (1.6% vs 1.0%; P < .001).
Conclusion
An initial miscarriage is independently associated with adverse pregnancy outcomes.
Spontaneous miscarriage refers to a pregnancy that ends spontaneously before the fetus has reached a viable gestational age (fetal death before 24 weeks). Most studies report that approximately 1 in 5 clinical pregnancies will end in a miscarriage, whereas prospective studies on conception and early pregnancy have reported fetal loss rates approaching one third.
A distinction should be made between spontaneous intermittent miscarriages and recurrent miscarriages. Spontaneous intermittent miscarriages are defined as nonconsecutive pregnancy losses occurring sporadically during a woman’s child-bearing years. The prevalence of sporadic miscarriages is 10-15% of all diagnosed pregnancies. Recurrent miscarriages are defined as 3 consecutive spontaneous miscarriages, with a recurrence rate of 33%. However, the risk of recurrence after 2 consecutive miscarriages is clinically similar to the risk of recurrence after 3 or more consecutive miscarriages and stands at 30%.
Thus, the 2001 American College of Obstetricians and Gynecologists recommendation is that women with 2 or more spontaneous consecutive miscarriages should be candidates for clinical and laboratory evaluation to find a possible etiology. Although the etiologies of recurrent miscarriages are heterogenic, in the majority of cases, single, sporadic, and spontaneous miscarriages have traditionally been attributed to chromosomal abnormalities.
Although a spontaneous miscarriage is distressing at any time, it is particularly so if it occurs in the first pregnancy. Previous studies have focused on the risk of further miscarriage in these women, but there have been few attempts to study obstetric and perinatal outcomes in subsequent pregnancies following a spontaneous miscarriage in an initial pregnancy. Only 2 recent studies were identified by searching the MEDLINE and other bibliographic databases. These studies reported that an initial miscarriage is associated with a higher risk of obstetric complications in the following pregnancy.
Because data regarding obstetric and perinatal outcomes in pregnancies following an initial miscarriage are scarce, we undertook this study to determine whether a previous spontaneous miscarriage is associated with an increased rate of adverse pregnancy outcomes in the following pregnancy.
Materials and Methods
A retrospective, population-based study was undertaken including all deliveries in the second pregnancy. Deliveries of women with a previous miscarriage in their first pregnancy (G2P1) were compared with deliveries of women without a previous miscarriage (G2P2). Hence, women with a miscarriage in their second pregnancy were not included in the study. Miscarriage refers to fetal death before 22 weeks. Deliveries occurred from 1988 to 2008 in the Soroka University Medical Center, the only hospital in the Negev, the southern region of Israel, serving the entire obstetrical population. Thus, the study represents nonselective population-based data. Women lacking prenatal care and multiple gestations were excluded from the analysis.
Data regarding adverse pregnancy outcomes were available from the perinatal database of the center, which was reported by an obstetrician immediately after delivery. Skilled medical secretaries routinely reviewed the information prior to entering it into the database. Coding was performed after assessing the medical prenatal care records together with the routine hospital documents. The local ethics institutional review broad approved the study. The perinatal database of our center contains information on all infants born (alive or stillborn) beyond 22 weeks of gestation or weighing 500 g or more.
The following clinical characteristics were evaluated: maternal age, gestational age, birthweight, neonatal sex, and ethnicity. The following obstetrical risk factors were examined: fertility treatments, diabetes mellitus, cervical os incompetence, preeclampsia, and chronic hypertension. Perinatal complications that were evaluated included intrauterine growth restriction (IUGR), breech presentation, first-stage nonprogressive labor, second-stage nonprogressive labor, placenta previa, induction of labor, placental abruption, preterm rupture of membranes (PROM), preterm delivery (PTD) before 37 weeks’ gestation, PTD before 34 weeks’ gestation, and cesarean delivery (CD). The following perinatal outcomes were assessed: a low Apgar score at 1 and 5 minutes (<7), fetal distress, congenital malformations, and perinatal mortality.
Statistical analysis was performed with the SPSS package, version 16 (SPSS Inc, Chicago, IL). Statistical significance of the categorical variables was tested using the χ 2 or Fisher’s exact test, as appropriate. For continuous variables, a Student t test was used. Multivariable logistic regression models were carried out to control for confounders. Odds ratios (ORs) and their 95% confidence interval (CI) were computed. A P < .05 was considered statistically significant.
Results
Of 35,125 singleton second deliveries, 5777 (16.4%) were of patients with an initial miscarriage. Demographic and clinical characteristics of pregnancies with and without a previous abortion are presented in Table 1 . Women with an initial miscarriage were significantly younger, delivered earlier, had lower birthweight neonates, and were more likely to be Jewish.
