Table Of ContentBIRTH DEFECTS INSTITUTE SYMPOSIA
Ernest B. Hook, Dwight T. Janerich, and Ian H. Porter, editors: MONITORING, BIRTH
DEFECTS, AND ENVIRONMENT: The Problem of Surveillance, 1971
Ian H. Porter and Richard G. Skalko, editors: HEREDITY AND SOCIETY, 1972
Dwight T. Janerich, Richard G. Skalko, and Ian H. Porter, editors: CONGENITAL DE
FECTS: New Directions in Research, 1973
Hilaire J. Meuwissen, Richard J. Pickering, Bernard Pollara, and Ian H. Porter, editors:
COMBINED IMMUNODEFICIENCY DISEASE AND ADENOSINE DEAMINASE
DEFICIENCY: A Molecular Defect, 1975
Sally Kelly, Ernest B. Hook, Dwight T. Janerich, and Ian H. Porter, editors: BIRTH
DEFECTS: Risks and Consequences, 1976
Ernest B. Hook and Ian H. Porter, editors: POPULATION CYTOGENETICS: Studies in
Humans, 1977
H. Lawrence Vallet and Ian H. Porter, editors: GENETIC MECHANISMS OF SEXUAL
DEVELOPMENT, 1979
Ian H. Porter and Ernest B. Hook, editors: SERVICE AND EDUCATION IN MEDICAL
GENETICS, 1979
Bernard Pollara, Richard J. Pickering, Hilaire J. Meuwissen, and Ian H. Porter, editors:
INBORN ERRORS OF SPECIFIC IMMUNITY, 1979
Ian H. Porter and Ernest B. Hook, editors: HUMAN EMBRYONIC AND FETAL
DEATH, 1980
Ernest B. Hook and Ian H. Porter, editors: POPULATION AND BIOLOGICAL AS
PECTS OF HUMAN MUTATION, 1981
Ann M. Willey, Thomas P. Carter, Sally Kelly, and Ian H. Porter, editors: CLINICAL
GENETICS: Problems in Diagnosis and Counseling, 1982
Anne Messer and Ian H. Porter, editors: RECOMBINANT DNA AND MEDICAL GE
NETICS, 1983
Gerald J. Mizejewski and Ian S. Porter, editors: ALPHA-FETOPROTEIN AND CON
GENITAL DISORDERS, 1985
Ian H. Porter, Norma H. Hatcher, and Ann M. Willey, editors: PERINATAL GENETICS:
Diagnosis and Treatment, 1986
PERINATAL GENETICS
Diagnosis and Treatment
Edited by
Ian H. Porter
Department of Pediatrics
Section of Medical Genetics
Albany Medical College
Albany, New York
Norma H. Hatcher
Laboratory for Human Genetics
Wadsworth Center for Laboratories and Research
New York State Department of Health
Albany, New York
Ann M. Willey
Laboratory for Human Genetics
Wadsworth Center for Laboratories and Research
New York State Department of Health
Albany, New York
1986
Θ
ACADEMIC PRESS, INC.
Harcourt Brace Jovanovich, Publishers
Orlando San Diego New York Austin
Boston London Sydney Tokyo Toronto
Proceedings of the Fifteenth Annual
New York State Health Department
Birth Defects Symposium
Academic Press Rapid Manuscript Reproduction
COPYRIGHT © 1986 BY ACADEMIC PRESS. INC
ALL RIGHTS RESERVED.
NO PART OF THIS PUBLICATION MAY BE REPRODUCED OR
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ACADEMIC PRESS, INC.
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United Kingdom Edition published bv
ACADEMIC PRESS INC. (LONDON) LTD.
24-28 Oval Road, London NW1 7DX
Library of Congress Cataloging in Publication Data
Perinatal genetics.
Based on the proceedings of the Fifteenth Annual
Birth Defects Symposium held Sept. 30-Oct. 1, 1984 in
Albany, N.Y.
"Birth Defects Institute symposia."
Includes index.
1. Fetus—Abnormalities—Genetic aspects—Congresses.
2. Prenatal diagnosis—Congresses. 3. Fetus—Abnormali
ties—Treatment—Congresses. 4. Genetic counseling-
Congresses. 5. Abortion—Moral and ethical aspects-
Congresses. I. Porter, Ian H. II. Hatcher, Norma H.
