Predictors of Headache Before, During, and After Pregnancy
Predictors of Headache Before, During, and After Pregnancy
Headache during and after pregnancy is a common occurrence resulting in significant public health consequences and resulting impairments in child care at a time that is integral to maternal bonding. Despite its prevalence, however, headache surrounding pregnancy remains poorly understood, and only recently have researchers attempted to identify potentially modifiable predictors of headache surrounding pregnancy. Limited cross-sectional data have implicated previous headache history, dural puncture, multiparity, and increasing age as risk factors associated with headache in the post-partum period.
The present study extended prior research to a very large and geographically diverse sample of 2434 women from 2 hospitals in the USA and 2 in Europe. Most notably, we found that prior headache history consistently emerged as a strong predictor of headache surrounding pregnancy. At each of the 3 time points (during pregnancy, within 72 hours after delivery, and at 8 weeks after delivery), a history of headache was more strongly associated with current headache than were multiple other health, demographic, and psychosocial variables. At the initial and last time point, prediction of headache was afforded most strongly by a prior history of headache pre-dating pregnancy, whereas headache shortly after pregnancy was most strongly predicted by a prior history of headache during pregnancy.
Specifically, headache during pregnancy and at 8 weeks after delivery were strongly predicted by a history of headache prior to pregnancy, with risk increasing nearly 2.5 times for headache during pregnancy and 6 times for headache at 8 weeks after delivery. These findings are consistent with the notion that many headaches during pregnancy and post-partum represent ongoing primary headache disorders. Headache within 72 hours after delivery was predicted very strongly by a history of headache during pregnancy (but not by headache prior to pregnancy) and by epidural/spinal/CSE injection, either for labor analgesia or cesarean delivery anesthesia. Patients with headache during pregnancy were nearly 4 times more likely to experience headache shortly after delivery, and those receiving regional anesthesia were 3 times more likely to experience headache. Participants with a history of headache during pregnancy and receiving regional anesthesia were far more likely than any other participants to experience a headache within 72 hours after delivery, confirming that these variables have independent but synergistic effects.
Inadvertent dural puncture with an epidural needle carries a high risk of headache due to leakage of cerebrospinal fluid into the epidural space through the large hole produced by the epidural needle. We did not have a clear representation of which women received spinal insertions vs epidurals for vaginal deliveries, and therefore, women who had spinal needle insertion in labor are not identified in this study. As such, we cannot determine the precise rate or risk of inadvertent dural puncture specifically as contributing to our findings regarding headache related to regional anesthesia. However, the majority of cesarean regional anesthesia in this study was spinal based (62% spinal/CSE), and thus, it is likely that the spinal route of administration strongly contributes to these findings. In contrast to dural puncture with an epidural needle, however, a dural puncture made with a pencil-pointed 25- or 27-gauge spinal needle, as used in these women for cesarean delivery, results in a smaller hole in the dura and a much lower incidence (1–2%) of headache after the procedure. The finding that headache history and needle-based regional anesthesia confer independent and synergistic effects can be used to inform physician practice, treatment choices, and regularity of monitoring following discharge. Because headache during the puerperium period is of central importance to predicting subsequent headache after delivery, identification and management of headache during pregnancy is essential. The relative benefits and headache risks, among others, of spinal anesthesia should be carefully weighed in a patient with a history of severe and frequent headaches. Women routinely are instructed to notify health-care personnel of the presence of headache within 72 hours of delivery, and most anesthesiologists inject autologous blood into the epidural space (epidural blood patch) to treat this headache prior to patient discharge from the hospital.
Strengths of this study include its large sample of participants from 3 countries and 4 research sites, multivariate data analytic strategy to adjust for other predictors of headache, and assessment of headache symptoms at multiple points surrounding pregnancy and childbirth. The assessment of numerous pain, general health, demographic, and psychosocial variables as risk factors also is more comprehensive than previous studies on headache surrounding pregnancy. Despite its strengths, the present study has several limitations, most of which center around the means by which headache was assessed and classified. The principal limitation of this study lies in our reliance on self-reported past and current headache problems rather than assessment using formal International Classification of Headache Disorders, 2nd Edition (ICHD-II) diagnostic criteria. Although this limitation was dictated by the format of the Entrance Questionnaire used in the main study, it did preclude precise specification and comparisons of specific headache subtypes, and thus, readers should exercise caution in extrapolating our findings as they pertain to specific headache subtypes. However, our observed rates of headache both before and after pregnancy were somewhat lower than those obtained in other studies, suggesting our participation characterization strategy did not result in overly liberal headache endorsement.
