25. Menstrual cycle, fertilisation embryo KEATS

Page 1: Introduction

  • Subject: Menstrual cycle, fertilisation & embryology

  • Course: Biosciences for Midwifery Practice 4KNIW001

  • Lecturer: Rebecca Daley, Florence Nightingale Faculty of Nursing, Midwifery & Palliative Care

Page 2: Learning Outcomes

  • Describe the phases of the menstrual cycle

  • Identify the main hormones involved

  • Explain the roles of primary hormones in the menstrual cycle

  • Outline key stages of fertilisation and embryology

  • Discuss the importance for midwives to understand these topics

Page 3: Preparation for Session

  • Core activities to complete before the teaching day:

    • Watch "The Ovarian Cycle" by Khan Academy (11 min)

    • Read "the 9 months that made you" poster

Page 4: Introduction to the Menstrual Cycle

  • Definition: Regular, cyclical process in women of reproductive age

  • Physiological changes prepare for potential pregnancy

  • Cycle duration: typically 28 days (normal range: 24-38 days)

  • Starts on the first day of menstruation (day 1)

Page 5: Dating Pregnancies

  • Naegle’s Rule calculates Estimated Due Date (EDD) from Last Menstrual Period (LMP)

  • Normal pregnancy duration: 40 weeks (280 days)

    • Calculation:

      • Add 1 year to LMP

      • Subtract 3 months

      • Add 7 days

  • Adjust for cycle length (shorter/longer)

  • First trimester ultrasound provides the most accurate dating

Page 6: Menstrual Cycle Phases

  • Follicular (Proliferative) Phase:

    • Days 6-14, preparation for ovulation

  • Luteal (Secretory) Phase:

    • Days 15-28, prepares uterus for fertilised ovum

  • Ovulation occurs between the two phases

  • Menstrual phase: uterine lining shed if fertilisation does not occur (Days 1-5)

Page 7: Structures Involved in the Menstrual Cycle

  • Key structures:

    • Hypothalamus

    • Pituitary gland

    • Ovaries

    • Endometrium

Page 8: Hormones in the Menstrual Cycle

  • Key hormones:

    • Gonadotropin-releasing hormone (GnRH)

    • Follicle-stimulating hormone (FSH)

    • Oestrogen

    • Luteinising hormone (LH)

    • Progesterone

Page 9: Ovary Anatomy

  • Newborn ovaries contain millions of immature oocytes

  • In each cycle, several primary follicles grow; one becomes the dominant Graafian follicle

  • Dominant follicle ruptures at ovulation, releasing the ovum

  • Remaining cells form corpus luteum, producing hormones

Page 10: Menstrual Cycle with and without Fertilisation

  • Without Fertilisation:

    • Corpus luteum degenerates, decreasing oestrogen & progesterone

  • With Fertilisation:

    • Blastocyst produces hCG, maintaining corpus luteum and preventing endometrial shedding

Page 11: Fertilisation Process

  • Ovum is captured by fimbriae and moved to uterus

  • Fertilisation (fusion of sperm and ovum) occurs in the Fallopian tubes

  • Only one sperm penetrates the ovum, preventing others from entering

Page 12: Cell Divisions Post-Fertilisation

  • Development stages:

    • Zygote: fertilised egg

    • Morula: 16-cell stage

    • Blastocyst: develops into placenta and embryo

  • hCG produced by blastocyst detectable by day 13

Page 13: Implantation

  • Blastocyst implants in the uterus ~day 7

  • Trophoblast secretes enzyme for implantation

  • Formation of chorionic villi to support implantation

  • Ectopic pregnancy: implantation outside the uterus

Page 14: Early Embryology

  • From implantation to 8 weeks, termed embryo

  • Formation of amniotic and yolk sacs

  • Three germ layers:

    • Ectoderm (skin, CNS)

    • Mesoderm (bones, muscles)

    • Endoderm (digestive organs)

Page 15: Developmental Timeline

  • Key developments from day 15 to week 8

    • Formation of blood vessels, organs, and limbs

    • External genitalia differentiation on ultrasound by week 8

Page 16: Fetal Development

  • Fetal stage: weeks 9 to birth

    • Developmental milestones from weeks 8 to 29

    • Fetus continues to grow and mature.

Page 17: Embryonic and Fetal Development

  • Developmental critical periods for prenatal sensitivity to teratogens

Page 18: Preconception Care

  • Importance of preconception care for reducing maternal and neonatal risks

  • Address preventable factors and pre-existing conditions effectively before pregnancy

Page 19: Infertility

  • Defined as unable to conceive after 12 months of unprotected intercourse

  • Male causes: low sperm count, poor motility

  • Female causes: ovarian failure, anovulation, PCOS, etc.

Page 20: Assisted Reproductive Technology (ART)

  • Techniques include IVF, ICSI, IUI

  • Used in cases of male factor infertility and donor scenarios

Page 21: Miscarriages

  • Common complications of pregnancy:

    • Early miscarriages (up to 10% of clinical pregnancies)

    • Causes include chromosomal abnormalities, uterine issues

  • Recurrent miscarriage defined as 3 or more consecutive losses

Page 22: Relevance to Clinical Practice

  • Understanding menstrual cycle, fertilisation, and embryology is essential for midwives for patient care and education

Page 23: Consolidating Learning

  • Post-teaching activities to enhance understanding

  • Suggested readings and podcasts for additional insights

Page 24: References

  • Various scholarly references used throughout the session

Page 25: Contact Information

  • Name: Rebecca Daley

  • Position: Lecturer in Midwifery Education

  • Email: beccy.daley@kcl.ac.uk