Data and sample
This study utilized deidentified Medicaid claims data from the South Carolina Revenue and Fiscal Affairs (SCRFA) Office for 2014–2019. Medical claims were acquired for mothers who had a live birth during the period 2015–2019 in the 12 months prior to delivery. Vital records were used to identify live births with a mom-baby linkage by the SCRFA office. Exemption for this study was obtained from the Institutional Review Board at the authors’ institute due to the secondary analysis using deidentifiable administrative data.
A total of 108,441 live births, with 2,155,076 associated claims, were found during the 2015–2018 period. Full date of birth (DOB) was not released due to privacy concerns. However, as allowed by our data use agreement, and using previously published algorithms as guidance, (17,18) month of birth was estimated by using the dates of service and International Classification of Diseases (ICD) associated with the claims and appended to SC RFA provided year of birth. Samples were delimited to those who had continuous enrollment in Medicaid for the duration of their pregnancies, resulting in 36,848 pregnancies. Among those, only 32,609 included at least one prenatal care claim in the data. Analyses were conducted at the pregnancy level.
Observed prenatal care
This study employed a series of variables to identify PNC visits from these claims. These variables included date of delivery (month/year); date of services (month/year); primary/secondary diagnosis (ICD 9/10 clinical modification (CM), Healthcare Common Procedure Coding System (HCPCS) and Current Procedural Terminology (CPT)); and provider specialty.
Delivery date and services date were used to calculate the duration from each claim to delivery, guided by the previously published algorithm(18). Claims within the gestational age were kept. PNC services were identified with procedure code, including CPT and HCPCS code, and primary diagnosis code. Details can be found in Appendix Table 1.
Table 1
Total prenatal care (PNC) visits and PNC visits at the specialty-specified provider level.
| Total PNC visit | Providers |
Provider Counts | N/A | 1,922 |
N | 32,609 | 93,712 |
Mean | 7.86 | 2.73 |
Standard deviation | 4.12 | 2.71 |
PNC > 14 (%) | 4.62 | 0.50 |
14 ≥ PNC > 8 (%) | 40.22 | 5.07 |
8 ≥ PNC > 1(%) | 48.99 | 48.51 |
PNC = 1 (%) | 6.18 | 45.92 |
Note: N/A-not applicable. |
Claims were selected by Medicaid provider specialty and type code, including midwife (06), primary care physician (12,14,19,78), Obstetrics and Gynecology specialist (16, 26, 27), organization (50-FQHC, 97-RHC), nurse practitioner (86), others (02, 10, 40, 48, 57, 94, 95, PA, missing). Specialties that were marked as missing and the supervisor’s specialties of PA (physician assistants) were unknown (0.24%). Although they only accounted for 0.05% of visits, specialties with codes of 02, 10, 40, 48, 57, 94 and 95 were kept for three reasons. First, a coded PNC visit to these specialties satisfies the three criteria of COC.(19) Second, those specialties may serve as a substitute for a traditional PNC provider given the limited access to PNC providers for some populations.(20,21) Finally, pregnancy complications may be different (22) for different women and therefore demand services from different specialties, especially when access to PNC providers is limited.
This study integrates PNC initiation, frequency of visits, and sequence of visits to inform the algorithm. Initiation refers to the provider that provided the initial visit during the pregnancy. Visit frequency at the provider level was then used to estimate the PNC fraction, that is, the percentage of PNC visits to a specific provider, given all PNC visits, for a specific pregnancy. The final PNC visit prior to birth plays a particularly important role in ensuring continuity of care during prenatal, delivery, and postpartum care, so the provider visited at the last PNC visit is considered the referrer for delivery. Therefore, the initial and last PNC visits were identified for each pregnancy.
Provider definition
To identify the predominant provider, this study constructed four categories based on the PNC fraction and sequential information: the exclusive provider (PNC(E)), the majority provider (PNC(M)), the uniquely most frequently visited (PNC(U)) providers, and the most visited providers (PNC(MFV)). The PNC(E)s are those who are the only observed provider throughout the pregnancy, with a fraction of 100%. The PNC(M)s are the providers providing more than half of PNC services for a pregnant woman, with a fraction of larger than 50% - the PNC(M) is aligned with the majority algorithm.(9) The PNC(U)s are providers providing the highest fraction within all visited provider but less than 50% for a pregnant woman - the PNC(U) is aligned with the plurality algorithm.(10) If there were multiple providers who provided equal fractions of PNC visits to a pregnant woman, they were classified as PNC (MFV). Providers who were not classified as any of these categories would not be identified as a predominant provider.
The data obtained from RFA included a unique provider identifier that may refer to a professional or a provider, whichever is applicable, enabling PNC frequency to be counted at the provider identifier level. Since different professionals may share the same provider identifier, frequency can be more accurately counted by combining specialty with this provider identifier. This study used the specialty-specified provider identifier (SSPI) to denote unique providers and calculate PNC frequency.
