Examination of the Human Embryo

Abstract

Adequate examination and evaluation of the products of conception can yield important information that may benefit future pregnancies. A study of the fertilized ova within the embryonic period shows that about 16 % exposed to sperm fail to divide and another 15 % fail to implant. Grossly abnormal embryos (27 %) may be spontaneously aborted at previous stages. Abortion is defined as the premature expulsion or removal of the conceptus from the uterus before it is able to sustain life on its own. Clinically, the term takes on many definitions such as threatened abortion, incomplete abortion, missed abortion, recurrent abortion, and induced/therapeutic abortion. Early spontaneous abortion occurs in the embryonic period up to the end of the 8th developmental week. Late spontaneous abortion occurs between the 9th and 20th week of development.

Appendices

Appendix 1: Specimen Evaluation and Collection

Appendix 2: Instructions for Mailing Aborted Tissue

In order to ensure complete examination morphologically, microbiologically, and cytogenetically, the following instructions must be followed:

1. The whole conceptus (everything aborted) should be submitted. This means the fetus and placenta and all the tissues spontaneously expelled or removed surgically by either a D&C or the suction method.

2. The aborted material should be placed in a clean container of appropriate size without additives.

3. Scant material should be kept moist by the naturally present blood or with a few milliliters of sterile normal saline.

4. Sterile technique should be used in preparing the specimen for transport.

5. The containers should be labeled appropriately and tightly sealed to prevent leakage.

6. Specimens shipped from long distance should be insulated with a cold pack. Do not freeze. To prevent tissue deterioration, the specimen should be sent immediately by postal service First Class, Special Delivery, or by courier service.

7. The requisition form should be completed and accompany the specimen. The clinical history is important because it is that information and the morphologic findings that dictate whether chromosome studies or other special tests are initiated.

Appendix 3: Timetable of Human Prenatal Development 1–6 Weeks/7–10 Weeks

From: Moore KL. The developing human. 3rd ed. Philadelphia: WB Saunders Co; 1982, With permission

Appendix 4: Criteria for Estimating Fertilization Age During the Fetal Period

Age (weeks)	Crown-rump length (mm)	Foot length (mm)	Fetal weight (g)	Main external characteristics	Microscopic appearance
Previable fetuses
9	50	7	8	Eyes closing or closed, head more rounded, external genitalia still not distinguishable as male or female, intestines are in umbilical cord
10	61	9	14	Intestine in abdomen, early fingernail development	Cartilage in trachea
→12	87	14	45	Sex distinguishable externally, well-defined neck	Bronchial glands and goblet cells evident
14	120	20	110	Head erect, lower limbs well developed	Prominent duct system in lung
→16	140	27	200	Ears stand out from head	Cartilage in segmental bronchi
18	160	33	320	Vernix caseosa present, early toenail development
20	190	39	460	Head and body hair (lanugo) visible	Lymphatics present in lung, periarteriolar lymphocytes in spleen, thymic cortex equal to medulla in thickness
22	210	45	630	Skin wrinkled and red
→24	230	50	820	Fingernails present, lean body

1. →, Important landmarks
2. From: Valdes-Dapena M, Kalousek DK, Huff DS. Perinatal, fetal and embryonic autopsy (chapter 14). In: Gilbert-Barness E, editor. Potter’s pathology of the fetus and infant. St. Louis: Mosby-Year Book, Inc.; 1997, With permission

