Utilization of fetal fibronectin testing and pregnancy outcomes among women with symptoms of preterm labor

Figures & data

Figure 1 Schematic of study design.

Abbreviations: dx, diagnosis; ELD, labor and delivery; PTL, preterm labor.

Figure 2 Study cohort identification.

Abbreviations: ELD, labor and delivery; PTL, preterm labor.

Table 1 Baseline characteristics of study cohort

Measure	Value
Overall	23,062
Age group, years (column %)
≤20	3,060 (13.3)
21–25	6,929 (30.1)
26–30	6,425 (27.9)
31–35	4,517 (19.6)
≥36	2,131 (9.2)
Age
Mean, SD	27.1 (5.9)
Geographic region (column %)
Midwest	4,520 (19.6)
Northeast	7,888 (34.3)
West	2,327 (10.1)
South	8,276 (36.0)
Insurance coverage (column %)
Managed Medicaid	14,094 (61.1)
Commercial	4,423 (19.2)
Commercial and managed Medicaid coverage	2,206 (9.6)
Other	2,339 (10.1)
Comorbid conditions (%)
Hypertension	1,889 (8.2)
Comorbid diabetes	1,035 (4.5)
Gestational diabetes	2,583 (11.2)
Cervical incompetence	76 (0.3)
Resource utilization
Number of physician visits (all cause; %)
0	2,777 (12.0)
1–5	7,252 (31.5)
6–10	5,293 (23.0)
11–15	4,304 (18.7)
16–20	2,075 (9.0)
≥21	1,361 (5.9)
Any transvaginal ultrasound prior to delivery (%)	4,953 (21.5)

Figure 3 Prenatal fFN by type of insurance.

Abbreviation: fFN, fetal fibronectin.

Figure 4 ELD triage status, timing of infant delivery and use of fFN testing.

Abbreviations: ELD, labor and delivery; fFN, fetal fibronectin.

Table 2 Predictors of fetal fibronectin testing

Measure	Odds ratio	95% CI
Overall
Age group (ref group: ≤20 years)
21–25	0.95	0.83–1.09
26–30	0.98	0.85–1.12
31–35	0.89	0.77–1.04
≥36	0.88	0.73–1.05
Geographic region (ref group: South)
Midwest	0.93	0.82–1.05
Northeast	0.44	0.39–0.49
West	1.16	1.01–1.32
Insurance coverage (ref group: commercial)
Managed Medicaid	0.94	0.83–1.07
Managed Medicaid and commercial	1.09	0.93–1.28
Other/unknown	1.15	0.95–1.38
Baseline comorbidities
Cervical incompetence (ref group: No)	1.00	0.57–1.76
Hypertension (ref group: No)	1.05	0.91–1.21
Comorbid diabetes (ref group: No)	1.04	0.85–1.27
Gestational diabetes (ref group: No)	1.06	0.93–1.22
Resource utilization
Number of physician visits (ref group: 6–10)
None	1.10	0.95–1.28
1–5	0.93	0.82–1.05
11–15	1.36	1.20–1.55
16–20	1.88	1.61–2.18
≥21	2.93	2.50–3.44
Any transvaginal ultrasound prior to delivery (ref group: No)	2.32	2.12–2.53

Figure 5 Sensitivity analysis: fFN and TVUS testing and time to delivery among patients discharged from ELD (N=17,512).

Note: Sensitivity analysis: fFN and TVUS testing among patients discharged from ELD who delivered within 3 days (N=17,512).
Abbreviations: ELD, labor and delivery; fFN, fetal fibronectin; TVUS, transvaginal ultrasound.

Table S1 Diagnosis and DRG codes for preterm labor

Code	Code description
ICD-9-CM diagnosis	Threatened PTL
644	Early or threatened labor
644.0	Threatened premature labor
644.00	Threatened premature labor, unspecified as to episode of care or not applicable (N/A)
644.01	Threatened premature labor delivered, with or without mention of antepartum condition
644.03	Threatened premature labor, antepartum condition or complication
644.1	Other threatened labor
644.10	Other threatened labor, unspecified as to episode of care or N/A
644.13	Other threatened labor, antepartum condition or complication
MS-DRG^*
780	False labor
APR-DRG^*
565-1 to 565-4	False labor
ICD-9-CM diagnosis	Actual PTL
644.2	Early onset of delivery
644.20	Early onset of delivery, unspecified as to episode of care or N/A
644.21	Early onset of delivery, delivered, with or w/o mention of antepartum condition

Abbreviations: DRG, diagnosis-related group; PTL, preterm labor; ICD-9-CM; International Classification of Diseases, Ninth Revision, Clinical Modification; APR-DRG, All Patient Refined- Diagnosis Related Group; MS-DRG, Medicare Severity- Diagnosis Related Group.

