Pregnancy outcomes of the patients with anti-smooth muscle antibody positivity

1. Introduction

Autoimmune disorders and antibodies such as anticardiolipin, antiphospholipids (aPL) or lupus anticoagulants are known to be closely related to various gestational complications [3, 15]. Furthermore, autoimmune antibody positivity is also thought to be associated with negative pregnancy outcomes such as miscarriage, preterm birth and stillbirth [17].

Anti-smooth muscle antibody (ASMA) is formed against smooth muscle. ASMA (antibody targeting rodent stomach smooth muscle structures) was initially found in the serum of patients with lupoid hepatitis and It was frequently detected with anti-nuclear antibody positivity (ANA) [7]. ASMA is an autoantibody that is highly specific for autoimmune hepatitis and is considered as positive when the titers are 1:80 or more [4]. Apart from autoimmune hepatitis, melanoma, breast and ovarian cancers, hepatitis C infection, infectious mononucleosis and rheumatic disorders might also be related to ASMA positivity [8].

In this study, we have assumed that ASMA positivity may affect uterine smooth muscle and this might influence the gestational outcomes. We retrospectively evaluated the pregnancy outcomes of the patients with ASMA positivity compared to patients without any known autoantibody positivity and/or autoimmune diseases. We have also evaluated the obstetric outcomes of the patients with ASMA positivity in terms of MTHFR polymorphisms, other hereditery trombophilia cases and other autoantibody positivities.

2. Material and methods

This retrospective study is consisted of pregnancy outcomes of 40 patients with detected ASMA positivity within one year before subsequent pregnancy. The required data were obtained from Hacettepe University Division of Perinatology registries and electronical database of the institution for the years 2010–2017.

We included 40 ASMA positive patients that fulfill the study criteria. Forty ASMA positive pregnancy outcomes were compared to 80 control cases without any known autoantibody positivity or autoimmune disease. Pregnant women with medical history suggestive of autoimmune hepatitis were screened for ASMA at our clinic. ASMA positive group was regarded as the study group while ASMA negative group was served as the control group in this study. Patients with irregular follow-ups, any systemic disease that may affect obstetric outcome and delivered at other institutions were also excluded from the study. Pregnancies reaching 32th gestational week were included in the study in order to compare pregnancies in terms of obstetric outcomes including birthweight, gestational week at delivery and APGAR scores. Patients were also evaluated in terms of other autoimmune antibody positivities such as anti-nuclear antibody (ANA), extractable nuclear antigen (ENA), anti-double stranded DNA (antidsDNA), anti-parietal antibody (APA), anti-mitochondrial antibody (AMA), anti-thyroid peroxidase (antiTPO), anti-thyroglobulin (anti-TG) and anti-phospholipid (aPL) and MTHFR polymorphisms because these factors are also thought to be associated with adverse perinatal outcomes.

The reason is that our institution is a reference center and a tertiary university hospital, most of our patients had poor obstetric histories. After investigating the etiologic factors, patients were included in a special antenatal care program at the perinatology division of our institution. Patients were administered low-dose low-molecular-weight heparin (LMWH) (enoxaparine 1 × 2000 Anti-XA IU/0.2 mL/day), low-dose-corticosteroid (methylprednisolone 1 × 4 mg p.o/day) and low-dose non steroid anti-inflamatuar (salysilic acid, 1 × 100 mg/day).

For the laboratory analysis, 5 ml of intravenous blood sample, irrespective of fasting status was obtained from each study subject in plain tubes and serum was separated. All the samples were stored at - 20 ∘ C. ANA, APA, ASMA and AMA levels were measured with the indirect immunofluorescence method (Euroimmun ® , Lübeck, Germany) in the biochemistry laboratory.

The enzyme-linked immunosorbent assay (ELISA) method was used to determine the concentration of anti-dsDNA and aPL antibodies following the manufacturer instructions (Euroimmun ® , Lübeck, Germany). Radioimmunoassay (Thermo Scientific BRAHMS ® , Annapolis, MD, USA) determined anti-TPO levels and anti-TG antibody levels were determined by the chemiluminescence method (Immulite ® 2000, DPC, Tarrytown, NY, USA). A titer of 1/80 for ASMA was accepted positive result. A titer of 1/40 for ANA and AMA was accepted as a positive result. Levels of 40 IU/ml, 80 IU/ml, 1.1 IU/ml and 12 MPLU/ml were considered positive for anti-TG, anti-TPO, anti-dsDNA and anti-phospholipid antibodies IgG/M, respectively.