Our relatively lower rates of headache prior to pregnancy are likely a function of the fact that prior headache was defined by endorsement of "chronic" head pain, regular medical visits for headache, or regular use of headache-specific agents in the year prior to pregnancy. Higher rates of prior headache likely would have been obtained had headache symptoms specifically been assessed in a more standardized format, in which case, less frequent or disabling headaches would more likely be identified. Lower rates of headache shortly after delivery may be attributable to potential sampling bias insofar as patients in extreme pain may have declined participation and patients delivering on weekends and holidays were not assessed, or to potential recall bias to the extent that assessment in the 72 hours postdelivery is a time beset with strong emotions and potential reporting inaccuracies. Higher rates of headache during this time frame might have been observed had we inquired about any headache within this 72-hour period rather than current head pain and included more frequent periodic assessment instead of 2 discrete follow-up intervals (72 hours and 8 weeks postdelivery).
More minor limitations surround the loss of the European participants at the 8-week follow-up and the different formats in which participants at the USA vs European sites provided data for the Entrance Questionnaire (scripted interview vs self-report measure). Although patients at all sites responded to the same questions, varied administration formats and translation into French (for the European sites) may have affected participant responses. We attempted to control for observed differences in prepregnancy headache across sites (ie, Brussels' participants endorsing higher prevalence of prior headache) by subsetting the analyses pertaining to prior headache history by using data only from the Winston-Salem, New York, and Geneva sites. In light of these limitations, replication with similarly large samples using ICHD-II nosology and longer follow-up intervals is warranted. Future studies of headache patterns during and after pregnancy also should focus on further disentangling the relative contributions of prior headache history and anesthesia procedures, with comparison between spinal and epidural routes of administration for identification of suspected dural puncture. Such studies should focus on following pregnant women longitudinally and further clarifying the clinical implications of these and other previously established risk factors.
Discussion
Headache during and after pregnancy is a common occurrence resulting in significant public health consequences and resulting impairments in child care at a time that is integral to maternal bonding. Despite its prevalence, however, headache surrounding pregnancy remains poorly understood, and only recently have researchers attempted to identify potentially modifiable predictors of headache surrounding pregnancy. Limited cross-sectional data have implicated previous headache history, dural puncture, multiparity, and increasing age as risk factors associated with headache in the post-partum period.
The present study extended prior research to a very large and geographically diverse sample of 2434 women from 2 hospitals in the USA and 2 in Europe. Most notably, we found that prior headache history consistently emerged as a strong predictor of headache surrounding pregnancy. At each of the 3 time points (during pregnancy, within 72 hours after delivery, and at 8 weeks after delivery), a history of headache was more strongly associated with current headache than were multiple other health, demographic, and psychosocial variables. At the initial and last time point, prediction of headache was afforded most strongly by a prior history of headache pre-dating pregnancy, whereas headache shortly after pregnancy was most strongly predicted by a prior history of headache during pregnancy.
Specifically, headache during pregnancy and at 8 weeks after delivery were strongly predicted by a history of headache prior to pregnancy, with risk increasing nearly 2.5 times for headache during pregnancy and 6 times for headache at 8 weeks after delivery. These findings are consistent with the notion that many headaches during pregnancy and post-partum represent ongoing primary headache disorders. Headache within 72 hours after delivery was predicted very strongly by a history of headache during pregnancy (but not by headache prior to pregnancy) and by epidural/spinal/CSE injection, either for labor analgesia or cesarean delivery anesthesia. Patients with headache during pregnancy were nearly 4 times more likely to experience headache shortly after delivery, and those receiving regional anesthesia were 3 times more likely to experience headache. Participants with a history of headache during pregnancy and receiving regional anesthesia were far more likely than any other participants to experience a headache within 72 hours after delivery, confirming that these variables have independent but synergistic effects.
