When does human life begin?

Transcription

1 When does human life begin? Professor Ray Iles Biomedical Science

2 Weeks of Gestation at which point human does life begin? Buddists, Hindu, Christianity (Catholic Church) conception 40 days 120 days Muslims and some Christians consider the soul to be imparted

3 When does human life begin? The definition of the beginning of human existence as an individual is set by the moral and religious views of society The beginning of human life is not easily defined. Rational definition is needed In order to set boundaries of legal, social and medical rights iht for the protection ti of human life.

4 Why do we need a specific definition? ART and the genetic selection of the conceptus Genetic manipulation of the conceptus Harvesting of germ line stem cells Termination of pregnancy Action leading to fetal death

5 Legal status of the unborn child An unborn child has no legal personality Paton v BPAS 1979 In England & Wales the unborn child has no rights until birth Once born alive, it can apply retrospective rights for criminal or civil wrong

6 Offences Against the Person Act 1861 s.58 Every woman being with child who with intent to procure her own miscarriage, shall unlawfully administer to herself any poison or other noxious thing.or unlawfully use any instrument or other means and whosoever, with intent to procure the miscarriage of any woman whether she be or not be with child shall unlawfully administer to her any poison or other noxious thing.or unlawfully use any instrument or other means shall be guilty of a felony

7 Infant Life (Preservation) Act 1929 s1(1) s.1(1).any person who with intent to destroy the life of a child capable of being born alive by any wilful act causes a child to die before it has an existence independent of its mother shall be guilty of a felony child destruction. no person shall be found guilty of an offence unless the act which hcaused the death was not done in good faith for the purpose only of preserving the life of the mother. S1(2) For the purpose of the Act evidence that a woman had at any material time been pregnant for a period of twenty eight weeks or more shall be prima facie proof that she was at that time pregnant of a child capable of being born alive

8 Abortion Act 1967 (as amended d by s37 Human Fertilisation and Embryology Act 1990) s.1(1).. A person shall not be guilty of an offence under the law relating to abortion when a pregnancy is terminated by a registered medical practitioner if two registered medical practitioners are of the opinion formed in good faith

9 Can Biomedical Science contribute to Social Policy in defining the beginning of human life? Several biological aspects of fetal development can be examined as markers of human life. The probability of the conceptus surviving to delivery at term Thedevelopment ofconsciousness Fetal independence from maternal in utero support

10 The probability bilit of the conceptus surviving to delivery at term From conception/implantation and development of body structure in the first trimester to maturation of the organs in the third trimester, the conceptus faces developmental gate events that can lead to spontaneous abortion/miscarriage

11 Conception and implantation In the most fertile couples, only about 1 in 4 conception events leads to a clinical pregnancy In about 50% of these cases this is probably due to failures at conception and implantation

12 Effects of maternal recognition of pregnancy At implantation the conceptus must activate its own genome and produce a hormone hcg that affects maternal recognition of pregnancy. If the hormonal signal fails to rescue the corpus luteum in time then we have a delayed menstruation by 1 2 weeks, and a biochemical pregnancy only. About 10 30% of conception events may fail, and are defined as biochemical pregnancies

13 1 st and 2 nd trimester loss In the first trimester, 80% of all clinical i l pregnancy miscarriages i occur (1 in 6 pregnancies are lost to miscarriage) A gate keeper event occurs at the end of the first trimester Second trimester losses are predominately due to cervical incompetence events.

14 Probability of progressing to a live term delivery 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Concept implant MRP 1st 2nd 3rd

15 Weeks of Gestation at which point does human life begin? Buddists, Hindu, Christianity (Catholic Church) conception 40 days 120 days Muslims and some Christians consider the soul to be imparted Week 13 End of the first trimester 80% chance of progressing to term

16 When does the fetus become conscious? How do we define consciousness? at its most basic level, consciousness can be defined as the ability of the developing organism to sense its surroundings and moderate its response.

