Long-term recall of pregnancy-related events

Abstract

Background

Early-life factors can be associated with future health outcomes and are often measured by maternal recall.

Methods

We used data from the North Carolina Early Pregnancy Study and Follow-up to characterize long-term maternal recall. We used data from the Early Pregnancy Study as the gold standard to evaluate the accuracy of pre-pregnancy weight, early pregnancy behaviors, symptoms and duration of pregnancy, and child’s birthweight reported at follow-up, for 109 women whose study pregnancies had resulted in a live birth.

Results

Most (81%) participants reported a pre-pregnancy weight at follow-up that correctly classified them by BMI category. Women reported experiencing pregnancy symptoms later at follow-up than what they reported in the Early Pregnancy Study. Accuracy of reporting of early pregnancy behaviors varied based on exposure. Overall, women who had abstained from a behavior were more likely to be classified correctly. Sensitivity of reporting was 0.14 for antibiotics, 0.30 for wine, 0.71 for brewed coffee, and 0.82 for vitamins. Most misclassification at follow-up was due to false-negative reporting. Among women who gave birth to singletons 94% could report their child’s correct birthweight within ½ pound and 86% could report duration of pregnancy within 7 days at follow-up.

Conclusions

Self-report of pre-pregnancy weight, duration of pregnancy, and child’s birthweight after almost 30 years was good whereas self-reported pregnancy-related exposures resulted in higher levels of reporting error. Social desirability appeared to influence women’s report of their behaviors at follow-up. Self-reported assessment of confidence in the recalled information was unrelated to accuracy.

Introduction

Interest in the associations between early life factors and adult health outcomes has rapidly expanded over the past decade. Additionally, exposures during pregnancy can affect the health of the mother later in life.¹ Studies of prenatal exposures and events at childbirth often rely on maternal recall decades later.^2–6 The literature is mixed regarding how well women are able to recall behaviors during pregnancy.^7–9 Studies have found good agreement between short-term maternal recall of routinely collected birth information (child’s birthweight and duration of pregnancy) and medical records,^10–12 but studies of the accuracy of long-term recall are limited.^13–15

The present study evaluated the long-term recall of maternal pre-pregnancy weight, several early pregnancy exposures, duration of pregnancy, and child’s birthweight in an actively engaged, healthy cohort of women originally enrolled during the early 1980s. We describe the accuracy of reporting at a follow-up interview approximately 30 years after the study pregnancy. We also assessed whether subjective certainty about a given answer at follow-up would predict accuracy of recall.

Methods

The North Carolina Early Pregnancy Study (“the baseline study” from here forward) was a prospective cohort study conducted in 1982–1986 to estimate the incidence of early pregnancy loss (eAppendix 1).¹⁶ Participants were re-contacted in 2010–2011 as part of the North Carolina Early Pregnancy Study Follow-up (“follow-up” from here forward); 173 of 210 survivors completed a follow-up questionnaire. Women reported previously collected information about their baseline study pregnancy. For recalled early pregnancy behaviors, participants were asked to indicate how sure they were of their responses using a 4-level scale (1-quite unsure, 2-unsure, 3-sure, and 4-quite sure).

Pre-pregnancy weight was reported in pounds in the baseline study and at follow-up. Body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. Using WHO BMI categories, the majority of participants had a normal BMI (18.5 – 24.9).¹⁷ In order to have more balanced groups, women’s BMI was categorized as lower normal (<21.0), higher normal (21.0–24.9), and overweight/obese (≥25.0).

In the baseline study, women prospectively recorded in their daily diary the presence or absence of symptoms they thought might be pregnancy-related (eAppendix 2). At follow-up, women were asked about the timing of the onset of pregnancy-related symptoms in the following categories: ≤6, 7–8, or >8 weeks from their last menstrual period.