Appendix 5: Crown-Rump Length and Developmental Age in Previable Fetuses

Crown-rump length (mm)	Days after ovulation		Crown-rump length (mm)	Days after ovulation
30–31	56	9th week	98–99	92	14th week
32–34	57		100–101	93
35–36	58		102–103	94
37	59		104	95
38–39	60		105–106	96
40–41	61		107–108	97
42	62		109–110	98
43–44	63		111–112	99	15th week
45–16	64	10th week	113–114	100
47–48	65		115–116	101
49	66		117–118	102
50–51	67		119–120	103
52–53	68		121–122	104
54	69		123–124	105
55–56	70		125–126	106	16th week
57–58	71	11th week	127–128	107
59–60	72		129	108
61–62	73		130–131	109
63–64	74		132–134	110
65	75		135–136	111
66–67	76		137–138	112
68–69	77		139	113	17th week
70–71	78	12th week	140–141	114
72–73	79		142–143	115
74	80		144–145	116
75	81		146–147	117
76–78	82		148–149	118
79–80	83		150	119
81	84		151–152	120	18th week
82	85	13th week	153	121
83–86	86		154–155	122
87–89	87		156–157	123
90–91	88		90–91	124
92–93	89		159–160	125
94	90		161–162	126
95–97	91		163–164	127	20th week
			165	128

1. Modified from McBride ML, Bailie J, Poland BJ. Growth parameters in normal fetuses. Teratology. 1984;29:185; supplemented with previously unpublished data. Kalousek DK, Fitch N, Paradice BA. Pathology of human embryo and previable fetus. New York: Springer; 1990, With permission

Appendix 6: Weights and Measurements of Fetuses of 8–26-Week Gestation (Mean Values)

Gestation (weeks)	Weight (g)	Crown-heel length (cm)	Crown-rump length (cm)	Foot length (cm)
8	10	2
9	11	3
10	14	4
11	18	6	4	0.9
12	25	7	6	1.1
13	27	9	7	1.4
14	38	10	8	1.7
15	53	13	9	2.1
16	73	14	10	2.2
17	122	17	12	2.4
18	161	19	13	2.6
19	188	20	14	2.9
20	227	21	15	3.2
21	303	24	16	3.4
22	384	26	18	3.8
24	389	27	19	4.1
26	394	28	20	4.5

1. Modified from Potter EL, Craig JM. Pathology of the fetus and infant. 3rd ed. Chicago: Year Book Medical; 1975, With permission

Appendix 7: Hand and Foot Lengths Correlated with Developmental Age in Previable Fetuses

Developmental age (weeks)	Hand length (mm)	Foot length (mm)
11	10  ±  2	12  ±  2
12	15  ±  2	17  ±  3
13	18  ±  1	19  ±  1
14	19  ±  1	22  ±  2
15	20  ±  3	25  ±  3
16	26  ±  2	28  ±  2
17	27  ±  3	29  ±  4
18	29  ±  2	33  ±  2

