Family Nurse Partnership evaluation: methods and process

5. Results

5.1. Application process 

Applications were made to PBPP and EAS and approved on 21^st Dec 2016 and 28^th October 2016 respectively. The EAS application was submitted, considered and approved within 1 month. The PBPP application was submitted 30^th September 2016, considered at Tier 1 on 2^nd November 2016 (comments responded to on 16^th November 2016); Tier 2 approval granted 21^st December 2017 (~2.5 months). Two additional amendments were then submitted. The first on 21^st April 2017, following the addition of data fields and sources, with approval given 12^th June 2017. The second amendment on 1^st March 2018, extended the project duration and added data fields and sources, with final approval on 1^st May 2018.

5.2. Population 

5.2.1. FNP Clients 

Identifiers for FNP Clients from the ten HB areas were sent from FNP SIS and pilot data were extracted separately from Lothian systems. FNP Clients who had transferred from one FNP area to another were kept in their originally assigned site. Where an FNP Client had enrolled into FNP more than once, the first episode was discarded and the more recent one included. These accounted for very small numbers.

Figure 3 shows the flow chart of the FNP Clients. A total of 3,277 FNP Clients were received by eDRIS from FNP SIS. Of these, six Clients were excluded (0.2%) and 3271 (99.8%) were eligible to be linked with the SMR02 maternity record. A total of 48 women could not be linked to the SMR02; 23 were missing an SMR02 record indicating that the CHI number was not present in the SMR02 dataset (possibly due to inaccuracies in CHI number) and 25 without a delivery record. 3,223 cases with a delivery record (live or stillbirth) remained and were imported alongside their maternal characteristics data into the eDRIS portal to be considered for inclusion in the evaluation. 

Further data cleaning found an additional 18 women who were not eligible for FNP based on the fields in either the FNP SIS or the SMR02 dataset. 11 women were recorded as greater than 19 years of age at enrolment into FNP (from FNP SIS). Seven women were found to be outside the gestation criteria of 28⁺⁶ weeks. 3,205 FNP Clients (97.8% of the initial cohort) remained for analysis. Comparison of age at LMP between the two data sources for FNP Clients showed some small discrepancies with a median age of 18.4 years (SMR02) vs 18.1 years (FNP SIS) but a high correlation between the two (r = 0.862, p<0.001) (Table 9). Age at booking/enrolment was also very similar. Gestation at enrolment in to FNP was on average nearly seven weeks after the gestation at booking with the FNP Clients and this is to be expected. 

All eligibility criteria based on SMR02 fields had no or very low missing data, demonstrating that the SMR02 fields are robust enough to identify Controls. 

Table 9: Comparison of SMR02 vs FNP SIS datasets for FNP Clients

	Data source
	SMR02 N=3,205	FNP SIS N=3,205
Age at LMP (years)
Mean (sd)	18.30 (1.41)	17.91 (1.28)
Median (25th to 75th centiles)	18.4 (17.3 to 19.3)	18.1 (17.0 to 19.0)
Gestation (weeks)	at booking N=3,200	at enrolment into FNP N=3,205
Mean (sd)	10.82 (6.37)	17.84 (4.24)
Median (25th to 75th centiles)	10.0 (8.0 to 12.0)	16.7 (15.0 to 20.1)
Age (years)	at booking N= 3,205	at enrolment into FNP N=3,205
Mean (sd)	18.14 (1.22)	18.23 (1.29)
Median (25th to 75th centiles)	18.3 (17.2 to 19.2)	18.4 (17.3 to 19.2)

5.2.2. Controls (eDRIS)

eDRIS identified a total of 31,906 potential women whose age at delivery was ≤20 years from the  period 1st January 2008 to 31st March 2016 based on SMR02 fields (Figure 3). From this figure 3,515 women were identified as being FNP Clients, 19 without a unique patient identifier, and the remainder of reasons were due to being outside the eligibility inclusion criteria. 

After deleting Controls found to be in the recruiting period (2,214) and those with a booking date more than one year pre or post the recruiting periods (n=13,175), 5,227 Controls remained. A further 211 were identified with a gestation at enrolment >28⁺⁶ week, leaving 5016 controls for the evaluation. 

Figure 3: Flow of eligible FNP Clients and potential Controls 

5.2.2.1 Maternal characteristics

Table 10 describes the maternal characteristics of the FNP Clients and the Controls identified from the 1-year pre and post recruitment periods and within intervals where recruiting stopped and also the standardised differences between FNP Clients and the Controls. Of the data requested, the education and social care data were not available. Imbalance between the FNP Clients and Control group can be observed in some maternal characteristics such as ethnicity, dispensing of medication for asthma and depression, age and gestation at booking. FNP Clients were on average younger (recorded at booking) and had a lower gestation at booking when compared to the Control population. However, age at last menstrual period was comparable (18.30 vs 18.22 years respectively). FNP also appear to recruit a higher proportion of white women (87.6% vs 78.7% respectively), with a higher proportion of drug misuse, and dispensing for asthma and depression. 

