Birth Defects in Singleton versus Multiple ART Births in Japan (2004–2008)

Table 1

Demographic and perinatal outcome data of the ART pregnancies with birth defects of known plurality.

		Singletons (𝑛=934)		Multiples (𝑛=229)		P
		n	%	n	%
Birth year
2004		88	71.5^a	35	28.5 ^a	<0.001
2005		119	77.3	35	22.7
2006		165	76.0	52	24.0
2007		240	79.5	62	20.5
2008		322	87.7	45	12.3
Maternal age
20–24		5	0.5	0	0.0	<0.001
25–29		85	9.1	30	13.1
30–34		328	35.1	105	45.9
35–39		394	42.2	82	35.8
≥40		122	13.1	12	5.2
Range			23–46		25–42
Mean±SD			35.0 ± 4.1		33.5 ± 3.7
Median			35.0		33.0
Gestational weeks						<0.001
<12		4	0.4	0	0.0
12–21		62	6.6	13	5.7
22–27		20	2.1	13	5.7
28–36		122	13.1	119	52.0
37–41		613	65.6	78	34.1
≥42		8	0.9	0	0.0
Unknown/missing values		105	11.2	6	2.6
Range			10–42		12–41
Mean ± SD			36.1 ± 6.3		34.0±5.2
Median			38.0		36.0
Sex
Male		453	48.5	111	48.5	n.s.
Female		350	37.5	91	39.7
Unknown/missing values		131	14.0	27	11.8
Neonatal outcome
Abortion (<22 weeks)		133	14.2	14	6.1	<0.001
Stillbirths (22 ≤ weeks)		37	4.0	5	2.2
Live-births		764	81.8	210	91.7
Early neonatal death (neonatal death up to day 6 after birth)
Yes		27	3.5	22	10.5	<0.001
No		539	70.6	153	72.9
Unknown/missing values		198	25.9	35	16.7

^a Percentage of singletons and multiples within each year were calculated.
n.s.: not significant.
Unknown/missing values were excluded in the statistic tests.