1. From: McBride ML, Bailie J, Poland BJ. Growth parameters in normal fetuses. Teratology. 1984;29:185, With permission

Appendix 8: Body Measurements with Relationship to Fetal Age

Developmentalal age		Gestational age	weight (g)	CRL (cm)	CHL (cm)	FL (cm)	HC (cm)	CC (cm)	Hand (cm)	Humerus (cm)	Lower arm (cm)	Femur (cm)	Lower leg (cm)	Between nipples (cm)	Inner canthus (cm)	Outer canthus (cm)
Days	Weeks	Weeks
77–83	11	13	29.5–37.5	7.4–8.6	8.0–10.0	1.0–1.5	8.5–9.0	6.0–7.6	0.8–1.3	1.5–2.0	1.3–1.8	1.5–2.0	1.1–1.8	1.1–1.6	0.6–0.7	1.5–1.7
84–91	12	14	31.0–93.0	8.9–10.2	8.0–13.0	1.4–2.0	9.1–10.1	8.4–10.0	1.2–1.7	2.0–2.4	1.6–2.3	1.9–2.5	1.5–2.3	1.7–2.0	0.8–1.2	1.8–2.4
91–97	13	15	65.0–94.0	10.3–11.4	11.0–15.0	1.7–2.0	10.4–11.9	8.7–10.0	1.6–1.95	2.4–2.8	2.1–2.6	2.4–2.8	2.0–2.5	1.8–2.3	0.9–1.1	2.0–2.4
98–104	14	16	91.0–140.0	11.5–12.8	11.0–17.0	1.9–2.4	11.2–13.8	9.5–12.0	1.8–2.2	2.5–3.15	2.2–2.8	2.6–3.2	2.2–2.8	2.1–2.6	1.0–1.25	2.2–2.7
106–111	15	17	140.0–194.0	13.0–14.1	15.0–20.0	2.1–2.8	12.5–15.3	11.1–12.6	1.7–2.3	3.0–3.4	2.5–3.1	3.0–3.5	2.6–3.0	2.2–2.8	1.0–1.3	2.6–3.0
112–118	16	18	212.0–249.0	14.2–15.3	17.0–23.0	2.7–3.2	15.0–16.4	12.9–14.1	2.4–2.9	3.4–4.0	3.2–3.6	3.3–3.9	3.1–3.5	2.5–2.9	1.0–1.5	2.5–3.1
119–125	17	19	214.0–300.0	15.4–16.5	17.0–24.0	2.5–3.3	15.4–17.6	12.8–15.3	2.3–3.0	3.2–4.1	3.1–3.9	3.5–4.3	3.2–3.9	2.5–3.3	1.0–1.5	3.1–3.8
126–132	18	20	272.0–349.0	16.5–16.9	18.0–25.0	3.1–3.5	17.0–19.5	13.6–16.0	2.7–3.1	3.9–4.2	3.7–4.0	3.6–4.0	4.0–4.4	2.1–3.8	1.1–1.45	3.0–3.7
133–139	19	21	365.0–411.0	17.0–18.0	22.0–26.0	3.5–3.8	18.0–19.5	15.5–16.8	3.0–3.4	4.1–4.7	3.7–4.3	4.3–4.8	3.9–4.3	3.1–3.7	1.2–1.5	3.3–3.75

1. Compiled from multiple sources

Appendix 9: Organ Weights with Relationship to Fetal Age

Developmental age		Gestational age	Brain (g)	Liver (g)	Lungs (paired) (g)	Kidneys (paired) (g)	Heart (g)	Spleen (g)	Thymus (g)	Adrenals (paired) (g)	Placenta (g)	Cord length (cm)
Days	Weeks	Weeks
77–83	11	13	4.8–6.3	1.2–2.3	0.5–1.4	0.15–0.28	0.12–0.31	0.005–0.02	0.015–0.025	0.105–0.20	42.4	11.3
84–91	12	14	7.0–13.5	1.8–2.88	1.6–2.94	0.29–0.58	0.19–0.48	0.015–0.05	0.017–0.03	0.116–0.294	56.1	12.9
91–97	13	15	10.2–18.4	3.6–5.4	2.3–3.8	0.48–0.86	0.30–0.65	0.028–0.078	0.03–0.11	0.22–0.44	69.7	14.5
98–104	14	16	13.1–22.4	4.3–7.1	2.5–5.5	0.56–1.48	0.42–1.14	0.029–0.097	0.039–0.21	0.33–0.61	83.3	16.1
106–111	15	17	19.4–29.0	5.87–10.6	3.75–7.8	0.99–1.55	0.62–1.49	0.042–0.167	0.078–0.24	0.486–0.95	96.9	17.7
112–118	16	18	26.2–38.0	6.4–12.0	5.58–9.88	1.37–2.47	1.16–1.55	0.09–0.28	0.09–0.318	0.58–1.59	110.5	19.4
119–125	17	19	33.3–45.2	9.4–14.7	7.19–11.95	1.81–2.82	1.19–2.4	0.12–0.29	0.27–0.45	0.79–1.62	124.2	21
126–132	18	20	37.5–56.8	13.8–19.9	8.48–12.5	2.1–3.5	1.76–2.89	0.19–0.32	0.31–0.63	1.15–1.76	137.8	22.6
133–139	19	21	48.0–59.0	17.2–23.8	9.15–13.9	2.2–3.65	1.90–2.92	0.367–0.58	0.375–1.07	1.16–2.07	126.0	35.0

1. Compiled from multiple sources