Maternal and infant outcomes among women vaccinated against pertussis during pregnancy

Figures & data

Figure 1. Number of women by gestational week of Tdap vaccine administration.

Table 1. Characteristics of pregnant women by Tdap vaccination status during pregnancy (N = 1,759)^aa.

Characteristics	Did not receive Tdap (n = 650)	Received Tdap vaccine (n = 1109)	p
Demographics
Age, years, M ± SD	27.5 ± 6.4	26.8 ± 5.9	0.02
Race/ethnicity, n (%)			<0.001
White	220 (33.8)	330 (29.8)
Black	137 (21.1)	179 (16.1)
Hispanic	253 (38.9)	555 (50.0)
Other^b	40 (6.2)	45 (4.1)
First pregnancy	335 (30.2)	178 (27.5)	0.22
Pregnancy health indicators
Prenatal visits during pregnancy, M ± SD	11.2 ± 4.2	11.9 ± 3.8	<0.001
Timing of first prenatal visit, n (%)			0.15
Before 12 weeks gestation	391 (60.2)	705 (63.6)
During or after 12 weeks gestation	259 (39.8)	404 (36.4)
Gravidity, n (%)			0.26
1	180 (27.7)	335 (30.2)
2 or more	470 (72.3)	774 (69.8)
Prior full-term deliveries, n (%)			0.56
0	270 (41.7)	476 (43.2)
1 or more	377 (58.3)	627 (56.8)
Prior premature deliveries, n (%)			0.10
0	573 (88.6)	1004 (91.0)
1 or more	74 (11.4)	99 (9.0)
Prior spontaneous abortions, n (%)			0.18
0	466 (71.9)	828 (74.8)
1 or more	182 (28.1)	279 (25.2)
Prior ectopic pregnancies, n (%)			0.72
0	635 (98.2)	1089 (98.4)
1 or more	12 (1.8)	18 (1.6)
History of sexually transmitted infection, n (%)	213 (32.8)	370 (33.4)	0.80
Other vaccinations received during pregnancy, n(%)
Influenza vaccine	233 (36.2)	714 (64.6)	<0.001
Hepatitis A vaccine	1 (0.2)	1 (0.1)	0.46^c
Hepatitis B vaccine	0	3 (0.3)	0.30^c
Meningococcal vaccine	2 (0.3)	1 (0.1)	0.56^c
Pneumococcal vaccine	0	1 (0.1)	0.63^c

^a Numbers do not add up due to missing values.

^b Asian, American Indian, Alaskan, other.

^c p-value based on 2-sided Fisher's exact test.

Table 2. Details on infant birth defects and intensive care admissions by maternal Tdap vaccination status.

Outcomes	Did not receive Tdap vaccine (n = 650)	Received Tdap vaccine (n = 1109)	p
Birth defects,^a n (%)
Spina bifida	1 ( 0.15)	1 (0.09)	0.48^b
Transposition of great arteries	0 (0.0)	2 (0.18)	0.53^b
Atrioventricular septal defect	9 (1.38)	16 (1.44)	0.92
Cleft palate	5 (0.77)	2 (0.18)	0.11^b
Cleft lip	2 (0.31)	1 (0.09)	0.56^b
Diaphragmatic hernia	1 (0.15)	0 (0.0)	0.37^b
NICU admission
Days in NICU, M ± SD	23.9 ± 31.1	11.5 ± 12.6	0.001
Reason for NICU admission,^c n (%)
Preterm birth	55 (64.0)	50 (48.5)	0.03
Transient tachypnea of the newborn	31 (36.0)	40 (38.8)	0.69
Anemia	18 (20.9)	10 (9.7)	0.03
Apnea	24 (27.9)	18 (17.5)	0.08
Bradycardia	7 (8.1)	4 (3.9)	0.23
Jaundice	46 (53.5)	42 (40.8)	0.08

Boldface indicates statistical significance (p < 0.05).

^a Birth defects were not mutually exclusive, so total count of infants with any birth defect may add up to fewer than total birth defects in sample.

^b Fisher's Exact test used due to frequencies <5.

^c Based on infants admitted into NICU; percentages do not add up to 100% as an infant may be admitted for more than one reason.

NICU, neonatal intensive care unit.

Table 3. Maternal and infant outcomes by Tdap vaccination status (N = 1,759).

Outcomes	Did not receive Tdap vaccine (n = 650)	Received Tdap vaccine (n = 1109)	AOR (95% CI)^a	p
Maternal outcomes^b	n (%)	n (%)
Chorioamnionitis^c	14 (2.2)	39 (3.5)	1.53 (0.80–2.90)	0.19
Postpartum endometritis^d	5 (0.8)	9 (0.8)	1.67 (0.51–5.50)^e	0.41
Preterm premature rupture of membranes	19 (2.9)	36 (3.2)	1.05 (0.57–1.95)	0.87
Preterm delivery	59 (9.1)	58 (5.2)	0.68 (0.45–1.03)	0.07
Any above maternal outcome	89 (13.7)	152 (13.7)	1.09 (0.81–1.48)	0.56
Induced labor	338 (52.0)	656 (59.2)	0.82 (0.66–1.51)	0.06
Mode of delivery^f
Vaginal	405 (62.3)	759 (68.4)
Cesarean	245 (37.7)	350 (31.6)	0.78 (0.63–0.98)	0.03
Infant outcomes	n (%)	n (%)
Low birth weight (<2500g)	59 (9.1)	61 (5.5)	0.76 (0.51–1.14)	0.19
Very low birth weight (<1500g)	12 (1.8)	2 (0.2)	0.24 (0.05–1.20)^e	0.08
Small for gestational age (<10^th percentile)	31 (4.8)	46 (4.2)	0.89 (0.55–1.46)	0.65
Apgar score at 5 min of life <8	10 (1.5)	14 (1.3)	0.87 (0.22–3.52)	0.85
Birth defect^g	15 (2.3)	18 (1.6)	0.80 (0.38–1.67)^e	0.55
NICU admission	86 (13.2)	103 (9.3)	0.78 (0.56–1.08)	0.14
Any infant outcome^h	123 (18.9)	159 (14.3)	0.80 (0.61–1.06)	0.12

Boldface indicates statistical significance (p<0.05).

^a All odds ratios were adjusted by mother's age, race, number of prenatal visits, influenza vaccination status during pregnancy, number of infants born prematurely, and whether the first prenatal visit occurred before 12 weeks gestation.

^b Outcomes occurring anytime during pregnancy were included. Only two patients in the Tdap group experienced one of these adverse outcomes prior to vaccination (both preterm premature rupture of membranes).

^c Included in analyses only if patient's chart included a physician's diagnosis for chorioamnionitis, fever >100.4°F, and 2 of the following clinical findings: uterine tenderness, maternal tachycardia, fetal tachycardia, maternal leukocytosis, or foul vaginal discharge.²⁴

^d Included in analyses only if a patient's chart included a physician's diagnosis for endometritis, fever ≥100.4 °F, and at least one of the following: uterine tenderness, foul-smelling vaginal discharge, or maternal leukocytosis.²⁵

^e Model not adjusted by race/ethnicity due to small cell sizes.

^f Vaginal compared to cesarean delivery. Tdap vaccinated women were less likely to deliver by cesarean.

^g Includes: spina bifida, transposition of great arteries, tetralogy of Fallot, atrioventricular septal defect, cleft palate, cleft lip, rectal and large intestinal atresia/stenosis, reduction deformity of upper limbs, gastroschisis, and/or diaphragmatic hernia.

^h Very low birthweight not included.

NICU, Neonatal intensive care unit; AOR = adjusted odds ratio.