Patterns and Predictors of Vaginal Bleeding in the First Trimester of Pregnancy

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Purpose

Although first-trimester vaginal bleeding is an alarming symptom, few studies have investigated the prevalence and predictors of early bleeding. This study characterizes first trimester bleeding, setting aside bleeding that occurs at time of miscarriage.

Methods

Participants (n = 4539) were women ages 18 to 45 enrolled in Right From the Start, a community-based pregnancy study (2000−2008). Bleeding information included timing, heaviness, duration, color, and associated pain. Life table analyses were used to describe gestational timing of bleeding. Factors associated with bleeding were investigated by the use of multiple logistic regression with multiple imputation for missing data.

Results

Approximately one fourth of participants (n = 1207) reported bleeding (n = 1656 episodes), but only 8% of women with bleeding reported heavy bleeding. Of the spotting and light bleeding episodes (n = 1555), 28% were associated with pain. Among heavy episodes (n = 100), 54% were associated with pain. Most episodes lasted less than 3 days, and most occurred between gestational weeks 5 to 8. Twelve percent of women with bleeding and 13% of those without experienced miscarriage. Maternal characteristics associated with bleeding included fibroids and prior miscarriage.

Conclusions

Consistent with the hypothesis that bleeding is a marker for placental dysfunction, bleeding is most likely to be observed around the time of the luteal-placental shift.

Introduction

Although first-trimester vaginal bleeding is an alarming symptom 1, 2, 3, 4, few studies have rigorously investigated the prevalence, timing, and predictors of bleeding. Estimates of bleeding prevalence in early pregnancy are imprecise and range from 7% to 24% 5, 6, 7, 8, 9. This wide range in estimates is likely attributable to differences in study design.

In only three reports have researchers attempted to systematically describe early pregnancy bleeding patterns 5, 8, 10. These studies are limited by small sample (10), observation through only the eighth week of gestation (10), and recruitment and data collection late during pregnancy 5, 8. In the latter two studies, the authors do not provide detailed information on first-trimester bleeding and exclude miscarriages 5, 8. Only one of these investigated maternal predictors of vaginal bleeding (5). This study found that women who were older, with passive smoking exposure, previous preterm birth, multiple previous elective terminations, or with previous miscarriages were more likely to experience “intense” vaginal bleeding, measured by heaviness, duration, and an index of total blood loss. We used data from Right From the Start (RFTS), a community-based early pregnancy cohort, to characterize the patterns and predictors of early pregnancy bleeding, setting aside bleeding episodes that occur at the time of miscarriage.

Section snippets

Study Population

RFTS is an ongoing cohort that began enrollment of pregnant women in 2000. Over time, the study has included three phases (RFTS 1, 2, and 3) and has been active in Galveston, Texas; Memphis and Nashville, Tennessee; and the Triangle region (including Raleigh, Durham, and Chapel Hill), North Carolina. Participants were at least 18 years of age, spoke English or Spanish, had not used assisted reproductive technologies to conceive, and intended to carry the pregnancy to term. Women who were not

Results

Most of the 4539 women in this study were 25 to 34 years of age and self-identified as white, black, or Hispanic (Table 1). Participants were generally of high educational attainment. Approximately one half were nulliparous. Pregnancy ended in miscarriage for 12% of women and approximately two thirds reported some bleeding during pregnancy. After excluding bleeding episodes that ended within 4 days of miscarriage, 25% of women with miscarriage reported at least one episode of bleeding during

Discussion

We provide new evidence that first trimester bleeding episodes tend to peak during the sixth and seventh weeks. Different characteristics of bleeding tend to cluster together. Heavy bleeding episodes (similar or heavier than those of a woman's normal menses) are more likely to be associated with pain, longer duration, bright red color, and presence of multiple episodes, whereas spotting episodes are more likely to occur in isolation and be of shorter duration and without pain. This finding

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The field research was supported in part by grants from the National Institute of Child and Human Development (5R01HD043883 and 5R01HD049675) and the American Water Works Association Research Foundation (2579). Additional funds were provided by the National Institute of Environmental Health Sciences (Intramural Research Program and P30ES10126).

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