The data were evaluated via descriptive statistics and Mann Whitney u test according to case numbers and data structure. A p value lesser than 0.05 is evaluated as significant. All the statistical calculations were performed with the Statistical Package for Social Sciences (SPSS) for Windows (SPSS version 23; SPSS Inc., Chicago, IL, USA) statistical software package.

This retrospective study was approved by Hacettepe University Ethics Committee (Number: GO 18/326).

In this study, 40 ASMA positive patient were evaluated and compared with 80 control cases.

Table 1 shows the characteristics of control and ASMA positive patients and their pregnancy outcomes. Median gestational week at delivery was 38, median birthweight was 3165 gr and median APGAR scores were 9, 10 and 10 for the 1st, 5th and 10th minutes respectively.

There was a statistically significant difference between the control group and ASMA positive group in terms of birth week, birth weight and APGAR scores (Table 2). The median birth week was 37 in the ASMA positive group, whereas it was 39 weeks in the control group ( 0.01 ). In the ASMA positive group, the median birthweight was 2815 g and the control group was 3200 g ( 0.01). Despite similar median values and ranges of APGAR scores, interquartile ranges were significantly lower at patients with ASMA positivity (APGAR scores 1st, 5th, 10th respectively 0.01, 0.01, p : 0.030).

Additionally, patients with ASMA positivity were also grouped as those with MTHFR polymorphisms, other hereditary thrombophilia cases, and other autoantibody positivity. We evaluated obstetric outcomes of the cases including the birth week, birthweight and APGAR scores. The statistical analysis revealed no significant differences between each pair of groups in terms of any obstetric outcome (Table 3). Homozygous and heterozygous MTHFR polymorphisms (MTHFR 677C- $>$ T or 1298A- $>$ C mutations) were observed in 92.5 % of the ASMA positive cases.

Adverse pregnancy outcomes such as recurrent miscarriage, preterm delivery or stillbirth can occur due to many factors such as autoantibody positivities and/or autoimmune diseases [17]. Some autoantibodies such as aPL, lupus anticoagulant or anti-beta2 glycoprotein 1 were related with recurrent pregnancy loss or complications such as preeclampsia for many years and relationship between these autoantibodies and adverse outcomes are well known according to the literature [11, 16]. In addition, various autoimmune diseases have been associated with poor obstetric outcomes (SLE, Hasimoto,Behçet’s disease, Celiac) [2, 9, 12]. Existence of autoimmune diseases, autoantibody positivities and chronic inflammatory diseases are shown to trigger systemic inflammatory processes and resulting in inflammation of maternal-fetal interface of the placenta which ends up with impaired oxygenization of fetus and poor perinatal outcomes [2] . ASMA is also critical in these terms, as they are strictly related with smooth muscle related pathophysiologies [1]. The increasing mass of uterine smooth muscle during pregnancy may also evoke questions about the possible relation of this autoantibody and obstetric outcomes.

In our study, we showed that ASMA positivity is related with poorer obstetric outcomes such as gestational week at birth, birthweight and APGAR scores at 1st, 5th and 10th minutes. We have suggested that ASMA positivity may affect the uterine smooth muscle, leading to negative pregnancy outcomes such as spontaneous preterm labour or relatively low oxygenization of fetus leading to lower APGAR scores.

We have also analysed additional risk factors such as MTHFR polymorphism(s), hereditery thrombophilia(s) and positivity of other autoantibodies in terms of pregnancy outcomes. We revealed no statistically significant difference between groups in terms of these variables. Prior studies revealed that more than one autoantibody positivity was also related with poorer obstetric outcome [10]. Further studies are necessary to confirm our results.

Several studies reported that MTHFR polymorphisms and inherited/acquired thrombophilias are related to various obstetric complications and poor pregnancy outcomes [5, 14, 17, 18]. However, presence of these factors did not influence the obstetric outcomes in the ASMA positive group in our series. This fact is most possibly related to the medical treatments used in the management of these high risk pregnancies. In this study, we have found that MTHFR polymorphism(s) rate was 92.5% though we have previously reported that allelic frequencies of MTHFR 677 and 1298 mutations were 0.296 and 0.283 in high risk population in terms of thrombotic events [6, 13].

Limitations of this study is it’s retrospective design, it’s relatively small sample size and the treatment modalities used in ASMA positive patients as these patients were under a special antenatal follow-up treatment protocol which leads better outcome. On the other hand, this study is the first study focusing on pregnancy outcomes of patients with ASMA positivity.

In conclusion, ASMA positive patients may also be evaluated carefully as these pregnancies may end up with relatively lower gestational week at delivery, birthweight and APGAR scores. Further prospective studies must be carried out to confirm our results.