17 Fetal Consciousness 21-40weeks of gestation

18 Weeks of Gestation at which point does human life begin? Buddists, Hindu, Christianity (Catholic Church) conception 40 days 120 days Muslims and some Christians consider the soul to be imparted Week 13 End of the first trimester 80% chance of progressing to term Fetal consciousness 21 wks term

19 Pain is a considered a model marker for the development of consciousness Linked to brain and neuronal development, the ability of the fetus to experience pain isan appropriate measure of this basic definition of a consciousness. Despite manycontentious definitions of what constitutes a pain response, significant research advances have been made in this area. Pain is a basic signal of sensing the environment and will elicit a basic non conscious motor response. Our ability to sense pain but block the automatic motor response is a clear indication of higher brain activity and conscious decision. The ability do this is reflected in neuro anatomy

20 Ftl Fetal pain and consciousness The dorsal (rear) root is the sensory root. The ventral (front) root is the motor root. The dorsal root ganglion contains cell bodies of general somatic afferent (inbound) neurons, mediates pain and temperature and synapse in the dorsal horn of the spinal cord. A-delta fibres are myelinated (insulated with a myelin sheath). The pain is fast and well localized, like the initial prick or stinging sensation following an injury. C fibres are nonmyelinated and smaller than A-delta fibres. They transmit pain much more slowly. The pain is longer lasting, generalized and described as a dull ache.

21 Fetal pain and consciousness Thalamocortical fibres from neurons in the thalamic nucei relay pain information to the cerebral cortex

22 Fetal pain and consciousness

23 When does the fetus feel pain? In November 1996, the Royal College of Obstetricians t i and Gynaecologists (RCOG) set up a Working Party in response to questions raised in Parliament relating to fetal pain and awareness. The findings of the Working Party were published in October 1997 and the main recommendations resulting from the Working Party s findings were: i. that practitioners who undertake diagnostic or therapeutic surgical procedures upon the fetus at or after 24 weeks gestation consider the requirements for fetal analgesia and sedation; ii. that practitioners who undertake termination of pregnancy at 24 weeks or later should consider the requirements for feticide or fetal analgesia and sedation; iii. further research be undertaken into specific areas

24 Fetal Pain and Consciousness Report of the MRC Expert Group on Fetal Pain 28 August 2001 More research needed Fetal Pain - A Systematic ti Multidisciplinary i li Review of the Evidence Susan J. Lee, JD; Henry J. Peter Ralston, MD; Eleanor A. Drey, MD, EdM; John Colin Partridge, MD, MPH; Mark A. Rosen, MD JAMA. 2005;294: Thalamocortical fibers begin appearing between 23 to 30 weeks gestational age, while electroencephalography suggests the capacity for functional pain perception in pre-term neonates probably does not exist before 29 or 30 weeks.

25 Weeks of Gestation at which point human life begins? Buddists, Hindu, Christianity (Catholic Church) conception 40 days 120 days Muslims and some Christians consider the soul to be imparted Week 13 End of the first trimester 80% chance of progressing to term Fetal consciousness 21 wks term Conscious perception of pain 29 weeks

26 Fetal independence from maternal in utero support The ability of premature babies bbi to survive beyond the first year of birth is often proposed as an argument of what constitutes the definition of the beginning of human life. Medical technology has driven this to earlier and earlier dates in gestation. Currently survival can be achieved for neonates born at weeks of gestation Is this a good thing? What about morbidity?

27 Pre maturity and survival Completed Weeks of Gestation at Birth (Using last menstrual period) Survival weeks and less 0% 22 weeks 0-10%* 23 weeks 10-40% % sur rvival weeks 40-70% weeks 50-80% 26 weeks 80-90% 27 weeks >90% 30 weeks >95% 34 weeks >98% Gestation in weeks

28 Pre maturity and Morbidity The EPICURE study The study showed that 4,004 babies were born in Britain between 20 and 25 weeks gestation in ,200 (30%) born alive 811 (20%) were admitted to a neonatal intensive care unit. 314 (8%) survived to go home.

29 Epicure Disability scores of premature babies at 6 years of follow up % surviva al Gestation in weeks

30 Weeks of Gestation at which point human life begins? Buddists, Hindu, Christianity (Catholic Church) conception 40 days 120 days Muslims and some Christians consider the soul to be imparted Week 13 End of the first trimester 80% chance of progressing to term Fetal consciousness 21 wks term Conscious perception of pain 29 weeks Survival and EPICURE study being bi born before bf weeks only a 4% 5 year survival with minor weeks developmental morbidity

31 When does human life begin? Can biomedical science give a precise answer? NO, But.. It can give a window within which h human life does (probably) begin. This would satisfy legal disputes that define unlawful killing of the unborn and the limits to which intervention and manipulation of the conceptus is allowed for tissue engineering However, public engagement in defining and accepting the criteria or biological measures of human life is ESSENTIAL. (.at 26 weeks of gestation +/ 3 weeks)

32 Ethics, Biomedical Scientists and public engagement with Si Science

33 Thank you