Hormonal Physiology of Childbearing: Evidence and Implications for Women, Babies, and Maternity Care Sarah J. Buckley January 2015 Contents with Full Outline a program of the
national partnership for women & families
Abstract .................................................................................................................................................. i Figures and Tables ................................................................................................................................ i ii Message from Debra L. Ness ................................................................................................................ i v Foreword ............................................................................................................................................... v Preface ................................................................................................................................................ vii Acknowledgments .................................................................................................................................ix Executive Summary ............................................................................................................................... x 1 Introduction: Overarching Themes and Scope ......................................................................... 1 1.1 Human Childbearing: Evolution and Safety .......... 2 1.2 Contemporary Childbirth Practices .......... 2 1.3 1.3.1 1.3.2 1.3.3 Current Understandings of the Hormonal Physiology of Childbearing .......... 4 Benefits for Mothers and Babies .......... 4 Possible Impacts of Maternity Care interventions .......... 5 The Hormonal Physiology Pathway .......... 5 1.4 Alignment with Other Frameworks .......... 7 1.5 1.5.1 1.5.2 Scope of This Report .......... 10 Content and Organization .......... 10 Inclusion of Animal Studies .......... 11 1.6 2 Introduction: Summary .......... 11 2.1 2.1.1 2.1.2 2.1.3 Physiologic Onset of Labor at Term .......... 15 Quiescent Phase .......... 15 Activation Phase .......... 16 Stimulation Phase .......... 18 2.2 Possible Impacts of Scheduled Birth .......... 20 2.3 2.3.1 2.3.2 3 Physiologic Onset of Labor and Scheduled Birth: Summary .......... 24 Physiologic Onset of Labor .......... 24 Possible Impacts of Scheduled Birth .......... 25 3.1 3.1.1 Oxytocin: Normal Physiology .......... 27 Oxytocin: Introduction .......... 27 Oxytocin Effects .......... 28 Physiologic roles of oxytocin .......... 29 Psychological and therapeutic roles of oxytocin .......... 30 Oxytocin Regulation and Receptors .......... 31 Physiologic Onset of Labor and Scheduled Birth .................................................................... 1 4 Oxytocin .............................................................................................................................. 26 CHILDBIRTH CONNECTION | H ORMONAL P HYSIOLOGY O F C HILDBEARING | CONTENTS WITH ALL HEADINGS 3.1.2 3.1.3 3.1.4 3.2 3.2.1 3.2.2 3.2.3 Oxytocin regulation .......... 31 Oxytocin receptors .......... 31 Oxytocin complexities .......... 32 Oxytocin in Pregnancy .......... 33 Maternal Oxytocin in Pregnancy .......... 33 Fetal Oxytocin in Pregnancy .......... 35
Oxytocin in Labor and Birth .......... 35 Maternal Oxytocin in Labor and Birth .......... 35 Other hormonal influences on oxytocin in labor and birth .......... 38 Positive feedback cycles .......... 38 Fetal neuroprotection .......... 39 Oxytocin-­‐deficient mice .......... 40 Fetal Oxytocin in Labor and Birth .......... 40 Oxytocin after Birth .......... 41 Maternal Oxytocin After Birth .......... 41 Oxytocin and maternal-­‐newborn contact and interactions .......... 41 Oxytocin and postpartum hemorrhage .......... 42 Newborn and Later Oxytocin .......... 42
Oxytocin and Breastfeeding .......... 44
Breastfeeding initiation .......... 44
Breastfeeding benefits .......... 45
Oxytocin and Maternal Adaptations and Attachment .......... 46
Postpartum sensitive period .......... 47
Skin-­‐to-­‐skin contact .......... 48
Maternal adaptations .......... 49
Pleasure and reward .......... 50
Maternal-­‐infant bonding and attachment .......... 52
