Introduction

Preeclampsia has particular importance since it is considered as one of the causes of maternal and fetal mortality and it is the main cause of hospitalization and preterm delivery¹. Early diagnosis of preeclampsia is one of the most important functions of prenatal care. With early diagnosis of this disease, maternal and fetal mortality rate decreases². No definitive method has yet been proven to diagnose this disease, and there is still no reliable criterion for early diagnosis of preeclampsia. There are several clinical, biophysical and biochemical tests to identify women at risk for preeclampsia. The results of recent studies suggested the negligible predictive value of them in early diagnosis of preeclampsia³.A few studies have been conducted on the level of thyroid-stimulating hormone and preeclampsia, but it is predicted that there is a correlation between preeclampsia and thyroid function⁴. Given what was stated above, this study was conducted to compare the serum levels of thyroid-stimulating hormone in preeclampsia and non-preeclampsia pregnant women and the use of thyroid-stimulating hormone as a predictive factor in preeclampsia.

Materials and methods

This study was a case-control study. Convenience sampling method was used in this study and the sample size was measured based on comparing two means using the G power 3.1.2 software. According to α =0.05 (first type error), β =0.2 (second type error) and d =0.6 (effect size), 90 pregnant women in the third trimester of pregnancy referred to Kamali Hospital of Karaj were selected. According to the scientific criteria in the obstetrics and gynecology references, they were divided into two groups of 45 preeclampsia pregnant women and non-preeclampsia pregnant women (each group included 45 women). Diagnosis of the patient group was performed by a gynecologist based on the following criteria: pressure greater than or equal to 140 / 90 mmHg (two times at time interval of at least 6 hours), protein excretion in urine more than or equal to + 1 in a random sample of urine and the presence of non-gravity dependent edema. The control group included healthy pregnant women who referred to one of the obstetric clinics for follow-up during pregnancy and had none of the signs and symptoms of pregnancy toxicity. The research exclusion criteria included the occurrence of any of hypothyroidism diseases, Graves, autoimmune thyroiditis, chronic blood pressure, thyroid nodule toxicity, kidney diseases, use of drugs affecting the thyroid function such as levothyroxine and anti-thyroid drugs, blood pressure-lowering drugs, blood sugar-lowering drugs, corticosteroids, diuretics and other drugs, such as amiodarone and lithium. In this study, 10 ml of venous blood was taken from each patient (control or patient) before delivery and serum TSH level was measured in both groups. Data were also collected through biographies, clinical examination, completion of the questionnaire and recording of the results of laboratory tests. The questionnaire contained personal and medical history including pregnancy status and signs and symptoms of preeclampsia.

Finally, the collected data were analyzed using SPSS, version 22, software and Student T-test. For more statistical tests, Chi-square, T-test and Mann-Whitney tests were used. P-values ​​ less than 5% were considered significant. The results were presented as mean ± standard deviation and number (percent).

Results

In this study, 45 healthy pregnant women without preeclampsia and 45 pregnant women with preeclampsia referring to the obstetric department of Kamali Hospital in Karaj were examined according to inclusion criteria from March to September 2018. The mean age of non- preeclampsia pregnant women was 29.2±0.61 and the mean age of preeclampsia pregnant women were 28.1±5.7 years, which did not show a significant difference (P=0.76). The mean gestational age in healthy women (non-preeclampsia pregnant women) was 39±1.32 weeks and mean gestational age in preeclampsia pregnant women was 37±1.95 weeks (P=0.85). Out of 45 pregnant women with preeclampsia, 33 cases (73.3%) had mild preeclampsia and 12 cases (26.7%) had severe preeclampsia.

The mean systolic blood pressure was 121±7.44 in non-preeclampsia pregnant women and it was 149.7±7.28 in preeclampsia pregnant women. The mean diastolic blood pressure was 75.00±7.69 in non-preeclampsia pregnant women and it was 90.00 ±11.94 in preeclampsia pregnant women. The mean serum TSH level was 2.55± 1.13 in non-preeclampsia pregnant women and 3.08±1.23 in preeclampsia pregnant women (P=0.013) (Table 1).

