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Association between fetal gender and the first stage labor curve: clinical consideration
Letters to the Editors
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Association between fetal gender and the first stage labor curve: clinical consideration TO THE EDITORS: This is indeed a high time to curb the increasing trend of caesarean section (CS) globally. This was shown in this excellent retrospective study by Cahill et al.1 A recent report on CS trend in the United States revealed the overall CS rate to be 30.5%.2 A total of 31.5% of all nulliparous were delivered with CS, and prelabor repeat CS delivery because of a previous uterine scar accounted for 30.9% of all.2 Another study showed that 20% were at risk for labor arrest, which could further increase the CS rate.3 Researchers described preterm delivery to be higher in the male fetuses, which was due to increased incidence of spontaneous preterm labor and preterm premature rupture of the membranes.4 This was again repeatedly proven significantly in the present study. In Table 1, the birthweight was significantly heavier in the male fetuses, which was contrary, and it was not concurrent with the findings of more medical problems in the mothers of female fetuses (MFF). In fact, the gestational diabetes was far more in these mothers compared with the mothers of the male fetus (MMF). We wonder how this could be explained because the risk of lighter fetuses (intrauterine growth retardation) was not really a big difference in those with maternal hypertension as seen in the MFF. Although not significant, MFF had a poorer cervical score to start with, needing more induction of labor (IOL) compared with the MMF. More augmentations were needed in the active process of labor in MMF (Table 1). Perhaps by having had more IOL, the cervical ripeness would have been better in MFF, resulting in better quality of contractions during progress of labor, which is in contrast to MMF and not just merely by gender factor alone, as claimed by the authors.1 Perhaps with reduced intervention with augmentation, resulting in fewer unnatural contractions, resulting in more vaginal deliveries observed in MFF compared with the number of operative delivery and CS in MMF. Thus, should sex alone be blamed for the arrest of the active phase of labor as seen in this observation (4.6 hours vs 4.0 hours; P ⫽ .002)? In Figure 2, MMF with multiparity (second curve) was progressing faster than MFF with nulliparity (third curve). Thus, parity still played a more potential role in the labor progress if compared with sex, which was not highlighted in the observation.1 f Nor Azlin MI, MD Department of Obstetrics and Gynaecology Universiti Kebangsaan Malaysia Medical Centre 56000 Cheras Kuala Lumpur, Malaysia
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American Journal of Obstetrics & Gynecology JULY 2012
Srijit Das, MBBS, MS Associate Professor Department of Anatomy Faculty of Medicine Universiti Kebangsaan Malaysia Jalan Raja Muda Abd Aziz 50300 Kuala Lumpur, Malaysia [email protected] The authors report no conflict of interest.
REFERENCES 1. Cahill AG, Roehl KA, Odibo AO, Zhao Q, Macones GA. Impact of fetal gender on the labor curve. Am J Obstet Gynecol 2012;206:335.e1-5. 2. Zhang J, Troendle J, Reddy UM, et al. Consortium on Safe Labor. Contemporary cesarean delivery practice in the United States. Am J Obstet Gynecol 2010;203:326.e1-10. 3. Zhang J, Troendle J, Mikolajczyk R, Sundaram R, Beaver J, Fraser W. The natural history of the normal first stage of labor. Obstet Gynecol 2010;115:705-10. Erratum in: Obstet Gynecol 2010;116:196. 4. Melamed N, Yogev Y, Glezerman M. Fetal gender and pregnancy outcome. J Matern Fetal Neonatal Med 2010;23:338-44. © 2012 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2012.03.011
REPLY We appreciate the interest of Drs MI and Das in our recently published study, entitled “Impact of fetal gender on the labor curve” in the American Journal of Obstetrics and Gynecology,1 as well as the opportunity to respond to their comments. It is true that we found that male fetuses, on average, weighed 89 g more than females. We also examined the differences between the groups in rates of comorbidities that you mentioned, but in fact found no differences in rates of gestational diabetes or hypertensive diseases of pregnancy. However, because observational data create the potential for inequality between comparison groups as you have highlighted, it is important to interpret the adjusted analyses.2 In this case, the best estimate of the relationship between first stage labor curve and fetal gender is that which accounts for potentially confounding factors such as group differences and many of the factors which you have raised concern for. The small, but statistically different medians in first stage labor progress between women carrying males compared with females were found while adjusting for parity, regional anesthesia, prostaglandin use, birthweight, and race. Labor type (induction vs augmentation vs spontaneous) was not a significant factor and did not remain in the final model. Although we were able to adjust for need for cervical ripening, we were not able to adjust for “unnatural contractions,” as this is not an entity recognized at our institution. Finally, we apologize for any confusion, but this was a cohort study of consecutive term deliveries from the second stage, thus there were no patients with active phase arrest. f