Common Maternity Care Practices That May Impact Oxytocin Physiology .......... 54
Maternity Care Provider and Birth Environment: Possible Impacts on Oxytocin .......... 54 Prostaglandins for Cervical Ripening and Labor Induction: Possible Impacts on Oxytocin .......... 55
Synthetic Oxytocin in Labor for Induction, Augmentation, and Postpartum Care: Possible Impacts on Oxytocin .......... 56 Induction of Labor .......... 56
Augmentation of Labor .......... 56
Synthetic Oxytocin and the Mother .......... 57
Physiologic versus synthetic oxytocin in labor and birth .......... 57
Synthetic oxytocin and central maternal oxytocin .......... 60
Synthetic oxytocin and oxytocin receptor desensitization .......... 61
Synthetic oxytocin and postpartum hemorrhage .......... 62 Synthetic oxytocin when administered postpartum .......... 63 Oxytocin Antagonist Drugs .......... 64 Synthetic Oxytocin and the Baby .......... 64 Synthetic Oxytocin and Breastfeeding .......... 66 CHILDBIRTH CONNECTION | H ORMONAL P HYSIOLOGY O F C HILDBEARING | CONTENTS WITH ALL HEADINGS 3.2.4 3.2.5 3.2.6 3.2.7 Synthetic Oxytocin and Maternal Adaptations and Attachment .......... 68 Synthetic Oxytocin and the Mother, Longer Term .......... 69 Synthetic Oxytocin and Offspring, Longer Term .......... 70 Synthetic oxytocin and offspring, animal studies .......... 70 Synthetic oxytocin and epigenetics .......... 71 Synthetic oxytocin and offspring, human studies .......... 72 Opioid Analgesic Drugs: Possible Impacts on Oxytocin Physiology .......... 73 Opioid Drugs and the Mother .......... 73 Opioid Drugs and the Fetus/Newborn .......... 74 Opioid Drugs and Breastfeeding .......... 74 Opioid Drugs and Offspring, Longer Term .......... 75 Epidural Analgesia: Possible Impacts on Oxytocin Physiology .......... 75 Epidural Analgesia and the Mother .......... 75 Epidural analgesia and oxytocin systems in labor .......... 76 Epidural analgesia and maternal temperature regulation in labor .......... 77 Epidural Analgesia and the Fetus/Newborn .......... 77 Epidural Analgesia and Breastfeeding .......... 78 Epidural Analgesia and Maternal Adaptations .......... 79 Epidural impacts on Memory and Reward .......... 80 Cesarean Section: Possible Impacts on Oxytocin Physiology .......... 81 Cesarean and the Mother .......... 83 Cesarean and the Fetus/Newborn .......... 84 Cesarean and Breastfeeding .......... 85 Cesarean and Maternal Adaptations and Attachment .......... 85 Cesarean and psychological well-­‐being .......... 85 Cesarean and attachment .......... 86 Cesarean and Offspring, Longer Term .......... 87 Early Separation of Healthy Mothers and Newborns: Possible Impacts on Oxytocin .......... 88 Early Separation and the Mother .......... 88 Early Separation and the Newborn .......... 89 Early Separation and Breastfeeding .......... 89 Early Separation and Maternal Adaptations and Attachment .......... 89 Early separation and attachment .......... 89 Early separation and maternal well-­‐being .......... 90 3.3 Oxytocin Physiology: Summary .......... 90 3.3.1 Oxytocin: Normal Physiology .......... 90 3.3.2 Common Maternity Care Practices That May Impact Oxytocin Physiology .......... 91 4 Beta-­‐Endorphins ...................................................................................................................... 9 3 4.1 4.1.1 Beta-­‐Endorphins: Normal Physiology .......... 94 Beta-­‐Endorphins: Introduction .......... 94 Beta-­‐Endorphins Effects .......... 94 Beta-­‐endorphins and the stress response .......... 95 Beta-­‐endorphins, other effects .......... 95 CHILDBIRTH CONNECTION | H ORMONAL P HYSIOLOGY O F C HILDBEARING | CONTENTS WITH ALL HEADINGS 4.1.2 4.1.3 4.1.4 4.2 4.2.1 4.2.2 4.2.3 4.2.4 4.2.5 4.2.6 4.2.7 4.3 4.3.1 4.3.2 5 5.1 5.1.1 5.1.2 Beta-­‐Endorphins: Regulation and Receptors .......... 96 Beta-­‐endorphins receptors .......... 96 Beta-­‐endorphins complexities .......... 97 Beta-­‐Endorphins in Pregnancy .......... 97 Beta-­‐Endorphins in Labor and Birth .......... 98 Maternal Beta-­‐Endorphins In Labor and Birth .......... 98 Fetal Beta-­‐Endorphins in Labor and Birth .......... 100 Beta-­‐Endorphins after Birth .......... 100 Maternal Beta-­‐Endorphins after Birth .......... 100 Newborn and Later Beta-­‐Endorphins .......... 101 Beta-­‐Endorphins and Breastfeeding .......... 101 Beta-­‐Endorphins and Maternal Adaptations and Attachment Common Maternity Care Practices That May Impact Beta-­‐Endorphins Physiology .......... 102 Maternity Care Provider and Birth Environment: Possible Impacts on Beta-­‐Endorphins .......... 103 Prostaglandins for Cervical Ripening and Labor Induction: Possible Impacts on Beta-­‐
