Implantation failure and infertility

Dr Uzma Fatema

It is a widely-held view that Anovulation is the only problem causing infertility in women. But there are other reasons too that stop a woman from becoming a mother. Let’s first know what is Anovulation? It is an ovary’s inability to release an ovum for three or more months in a row.

In a healthy woman, an ovary secrets an ovum every 25-28 days depending on her cycles. Pregnancy occurs when a sperm, a male gamet, unites with an ovum, a female gamete. If one of these two is not present then pregnancy does not happen.

Implantation failure

Not many know implantation failure is another big reason for infertility in women. But before knowing implantation failure we must know what is implantation process?

Definition of implantation

Implantation is the process of attachment of a fertilized egg i.e. zygote with endometrial wall of uterus. The sperm enters the ovum and then after a few days the new cell or zygote rolls down through fallopian tube and lands in the uterus. In the uterus, the zygote attaches with endometrium wall. The zygote gets nourishment and grows into a foetus while handing on to the uterus wall.

Release of HCG

The process is slow and crucial as the zygote can take three to five days to get completely embeded into uterine endometrium. As it starts to dig deep into endometrial lining, there is secretion of HCG (Human Chorionic Gonadotropin) hormone from the endometrial tissues which are in constant touch with the embryo.

HCG hormone will protect new growing tissues of the zygote from immune response of mother’s body. HCG increases suitability of a mother’s womb for embryo to implant in it. After implantation process has completed formation of Chorionic Villi occurs which sucks blood and nutrients directly from uterus.

So implantation failure leads to infertility?

Four factors are responsible for implantation failure.

1.    Endometrial problem

During folicular phase of menstrual cycle i.e. just after bleeding phase uterus starts to make new endometrial lining under control of estrogen secreted by growing follicle in ovaries.

More than 8 mm thickness of endometriaum is considered favourable for implantation. Females with hormonal imbalance or having low estrogen level can face thin endometrium or of less than 7 mm if thickness at time of ovulation. Endometrium thickness can be measured at the time of folicular study.

Normal endometrial growth

Normal endometrial growth rate is 0.5-1 mm in a day. If it is less than that it could be enhanced with estrogen supplements and with circulation booster medicines.

2.    Maternal immunity factors

Implantation starts HCG hormone secretion which maintains necessary level of estrogen and progesterone to support a pregnancy. Progesterone suppresses immune response in a mother’s body which is alert due to new tissue embeding into uterine wall.

If not, the mother’s immune system will consider embryo as a foreign obect and try to will kill it. In cases with a history of auto immune diseases or presence of any such infection immune suppressants are given in order to protect embryo.

3.    Infection or hydrosalphynx

It is another reason for implantation failure. A previous infection or hydrosalphynx or any other infection of uterus and fallopian tube hinder implantation proces as immune cells are present in large number in uterus. They kill embryo as they consider it a foreign object.

4.    Abnoraml karyotype

If an embryo contains any abnormal set of chromosomes (sex chromosome or autosomes) then it can't implant normally. 

CONCLUSION

Out of these four factors, first three factors can be controlled with medicines. Whereas the fourth requires genetic selection of gametes in IVF cycles.

1.    Endometrial factor can be treated by giving medicines to increase circulation and estrogen level so that  endometrial thickness can be more than 8 mm.

2.    Immune response can be suppressed by immune suppressant drugs which are safe for pregnancy.

3.    Infections and hydrosalphynx should be treated first with antibiotics and suitable drugs before trials for a pregnancy.

4.    Abnormal karyotype of embryo can be avoided by genetic selection of gamete before fertilization.