www. AJOG.org
Association between fetal gender and the first stage labor curve: clinical consideration TO THE EDITORS: This is indeed a high time to curb the increasing trend of caesarean section (CS) globally. This was shown in this excellent retrospective study by Cahill et al.1 A recent report on CS trend in the United States revealed the overall CS rate to be 30.5%.2 A total of 31.5% of all nulliparous were delivered with CS, and prelabor repeat CS delivery because of a previous uterine scar accounted for 30.9% of all.2 Another study showed that 20% were at risk for labor arrest, which could further increase the CS rate.3 Researchers described preterm delivery to be higher in the male fetuses, which was due to increased incidence of spontaneous preterm labor and preterm premature rupture of the membranes.4 This was again repeatedly proven significantly in the present study. In Table 1, the birthweight was significantly heavier in the male fetuses, which was contrary, and it was not concurrent with the findings of more medical problems in the mothers of female fetuses (MFF). In fact, the gestational diabetes was far more in these mothers compared with the mothers of the male fetus (MMF). We wonder how this could be explained because the risk of lighter fetuses (intrauterine growth retardation) was not really a big difference in those with maternal hypertension as seen in the MFF. Although not significant, MFF had a poorer cervical score to start with, needing more induction of labor (IOL) compared with the MMF. More augmentations were needed in the active process of labor in MMF (Table 1). Perhaps by having had more IOL, the cervical ripeness would have been better in MFF, resulting in better quality of contractions during progress of labor, which is in contrast to MMF and not just merely by gender factor alone, as claimed by the authors.1 Perhaps with reduced intervention with augmentation, resulting in fewer unnatural contractions, resulting in more vaginal deliveries observed in MFF compared with the number of operative delivery and CS in MMF. Thus, should sex alone be blamed for the arrest of the active phase of labor as seen in this observation (4.6 hours vs 4.0 hours; P ⫽ .002)? In Figure 2, MMF with multiparity (second curve) was progressing faster than MFF with nulliparity (third curve). Thus, parity still played a more potential role in the labor progress if compared with sex, which was not highlighted in the observation.1 f Nor Azlin MI, MD Department of Obstetrics and Gynaecology Universiti Kebangsaan Malaysia Medical Centre 56000 Cheras Kuala Lumpur, Malaysia
e16
American Journal of Obstetrics & Gynecology JULY 2012
Srijit Das, MBBS, MS Associate Professor Department of Anatomy Faculty of Medicine Universiti Kebangsaan Malaysia Jalan Raja Muda Abd Aziz 50300 Kuala Lumpur, Malaysia [email protected] The authors report no conflict of interest.
REFERENCES 1. Cahill AG, Roehl KA, Odibo AO, Zhao Q, Macones GA. Impact of fetal gender on the labor curve. Am J Obstet Gynecol 2012;206:335.e1-5. 2. Zhang J, Troendle J, Reddy UM, et al. Consortium on Safe Labor. Contemporary cesarean delivery practice in the United States. Am J Obstet Gynecol 2010;203:326.e1-10. 3. Zhang J, Troendle J, Mikolajczyk R, Sundaram R, Beaver J, Fraser W. The natural history of the normal first stage of labor. Obstet Gynecol 2010;115:705-10. Erratum in: Obstet Gynecol 2010;116:196. 4. Melamed N, Yogev Y, Glezerman M. Fetal gender and pregnancy outcome. J Matern Fetal Neonatal Med 2010;23:338-44. © 2012 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2012.03.011
REPLY We appreciate the interest of Drs MI and Das in our recently published study, entitled “Impact of fetal gender on the labor curve” in the American Journal of Obstetrics and Gynecology,1 as well as the opportunity to respond to their comments. It is true that we found that male fetuses, on average, weighed 89 g more than females. We also examined the differences between the groups in rates of comorbidities that you mentioned, but in fact found no differences in rates of gestational diabetes or hypertensive diseases of pregnancy. However, because observational data create the potential for inequality between comparison groups as you have highlighted, it is important to interpret the adjusted analyses.2 In this case, the best estimate of the relationship between first stage labor curve and fetal gender is that which accounts for potentially confounding factors such as group differences and many of the factors which you have raised concern for. The small, but statistically different medians in first stage labor progress between women carrying males compared with females were found while adjusting for parity, regional anesthesia, prostaglandin use, birthweight, and race. Labor type (induction vs augmentation vs spontaneous) was not a significant factor and did not remain in the final model. Although we were able to adjust for need for cervical ripening, we were not able to adjust for “unnatural contractions,” as this is not an entity recognized at our institution. Finally, we apologize for any confusion, but this was a cohort study of consecutive term deliveries from the second stage, thus there were no patients with active phase arrest. f