Endorphins .......... 103 Synthetic Oxytocin for Induction, Augmentation, and Postpartum Care: Possible Impacts on Beta-­‐Endorphins .......... 103 Opioid Analgesic Drugs: Possible Impacts on Beta-­‐Endorphins .......... 104 Opioid Drugs and the Mother .......... 104 Opioid Drugs and the Fetus/Newborn .......... 104 Epidural Analgesia: Possible Impacts on Beta-­‐Endorphins .......... 105 Epidural Analgesia and the Mother .......... 106 Epidural Analgesia and the Fetus/Newborn .......... 107 Cesarean Section: Possible Impacts on Beta-­‐Endorphins .......... 107 Cesarean and the Mother .......... 107 Cesarean and the Fetus/Newborn .......... 108 Early Separation of Healthy Mothers and Newborns: Possible Impacts on Beta-­‐
Endorphins .......... 108 Beta-­‐Endorphins: Summary .......... 109 Beta-­‐Endorphins: Normal Physiology .......... 109 Common Maternity Care Practices That May Impact Beta-­‐Endorphins Physiology .......... 110 Epinephrine-­‐Norepinephrine and Related Stress Hormones .............................................. .111 Epinephrine-­‐Norepinephrine and Related Stress Hormones: Normal Physiology .......... 112 Epinephrine-­‐Norepinephrine and Related Stress Hormones: Introduction .......... 112 Epinephrine-­‐Norepinephrine and Related Stress Hormones Effects .......... 112 Epinephrine-­‐Norepinephrine and Related Stress Hormones: Regulation and Receptors .......... 114 Epinephrine-­‐Norepinephrine and Related Stress Hormones in Pregnancy .......... 115 Maternal Epinephrine-­‐Norepinephrine and Related Stress Hormones in Pregnancy .......... 115 Fetal Epinephrine-­‐Norepinephrine and Related Stress Hormones in Pregnancy .......... 116 CHILDBIRTH CONNECTION | H ORMONAL P HYSIOLOGY O F C HILDBEARING | CONTENTS WITH ALL HEADINGS 5.1.3 5.1.4 5.2 5.2.1 5.2.2 5.2.3 5.2.4 5.2.5 5.2.6 5.2.7 5.3 5.3.1 Epinephrine-­‐Norepinephrine and Related Stress Hormones in Labor And Birth .......... 117 Evolutionary Model .......... 117 Maternal Epinephrine-­‐Norepinephrine and Related Stress Hormones in Labor and Birth .......... 118 Maternal epinephrine-­‐norepinephrine in labor and birth .......... 118 The fetus ejection reflex .......... 120 Maternal related stress hormones in labor and birth .......... 121 Fetal Epinephrine-­‐Norepinephrine and Related Stress Hormones in Labor and Birth .......... 121 Fetal catecholamine surge .......... 121 Fetal cortisol .......... 123 Epinephrine-­‐Norepinephrine and Related Stress Hormones after Birth .......... 123 Maternal Epinephrine-­‐Norepinephrine and Related Stress Hormones After Birth .......... 123 Newborn and Later Epinephrine-­‐Norepinephrine and Related Stress Hormones .......... 124 Epinephrine-­‐Norepinephrine and Related Stress Hormones, and Breastfeeding and Maternal Adaptations and Attachment .......... 124 Common Maternity Care Practices That May Impact Epinephrine-­‐Norepinephrine and Related Stress Hormones .......... 125 Maternity Care Provider and Birth Environment, Including Prenatal and Childbirth Care: Pos-­‐
sible Impacts on Epinephrine-­‐Norepinephrine and Related Stress Hormones .......... 125 Prenatal Care and Stress .......... 126 Childbirth and Stress .......... 127 Labor and Birth Stress in Animals .......... 129 Prostaglandins for Cervical Ripening and Labor Induction: Possible Impacts on Epinephrine-­‐
Norepinephrine and Related Stress Hormones .......... 130 Synthetic Oxytocin For Induction, Augmentation, and Postpartum Care: Possible Impacts on Epinephrine-­‐Norepinephrine and Related Stress Hormones .......... 130 Opioid Analgesic Drugs: Possible Impacts on Epinephrine-­‐Norepinephrine and Related Stress Hormones .......... 131 Epidural Analgesia: Possible Impacts on Epinephrine-­‐Norepinephrine and Related Stress Hormones .......... 131 Epidural Analgesia and the Mother .......... 131 Epidural Analgesia and the Fetus/Newborn .......... 133 Cesarean Section: Possible Impacts on Epinephrine-­‐Norepinephrine and Related Stress Hormones .......... 134 Cesarean and the Mother .......... 135 Cesarean and the Fetus/Newborn .......... 135 Early Separation of Healthy Mothers and Newborns: Possible Impacts on Epinephrine-­‐
