Reliability of recurrent pregnancy loss diagnosis coding in the Swedish National Patient Register: a validation study

Figures & data

Figure 1 Flowchart of women diagnosed with recurrent pregnancy loss in the national patient register and validated with medical records.

Table 1 Validation of RPL diagnosis in medical records, randomly selected from women diagnosed with RPL in the NPR

Diagnoses in medical records	Number of cases, n	Positive predictive value % (95% CI)
Total medical records reviewed	238
3 consecutive miscarriages	202	85 (80–89%)
Incorrect diagnoses	36	–
– 3 non-consecutive miscarriages	7
– Only 2 miscarriages	16
– 1 of the 3 miscarriages was a IUFD (>gw.22)	4
– 1 of the 3 miscarriages was a termination of pregnancy because of chromosome abnormality	1
– 1 or 0 miscarriages	7
– Other reason	1

Abbreviations: RPL, recurrent pregnancy loss; ICD, International Classification of Diseases; NBHW, National Board of Health and Welfare (responsible for the NPR); NPR, national patient register; IUFD, intrauterine fetal demise; gw, gestational week.

Table 2 Women with correct diagnosis of recurrent pregnancy loss and pregnancy variables

Variables	Number of women (%) (Total n: 202)
Method for verifying pregnancy
All three pregnancies verified by ultrasound	120 (59)
One or more pregnancies only verified by hCG measurement	70 (35)
Unknown	12 (6)
Conception method
3 spontaneous	186 (92)
2 spontaneous +1 IVF	5 (2.5)
2 or 3 IVF	11 (5.5)
Possible cause of RPL
Uterine malformation	5 (2.5)
Uterine septae	11 (5.5)
Uterine fibroma	3 (1.5)
Uterine polyp	3 (1.5)
Uterine synechiae	5 (2.5)
Hypothyroidism	7 (3.5)
Parental chromosomal translocation	8 (4)
Antiphospholipid syndrome (positive anticardiolipin antibodies or lupus anticoagulant)	5 (2.5)
Cervical insufficiency	1 (0.5)
Thrombophilia	4 (2)
None found	100 (50)
Not examined	49 (24)
RPL
Primary	111 (55)
Secondary	88 (44)
Tertiary	1 (0.5)
Inconclusive	2 (1)

Abbreviations: hCG, human choriogonadotropin; IVF, in vitro fertilization; RPL, recurrent pregnancy loss; Primary RPL, no children before recurrent miscarriages; Secondary RPL, childbirth before recurrent miscarriages; Tertiary RPL, recurrent pregnancy loss with childbirth after and subsequently again recurrent pregnancy loss.