Both in the baseline study and at follow-up, women reported their caffeinated and alcoholic beverage intake during the first 8 weeks of pregnancy as number of servings per day, week, or month, which we converted to servings per month for analysis. Because high caffeine intake is a potential concern during pregnancy,¹⁸ we evaluated accuracy of recalled total caffeine as calculated from coffee, tea, and soft drinks, the primary sources assessed in the baseline study. Overall caffeine intake was calculated by multiplying the number of monthly servings of each beverage type by their typical caffeine content in the early 1980s.¹⁹ A serving of alcohol was defined as 12 ounces of beer, 4 ounces of wine, or 1.5 ounces of hard liquor, and considered equivalent. Monthly servings of all alcoholic beverages were summed for overall alcohol intake.

During the baseline study, duration of pregnancy was calculated as the number of days from last menstrual period (based on bleeding recorded in the daily diary) to the birth date of the child. At follow-up, participants reported duration of pregnancy (in weeks) for their baseline study pregnancy; women with live births also reported how many days before or after their due date they delivered. Birthweight was reported as pounds and ounces.

Measures collected during the baseline study were considered the gold standard. Sensitivity was calculated as the proportion of women who reported being exposed at follow-up among those who were ‘truly exposed’ based on their baseline study data. Specificity was calculated as the proportion of women who reported no exposure at follow-up among those who were ‘truly not exposed’. Accuracy was calculated as the proportion of women who correctly reported being exposed or not exposed at follow-up. The proportion with accurate recall who reported they were quite sure or sure of their responses at follow-up was compared with the proportion quite sure or sure with inaccurate recall. For women with inaccurate responses at follow-up, we calculated the proportion over- and under- reporting to characterize the direction of misclassification at recall. For reported continuous measures including pre-pregnancy weight, duration of pregnancy, and child’s birthweight we calculated the difference in reported weight or age (baseline study–follow-up).

Results

There were 120 women who completed both the 8-week pregnancy and follow-up questionnaires (Figure 1). The analysis was limited to the 109 women whose pregnancies resulted in a live birth (104 singletons, 5 sets of twins). The majority of women were white (95%) and well-educated (78% had a college degree or greater). The median age at follow-up was 55 years (eTable 1). Half of the women were nulliparous at the time of baseline enrollment.

Figure 1.

Flowchart of participants from the baseline Early Pregnancy Study and Early Pregnancy Study Follow-up who were included in the analysis

Pre-pregnancy weight

Of the 106 women who were able to provide their pre-pregnancy weight at follow-up, 89% reported a weight within 10 pounds of what they had reported at enrollment. Women reporting a different pre-pregnancy weight (n=90), were more likely to over-estimate their weight (68%) than under-estimate (32%). When we categorized women by the three BMI categories created for this study, 81% of participants recalled a pre-pregnancy weight that placed them in the same BMI category as their originally reported weight. Stratifying by parity at the time of enrollment, more nulliparous women recalled a weight in the correct BMI category (nulliparous 88%, parous 74%).

Onset of symptoms of pregnancy

Most women (78%) had prospectively reported the onset of symptoms of pregnancy within the first 6 weeks from their last menstrual period while on the follow-up questionnaire women tended to report later onset of symptoms. Using the response choices provided for women at follow-up (≤6, 7–8, or >8 weeks from last menstrual period), 52% recalled the timing correctly, 39% chose a longer time, and 9% chose a shorter time to onset of symptoms, compared with their prospective reports (eTable 2).

Early pregnancy exposures

The Table and eTable 3 provide a summary of how well women were able to recall behaviors (yes/no) during early pregnancy. Brewed coffee and tea accounted for 75% of the caffeine consumption. Both were recalled with at least 70% accuracy, and with sensitivity and specificity close to 0.70 (Table, eTable 4). Women tended to over-report overall caffeine consumption at follow-up (eFigure 1).

Table.