Table 10: Maternal characteristics All results are n(%) unless otherwise stated

	FNP Clients N=3,205		Controls N=5,016
Health board of residence
NHS Ayrshire/ Arran	227	7.1	483	9.6
NHS Borders	24	0.8	42	0.8
NHS Fife	380	11.9	450	9.0
NHS Forth Valley	100	3.1	263	5.2
NHS Grampian	93	2.9	172	3.4
Greater Glasgow and Clyde	404	12.6	1391	27.7
NHS Highland	100	3.1	197	3.9
Lanarkshire	250	7.8	722	14.4
Edinburgh	895	27.9	862	17.2
NHS Tayside	732	22.8	434	8.7
Missing	0	0	0	0
Ethnicity
White	2,724	87.6	3,573	78.7
Other	384	12.4	969	21.3
Missing	97	3.0	474	9.4
Scottish Index of Multiple Deprivation Quintile
1 - most deprived	1,532	47.9	2,478	49.4
2	821	25.7	1,221	24.3
3	441	13.8	643	12.8
4	264	8.3	459	9.2
5 least deprived	140	4.4	215	4.3
Missing	7	0.02	0	0
Age at last menstrual period (LMP) (years) (SMR02)
Mean (SD)	18.30 (1.41)		18.22 (1.23)
Median (25th to 75th centiles)	18.4 (17.3 to 19.3)		18.4 (17.4 to 19.2)
Missing	0	0	0	0
Age at antenatal booking (years) (SMR02)
Mean (SD)	18.14 (1.22)		18.45 (1.22)
Median (25th to 75th centiles)	18.3 (17.2 to 19.2)		18.7 (17.6 to 19.5)
Missing	0	0	0	0
Gestation at antenatal booking (weeks) (SMR02)
Mean (sd)	10.86 (6.25)		11.53 (4.69)
Median (25th to 75th centiles)	10.0 (8.0 to 12.0)		11.0 (8 to 13)
Missing	9	0.3	0	0
Body mass index (BMI) (kg/m2) at antenatal booking
Mean (SD)	23.94 (5.0)		24.3 (5.1)
Median (25th to 75th centiles)	22.9 (20.4 to 26.4)		23.2 (20.6 to 27.0)
Missing	51	1.6	483	9.6
BMI category at antenatal booking
Underweight	259	8.2	325	7.2
Healthy	1840	58.3	2585	57.0
Overweight	680	21.6	1005	22.2
Obese	375	11.9	618	13.6
History of smoking during pregnancy
No	1,891	61.4	3,036	64.3
Yes	1,191	38.6	1,684	35.7
Not known/missing	123	3.8	299	6.0
Smoking history at antenatal booking
Never smoked, non-smoker/former smoker	1,856	59.1	3,000	62.9
Never smoked, non-smoker	1,254	39.1	2,212	46.4
Former smoker	602	18.8	788	16.5
Current smoker	1,285	40.9	1,767	37.1
Not known/Missing	64	2.0	249	5.0
Drug misuse at any time during the current pregnancy
No	2,788	94.7	3,768	96.8
Yes	156	5.3	123	3.2
Not known/Missing	260	8.1	1,125	22.6
Ever injected illegal drugs
No	2,927	99.8	3,856	99.7
Yes (during /prior to current pregnancy / yes but not know when)	7	0.2	13	0.3
Not know/Missing	270	8.4	1,147	22.0
Number of units of alcohol consumed in the course of a typical week at antenatal booking
None	2897	94.9	4174	95.4
At least one unit	156	5.1	203	4.6
Missing	152	4.7	639	12.7
Patient has diabetes or not
Yes (pre-existing, gestational, time of diagnosis unknown)	43	1.4	48	1.0
No (no diabetes during this pregnancy)	3,119	98.6	4,836	99.0
Unknown/Missing	43	1.3	132	2.6
Ever dispensed medication for asthma
No	2,504	78.1	4,431	88.3
Yes	701	21.9	585	11.7
Missing1	0	0	0	0
Ever dispensed medication for depression
No	2,614	81.6	4,598	91.7
Yes	591	18.4	418	8.3
Missing	0	0	0	0
Previous pregnancy
No	2,350	74.0	3,716	74.1
Yes	827	26.0	1,296	25.9
Missing	28	0.9	4	0.1
Births
Singleton	3,184	99.3	4,989	99.5
Multiple (2+ births)	21	0.7	27	0.5
Missing	0	0	0	0
Total Babies	n=3,227		n=5,043
Outcome
Live births	3,210	99.5	5,010	99.3
Still births	17	0.5	33	0.7

1. Women with no medication flag were not linked to medications data and thus are assumed not to have any medication

5.2.2.2 Missing data

Table 11 shows the completeness of the variables used to describe the maternal characteristics. The dataset provided had a higher degree of missing data than anticipated in 11 important maternal characteristics (possibly associated with outcomes in the evaluation e.g. smoking, drug use, BMI, alcohol use, ethnicity etc.) thus rendering the propensity score matching method as unusable.

