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Introduction

Unexplained abdominal pain in pregnancy is common. While many find this pain trivial, for some it is severe and prolonged. Our in-hospital audit of the obstetric emergency department revealed that non-visceral abdominal pain accounted for 3.4% of all presentations in 2020.

‘Round Ligament Pain’ (RLP) has been described as one of the commonest ailments of pregnancy. This abdominal pain has been traditionally attributed to the stretching of the uterine round ligaments during pregnancy. There is little anatomical support for this idea, as there is only one branch of the genitofemoral nerve running through the ligament. The round ligament is routinely ligated at hysterectomy with no recognised sequelae. RLP is described in medical textbooks such as the Oxford Handbook of Obstetrics and Gynaecology [1]. However, apart from occasional mentions in review articles [2-4] and a description of helpful stretches to alleviate RLP [5], it is nowhere to be seen in peer-reviewed English Language scientific literature. A search through online databases PubMed, Google Scholar and the Cochrane Central Register of Controlled Trials yielded no other results.

Materials And Methods

We conducted a single centre, prospective, observational cohort study of patients attending antenatal clinic at a tertiary hospital in the North Island of New Zealand. 203 pregnant people were surveyed anonymously using a written questionnaire. No funding was sought.

The primary outcomes were the incidence of unexplained abdominal pain in pregnancy and awareness of RLP. The secondary outcome was the reported source of the patients’ education about RLP.

The questionnaire contained a second part, which asked participants to describe their pain using markers for visceral versus somatic abdominal pain. These results will be reported in a subsequent report.

Recruitment occurred between July and September 2021. To be included, subjects had to provide informed written consent, speak English or have a formal interpreter present, be at least 20 weeks’ pregnant and be 18 years of age or older.

After cultural consultation, the study received approval from Waikato District Health Board’s Te Puna Oranga Māori Health Service. It was approved by the New Zealand Central Health and Disability Ethics Committee on the 9th of June, 2021 with the reference: 21/CEN/133. All participants provided written informed consent to participate in the study.

Results

After initially planning for 200 respondents, we overrecruited to 203. The mean participant age was 32.1 years. There were no incomplete questionnaires.

Māori made up 34% of participants. New Zealand Europeans: 40.4% and Pacific peoples: 3.4%.

The third most common ethnicity was Indian at 6.9%. Other ethnicities constituted the remaining 15.3%. Unexplained abdominal pain in pregnancy was common, and was reported by 68.5% (139/203) of participants. Recognition of RLP was high, with 54% of participants (109/203) having heard of it before.

As shown in figure 1, of those who had heard of RLP 59.6% (65/109) said they heard about it from a medical carer. 56.9% (62/109) had heard about it online and 14.7% (16/109) heard about it from whānau (Te Reo Māori for extended family), family and friends. For other sources, one participant cited podcasts, and another identified the smartphone applications ‘What to Expect’ and ‘Baby Tracker’ as their source.

The majority (64%, 89/139) of participants with pain had heard about RLP. Specifically, 43.9% (61/139) of patients with pain had been told about RLP by a medical carer, making this the commonest cited source of RLP information. Conversely, only 7.8% (5/64) of participants without unexplained abdominal pain cited a medical carer as a source of RLP information, giving an odds ratio of 9.23 (95% CI 3.5-24.4).

As will be published in part 2 of this study, the commonest descriptors participants used for unexplained abdominal pain in pregnancy were: pain worsened by walking, bending moving to sit (72.6%); sharp pain (56.8%); pain that feels like it is coming from deep within the pelvis (46.7%); pain that is always in the same location (45.3%), that is worsened by coughing, sneezing, pushing to defecate (45.3%); and that is lateral to the midline (37.4%).

Discussion

Evidence Based Medicine (EBM) is a movement that aims to increase the use of good quality clinical research in clinical decision making. When the term was applied to Guyatt et al’s work in 1992, the goal was to shift away from “intuition, unsystematic clinical experience and pathophysiologic rationale” (5). EBM has been celebrated by the New Zealand Medical Council’s as the expected mode of practice (6) and yet this small study shows that for our participants with unexplained abdominal pain in pregnancy, 43.9% reported that a medical carer described an evidence-free condition to them.

New Zealand’s antenatal healthcare model is multidisciplinary. The patient’s Lead Maternity Carer provides all routine antenatal visits. These are most often midwives, but can be general practitioners or obstetricians. It is routine for low-risk patients to never meet a doctor during their pregnancy and for high-risk patients to receive most of their care from obstetricians. Patients with abdominal pain in pregnancy often have consultations with physiotherapists or pain physicians. Participants in this study were recruited from obstetric clinics. We emphasise that when participants label ‘medical carers’ as the source of their education on RLP, we are not indicting one discipline over another. The interrogation of the concept of RLP should be shared amongst all antenatal clinicians.

Unless evidence supporting the phrase can be identified, medical carers should stop referring to RLP as a diagnosis for their patients. Instead, attention should be given to the features of their pain, with a goal to provide a clinically useful diagnosis and therapy. The participants of this study also completed a pilot questionnaire differentiating their abdominal pain as somatic versus visceral, the results of which will be published separately.

While not the direct subject of this article, it is our long-term hypothesis: that abdominal wall pain (AWP) plays a larger role in obstetric abdominal pain than is currently appreciated. AWP and its subgroup of Anterior Cutaneous Nerve Entrapment Syndrome (ACNES) are easily diagnosed and immediately treatable pathologies [8]. It is thought to account for 10% of chronic abdominal pain in the outpatient setting and has a reputation in the literature for being underrecognized [9]. The aetilogy is that the thoracic and anterior cutaneous nerves make 90⁰ turns through the posterior abdominal wall sheath in fibrous rings to provide cutaneous sensation to the midline anterior abdomen. Irritation or entrapment of these nerves provokes pain [9].

As the growing gravid uterus exits the pelvic cavity at 12 weeks’ gestation, it is logical that a pain condition related to the displacement of the nerves of the abdominal wall could be provoked by a distending pregnant abdomen. To date, only single case reports of AWP in pregnancy have been published [10-12]. We are currently writing a case series of the successful treatment of 20 pregnant patients at our hospital with AWP over the last 18 months.

Acknowledgments

Dr Isabel Camaño is the Clinical Director of Obstetrics at Waikato Hospital and we are grateful for her support and governance. Thank you to Dr Tanne Daniels, who recruited participants. We thank the midwives and reception staff from the antenatal clinic for their vital promotion of the study.