Report of exposures during early pregnancy at 8 weeks of pregnancy and at follow-up from the North Carolina Early Pregnancy Study (Total n = 109)

Characteristic	Report at 8 weeksa n (%)	Recall at follow-up n (%)	Sensitivity Specificityb	Accuracy %
Brewed Coffee
Yes	49 (45)	52 (48)	0.71	70
No	60 (55)	56 (52)	0.70
Missing		1
Instant Coffee
Yes	17 (16)	13 (12)	0.24	69
No	92 (84)	95 (88)	0.90
Missing		1
Tea
Yes	66 (61)	55 (52)	0.67	80
No	43 (39)	50 (48)	0.71
Missing		4
Soda
Yes	64 (59)	59 (56)	0.71	69
No	45 (41)	47 (44)	0.66
Missing		3
Beer
Yes	20 (18)	12 (11)	0.25	80
No	89 (82)	96 (89)	0.92
Missing		1
Wine
Yes	31 (28)	24 (22)	0.30	67
No	78 (72)	84 (78)	0.81
Missing		1
Hard liquor
Yes	15 (14)	2 (2)	0.07	87
No	94 (86)	106 (98)	0.99
Missing		1
Antibiotics
Yes	8 (7.3)	1 (1.0)	0.14	94
No	101 (92.7)	100 (99.0)	1.00
Missing		8
Vitamins
Yes	77 (70.6)	85 (79.4)	0.82	65
No	32 (29.4)	22 (20.6)	0.26
Missing		2

^aReports of exposures at 8 weeks were considered the gold standard.

^bSensitivity: proportion of women who were ‘truly exposed’ based on their 8-week questionnaire response and who reported the exposure at follow-up; specificity: proportion of women who were ‘truly not exposed’ based on their 8 week questionnaire response and who reported no exposure at follow-up.

During the baseline study, 39% of women had reported drinking alcoholic beverages in early pregnancy (28% reported drinking wine). The accuracy of recall for drinking wine was 67% (sensitivity: 0.30, specificity: 0.81). All of the 19 women who reported infrequent wine drinking during early pregnancy (1–2 servings/month) reported inaccurately at follow-up (four reported drinking a greater amount and 15 reported abstaining) (eTable 5). Recall of beer drinking at follow-up was 80% accurate (sensitivity: 0.25, specificity: 0.92). Consumption of hard liquor was uncommon. Women tended to under-report overall alcohol consumption at follow-up (eFigure 2). A woman’s confidence in her report of caffeinated and alcoholic beverages at follow-up was not associated with greater accuracy (eTable 6).

Women over-reported their use of vitamins at follow-up and under-reported their use of antibiotics. The accuracy of recall for vitamin use was 65% (sensitivity: 0.82, specificity: 0.26). The sensitivity for antibiotic use recall was 0.14; only one woman reported antibiotic use at the follow-up interview out of the eight that had reported this exposure during pregnancy. All women who reported no use of antibiotics at 8 weeks correctly reported their nonuse in the follow-up questionnaire (specificity 1.00).

Birthweight

Among women at follow-up who had given birth to singletons, 94% reported their child’s birthweight within ½ pound (Figure 2a). All five women who gave birth to twins reported the same two birthweights in the baseline study and at follow-up.

Figure 2.

a. Differences in report of child’s birthweight (in ounces; baseline study report – follow-up report)

b. Differences in report of duration of pregnancy (in weeks, based on how many days before or after their due date women reported their pregnancy lasted at follow-up; baseline study report – follow-up report)

Duration of pregnancy

Using women’s follow-up responses to how many days before or after their due date they gave birth, only 16% of women correctly reported exact duration of pregnancy in days. However, 86% of women correctly reported within plus-or-minus 7 days (14-day window) (Figure 2b). Using women’s responses of how many weeks their pregnancy lasted, at follow-up, 43% of women accurately reported the number of weeks (7-day window) and 86% reported accurately within plus-or-minus 1 week (21-day window).