Different scenarios
This algorithm first counted the PNC frequency at both the pregnancy and provider levels for each pregnancy. The number of PNC providers was also counted for each pregnancy. Every PNC provider was then classified into one of five categories: PNC(E), PNC(M), PNC(U), PNC(MFV) and PNC (non-MFV). The predominant provider was identified initially as PNC(E) through PNC(MFV) as shown in Fig. 1. In the initial scenario, the PNC(E) provider was identified as the predominant provider. Both PNC(E) and PNC(M) were identified as the predominant provider in the second scenario. Beyond PNC(E) and PNC(M), PNC(U) was identified as the predominant provider in the third scenario. The PNC(MFV) was further included as the predominant provider in the fourth, fifth and sixth scenarios. (see Appendix Table 2)
Table 2
The percentage of providers for a pregnant woman at the specialty specified provider level.
Percentage | Definition | Providers |
PNC provider counts | All PNC providers | 2.87 |
PNC(E) | Fraction = 100% | 28.40 |
PNC(M) | Fraction (50%, 100%) | 19.55 |
PNC(U) | Largest fraction (N = 1) | 33.49 |
PNC(MFV) | Largest fraction (N > 1) | 18.55 |
Dispersal PNC(MFV) | Largest fraction & COC = 0 | 7.12 |
PNC(MFVI) | Largest fraction & 1st visit | 7.31 |
PNC(MFVF) | Largest fraction & last visit | 3.06 |
PNC(MFVIF) | Largest fraction, 1st & last visit | 1.42 |
2 | Largest fraction (N = 2) | 12.18 |
3 | Largest fraction (N = 3) | 3.87 |
4 | Largest fraction (N = 4) | 1.41 |
5 | Largest fraction (N = 5) | 0.63 |
6 | Largest fraction (N = 6) | 0.29 |
7 | Largest fraction (N = 7) | 0.12 |
8 | Largest fraction (N = 8) | 0.03 |
9 | Largest fraction (N = 9) | 0.02 |
10 | Largest fraction (N = 10) | 0.00 |
11 | Largest fraction (N = 11) | 0.00 |
Note: n = 32,609. NA-not applicable. PNC(E) – The exclusive PNC provider for one pregnancy. PNC(M) – this provider served more than half of all visits for one pregnancy. PNC(U) – the uniquely most frequently visited provider, who is the only one who served the most visits for a patient (the percentage of this category equals that of PNC(MFV) at count level 1). PNC(MFV) – most frequently visited provider, who served the most visits for a patient. PNC(MFVI) - most frequently visited provider, who served the most visits and the first visit for a patient. PNC(MFVF) - most frequently visited provider, who served the most visits and the last visit for a patient. PNC(MFVIF) - most frequently visited provider, who served the most visits, first and the last visits for a patient. Dispersal PNC (MFV): the number of total PNC visits equals the number of total providers. COC: continuity of care index. |
As pregnant women may utilize additional providers that differ from the initial provider accessed during their pregnancy(23), different providers may cover different gestation periods for different women. For example, some of the most visited providers may serve the early pregnancy period, while others may serve later terms. In the early visit (fourth) scenario, the PNC(MFV) provides the initial visit, defined as PNC(MFVI). In the late visit (fifth) scenario, the PNC(MFV) provides the final visit, defined as PNC(MFVF). In the hybrid (sixth) scenario, the PNC(MFV) provides the initial or the final visits. Therefore, PNC(MFV)s in different scenarios may provide care for different needs. The PNC(MFVI) in the early scenario may be associated with PNC initiation, while the PNC(MFVF) in the late scenario may be associated with actual delivery. The PNC(MFV) in the hybrid scenario may be associated with either or both needs. If there is a tie between PNC(MFVI) and PNC(MFVF), this algorithm gave priority to PNC(MFVI) because APNCU listed PNC initiation as one major measurement. (16) The algorithm developed here will include all three scenarios for the PNC(MFV). The percentage of pregnant women with a predominant provider was reported for all six scenarios.
A special case occurs when a pregnant woman visits a different provider at each PNC visit. That means that the number of total visits equals the number of providers. The dispersed nature of all visits makes the first and last visits contain no meaningful sequential information. The predominant provider cannot be reasonably identified under such a situation. Predominant providers could not be identified for those pregnancies.
Application example with travel distance
The results of this algorithm were then applied to examine travel distance differences between the nearest PNC provider and the identified predominant PNC provider. For simplicity, this was delimited to visits that occurred within the state boundaries. Distance was estimated using Google Maps, which calculated the distance from the pregnant woman’s zip-code of residence to the provider’s billing zip-code, measured as centroid to centroid. In cases where the zip-codes were the same, the radius of the zip-code area was estimated using the formula area = π r2, where the zip-code area was acquired from the 2010 census. A paired t test was used to compare the travel distances between the two provider types. All analyses were performed using SAS software version 9.4 (SAS Institute Inc., Cary, NC) at a significance level of 95%.