Transcript 双生児の出産時体重に及ぼす影響

双胎分娩34〜40週の出産結果に及ぼす
胎児の性、性組合せ、経産の影響
野中浩一（帝京大・医・衛生公衛）
今泉洋子（兵庫大学附属研究所）
【目的】
日本全体の双胎出産のデータ（79-94年）
分娩週数
児の性
性組み合わせ
初産・経産の別
出産数
死産割合
出産時体重
【資料と方
法】
●
1979〜94年の人口動態統計の双胎分
出生票n=284,259 と 死産票n=30,803 計n=315,062
●
ペア作成 155,094組(310,188人）⇨
●
出産時体重情報が入手できた出産（n=313,892）
●
●
98.5%
体重の推定
79-91年 100ｇ単位、切り捨て（2500ｇは別掲）
92-94年 1ｇ単位
※ 79-91年については階級の中央値を代用して計算
分娩時在胎週数：34-40週に限定
出産数割合（種類別の相対値、％）
30%
25%
単胎児
双胎児
20%
トピック
3
品胎児
15%
10%
5%
0%
21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
出産時の妊娠週数（満・週）
図１　単胎、双胎、品胎の出産時妊娠週数分布
1.0000
死産児割合
0.1000
トピック 2
0.0100
単胎児
0.0010
双胎児
品胎児
0.0001
21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
出産時の妊娠週数（満・週）
図２　出産時妊娠週数別死産児割合
4000
平均出生時体重　(g)
単胎児
3000
トピック 1
双胎児
品胎児
2000
1000
0
21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
出産時の妊娠週数（満・週）
図３　出産時妊娠週数別平均出生体重(g)
Mean twin birth weight by gestational weeks, sex, and sex combination, all Japan, 1979-94
(Stillbirths)
3500
Birth weight (g)
3000
Male (Male+Male)
Male (Male+Female)
Female (Male+Female)
Female (Female+Female)
2500
2000
1500
1000
500
0
-25
26-27
28-29
30-31
32-33
34-35
36-37
38-39
Gestational week at birth (weeks)
40-41
42+
Mean triplet birth weight by gestational weeks and sex of child, all Japan
(Stillbirths, sex-unknown excluded)
2500
male
female
2000
malesm
1500
1000
500
0
-23
24-25
26-27
28-29
30-31
32-33
34-35
36-37
gestational week (weeks)
38-39
40+
Triplet pregnancy
38weeks
Period when male fetus (or embryo) is
more susceptible to growth retardation
Twin pregnancy
26weeks
Period when male fetus (or embryo) is
more susceptible to growth retardation
Singleton pregnancy
？
Conception
Gestation period
Birth
Number of twin births and stillbirth rate, all Japan, 1979-1994
30000
15
Live births
Stillbirths
25000
20000
10
15000
10000
5
5000
0
0
79 80
81
82 83
84
85 86
87 88
Year
89
90 91
92
93 94
Stillbirth rate (%)
Number (per year)
Stillbirth rate (%)
Mean birth weight of twin according to year,
all Japan, 1979-1994
3000
Birth weight (g)
2500
2000
Live births
Stillbirths
1500
1000
500
0
78 80 82 84 86 88 90 92 94 96
Year
Mean twin birth weight by gestational weeks and birth year period, all Japan (Live births)
1979-82
1983-86
1987-90
1991-94
3000
Birth weight (g)
2500
2000
1500
1000
500
0
-25
26-27
28-29
30-31
32-33
34-35
36-37
38-39
Gestational weeks at birth (weeks)
40-41
42+
Mean twin birth weight by gestational weeks and sex (Live), all Japan, 1979-94
3000
Male
Female
Birth weight (g)
2500
2000
1500
1000
500
0
-25
26-27
28-29
30-31
32-33
34-35
36-37
38-39
Gestational weeks at birth (weeks)
40-41
42+
15000
2nd+ Like-sexed Male
Female
Number of births
1st Like-sexed Male
10000
Female
2nd+ Unlike-sexed Male
Female
5000
1st Unlike-sexed Male
Female
0
33
34
35
36
37
38
39
Gestation period (weeks)
40
41
2001fig.d.cg3
3000
2nd+ Unlike-sexed Male
Female
2750
Birth weight (g)
2nd+ Like-sexed Male
Female
2500
1st Unlike-sexed Male
Female
2250
1st Like-sexed Male
Female
2000
1750
33
34
35
36
37
38
39
Gestation period (weeks)
40
41
2001fig.d.cg3
3000
Female
Male
Birth weight (g)
2750
2500
2250
2000
1750
33
34
35
36
37
38
39
2nd+ Unlike-sexed
2nd+ Like-sexed
1st Unlike-sexed
1st Like-sexed
40
41
33
34
35
36
Gestation period (weeks)
37
38
39
40
41
6.0%
2nd+ Like-sexed Male
Stillbirth rate (%)
5.0%
Female
4.0%
1st Like-sexed Male
Female
3.0%
2nd+ Unlike-sexed Male
2.0%
Female
1.0%
1st Unlike-sexed Male
Female
0.0%
33
34
35
36
37
38
39
40
41
Gestation period (weeks)
2001fig.d.cg3
6.0%
Male
Stillbirth rate (%)
5.0%
4.0%
3.0%
2nd+ Like-sexed
1st Like-sexed
2.0%
2nd+ Unlike-sexed
1.0%
0.0%
32
1st Unlike-sexed
34
36
38
40
42
Gestation period (weeks)
2001fig.d.cg3
4.0%
Female
Stillbirth rate (%)
3.0%
2nd+ Like-sexed
2.0%
1st Like-sexed
2nd+ Unlike-sexed
1.0%
1st Unlike-sexed
0.0%
32
34
36
38
40
42
Gestation period (weeks)
2001fig.d.cg3
15000
2nd+ Like-sexed Male
Female
Number of births
1st Like-sexed Male
10000
Female
2nd+ Unlike-sexed Male
Female
5000
1st Unlike-sexed Male
Female
0
33
34
35
36
37
38
39
Gestation period (weeks)
40
41
2001fig.d.cg3
Live births
Twin births in Japan, 1979-1994
30000
25000
Number of Live Males
Number of Live Females
20000
15000
10000
5000
Gestation Weeks
42
+w
41
40
39
38
37
36
35
0
-2
3w
24
-2
9
30
-3
1
32
-3
3
34
Number of live births
35000
55.0%
Like-sexed, 1st
Male proportion (%)
54.0%
Like-sexed, 2nd or later
テーマについて
53.0%
Unlike-sexed, 1st
52.0%
Unlike-sexed, 2nd or later

