Progesterone in pregnancy

A miscarriage is the loss of a pregnancy before 24 weeks, with most occurring in the first 12 weeks. It can happen for many reasons, often due to chromosomal abnormalities in the developing baby that make the pregnancy non-viable. Miscarriages are common, affecting around one in four pregnancies, and in most cases they are not caused by anything the mother did or did not do.

In the UK, early miscarriages often happen before a woman even realises she is pregnant. While it can be a deeply emotional experience, medical support and post-miscarriage care can help ensure a safe physical recovery and prepare you for future pregnancies.

If you carry a balanced translocation or other chromosomal rearrangement, progesterone supplementation alone is unlikely to resolve fertility difficulties, as the underlying issue relates to chromosomal imbalance in embryos rather than inadequate progesterone production. However, progesterone may offer some support in early pregnancy once conception has occurred, potentially reducing miscarriage risk. The most effective approach for couples where one partner carries a balanced translocation is preimplantation genetic testing (PGT) combined with in vitro fertilisation (IVF), which allows embryos to be screened for chromosomal balance before implantation, significantly improving live birth rates.

Your fertility specialist or consultant gynaecologist can discuss whether progesterone is appropriate alongside other fertility treatments in your situation. For chromosomal abnormalities affecting fertility, addressing the underlying reproductive issue through appropriate assisted reproduction is typically more effective than progesterone supplementation alone.

Progesterone supplementation, if recommended, is typically started as soon as possible after a positive pregnancy test or at the first signs of vaginal bleeding in early pregnancy. Current NICE guidance suggests continuing progesterone until 16 completed weeks of pregnancy, though some specialists recommend reassessment at 12 weeks when the placenta begins producing sufficient progesterone naturally. The optimal timing and duration of progesterone therapy remains an area where evidence is not fully conclusive, and your consultant gynaecologist will advise on the most appropriate approach for your individual circumstances.

Starting progesterone early in pregnancy, particularly within the first two weeks of a positive test, is considered important for maximising any potential protective effect. However, the decision to start and continue progesterone should always be based on clinical assessment and discussion with your healthcare provider.

Vaginal micronised progesterone is the most commonly recommended form of progesterone supplementation in the UK, based on current NICE guidelines and evidence from major clinical trials. It is typically administered as a vaginal pessary at a dose of 400 mg twice daily. Alternative formulations may include intramuscular progesterone injections or oral micronised progesterone, though these are less commonly used for early pregnancy support. The choice of progesterone preparation and route of administration should be discussed with your consultant gynaecologist, who will recommend the most appropriate option based on your medical history and individual needs.

Vaginal progesterone has the advantage of delivering the hormone directly to the reproductive tract and is well-tolerated with minimal systemic absorption. Your healthcare provider will explain how to use progesterone correctly and discuss any side effects or concerns you may experience during treatment.

Whether progesterone supplementation is necessary during fertility treatment depends on your individual circumstances and the type of assisted reproduction you are undergoing. In natural conception cycles where you have a history of miscarriage, progesterone may be considered if you experience bleeding or if your consultant gynaecologist identifies other clinical indicators. During assisted reproduction cycles such as IVF, progesterone support (known as luteal phase support) is routinely provided as part of standard treatment protocols, though the specific regimen varies between fertility centres.

If you are undergoing fertility treatment, your fertility specialist will discuss progesterone requirements as part of your individualised treatment plan. For couples with chromosomal abnormalities or recurrent miscarriage, progesterone may be combined with preimplantation genetic testing (PGT) to optimise outcomes. Your healthcare team will explain the role of progesterone in your specific fertility treatment pathway.