Discussion

Our data suggest that long-term recall of early pregnancy exposures is difficult, and self-report of this type of information close to 30 years after pregnancy results in high levels of misclassification (median sensitivity was 0.30, range: 0.07–0.82 and median specificity was 0.81, range: 0.26–1.00). Some of the inaccuracy in reporting pregnancy behaviors at follow-up appeared to be influenced by social desirability (under-reporting original alcohol intake and antibiotic use, but over-reporting vitamin use). Recall was better for those never or frequently consuming caffeinated or alcoholic beverages, suggesting these behavior patterns are more memorable, or perhaps more consistent over time. Further, while women in our study were not good at recalling how much caffeine they had consumed, the majority reported consuming less than the recommended limit of 200 mg of caffeine per day at both time points.¹⁸ Women’s reporting at follow-up may have been influenced by behaviors during subsequent pregnancies. However, when we calculated sensitivities and specificities for each of the early pregnancy behaviors stratified by whether women had a child after the baseline study, we did not observe a pattern of poorer recall among women who had additional children (n=66) compared with women who did not (n=42). In contrast to the relatively poor ability to recall specific common exposures during pregnancy, most women were able to recall their pre-pregnancy weight, duration of pregnancy, and child’s birthweight with reasonable accuracy.

Two previous studies of long-term maternal recall (4–12 years) of early pregnancy behaviors reported moderate accuracy. These studies differed from ours in that medical records and registry data were used as the gold standard for comparison, which were incomplete for early pregnancy exposures.^8,9 In some studies, greater quantities of alcohol have been reported retrospectively compared with prospectively.^20,21 This difference may be a result of study populations that differed from ours on demographic and health-related factors.

As in another study,²² we found women accurately recalled their pre-pregnancy weight. Women were also able to recall the duration of pregnancy and birthweight of their baseline study baby with a high level of accuracy, consistent with other studies of both long- and short-term recall.^10,14 Recalled duration of pregnancy was more accurate when asked as days before or after due date compared with total weeks of pregnancy. At follow-up, women recalled the onset of pregnancy symptoms later than their prospective report.

The women in this study all survived to the follow-up period, were able to be re-contacted, and agreed to participate in the follow-up study. Additionally, these committed volunteers were well-educated and white and all had planned their pregnancies, which may limit the generalizability of our results to more diverse populations (e.g, too few smokers to allow for meaningful analysis of smoking behavior). Our results are likely a best-case scenario of long-term maternal recall. Although our sample was small, item non-response was rare on the follow-up questionnaire, unlike other previous studies of long-term maternal recall.^8,9,13 As our gold standard, we had prospective measures for duration of pregnancy, onset of pregnancy symptoms, and pre-pregnancy weight. The baseline study questionnaire data on behaviors during early pregnancy were based on a very short recall time. This allowed us to study recall of early pregnancy behaviors, while most studies on maternal recall of pregnancy-related events have focused on labor and birth outcomes.

The sensitivities and specificities for early pregnancy behaviors presented in this paper can be used to inform investigators of the potential level of misclassification of various early pregnancy behaviors in studies where this information is collected retrospectively years later and may aid in decision-making when considering a bias analysis. The lack of concordance between perceived confidence in recall and its accuracy suggest no benefit from including such questions.

Supplementary Material

Supplemental Digital Content

Supplemental Digital Content 1. Text that further describes the study methods.

Supplemental Digital Content 2. Text that further describes the definition of pregnancy-related symptoms.

Supplemental Digital Content 3. Table showing the characteristic of participants in the baseline study.

Supplemental Digital Content 4. Table showing the recall of the timing of the onset of pregnancy related symptoms.

Supplemental Digital Content 5. Table showing the recall of exposures during the first 8 weeks of pregnancy.

Supplemental Digital Content 6. Table showing the recall of brewed coffee and tea exposure (servings per month) at 8 weeks of pregnancy.

Supplemental Digital Content 7. Figure showing the category of monthly caffeine intake reported at 8 weeks by category of monthly caffeine intake reported at follow-up (The size of the dots on the figure are proportional to the number of observations with that paired value.).

Supplemental Digital Content 8. Table showing the recall of wine exposure (servings per month) at 8 weeks of pregnancy.

Supplemental Digital Content 9. Figure showing the category of monthly alcohol intake reported at 8 weeks by category of monthly alcohol intake reported at follow-up (The size of the dots on the figure are proportional to the number of observations with that paired value.).

Supplemental Digital Content 10. Table showing the sureness and accuracy of recall of caffeine and alcohol exposures during the first 8 weeks of pregnancy.