51.0%
テーマ (自分の主張) の説明
50.0%
49.0%
48.0%
47.0%
46.0%
45.0%
33
34
35
36
37
38
39
Gestation period (weeks)
40
41
まとめ



出産時体重は妊娠34〜40週で単調に増加していたが、初産・
経産の別、男女別のほかに、異性・同性ペア別による違いが
観察された。すなわち、単胎と同様に、経産が初産より重く、男
児が女児より重かったほか、同じ性でも、ペアが同性より異性
の組合せのほうで重くなっていた。
死産率は、全体では妊娠３８週の分娩で最低になり、男児が
女児よりやや高いが、ペアが同性か異性かの違いのほうが影
響が大きく、異性の組み合わせで低かった。これらの結果は、
同性双胎に含まれる１卵性双胎が影響しているものと思われ
る。経産でやや高くなるのは年齢が交絡している可能性があ
る。
なお、同性双生児の場合、女児では男児よりも分娩週数が長
くなる傾向があり、死産率が最低になるのも妊娠３９週での分
娩であり、全体より１週程度遅くなっていた。
Mean twin birth weight by gestational weeks, sex and sex combination, all Japan, 1979-94
(Live births)
3000
Male (Male+Male)
Male (Male+Female)
Female (Male+Female)
Female (Female+Female)
Birth weight (g)
2500
2000
1500
1000
500
0
-25
26-27
28-29
30-31
32-33
34-35
36-37
38-39
Gestational week at birth (weeks)
40-41
42+
Mean twin birth weight by gestational weeks, sex and type of birth, all Japan, 1979-94
(Live births)
3500
3000
Male(Live+Live)
Male (Live+Still)
Female (Live+Live)
Female (Live+Still)
Birth weight (g)
2500
2000
1500
1000
500
0
-25
26-27
28-29
30-31
32-33
34-35
36-37
38-39
Gestational week at birth (weeks)
40-41
42+
Mean twin birth weight by gestational weeks, sex and type of birth, all Japan, 1979-94
(Live births)
3500
3000
Male(Live+Live)
Male (Live+Still)
Female (Live+Live)
Female (Live+Still)
Birth weight (g)
2500
2000
1500
1000
500
0
-25
26-27
28-29
30-31
32-33
34-35
36-37
38-39
Gestational week at birth (weeks)
40-41
42+
Proportion of gestational weeks for twin births, all Japan (Live births)
Year period
1979-1982
1983-1986
1987-1990
1991-1994
0
10
20
30
40
50
60
70
80
90
Percentage
-25w
26-27w
28-29w
30-31w
32-33w
34-35w
36-37w
38-39w
40-41w
42+w
100
Proportion of gestational weeks for twin births, all Japan (live- + stillbirths)
Year period
1979-1982
1983-1986
1987-1990
1991-1994
0
10
20
30
40
50
60
70
80
90
Percentage
-25w
26-27w
28-29w
30-31w
32-33w
34-35w
36-37w
38-39w
40-41w
42+w
100
Mean birth weight of twin by year, type of birth,
and sex, all Japan, 1979-1994
3000
Birth weight (g)
2500
2000
Live births, Male
Live births, Female
1500
Stillbirths, Male
Stillbirths, Female
1000
500
0
78 80 82 84 86 88 90 92 94 96
Year