Inadvertent dural puncture with an epidural needle carries a high risk of headache due to leakage of cerebrospinal fluid into the epidural space through the large hole produced by the epidural needle. We did not have a clear representation of which women received spinal insertions vs epidurals for vaginal deliveries, and therefore, women who had spinal needle insertion in labor are not identified in this study. As such, we cannot determine the precise rate or risk of inadvertent dural puncture specifically as contributing to our findings regarding headache related to regional anesthesia. However, the majority of cesarean regional anesthesia in this study was spinal based (62% spinal/CSE), and thus, it is likely that the spinal route of administration strongly contributes to these findings. In contrast to dural puncture with an epidural needle, however, a dural puncture made with a pencil-pointed 25- or 27-gauge spinal needle, as used in these women for cesarean delivery, results in a smaller hole in the dura and a much lower incidence (1–2%) of headache after the procedure. The finding that headache history and needle-based regional anesthesia confer independent and synergistic effects can be used to inform physician practice, treatment choices, and regularity of monitoring following discharge. Because headache during the puerperium period is of central importance to predicting subsequent headache after delivery, identification and management of headache during pregnancy is essential. The relative benefits and headache risks, among others, of spinal anesthesia should be carefully weighed in a patient with a history of severe and frequent headaches. Women routinely are instructed to notify health-care personnel of the presence of headache within 72 hours of delivery, and most anesthesiologists inject autologous blood into the epidural space (epidural blood patch) to treat this headache prior to patient discharge from the hospital.
Limitations and Future Directions
Strengths of this study include its large sample of participants from 3 countries and 4 research sites, multivariate data analytic strategy to adjust for other predictors of headache, and assessment of headache symptoms at multiple points surrounding pregnancy and childbirth. The assessment of numerous pain, general health, demographic, and psychosocial variables as risk factors also is more comprehensive than previous studies on headache surrounding pregnancy. Despite its strengths, the present study has several limitations, most of which center around the means by which headache was assessed and classified. The principal limitation of this study lies in our reliance on self-reported past and current headache problems rather than assessment using formal International Classification of Headache Disorders, 2nd Edition (ICHD-II) diagnostic criteria. Although this limitation was dictated by the format of the Entrance Questionnaire used in the main study, it did preclude precise specification and comparisons of specific headache subtypes, and thus, readers should exercise caution in extrapolating our findings as they pertain to specific headache subtypes. However, our observed rates of headache both before and after pregnancy were somewhat lower than those obtained in other studies, suggesting our participation characterization strategy did not result in overly liberal headache endorsement.
Our relatively lower rates of headache prior to pregnancy are likely a function of the fact that prior headache was defined by endorsement of "chronic" head pain, regular medical visits for headache, or regular use of headache-specific agents in the year prior to pregnancy. Higher rates of prior headache likely would have been obtained had headache symptoms specifically been assessed in a more standardized format, in which case, less frequent or disabling headaches would more likely be identified. Lower rates of headache shortly after delivery may be attributable to potential sampling bias insofar as patients in extreme pain may have declined participation and patients delivering on weekends and holidays were not assessed, or to potential recall bias to the extent that assessment in the 72 hours postdelivery is a time beset with strong emotions and potential reporting inaccuracies. Higher rates of headache during this time frame might have been observed had we inquired about any headache within this 72-hour period rather than current head pain and included more frequent periodic assessment instead of 2 discrete follow-up intervals (72 hours and 8 weeks postdelivery).
More minor limitations surround the loss of the European participants at the 8-week follow-up and the different formats in which participants at the USA vs European sites provided data for the Entrance Questionnaire (scripted interview vs self-report measure). Although patients at all sites responded to the same questions, varied administration formats and translation into French (for the European sites) may have affected participant responses. We attempted to control for observed differences in prepregnancy headache across sites (ie, Brussels' participants endorsing higher prevalence of prior headache) by subsetting the analyses pertaining to prior headache history by using data only from the Winston-Salem, New York, and Geneva sites. In light of these limitations, replication with similarly large samples using ICHD-II nosology and longer follow-up intervals is warranted. Future studies of headache patterns during and after pregnancy also should focus on further disentangling the relative contributions of prior headache history and anesthesia procedures, with comparison between spinal and epidural routes of administration for identification of suspected dural puncture. Such studies should focus on following pregnant women longitudinally and further clarifying the clinical implications of these and other previously established risk factors.
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