Table S2 Diagnosis codes for exclusion criteria

ICD-9-CM diagnosis	Code description
642.4	Mild or unspecified preeclampsia
642.5	Severe preeclampsia
642.6	Eclampsia complicating pregnancy childbirth or the puerperium
642.7	Preeclampsia or eclampsia superimposed on preexisting hypertension
658.1	Premature rupture of membranes
640.0	Threatened abortion
640.00	Threatened abortion, unspecified as to episode of care or not applicable
640.01	Threatened abortion, delivered, with or without mention of antepartum condition
640.03	Threatened abortion, antepartum condition or complication
MS-DRG
778	Threatened abortion
APR-DRG
563-1 to 563-4	Threatened abortion
Infections
647.30	Tuberculosis of mother, complicating pregnancy, childbirth or the puerperium, unspecified as to episode of care or not applicable
647.31	Tuberculosis of mother, complicating pregnancy, childbirth or the puerperium, delivered, with or without mention of antepartum condition
647.32	Tuberculosis of mother, complicating pregnancy, childbirth or the puerperium, delivered, with mention of postpartum complication
647.33	Tuberculosis of mother, complicating pregnancy, childbirth or the puerperium, antepartum condition or complication
647.34	Tuberculosis of mother, complicating pregnancy, childbirth or the puerperium, postpartum condition or complication
647.40	Malaria in the mother, unspecified as to episode of care or not applicable
647.41	Malaria in the mother, delivered, with or without mention of antepartum condition
647.43	Malaria in the mother, antepartum condition or complication
647.50	Rubella in the mother, unspecified as to episode of care or not applicable
647.51	Rubella in the mother, delivered, with or without mention of antepartum condition
647.53	Rubella in the mother, antepartum condition or complication
647.60	Other viral diseases in the mother, unspecified as to episode of care or not applicable
647.61	Other viral diseases in the mother, delivered, with or without mention of antepartum condition
647.63	Other viral diseases in the mother, antepartum condition or complication
647.80	Other specified infectious and parasitic diseases of mother, unspecified as to episode of care or not applicable
647.81	Other specified infectious and parasitic diseases of mother, delivered, with or without mention of antepartum condition
647.83	Other specified infectious and parasitic diseases of mother, antepartum condition or complication
647.90	Unspecified infection or infestation of mother, unspecified as to episode of care or not applicable
647.91	Unspecified infection or infestation of mother, delivered, with or without mention of antepartum condition
647.93	Unspecified infection or infestation of mother, antepartum condition or complication
655.30	Suspected damage to fetus from viral disease in the mother, affecting management of mother, unspecified as to episode of care or not applicable
655.31	Suspected damage to fetus from viral disease in the mother, affecting management of mother, delivered, with or without mention of antepartum condition
655.33	Suspected damage to fetus from viral disease in the mother, affecting management of mother, antepartum condition or complication
655.40	Suspected damage to fetus from other disease in the mother, affecting management of mother, unspecified as to episode of care or not applicable
Other complications
655.41	Suspected damage to fetus from other disease in the mother, affecting management of mother, delivered, with or without mention of antepartum condition
655.43	Suspected damage to fetus from other disease in the mother, affecting management of mother, antepartum condition or complication
655.80	Other known or suspected fetal abnormality, not elsewhere classified, affecting management of mother, unspecified as to episode of care or not applicable
655.81	Other known or suspected fetal abnormality, not elsewhere classified, affecting management of mother, delivered, with or without mention of antepartum condition
655.83	Other known or suspected fetal abnormality, not elsewhere classified, affecting management of mother, antepartum condition or complication
646.80	Other specified complications of pregnancy, unspecified as to episode of care or not applicable
646.81	Other specified complications of pregnancy, delivered, with or without mention of antepartum condition
646.83	Other specified complications of pregnancy, antepartum condition or complication
646.90	Unspecified complication of pregnancy, unspecified as to episode of care or not applicable
646.91	Unspecified complication of pregnancy, delivered, with or without mention of antepartum condition
646.93	Unspecified complication of pregnancy, antepartum condition or complication
752.35	Uterine septum
740–759	Congenital anomalies
764.9	Intrauterine growth retardation

Abbreviations: DRG, diagnosis-related group; PTL, preterm labor.

Table S3 ICD-9 Diagnosis codes for comorbid conditions

Condition	Code type	Code set
Cervical incompetence	ICD 9 CM	622.5x
Hypertension	ICD 9 CM	401.xx, 405.xx, 642.0x, 642.2x, 642.3x
Gestational diabetes	ICD 9 CM	648.80, 648.81, 648.82, 648.83, 648.84
Comorbid diabetes	ICD 9 CM	250.xx, 648.0x