Which factors affect neonatal outcome? Impact of time of birth, maternity units' volume and staff's experience level on the neonatal outcome of deliveries

Background:

Evidence regarding the impact of hospital structures on neonatal outcome remains controversial. Various risk factors possibly influencing the perinatal outcome during nights and weekend were discussed previously. Reduced staff size and limited availability of services during off-hours were associated with the highest incidence in obstetric adverse events. However, this evidence is not unchallenged, since other studies report no impact of the time point of birth on perinatal outcome. The aim of this study was to evaluate the possible impact of time point of birth, delivery volume of the maternity units and educational level of the attending medical staff during delivery on adverse neonatal outcome.

Methods:

For this population-based observational study perinatal data from all public obstetric departments in the region of Styria between 01/01/2004 and 31/12/2015 were prospectively gathered. Intrapartum and early neonatal information was used to create a composite „adverse outcome” and a „severe adverse outcome” measure. The study population was divided into two groups with deliveries ≥34+0 weeks of gestation and < 34+0 weeks of gestation. Generalized Linear Mixed Models (GLMM) with logit link were used for statistical analysis.

Results:

104,452 (98.1%) neonates belonging to the group with a gestational age of ≥34+0 weeks and 1,978 (1.86%) infants of < 34+0 weeks were included in the study. In the group ≥34+0 weeks of gestation 3,466 cases (4.8%) showed adverse and 423 cases (0.6%) severe adverse neonatal outcome. Odds ratio for adverse events during off-hours is 1.1 (p = 0.023) and for severe adverse events 1.49 (p < 0.001). The maternity unit volume was only relevant for adverse outcome measures. In < 34+0 weeks of gestation group only the severe adverse outcome measure was calculated, leading to 38 (4.4%) cases of severe adverse neonatal outcome. Only gestational age turned out to be of significant impact in the preterm group (OR 0.57, p < 0.001). Detailed results of the GLMM analysis are shown in table 1.

Conclusion:

This study demonstrates an impact of the time of birth on the neonatal short-term outcome. There was a higher number of cases with severe adverse and with adverse outcome during off-hours compared to standard office-hours for pregnancies ≥34+0 weeks' gestation. This effect appears to be based more on the reduced personnel coverage during off-hours than on fatigue of the attending midwives and doctors, as we could not see differences between daytime-off-hours and nighttime. In contrast to prior reports we detected more cases of adverse outcome with increasing seniority of the obstetricians attending deliveries. This might be surprising at first sight, but proves that the system is working properly and staff awareness for impending, sometimes unavoidable, neonatal adverse events leads to involvement of more experienced staff members.

Tab. 2: Factors impacting adverse and severe adverse outcome in pregnancies with a gestational age ≥34+0 weeks in the GLMM. * category excluded during GLMM analysis due to non-significance.

	adverse outcome		severe adverse outcome
	odds ratio	p	odds ratio	p
Mode of delivery
Spontanous delivery	1 (ref)		1 (ref)
Vacuum extractor	1.57	< 0.001	2.50	< 0.001
Sec. Caesarean section	2.13	< 0.001	3.58	< 0.001
Breech delivery	1.71	0.143	3.82	0.064
Forceps	2.57	< 0.001	4.97	< 0.001
Induction/augementation of labor
No	1 (ref)		1 (ref)
Yes	1.34	< 0.001	1.40	0.003
Fetal gender
Male	1 (ref)		*
Female	0.79	< 0.001
Singleton/multiple preg.
Singleton	1 (ref)		*
Multiple	1.64	< 0.001
Parity
Primipara	1 (ref)		*
Multipara	0.86	< 0.001
Analgesics
None	1 (ref)		1 (ref)
i.v. analgesics	1.12	0.006	1.23	0.059
Epidural anesthesia	0.95	0.436	0.50	< 0.001
Time of delivery
Standard office-hours	1 (ref)		1 (ref)
Off-hours (3 p.m. – 7:30 a.m.)	1.10	0.023	1.49	0.001
Staff attending delivery
Resident	1 (ref)		1 (ref)
Midwife	0.68	0.039	0.35	0.142
Intern/GP	0.84	0.011	0.64	0.054
Consultant	1.36	< 0.001	1.86	< 0.001
Units delivery volume
500 – 1000 deliveries/year	1 (ref)		*
< 500 deliveries/year	1.15	0.415
> 1000 deliveries/year	1.10	0.695
Tertiary perinatal center	1.91	< 0.001

No conflict of interest has been declared by the author(s).