Table 11: Completeness of maternal characteristic variables

Variable	N	Categorised as ‘Not known’	Missing (%)
Exposure (FNP/Control)	11,638	0	0
Health Board of residence	11,638	0	0
SIMD quintiles (least to most deprived)	11,631	0	7 (0.06%)
Ethnicity (White/Other)	10,469	0	1,169 (10.0%)
Age at booking (SMR02 only) (years)	11,638	0	0
Age at LMP (SMR02 only) (years)	11,638	0	0
Gestation at booking (SMR02 only) (weeks)	11,629	0	9 (0.09%)
BMI (kg/m2) at booking	10,580	0	1,058 (9.1%)
History of smoking during pregnancy	11,002	636 (5.5%)	0
History of smoking recorded at booking	11,135	496 (4.3%)	0
Drug misuse (yes/no)	9,664	1,872 (16.1%)	102 (1.0%)
Injected (yes/no)	9,625	1,910 (16.4%)	103 (1.0%)
Alcohol or not (yes/no)	10,276	0	1,362 (11.7%)
Diabetes (yes/no)	11,385	253 (2.2%)	0
Asthma meds (yes/no)	11,638	0	0
Antidepressant (yes/no)	11,638	0	0
Previous pregnancy (yes/no)	11,601	0	37 (0.3%)
Births (singleton/multiple)	11,638	0	0
Outcome of birth (live/still)	11,638	0	0

5.3. Controls offered FNP but not enrolled or not offered FNP

Table 12 shows selected characteristics for women who were eligible for FNP but did not enroll in the FNP programme compared to women who did enroll (FNP Clients) and Controls. Women who were offered FNP but not enrolled appeared to be more likely to be of ethnic background, a non-smoker and less likely to misuse drugs. All other characteristics such as deprivation profile, age at last menstrual period, BMI and rate of previous pregnancy were comparable.    

Table 12: Controls offered FNP but not enrolled or not offered FNP

	FNP Clients N=3,205		Controls N=5,016		Women offered FNP but not enrolled or not offered FNP N=2,214
Ethnicity
White	2,724	87.6	3,573	78.7	1,733	78.3
Other	384	12.4	969	21.3	360	16.3
Missing	97	3.0	474	9.4	121	5.5
Scottish Index of Multiple Deprivation Quintile
1 - most deprived	1,532	47.9	2,478	49.4	992	44.8
2	821	25.7	1,221	24.3	588	26.6
3	441	13.8	643	12.8	316	14.3
4	264	8.3	459	9.2	214	9.7
5 least deprived	140	4.4	215	4.3	101	4.6
Missing	7	0.02	0	0	3	0.1
Age at last menstrual period (LMP) (years) (SMR02)
Mean (SD)	18.30 (1.41)		18.22 (1.23)		18.4 (2.20)
Median (25th to 75th centiles)	18.4 (17.3 to 19.3)		18.4 (17.4 to 19.2)		18.7 (1.7)
Missing	0	0	0	0	0	0
Body mass index (BMI) (kg/m2) at antenatal booking
Mean (SD)	23.94 (5.0)		24.3 (5.1)		24.4 (5.1)
Median (25th to 75th centiles)	22.9 (20.4 to 26.4)		23.2 (20.6 to 27.0)		23.3 (6.3)
Missing	51	1.6	483	9.6	87	3.9
Smoking history at antenatal booking
Never smoked, former smoker	1,856	59.1	3,000	62.9	1,389	62.7
Never smoked	1,254	39.1	2,212	46.4	1,048	47.3
Former smoker	602	18.8	788	16.5	341	15.4
Current smoker	1,285	40.9	1,767	37.1	739	33.4
Not known/Missing	64	2.0	249	5.0	86	3.9
Drug misuse at any time during the current pregnancy
No	2,788	94.7	3,768	96.8	1,866	84.3
Yes	156	5.3	123	3.2	59	2.7
Not known/Missing	260	8.1	1,125	22.6	289	13.1
Previous pregnancy
No	2,350	74.0	3,716	74.1	1,656	74.8
Yes	827	26.0	1,296	25.9	555	25.1
Missing	28	0.9	4	0.1	3	0.1

5.4. Final cohort

Consistent with our commitment to minimum processing by using only those Controls that are required, we will only use the Controls identified within one year pre and post recruitment and in the interval period. This means that we would require outcome data on 3,205 FNP Clients and 5,016 Controls (approximately a 1:1.56 ratio) mothers for this evaluation and we should expect data on 3227 and 5043 children respectively.