III. Willey, Ann M. IV. Birth Defects Institute
Symposium (15th : 1984 : Albany, N.Y.) [DNLM:
1. Abnormalities—congresses. 2. Fetal Diseases—therapy
—congresses. 3. Genetics, Medical—congresses.
4. Perinatology—congresses. 5. Prenatal Diagnosis-
congresses. QZ50 P445]
RG627.P46 1986 618.3'2042 86-45582
ISBN 0-12-562855-2 (alk. paper)
PRINTED IN THE UNITED STATES OF AMERICA
86 87 88 89 9 8 7 6 5 4 3 2 1
Preface
This volume is based on the proceedings of the Fifteenth Annual Birth
Defects Institute Symposium. For the celebration of this event we chose
the general theme of Perinatal Genetics. Genetics now is part of the stock
in trade of perinatologists and neonatologists—a significant common
ground for obstetricians and pediatricians. The themes addressed in this
volume illustrate the diversity of medical geneticists in the evolution of a
specialty which now is an important component of almost all medical
specialties. Birth control and restriction of family size have placed an
even greater emphasis on the optimum outcome of each pregnancy. Phy
sicians engaged in perinatal care have become increasingly aware of the
need to evaluate genetic and environmental risks and to offer appropriate
diagnostic services.
The aim of this volume is to clarify and rationalize certain aspects of
diagnosis, genetic counseling, and management. And our hope is that it
will serve as a useful guide for health professionals who provide care to
pregnant women and their newborns.
The translation of ethical precepts into legal precedent and the promo
tion of patients' rights over professional allegiance have made ethics an
important part of medical genetics. The Eugenics Society thought it sig
nificantly important to consider the ethical influence of recent technical
developments on the occasion of their 75th Anniversary in 1982. It was
for this reason that we asked Drs. Sherman Elias and Frank Chervenak to
lead our discussion on ethical issues.
This volume contains a great quantity of practical information applica
ble to genetic diagnosis and counseling as well as serving as a summary of
the current state of the art.
IX
Acknowledgements
The Birth Defects Institute Symposia are, for the staff, a climax to a
year's work—a kind of celebration—in which all members of the Institute
take part, and contribute to the running of the event and the production of
the proceedings. It also gives us the opportunity to thank Drs. David
Axelrod, our Commissioner of Health, and David Carpenter, the then
Director of the Center for Laboratories and Research of the New York
State Department of Health, for their help and encouragement.
And we would all like to especially thank Anne Kondrat, our Secretary-
in-Chief and Sandra Krug Williams, our Editorial Assistant for their esti
mable efforts.
XI
VERY EARLY PREGNANCY: FERTILIZATION AND IMPLANTATION
FREQUENCY AND CAUSE OF LOSS
Jennie Kline
Zena Stein
Gertrude H. Sergievsky Center
Columbia University
and
Epidemiology of Brain Disorders Research Department
New York State Psychiatric Institute
New York, New York
Mervyn Susser
Gertrude H. Sergievsky Center
Columbia University
New York, New York
INTRODUCTION
In this epidemiological review of very early pregnancy loss, we concen
trate on a small but growing body of observations concerning the first few
weeks after fertilization. The paper is organized in three sections: the first
is on fertilization and implantation, more precisely, on the probability that
pregnancy will occur when a presumably fecund couple have had intercourse
around the time of ovulation. The second section, drawing on much of the
same material, is on the probability of loss between fertilization and implanta
tion (on about day six), and between implantation and day 14 (the first day of
the expected next period in a nonpregnant woman). The third section is a re
view of six topics of cytogenetic research that bear on the contribution of
chromosomal errors in the sperm, ovum and zygote to early reproductive
loss.
This work was supported in part by a grant from the National Institute of Health (1-ROI-
HD-15909).
PERINATAL GENETICS: Copyright © 1986 by Academic Press, Inc.
DIAGNOSIS AND TREATMENT 3 All rights of reproduction in any form reserved.