Table 1.
The mean serum TSH level in both groups of non-preeclampsia pregnant women and preeclampsia pregnant women

Table 1. The mean serum TSH level in both groups of non-preeclampsia pregnant women and preeclampsia pregnant women
	Non-preeclampsia pregnant women	Preeclampsia pregnant women	P value
TSH (μIU/ml)	13.1 ± 55.2	23.1 ± 08.3	013.0

According to the results, out of 45 non-preeclampsia pregnant women, 35 (77.8%) had a normal delivery and 10 (22.2%) had a cesarean delivery. Besides, out of 45 preeclampsia pregnant women, 26 (57.8%) had a normal delivery and 19 (42.2%) had cesarean delivery (P=0.07) (Table 2). Based on Table 2, the Chi-square test also showed a significant relationship between preeclampsia and preterm delivery (P=000), while no significant relationship was found between preeclampsia and IUFD (P=0.500) and gender of neonates (P=0.522). Besides, based on Table 2, Independent T-test showed that there was a significant relationship between birth weight and preeclampsia (P=000). According to the Mann-Whitney test, there was a significant relationship between preeclampsia and first minute Apgar (P=0.003).

Table 2.
Results of pregnancy-gender, preterm delivery, and intrauterine death (IUFD), preterm delivery, and first minute Apgar and cesarean frequency

Table 2. Results of pregnancy-gender, preterm delivery, and intrauterine death (IUFD), preterm delivery, and first minute Apgar and cesarean frequency
	Non-preeclampsia pregnant women	Preeclampsia pregnant women	P value
Gender N(%) male	24 (53.3 %)	28 (62.2 %)	0.522
Preterm delivery N (%)	2 (4.4 %)	22 (48.9 %)	0.000
IUFD N(%)	0 (0 %)	1 (1.1 %)	0.500
First minute Apgar Mean±SD	36.0 ± 84.9	56.1 ± 28.9	0.003
Birth weight (g) Mean±SD	23.466 ± 3230	25.656 ± 2700	0.000
Caesarean delivery N(%)	10 (22.2 %)	19 (42.2 %)	0.07

Discussion

In the present study, a significant difference was found between the mean serum TSH level in the two groups of preeclampsia and non-preeclampsia pregnant women, which strongly supported the hypothesis that thyroid dysfunctions could be one of the causes of preeclampsia. As a result, measuring serum TSH level in the third trimester of pregnancy could predict preeclampsia to reduce maternal and fetal complications. However, due to the small sample size, further studies are needed to confirm this hypothesis. In a study conducted by Kharb et al., the mean TSH in non-preeclampsia pregnant women was less than that of pregnant women with severe preeclampsia and the mean weight of neonates of preeclampsia women was less than the mean weight of neonates of non-preeclampsia women⁵. In the present study, the mean weight of neonates of preeclampsia pregnant women was lower than the mean weight of neonates of non-preeclampsia women. However, in the study conducted by Naghshineh et al, there was no significant relationship between neonatal weight and hypothyroidism and preeclampsia⁶.

Conclusion

Additionally, the results showed that the prevalence of preterm delivery in preeclampsia pregnant women was different from that in non-preeclampsia pregnant women⁷. In a study conducted by Swati et al., the results also showed that the mean serum TSH level in preeclampsia pregnant women was higher than the mean serum TSH level in non-preeclampsia pregnant women⁸. In a study conducted by Sardana et al, it was concluded that the mean serum TSH level in both preeclampsia pregnant women and non- preeclampsia pregnant women was higher than the mean serum TSH level in non-pregnant women^9-10.

Acknowledgment: The researcher appreciated Clinical Research Development Center of Kamali Hospital in Alborz University of Medical Sciences.

References

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Author notes

ataee.mina@yahoo.com