Hormonal!Physiology!of!Childbearing:! Evidence ... · Hormonal!Physiology!of!Childbearing:!...

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 thenational partnership for women & families

CHILDBIRTH CONNECTION | HORMONAL PHYSIOLOGY OF CHILDBEARING | CONTENTS WITH ALL HEADINGS

Abstract .................................................................................................................................................. i

Figures and Tables ................................................................................................................................ i i i

Message from Debra L. Ness ................................................................................................................ iv 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 Current Understandings of the Hormonal Physiology of Childbearing .......... 4 1.3.1 Benefits for Mothers and Babies .......... 4 1.3.2 Possible Impacts of Maternity Care interventions .......... 5 1.3.3 The Hormonal Physiology Pathway .......... 5

1.4 Alignment with Other Frameworks .......... 7

1.5 Scope of This Report .......... 10 1.5.1 Content and Organization .......... 10 1.5.2 Inclusion of Animal Studies .......... 11

1.6 Introduction: Summary .......... 11 2 Physiologic Onset of Labor and Scheduled Birth .................................................................... 14

2.1 Physiologic Onset of Labor at Term .......... 15 2.1.1 Quiescent Phase .......... 15 2.1.2 Activation Phase .......... 16 2.1.3 Stimulation Phase .......... 18

2.2 Possible Impacts of Scheduled Birth .......... 20

2.3 Physiologic Onset of Labor and Scheduled Birth: Summary .......... 24

2.3.1 Physiologic Onset of Labor .......... 24 2.3.2 Possible Impacts of Scheduled Birth .......... 25 3 Oxytocin .............................................................................................................................. 26

3.1 Oxytocin: Normal Physiology .......... 27 3.1.1 Oxytocin: Introduction .......... 27 Oxytocin Effects .......... 28 Physiologic roles of oxytocin .......... 29 Psychological and therapeutic roles of oxytocin .......... 30 Oxytocin Regulation and Receptors .......... 31


Oxytocin regulation .......... 31 Oxytocin receptors .......... 31 Oxytocin complexities .......... 32 3.1.2 Oxytocin in Pregnancy .......... 33 Maternal Oxytocin in Pregnancy .......... 33 Fetal Oxytocin in Pregnancy .......... 35 3.1.3 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 3.1.4 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 3.2 Common Maternity Care Practices That May Impact Oxytocin Physiology .......... 54 3.2.1 Maternity Care Provider and Birth Environment: Possible Impacts on Oxytocin .......... 54 3.2.2 Prostaglandins for Cervical Ripening and Labor Induction: Possible Impacts

on Oxytocin .......... 55 3.2.3 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


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 3.2.4 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 3.2.5 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 3.2.6 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 3.2.7 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 ...................................................................................................................... 93

4.1 Beta-‐Endorphins: Normal Physiology .......... 94 4.1.1 Beta-‐Endorphins: Introduction .......... 94 Beta-‐Endorphins Effects .......... 94 Beta-‐endorphins and the stress response .......... 95 Beta-‐endorphins, other effects .......... 95


Beta-‐Endorphins: Regulation and Receptors .......... 96 Beta-‐endorphins receptors .......... 96 Beta-‐endorphins complexities .......... 97 4.1.2 Beta-‐Endorphins in Pregnancy .......... 97 4.1.3 Beta-‐Endorphins in Labor and Birth .......... 98 Maternal Beta-‐Endorphins In Labor and Birth .......... 98 Fetal Beta-‐Endorphins in Labor and Birth .......... 100 4.1.4 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

4.2 Common Maternity Care Practices That May Impact Beta-‐Endorphins Physiology .......... 102 4.2.1 Maternity Care Provider and Birth Environment: Possible Impacts on Beta-‐Endorphins

.......... 103 4.2.2 Prostaglandins for Cervical Ripening and Labor Induction: Possible Impacts on Beta-‐

Endorphins .......... 103 4.2.3 Synthetic Oxytocin for Induction, Augmentation, and Postpartum Care: Possible Impacts on

Beta-‐Endorphins .......... 103 4.2.4 Opioid Analgesic Drugs: Possible Impacts on Beta-‐Endorphins .......... 104 Opioid Drugs and the Mother .......... 104 Opioid Drugs and the Fetus/Newborn .......... 104 4.2.5 Epidural Analgesia: Possible Impacts on Beta-‐Endorphins .......... 105 Epidural Analgesia and the Mother .......... 106 Epidural Analgesia and the Fetus/Newborn .......... 107 4.2.6 Cesarean Section: Possible Impacts on Beta-‐Endorphins .......... 107 Cesarean and the Mother .......... 107 Cesarean and the Fetus/Newborn .......... 108 4.2.7 Early Separation of Healthy Mothers and Newborns: Possible Impacts on Beta-‐