4 JENNIE KLINE ET AL,
THE PROBABILITY OF FERTILIZATION
Fertilization is a process that begins with the fusion of the membranes of
sperm and egg and ends with the formation of the diploid zygote. If fertiliza
tion is to occur, the sperm must be present in the female genital tract at the
time of ovulation or shortly before. The time span is narrow (perhaps 24
hours), and thus, estimates of fertility from study samples where sexual inter
course is reported "around the time of ovulation" are probably underestimates
of fertility when the presence of sperm does in fact coincide with the release
of the ovum. Artificial insemination is an exception in that the timing of ovu
lation and introduction of sperm is known, but it is uncertain if this process is
physiologically identical with coital insemination. Thus the reader is cautioned
that some underestimate of fertilization is inherent in all the in vivo studies
discussed below, for none established all the needed parameters (the presence
of adequate sperm, the time of coitus, and the time and fact of ovulation).
Estimates of the probability of fertilization in an ovulatory cycle can be
made most directly, although with difficulty, from observations made before
implantation. Estimates from observations after implantation can be made
easily, but these will necessarily be incomplete, having missed those zygotes
lost before implantation.
In a 28 day menstrual cycle ovulation occurs 14 days after the first day
of menstruation, and the ovum remains susceptible to fertilization over a 24
hour period. If fertilization ensues, the ovum moves down the Fallopian tube,
dividing as it goes into the many-celled morula. On about day five after ovula
tion, the embryo, now in the blastocyst stage, has reached the uterine cavity.
The trophoblast attaches to the uterine wall and on about day seven to nine
after fertilization, the syncytiotrophoblast establishes vascular connections
between the growing embryo and the maternal circulation. At this time, or
possibly sooner, the trophoblast begins secretion of human chorionic gonado
tropa! (hCG). One effect of circulating hCG is to prolong the activity of the
corpus luteum in producing progesterone, thereby preventing the menstrual
shedding of the uterine lining. It is clear that the appearance of measurable
hCG in maternal serum can be expected to coincide not with fertilization,
but with the beginning of implantation. In a normal pregnancy the low initial
hCG level rises fairly steeply during the first trimester. The less well-studied
Early Pregnancy Factor (EPF) is reported to be detectable as soon as 48
hours after fertilization has taken place, and is, therefore, seen to represent
a pre-implantation response to fertilization.
Pre-implantation is designated by the time intervals A and B, post-im
plantation by the intervals C, D, E, F, and G (Table 1). Although by prefer
ence we would measure the duration of a pregnancy from ovulation (day 0
refers to the day of ovulation), we also give the measure of duration from the
last menstrual period (day 0 refers to the first day of the LMP), since the lat
ter measure corresponds to most observations in the literature. To avoid am-
VERY EARLY PREGNANCY 5
Table 1. Clinical and Hormonal Indications of Pregnancy by Length
of Gestation and Development of the Zygote.
Days (OV) Days (LMP)
After From Last
Ovulation Menstrual Period0 Zygote Clinical Hormonal
A 0 14 Fertilization^ none 7
B 1-6 15-20 Blastocyst to none EPF
(6,7) (20,21) implantation - (EPF)
C 7-13 21-27 Post-implan none hCG, EPF
tation embryo
D 14-34 2848 Later post- First hCG, EPF
implantation missed
embryo period
E 35-48 49-62 Embryo Conventional hCG
ly recognized
pregnancy
F 49-181 63-195 Fetus
G 182+ 196+ Viable
infant
a Approximate days in a 28 day menstrual cycle.
b There is evidence that fertilization may take place shortly after ovulation.
(taken from Kline and Stein, 19851:J)
6 JENNIE KLINE ET AL.
biguity, throughout this paper, we use the notations "days (OV)" for days
from ovulation and "days (LMP)" for days from the first day of the last
menstrual period. We have on occasion taken liberties with reports that were
based on LMP by adapting them to an assumed OV date. This modification is
noted whenever used.
