Immunology and progestins in pregnancy

Review on role of progestogen (dydrogesterone) in the prevention of gestational hypertension

INTRODUCTION

Gestational hypertension remains one of the main causes of maternal deaths all over the world. Attempts to reduce/prevent the incidence had failed due to lack of understanding of the disease's aetiology. One of the early roles of natural progesterone in the first trimester of pregnancy is to promote formation of wide-calibre spiral vessels that invade into the myometrial layer of the gravid uterus. Theoretically, this will prevent or reduce the incidence of gestational hypertension in the latter half of the pregnancy.

REVIEW

The progestogen, dydrogesterone, has similar molecular structure and properties to natural progesterone. A pilot study was undertaken on primigravidae, who have higher risk of developing gestational hypertension. They were supplemented with dydrogesterone in the first trimester (Study Group) and compared with a similar number of primigravidae (Control Group) without supplementation with the progestogen. The incidence of gestational hypertension was significantly lower in the Study Group as compared to the Control Group (1.7% vs. 12.9%, respectively, p<0.001). The incidence of foetal distress was also significantly lower in the Study Group compared to the Control Group (4.3% vs. 18.1%, respectively, p<0.001).

CONCLUSION

Supplementation of the progestogen, dydrogesterone, in the first trimester to primigravidae has shown great potential in reducing or preventing the incidence of gestational hypertension.

A pilot study to determine whether progestogen supplementation using dydrogesterone during the first trimester will reduce the incidence of gestational hypertension in primigravidae

BACKGROUND

Gestational hypertension (GH) remains one of the main causes of high maternal and perinatal morbidity and mortality worldwide with the highest incidence among primigravidae of about 10%-15%. However, it was noted that the incidence of GH in primigravidae who conceived following assisted reproductive technique (ART) or intrauterine insemination (IUI) supplemented with dydrogesterone during the first trimester was low.

AIM

To determine whether dydrogesterone supplementation during the first trimester can reduce the incidence of GH among primigravidae.

METHOD

A prospective cross-sectional comparative study was undertaken in 2010 on 116 primigravidae (study group) who conceived following ART or IUI and supplemented with dydrogesterone up to 16 weeks gestation. They were matched for age and race at 16 weeks gestation with a control patient from the early pregnancy clinic who were primigravidae (n = 116) who conceived spontaneously without dydrogesterone supplementation.

FINDINGS

The incidence of GH in the study group was significantly lower than the control group (1.7% versus 12.9%, p = 0.001). The incidence of fetal distress was also significantly lower in the study group compared to the control group (4.3% versus 18.1%, p = 0.001).

INTERPRETATION

Dydrogesterone supplementation during the first trimester significantly reduced the incidence of GH and fetal distress in primigravidae.

TLR-mediated preterm birth in response to pathogenic agents

The incidence of preterm birth in developed countries has risen in the past decades. Underlying causes for this enigmatic pregnancy complication are numerous, yet infectious agents that induce dysregulation of immunity at the maternal-fetal interface pose one of the most probable causes of preterm birth. This paper highlights two factors regarding maternal infections that trigger unscheduled inflammatory sequences that are deleterious to the maternal-fetal balance necessary to maintain pregnancy. Firstly, we discuss the role of Toll-like receptors (TLRs) as sentinels of uterine immunity in the context of response to pathogens. We highlight the idea that particular TLR activations lead to differential immune cascades that induce preterm birth. Secondly, two alternative routes of pathogenic entry may prove to be critical for inducing preterm birth via a cytokine storm or a secondary and currently unknown cell-mediated mechanism of uterine inflammation. This paper summarizes pathways that underlie activation of adverse and diverse immune responses to foreign agents that may result in preterm birth.

Progestational effects of dydrogesterone in vitro, in vivo and on the human endometrium

Dydrogesterone has a molecular structure closely related to that of natural progesterone, but it has enhanced oral availability compared with progesterone. The hormonal profile and the progestational potency of dydrogesterone has been determined in vitro, in vivo and in humans, in combination with estrogens or without. It showed varying affinity for progesterone-binding proteins in uterine tissue in vitro, depending on the species. It exerted a clear progestational response in the rabbit in vivo, although the potency was influenced somewhat by the route of administration. When used in hormone replacement therapy, 10mg dydrogesterone given sequentially provides adequate protection against endometrial hyperplasia in postmenopausal women using 2mg estradiol. Similarly, a dydrogesterone dose of 5mg also protects the endometrium when continuously combined with 1mg estradiol. Dydrogesterone also has beneficial effects in women with amenorrhea/oligomenorrhea, dysfunctional uterine bleeding and irregular cycles. In conclusion, having a similar profile to progesterone but with better oral availability, dydrogesterone has been used successfully to treat disorders related to absolute or relative progesterone deficiency.

Progesterone and the immunology of pregnancy

The foetal-placental unit is a semi-allograft and the immunological recognition of pregnancy, together with the subsequent response of the maternal immune system, is necessary for a successful pregnancy. This recognition of pregnancy results in an upregulation of progesterone receptors on activated lymphocytes amongst placental cells and decidual CD56+ cells. In the presence of sufficient progesterone, these cells synthesise progesterone induced blocking factor (PIBF), a mediator that exerts substantial anti-abortive activities. PIBF affects B cells and induces an increased production of asymmetric, non-cytotoxic antibodies. It also alters the profile of cytokine secretion by activated lymphocytes resulting in an increase in the production of non-inflammatory, non-cytotoxic interleukins (IL) (e.g. IL-3, IL-4 and IL-10) and a reduction in the production of inflammatory, cytotoxic cytokines (e.g. interferon (IFN)-delta, tumour necrosis factor (TNF)-alpha and IL-2). PIBF also inhibits the cytotoxicity of natural killer (NK) cells by blocking their degranulation and perforin release, as well as inhibiting IFN-delta, TNF-alpha and IL-2-mediated transformation of NK cells into detrimental lymphokine activated killer (LAK) cells.