Endorphins .......... 108

4.3 Beta-‐Endorphins: Summary .......... 109 4.3.1 Beta-‐Endorphins: Normal Physiology .......... 109 4.3.2 Common Maternity Care Practices That May Impact Beta-‐Endorphins Physiology .......... 110 5 Epinephrine-‐Norepinephrine and Related Stress Hormones .............................................. .111 5.1 Epinephrine-‐Norepinephrine and Related Stress Hormones: Normal Physiology .......... 112 5.1.1 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

5.1.2 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


5.1.3 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 5.1.4 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

5.2 Common Maternity Care Practices That May Impact Epinephrine-‐Norepinephrine and Related Stress Hormones .......... 125

5.2.1 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 5.2.2 Prostaglandins for Cervical Ripening and Labor Induction: Possible Impacts on Epinephrine-‐

Norepinephrine and Related Stress Hormones .......... 130 5.2.3 Synthetic Oxytocin For Induction, Augmentation, and Postpartum Care: Possible Impacts on

Epinephrine-‐Norepinephrine and Related Stress Hormones .......... 130 5.2.4 Opioid Analgesic Drugs: Possible Impacts on Epinephrine-‐Norepinephrine and Related Stress

Hormones .......... 131 5.2.5 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 5.2.6 Cesarean Section: Possible Impacts on Epinephrine-‐Norepinephrine and Related Stress

Hormones .......... 134 Cesarean and the Mother .......... 135 Cesarean and the Fetus/Newborn .......... 135 5.2.7 Early Separation of Healthy Mothers and Newborns: Possible Impacts on Epinephrine-‐

Norepinephrine and Related Stress Hormones .......... 136

5.3 Epinephrine-‐Norepinephrine and Related Stress Hormones: Summary .......... 138 5.3.1 Epinephrine-‐Norepinephrine and Related Stress Hormones: Normal Physiology .......... 138


5.3.2 Common Maternity Care Practices that May Impact Epinephrine-‐Norepinephrine and Related Stress Hormones Physiology .......... 139

6 Prolactin ................................................................................................................................ 140

6.1 Prolactin: Normal Physiology .......... 141 6.1.1 Prolactin: Introduction .......... 141 Prolactin Effects .......... 141 Prolactin Regulation and Receptors .......... 142 6.1.2 Prolactin in Pregnancy .......... 143 Maternal Prolactin in Pregnancy .......... 143 Fetal Prolactin in Pregnancy .......... 144 6.1.3 Prolactin in Labor and Birth .......... 144 Maternal Prolactin in Labor and Birth .......... 144 Fetal Prolactin in Labor and Birth .......... 145 6.1.4 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 Common Maternity Care Practices That May Impact Prolactin Physiology .......... 149 6.2.1 Maternity Care Provider and Birth Environment: Possible Impacts on Prolactin .......... 149 6.2.2 Prostaglandins for Cervical Ripening and Labor Induction: Potential Impacts on Prolactin

.......... 149 6.2.3 Synthetic Oxytocin For Induction, Augmentation, and Postpartum Care: Possible Impacts on

Prolactin .......... 150 6.2.4 Opioid Analgesic Drugs: Possible Impacts on Prolactin .......... 151 6.2.5 Epidural Analgesia: Possible Impacts on Prolactin .......... 151 6.2.6 Cesarean Section: Possible Impacts on Prolactin .......... 152 6.2.7 Early Separation of Healthy Mothers and Newborns: Possible Impacts on Prolactin ..........

154

6.3 Prolactin: Summary .......... 154 6.3.1 Prolactin: Normal Physiology .......... 154 6.3.2 Common Maternity Care Practices That May Impact Prolactin Physiology .......... 155 7 Conclusions and Recommendations ........................................................................................ 156

7.1 Conclusions .......... 157

7.2 Recommendations to Promote, Support, and Protect Physiologic Childbearing .......... 163 7.2.1 Education, Policy, and Consumer Engagement Recommendations .......... 163 Education .......... 163 Policy .......... 164 Engaging and Supporting Childbearing Women .......... 165


7.2.2 Care Practice Recommendations Whenever Safely Possible .......... 165 Prenatal Care .......... 165 Postpartum Care .......... 168 7.2.3 Research Recommendation .......... 169

7.3 Conclusions and Recommendations: Summary .......... 169

Appendix: Resources for Learning More and Improving Practice .................................................... 171

References ........................................................................................................................................ 175

Abbreviations .................................................................................................................................... 224

Photo Credits .................................................. .................................................................................. 225

© 2015 National Partnership for Women & Families. All rights reserved.

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