Norepinephrine and Related Stress Hormones .......... 136 Epinephrine-­‐Norepinephrine and Related Stress Hormones: Summary .......... 138 Epinephrine-­‐Norepinephrine and Related Stress Hormones: Normal Physiology .......... 138 CHILDBIRTH CONNECTION | H ORMONAL P HYSIOLOGY O F C HILDBEARING | CONTENTS WITH ALL HEADINGS 5.3.2 Common Maternity Care Practices that May Impact Epinephrine-­‐Norepinephrine and Related Stress Hormones Physiology .......... 139 6 Prolactin ................................................................................................................................ 1 40 6.1 6.1.1 6.1.2 6.1.3 6.1.4 Prolactin: Normal Physiology .......... 141 Prolactin: Introduction .......... 141 Prolactin Effects .......... 141 Prolactin Regulation and Receptors .......... 142 Prolactin in Pregnancy .......... 143 Maternal Prolactin in Pregnancy .......... 143 Fetal Prolactin in Pregnancy .......... 144 Prolactin in Labor and Birth .......... 144 Maternal Prolactin in Labor and Birth .......... 144 Fetal Prolactin in Labor and Birth .......... 145 Prolactin after Birth .......... 145 Maternal Prolactin after Birth .......... 145 Newborn and Later Prolactin .......... 146 Prolactin and Breastfeeding .......... 146 Prolactin release with lactation .......... 147 Prolactin receptor theory .......... 147 Prolactin and Maternal Adaptations .......... 148 6.2 6.2.1 6.2.2 Common Maternity Care Practices That May Impact Prolactin Physiology .......... 149 Maternity Care Provider and Birth Environment: Possible Impacts on Prolactin .......... 149 Prostaglandins for Cervical Ripening and Labor Induction: Potential Impacts on Prolactin .......... 149 Synthetic Oxytocin For Induction, Augmentation, and Postpartum Care: Possible Impacts on Prolactin .......... 150 Opioid Analgesic Drugs: Possible Impacts on Prolactin .......... 151 Epidural Analgesia: Possible Impacts on Prolactin .......... 151 Cesarean Section: Possible Impacts on Prolactin .......... 152 Early Separation of Healthy Mothers and Newborns: Possible Impacts on Prolactin .......... 154 6.2.3 6.2.4 6.2.5 6.2.6 6.2.7 6.3 6.3.1 6.3.2 7 Prolactin: Summary .......... 154 Prolactin: Normal Physiology .......... 154 Common Maternity Care Practices That May Impact Prolactin Physiology .......... 155 7.1 Conclusions .......... 157 7.2 7.2.1 Recommendations to Promote, Support, and Protect Physiologic Childbearing .......... 163 Education, Policy, and Consumer Engagement Recommendations .......... 163 Education .......... 163 Policy .......... 164 Engaging and Supporting Childbearing Women .......... 165 Conclusions and Recommendations ........................................................................................ 1 56 CHILDBIRTH CONNECTION | H ORMONAL P HYSIOLOGY O F C HILDBEARING | CONTENTS WITH ALL HEADINGS 7.2.2 7.2.3 Care Practice Recommendations Whenever Safely Possible .......... 165 Prenatal Care .......... 165 Postpartum Care .......... 168 Research Recommendation .......... 169 7.3 Conclusions and Recommendations: Summary .......... 169 Appendix: Resources for Learning More and Improving Practice .................................................... 171 References ........................................................................................................................................ 175 Abbreviations .................................................................................................................................... 2 24 Photo Credits .................................................. .................................................................................. 2 25 © 2015 National Partnership for Women & Families. All rights reserved. Find full report, Hormonal Physiology of Childbearing: Evidence and Implications for Women, Babies, and Maternity Care, and related materials at www.ChildbirthConnection.org/HormonalPhysiology. CHILDBIRTH CONNECTION | H ORMONAL P HYSIOLOGY O F C HILDBEARING | CONTENTS WITH ALL HEADINGS