Prevalence and factors associated with congenital malformations in live births

Cross-sectional study, population-based, with data from the Live Births Information System. A bivariate statistical analysis (Chi-square test) and a multivariate statistical analysis (multiple logistic regression) were performed to evaluate the association between the variables and the outcome (live-births with or without congenital malformations).

Results:

A total of 346,874 live births were registered, of which 3,473 presented some type of congenital malformation, with an average prevalence of 1.0%. In the multiple analysis, the factors positively associated with prevalence were: duration of pregnancy less than 37 weeks (OR = 1.17), maternal age between 20 and 29 years (OR = 0.893), singleton pregnancy (OR = 1.775), type of delivery (OR – 0.827), and number of prenatal consultations inferior to six (OR = 1.214).

Conclusion:

The variables pointed out in the study integrated a predictive model that can help in the planning of health services, suggest hypotheses regarding etiological factors, and finance prenatal care actions with attention to the identified factors.

Keywords
Congenital abnormalities; Vital statistics; Health information systems; Live birth; Prevalence

Year	Number of live births	Number of live births with CMF	Prevalence of live births with CMF (%)
2001	25,294ᵃ	296	1.2
2002	24,307^b	207	0.9
2003	24,676^c	275	1.1
2004	22,898^d	250	1.1
2005	23,207^e	227	1.0
2006	22,646^f	240	1.1
2007	22,046^g	204	0.9
2008	22,261^h	184	0.8
2009	22,546ⁱ	215	1.0
2010	21,796^j	225	1.0
2011	22,218^k	178	0.8
2012	22,633^l	151	0.7
2013	23,176^m	224	1.0
2014	23,506ⁿ	262	1.1
2015	23,664^o	335	1.4
Total	346,874	3,473	1.0
Δ%	-6.4	13.2	21

Characteristics		Malformation		p-value
Characteristics		Yes No. (%)	No No. (%)	p-value
Sexᵃ				< 0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%). Proportion of live births with information ignored: a) 0.04%; b) 0.02%; c) 0.8%; d) 0.5%; e) 0.06%; f) 1.2%; g) 0.04%; h) 1.4%; i) 0.5%; j) 0.05%
	Female	1310(39.9)	160296(48.9)
	Male	1974(60.1)	167694(51.1)
Birth weight (grams)^b				< 0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%). Proportion of live births with information ignored: a) 0.04%; b) 0.02%; c) 0.8%; d) 0.5%; e) 0.06%; f) 1.2%; g) 0.04%; h) 1.4%; i) 0.5%; j) 0.05%
	<2.500	745(22.7)	28204(8.6)
	≥2.500	2539(77.3)	299786(91.4)
Apgar 1st minute^c				<0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%). Proportion of live births with information ignored: a) 0.04%; b) 0.02%; c) 0.8%; d) 0.5%; e) 0.06%; f) 1.2%; g) 0.04%; h) 1.4%; i) 0.5%; j) 0.05%
	<7	1039(31.6)	44221(13.5)
	≥7	2245(68.4)	283769(86.5)
Apgar 5th minute^d				<0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%). Proportion of live births with information ignored: a) 0.04%; b) 0.02%; c) 0.8%; d) 0.5%; e) 0.06%; f) 1.2%; g) 0.04%; h) 1.4%; i) 0.5%; j) 0.05%
	<7	439(13.4)	7257(2.2)
	≥7	2845(86.6)	320733(97.8)
Maternal age^e (in complete years)				0.003^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%). Proportion of live births with information ignored: a) 0.04%; b) 0.02%; c) 0.8%; d) 0.5%; e) 0.06%; f) 1.2%; g) 0.04%; h) 1.4%; i) 0.5%; j) 0.05%
	< 20	663(20.2)	62962(19.2)
	20-29	1611(46.0)	170666(52.0)
	≥ 30	1010(30.8)	9436(28.8)
Educational level (years)^f				0.011^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%). Proportion of live births with information ignored: a) 0.04%; b) 0.02%; c) 0.8%; d) 0.5%; e) 0.06%; f) 1.2%; g) 0.04%; h) 1.4%; i) 0.5%; j) 0.05%
	<8 years	1140(34.7)	106991(32.6)
	≥8 years	2144(65.3)	220999(67.4)
Type of pregnancy^g				0.085
	Singleton	3201(97.5)	321167(97.9)
	Multiple	83(2.5)	6823(2.1)
Prenatal consultation^h				< 0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%). Proportion of live births with information ignored: a) 0.04%; b) 0.02%; c) 0.8%; d) 0.5%; e) 0.06%; f) 1.2%; g) 0.04%; h) 1.4%; i) 0.5%; j) 0.05%
	<6	1736(52.9)	146588(44.7)
	≥6	1548(47.1)	181402(55.3)
Pregnancy duration (in weeks)ⁱ				< 0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%). Proportion of live births with information ignored: a) 0.04%; b) 0.02%; c) 0.8%; d) 0.5%; e) 0.06%; f) 1.2%; g) 0.04%; h) 1.4%; i) 0.5%; j) 0.05%
	<37	693(21.1)	29950(9.1)
	≥37	2591(78.9)	298040(90.9)
Type of delivery^j				0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%). Proportion of live births with information ignored: a) 0.04%; b) 0.02%; c) 0.8%; d) 0.5%; e) 0.06%; f) 1.2%; g) 0.04%; h) 1.4%; i) 0.5%; j) 0.05%
	Vaginal	1459(44.4)	155571(47.4)
	Cesarean	1825(55.5)	172419(52.6)

Variable		Odds ratio (adjusted)	Confidence interval (95%)	p-value
Sex				-
	Female	0.70	(0.65-0.75)	<0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%).
	Male	1	-	-
Birth weight (grams)
	< 2,500	2.09	(1.86-2.36)	<0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%).
	≥ 2,500	1	-	-
Apgar 1^st minute
	<7	1.82	(1.67-2.00)	<0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%).
	≥7	1	-	-
Apgar 5t^h minute
	<7	3	(2.64-3.41)	<0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%).
	≥7	1	-	-
Maternal age (in complete years)
	< 20	0.92	(0.83-1.02)	0.115
	20-29	0.89	(0.82-0.97)	0.006^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%).
	≥30	1	-	-
Educational level (years)
	<8 years	1.05	(0.98-1.14)	0.181
	≥8 years	1	-	-
Type of pregnancy
	Singleton	1.77	(1.41-2.23)	<0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%).
	Multiple	1	-	-
Prenatal consultation
	<6	1.21	(1.13-1.31)	<0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%).
	≥6	1	-
Pregnancy duration (in weeks)
	<37	1.17	(1.04-1.32)	0.012^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%).
	≥37	1	-	-
Type of delivery
	Vaginal	0.82	(0.77-0.89)	<0.001^* * The Null Hypothesis was rejected, because the p-value is smaller than the significance level of 0.05 (5%).
	Cesarean	1	-	-

Escola Paulista de Enfermagem, Universidade Federal de São Paulo R. Napoleão de Barros, 754, 04024-002 São Paulo - SP/Brasil, Tel./Fax: (55 11) 5576 4430 - São Paulo - SP - Brazil
E-mail: actapaulista@unifesp.br

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[1] Corresponding author Cristine Vieira do Bonfim, E-mail: cristine.bonfim@uol.com.br