Three sets of published data, derived from observation in the pre-implan-
tation period can be used to estimate the probability of fertilization: 1) direct
observations of fertilized ova made by Hertig et al.;1_4 2) prospective studies
using the Early Pregnancy Factor (EPF);5>° 3) experience with in vitro fer
tilization.7
In a pioneering and still unique study, Hertig and colleagues attempted
to retrieve fertilized ova from hysterectomy specimens. These were ova from
women who, in anticipation of hysterectomy, were asked to engage in sexual
intercourse around the presumed time of ovulation. This material has been
variously interpreted, but it is so well known that we shall deal with it only
briefly (Table 2). From observations in the pre-implanatation period only
eight among a possible 24 fertilizations (33 percent) could be established. This
is obviously an underestimate of the probability of fertilization, presumably
due to technical problems, since at least 58 percent (21 of 36) of possible fer
tilizations were successful as judged by retrievals made in the post-implantation
period. From these postimplantation data, it may be argued, with Hertig and
colleagues, that fertilization must have occurred at least 58 percent, and
possibly even 100 percent, of the time.
The second set of observations bearing on the probability of fertiliza
tion derives from a prospective study that used the EPF to identify fertiliza
tions. The sample comprised 11 couples reported to have had intercourse
at the presumed time of ovulation (days 13-17 LMP).6 No information on the
fertility of the men is reported. Serum tests were used to establish whether
and when ovulation occurred and to measure the EPF. EPF, a protein mea
sured by a rosette inhibition test, is supposedly always raised in women with
clinically recognized pregnancy and never raised in non-pregnant women.
Table 2. Observations on 34 Ova from 107 Women.
Stage studied (days LMP) Normal Ova Abnormal Ova Total Women
Pre-implantation 16-19 4 4 24
Peri-implantation 20-24 5 0 47
Post-implantation 25-30 15 6 36
TOTALS 24 10 107
(By Hertig et al.1)
VERY EARLY PREGNANCY 7
Twenty-six ovulatory cycles were studied in these women; in 18, EPF indicated
fertilization (69 percent). In 14 of the 18 cycles, EPF declined within a few
days to a level below that thought indicative of pregnancy and bleeding oc
curred around the time of the expected menses. For these cycles the decline in
EPF opens up at least two possibilities: fertilization occurred but was followed
by early loss, indicated by bleeding; or EPF is an unreliable indicator of fer
tilization, with a tendency to produce false positive results, and the bleeding
indicated only normal menses. In the four cycles remaining, a clinically
recognized pregnancy resulted.
If the EPF indicator is taken at face value, the probability of fertiliza
tion is high (69 percent) and the probability of pregnancy loss between fer
tilization and the date of expected menses is even higher (78 percent). This is a
first observation of a new technique and must be considered as tentative. The
estimate of 69 percent for the probability of fertilization is however, compat
ible with the 58 percent minimum estimate from Hertig et al. reported above.
A third set of observations derives from efforts to obtain in vitro fertiliz
ations. In this procedure, it is usual for the woman to be given hormonal ther
apy during the follicular stage of the cycle. The hormones stimulate the ripen
ing of numerous ova (perhaps between three and eight), instead of the single
ovum expected in a natural cycle. The sperm may also be treated to concen
trate fertilizing capacity. These circumstances, coupled with unknowns that
might prove advantageous or disadvantageous to fertilization and that are in
tegral to the in vitro procedure, caution against generalizing from the in vitro
to the in vivo situation. The common sense, although untested, assumption is
that in vitro fertilization would succeed less often than in vivo. It is salutory
that with experience, the success rate for fertilization can be over 80 percent,
with some claiming success rates as high as 90 percent. The criteria for "fertil
ization" differ from laboratory to laboratory, but always include at least two
cleavages of the egg.
From these three somewhat scanty and diverse sets of observations, we
may expect that fertilization will result from insemination at the time of
ovulation in 60 to 90 percent of cycles. It is perhaps surprising that the success
rate is this high, for in the early hours and days of fertilization, from the
penetration of the vestments of the ovum by the sperm until the first cleavage,
much could go wrong. The fertilization process includes the blocking of
polyspermy; the completion of maternal meiosis II with the extrusion of the
second polar body; the development of the two pro-nuclei, and the joining of
the two haploid gametes. Even at that early stage, the presence of certain
anomalies in the genome of either ovum or sperm could prevent further de
velopment. The impediments to fertilization remain obscure; we may hope that
studies of human in vitro fertilization will advance our understanding.
We turn now to estimates of the probability of fertilization derived from
studies of conceptions which survived to implantation. In the section above,
